// jpgd.cpp - C++ class for JPEG decompression.
// Public domain, Rich Geldreich <richgel99@gmail.com>
// Alex Evans: Linear memory allocator (taken from jpge.h).
// v1.04, May. 19, 2012: Code tweaks to fix VS2008 static code analysis warnings (all looked harmless)
//
// Supports progressive and baseline sequential JPEG image files, and the most common chroma subsampling factors: Y, H1V1, H2V1, H1V2, and H2V2.
//
// Chroma upsampling quality: H2V2 is upsampled in the frequency domain, H2V1 and H1V2 are upsampled using point sampling.
// Chroma upsampling reference: "Fast Scheme for Image Size Change in the Compressed Domain"
// http://vision.ai.uiuc.edu/~dugad/research/dct/index.html

#include "jpgd.h"
#include <string.h>

#include <assert.h>
#define JPGD_ASSERT(x) assert(x)

#ifdef _MSC_VER
#pragma warning (disable : 4611) // warning C4611: interaction between '_setjmp' and C++ object destruction is non-portable
#endif

// Set to 1 to enable freq. domain chroma upsampling on images using H2V2 subsampling (0=faster nearest neighbor sampling).
// This is slower, but results in higher quality on images with highly saturated colors.
#define JPGD_SUPPORT_FREQ_DOMAIN_UPSAMPLING 1

#define JPGD_TRUE (1)
#define JPGD_FALSE (0)

#define JPGD_MAX(a,b) (((a)>(b)) ? (a) : (b))
#define JPGD_MIN(a,b) (((a)<(b)) ? (a) : (b))

namespace jpgd {

static inline void *jpgd_malloc(size_t nSize)
{
    return malloc(nSize);
}
static inline void jpgd_free(void *p)
{
    free(p);
}

// DCT coefficients are stored in this sequence.
static int g_ZAG[64] = {  0,1,8,16,9,2,3,10,17,24,32,25,18,11,4,5,12,19,26,33,40,48,41,34,27,20,13,6,7,14,21,28,35,42,49,56,57,50,43,36,29,22,15,23,30,37,44,51,58,59,52,45,38,31,39,46,53,60,61,54,47,55,62,63 };

enum JPEG_MARKER {
    M_SOF0  = 0xC0, M_SOF1  = 0xC1, M_SOF2  = 0xC2, M_SOF3  = 0xC3, M_SOF5  = 0xC5, M_SOF6  = 0xC6, M_SOF7  = 0xC7, M_JPG   = 0xC8,
    M_SOF9  = 0xC9, M_SOF10 = 0xCA, M_SOF11 = 0xCB, M_SOF13 = 0xCD, M_SOF14 = 0xCE, M_SOF15 = 0xCF, M_DHT   = 0xC4, M_DAC   = 0xCC,
    M_RST0  = 0xD0, M_RST1  = 0xD1, M_RST2  = 0xD2, M_RST3  = 0xD3, M_RST4  = 0xD4, M_RST5  = 0xD5, M_RST6  = 0xD6, M_RST7  = 0xD7,
    M_SOI   = 0xD8, M_EOI   = 0xD9, M_SOS   = 0xDA, M_DQT   = 0xDB, M_DNL   = 0xDC, M_DRI   = 0xDD, M_DHP   = 0xDE, M_EXP   = 0xDF,
    M_APP0  = 0xE0, M_APP15 = 0xEF, M_JPG0  = 0xF0, M_JPG13 = 0xFD, M_COM   = 0xFE, M_TEM   = 0x01, M_ERROR = 0x100, RST0   = 0xD0
};

enum JPEG_SUBSAMPLING { JPGD_GRAYSCALE = 0, JPGD_YH1V1, JPGD_YH2V1, JPGD_YH1V2, JPGD_YH2V2 };

#define CONST_BITS  13
#define PASS1_BITS  2
#define SCALEDONE ((int32)1)

#define FIX_0_298631336  ((int32)2446)        /* FIX(0.298631336) */
#define FIX_0_390180644  ((int32)3196)        /* FIX(0.390180644) */
#define FIX_0_541196100  ((int32)4433)        /* FIX(0.541196100) */
#define FIX_0_765366865  ((int32)6270)        /* FIX(0.765366865) */
#define FIX_0_899976223  ((int32)7373)        /* FIX(0.899976223) */
#define FIX_1_175875602  ((int32)9633)        /* FIX(1.175875602) */
#define FIX_1_501321110  ((int32)12299)       /* FIX(1.501321110) */
#define FIX_1_847759065  ((int32)15137)       /* FIX(1.847759065) */
#define FIX_1_961570560  ((int32)16069)       /* FIX(1.961570560) */
#define FIX_2_053119869  ((int32)16819)       /* FIX(2.053119869) */
#define FIX_2_562915447  ((int32)20995)       /* FIX(2.562915447) */
#define FIX_3_072711026  ((int32)25172)       /* FIX(3.072711026) */

#define DESCALE(x,n)  (((x) + (SCALEDONE << ((n)-1))) >> (n))
#define DESCALE_ZEROSHIFT(x,n)  (((x) + (128 << (n)) + (SCALEDONE << ((n)-1))) >> (n))

#define MULTIPLY(var, cnst)  ((var) * (cnst))

#define CLAMP(i) ((static_cast<uint>(i) > 255) ? (((~i) >> 31) & 0xFF) : (i))

// Compiler creates a fast path 1D IDCT for X non-zero columns
template <int NONZERO_COLS>
struct Row {
    static void idct(int *pTemp, const jpgd_block_t *pSrc) {
        // ACCESS_COL() will be optimized at compile time to either an array access, or 0.
#define ACCESS_COL(x) (((x) < NONZERO_COLS) ? (int)pSrc[x] : 0)

        const int z2 = ACCESS_COL(2), z3 = ACCESS_COL(6);

        const int z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
        const int tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
        const int tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);

        const int tmp0 = (ACCESS_COL(0) + ACCESS_COL(4)) << CONST_BITS;
        const int tmp1 = (ACCESS_COL(0) - ACCESS_COL(4)) << CONST_BITS;

        const int tmp10 = tmp0 + tmp3, tmp13 = tmp0 - tmp3, tmp11 = tmp1 + tmp2, tmp12 = tmp1 - tmp2;

        const int atmp0 = ACCESS_COL(7), atmp1 = ACCESS_COL(5), atmp2 = ACCESS_COL(3), atmp3 = ACCESS_COL(1);

        const int bz1 = atmp0 + atmp3, bz2 = atmp1 + atmp2, bz3 = atmp0 + atmp2, bz4 = atmp1 + atmp3;
        const int bz5 = MULTIPLY(bz3 + bz4, FIX_1_175875602);

        const int az1 = MULTIPLY(bz1, - FIX_0_899976223);
        const int az2 = MULTIPLY(bz2, - FIX_2_562915447);
        const int az3 = MULTIPLY(bz3, - FIX_1_961570560) + bz5;
        const int az4 = MULTIPLY(bz4, - FIX_0_390180644) + bz5;

        const int btmp0 = MULTIPLY(atmp0, FIX_0_298631336) + az1 + az3;
        const int btmp1 = MULTIPLY(atmp1, FIX_2_053119869) + az2 + az4;
        const int btmp2 = MULTIPLY(atmp2, FIX_3_072711026) + az2 + az3;
        const int btmp3 = MULTIPLY(atmp3, FIX_1_501321110) + az1 + az4;

        pTemp[0] = DESCALE(tmp10 + btmp3, CONST_BITS-PASS1_BITS);
        pTemp[7] = DESCALE(tmp10 - btmp3, CONST_BITS-PASS1_BITS);
        pTemp[1] = DESCALE(tmp11 + btmp2, CONST_BITS-PASS1_BITS);
        pTemp[6] = DESCALE(tmp11 - btmp2, CONST_BITS-PASS1_BITS);
        pTemp[2] = DESCALE(tmp12 + btmp1, CONST_BITS-PASS1_BITS);
        pTemp[5] = DESCALE(tmp12 - btmp1, CONST_BITS-PASS1_BITS);
        pTemp[3] = DESCALE(tmp13 + btmp0, CONST_BITS-PASS1_BITS);
        pTemp[4] = DESCALE(tmp13 - btmp0, CONST_BITS-PASS1_BITS);
    }
};

template <>
struct Row<0> {
    static void idct(int *pTemp, const jpgd_block_t *pSrc) {
#ifdef _MSC_VER
        pTemp; pSrc;
#endif
    }
};

template <>
struct Row<1> {
    static void idct(int *pTemp, const jpgd_block_t *pSrc) {
        const int dcval = (pSrc[0] << PASS1_BITS);

        pTemp[0] = dcval;
        pTemp[1] = dcval;
        pTemp[2] = dcval;
        pTemp[3] = dcval;
        pTemp[4] = dcval;
        pTemp[5] = dcval;
        pTemp[6] = dcval;
        pTemp[7] = dcval;
    }
};

// Compiler creates a fast path 1D IDCT for X non-zero rows
template <int NONZERO_ROWS>
struct Col {
    static void idct(uint8 *pDst_ptr, const int *pTemp) {
        // ACCESS_ROW() will be optimized at compile time to either an array access, or 0.
#define ACCESS_ROW(x) (((x) < NONZERO_ROWS) ? pTemp[x * 8] : 0)

        const int z2 = ACCESS_ROW(2);
        const int z3 = ACCESS_ROW(6);

        const int z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
        const int tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
        const int tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);

        const int tmp0 = (ACCESS_ROW(0) + ACCESS_ROW(4)) << CONST_BITS;
        const int tmp1 = (ACCESS_ROW(0) - ACCESS_ROW(4)) << CONST_BITS;

        const int tmp10 = tmp0 + tmp3, tmp13 = tmp0 - tmp3, tmp11 = tmp1 + tmp2, tmp12 = tmp1 - tmp2;

        const int atmp0 = ACCESS_ROW(7), atmp1 = ACCESS_ROW(5), atmp2 = ACCESS_ROW(3), atmp3 = ACCESS_ROW(1);

        const int bz1 = atmp0 + atmp3, bz2 = atmp1 + atmp2, bz3 = atmp0 + atmp2, bz4 = atmp1 + atmp3;
        const int bz5 = MULTIPLY(bz3 + bz4, FIX_1_175875602);

        const int az1 = MULTIPLY(bz1, - FIX_0_899976223);
        const int az2 = MULTIPLY(bz2, - FIX_2_562915447);
        const int az3 = MULTIPLY(bz3, - FIX_1_961570560) + bz5;
        const int az4 = MULTIPLY(bz4, - FIX_0_390180644) + bz5;

        const int btmp0 = MULTIPLY(atmp0, FIX_0_298631336) + az1 + az3;
        const int btmp1 = MULTIPLY(atmp1, FIX_2_053119869) + az2 + az4;
        const int btmp2 = MULTIPLY(atmp2, FIX_3_072711026) + az2 + az3;
        const int btmp3 = MULTIPLY(atmp3, FIX_1_501321110) + az1 + az4;

        int i = DESCALE_ZEROSHIFT(tmp10 + btmp3, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*0] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp10 - btmp3, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*7] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp11 + btmp2, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*1] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp11 - btmp2, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*6] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp12 + btmp1, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*2] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp12 - btmp1, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*5] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp13 + btmp0, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*3] = (uint8)CLAMP(i);

        i = DESCALE_ZEROSHIFT(tmp13 - btmp0, CONST_BITS+PASS1_BITS+3);
        pDst_ptr[8*4] = (uint8)CLAMP(i);
    }
};

template <>
struct Col<1> {
    static void idct(uint8 *pDst_ptr, const int *pTemp) {
        int dcval = DESCALE_ZEROSHIFT(pTemp[0], PASS1_BITS+3);
        const uint8 dcval_clamped = (uint8)CLAMP(dcval);
        pDst_ptr[0*8] = dcval_clamped;
        pDst_ptr[1*8] = dcval_clamped;
        pDst_ptr[2*8] = dcval_clamped;
        pDst_ptr[3*8] = dcval_clamped;
        pDst_ptr[4*8] = dcval_clamped;
        pDst_ptr[5*8] = dcval_clamped;
        pDst_ptr[6*8] = dcval_clamped;
        pDst_ptr[7*8] = dcval_clamped;
    }
};

static const uint8 s_idct_row_table[] = {
    1,0,0,0,0,0,0,0, 2,0,0,0,0,0,0,0, 2,1,0,0,0,0,0,0, 2,1,1,0,0,0,0,0, 2,2,1,0,0,0,0,0, 3,2,1,0,0,0,0,0, 4,2,1,0,0,0,0,0, 4,3,1,0,0,0,0,0,
    4,3,2,0,0,0,0,0, 4,3,2,1,0,0,0,0, 4,3,2,1,1,0,0,0, 4,3,2,2,1,0,0,0, 4,3,3,2,1,0,0,0, 4,4,3,2,1,0,0,0, 5,4,3,2,1,0,0,0, 6,4,3,2,1,0,0,0,
    6,5,3,2,1,0,0,0, 6,5,4,2,1,0,0,0, 6,5,4,3,1,0,0,0, 6,5,4,3,2,0,0,0, 6,5,4,3,2,1,0,0, 6,5,4,3,2,1,1,0, 6,5,4,3,2,2,1,0, 6,5,4,3,3,2,1,0,
    6,5,4,4,3,2,1,0, 6,5,5,4,3,2,1,0, 6,6,5,4,3,2,1,0, 7,6,5,4,3,2,1,0, 8,6,5,4,3,2,1,0, 8,7,5,4,3,2,1,0, 8,7,6,4,3,2,1,0, 8,7,6,5,3,2,1,0,
    8,7,6,5,4,2,1,0, 8,7,6,5,4,3,1,0, 8,7,6,5,4,3,2,0, 8,7,6,5,4,3,2,1, 8,7,6,5,4,3,2,2, 8,7,6,5,4,3,3,2, 8,7,6,5,4,4,3,2, 8,7,6,5,5,4,3,2,
    8,7,6,6,5,4,3,2, 8,7,7,6,5,4,3,2, 8,8,7,6,5,4,3,2, 8,8,8,6,5,4,3,2, 8,8,8,7,5,4,3,2, 8,8,8,7,6,4,3,2, 8,8,8,7,6,5,3,2, 8,8,8,7,6,5,4,2,
    8,8,8,7,6,5,4,3, 8,8,8,7,6,5,4,4, 8,8,8,7,6,5,5,4, 8,8,8,7,6,6,5,4, 8,8,8,7,7,6,5,4, 8,8,8,8,7,6,5,4, 8,8,8,8,8,6,5,4, 8,8,8,8,8,7,5,4,
    8,8,8,8,8,7,6,4, 8,8,8,8,8,7,6,5, 8,8,8,8,8,7,6,6, 8,8,8,8,8,7,7,6, 8,8,8,8,8,8,7,6, 8,8,8,8,8,8,8,6, 8,8,8,8,8,8,8,7, 8,8,8,8,8,8,8,8,
};

static const uint8 s_idct_col_table[] = { 1, 1, 2, 3, 3, 3, 3, 3, 3, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8 };

void idct(const jpgd_block_t *pSrc_ptr, uint8 *pDst_ptr, int block_max_zag)
{
    JPGD_ASSERT(block_max_zag >= 1);
    JPGD_ASSERT(block_max_zag <= 64);

    if (block_max_zag <= 1) {
        int k = ((pSrc_ptr[0] + 4) >> 3) + 128;
        k = CLAMP(k);
        k = k | (k<<8);
        k = k | (k<<16);

        for (int i = 8; i > 0; i--) {
            *(int *)&pDst_ptr[0] = k;
            *(int *)&pDst_ptr[4] = k;
            pDst_ptr += 8;
        }
        return;
    }

    int temp[64];

    const jpgd_block_t *pSrc = pSrc_ptr;
    int *pTemp = temp;

    const uint8 *pRow_tab = &s_idct_row_table[(block_max_zag - 1) * 8];
    int i;
    for (i = 8; i > 0; i--, pRow_tab++) {
        switch (*pRow_tab) {
        case 0: Row<0>::idct(pTemp, pSrc); break;
        case 1: Row<1>::idct(pTemp, pSrc); break;
        case 2: Row<2>::idct(pTemp, pSrc); break;
        case 3: Row<3>::idct(pTemp, pSrc); break;
        case 4: Row<4>::idct(pTemp, pSrc); break;
        case 5: Row<5>::idct(pTemp, pSrc); break;
        case 6: Row<6>::idct(pTemp, pSrc); break;
        case 7: Row<7>::idct(pTemp, pSrc); break;
        case 8: Row<8>::idct(pTemp, pSrc); break;
        }

        pSrc += 8;
        pTemp += 8;
    }

    pTemp = temp;

    const int nonzero_rows = s_idct_col_table[block_max_zag - 1];
    for (i = 8; i > 0; i--) {
        switch (nonzero_rows) {
        case 1: Col<1>::idct(pDst_ptr, pTemp); break;
        case 2: Col<2>::idct(pDst_ptr, pTemp); break;
        case 3: Col<3>::idct(pDst_ptr, pTemp); break;
        case 4: Col<4>::idct(pDst_ptr, pTemp); break;
        case 5: Col<5>::idct(pDst_ptr, pTemp); break;
        case 6: Col<6>::idct(pDst_ptr, pTemp); break;
        case 7: Col<7>::idct(pDst_ptr, pTemp); break;
        case 8: Col<8>::idct(pDst_ptr, pTemp); break;
        }

        pTemp++;
        pDst_ptr++;
    }
}

void idct_4x4(const jpgd_block_t *pSrc_ptr, uint8 *pDst_ptr)
{
    int temp[64];
    int *pTemp = temp;
    const jpgd_block_t *pSrc = pSrc_ptr;

    for (int i = 4; i > 0; i--) {
        Row<4>::idct(pTemp, pSrc);
        pSrc += 8;
        pTemp += 8;
    }

    pTemp = temp;
    for (int i = 8; i > 0; i--) {
        Col<4>::idct(pDst_ptr, pTemp);
        pTemp++;
        pDst_ptr++;
    }
}

// Retrieve one character from the input stream.
inline uint jpeg_decoder::get_char()
{
    // Any bytes remaining in buffer?
    if (!m_in_buf_left) {
        // Try to get more bytes.
        prep_in_buffer();
        // Still nothing to get?
        if (!m_in_buf_left) {
            // Pad the end of the stream with 0xFF 0xD9 (EOI marker)
            int t = m_tem_flag;
            m_tem_flag ^= 1;
            if (t) {
                return 0xD9;
            } else {
                return 0xFF;
            }
        }
    }

    uint c = *m_pIn_buf_ofs++;
    m_in_buf_left--;

    return c;
}

// Same as previous method, except can indicate if the character is a pad character or not.
inline uint jpeg_decoder::get_char(bool *pPadding_flag)
{
    if (!m_in_buf_left) {
        prep_in_buffer();
        if (!m_in_buf_left) {
            *pPadding_flag = true;
            int t = m_tem_flag;
            m_tem_flag ^= 1;
            if (t) {
                return 0xD9;
            } else {
                return 0xFF;
            }
        }
    }

    *pPadding_flag = false;

    uint c = *m_pIn_buf_ofs++;
    m_in_buf_left--;

    return c;
}

// Inserts a previously retrieved character back into the input buffer.
inline void jpeg_decoder::stuff_char(uint8 q)
{
    *(--m_pIn_buf_ofs) = q;
    m_in_buf_left++;
}

// Retrieves one character from the input stream, but does not read past markers. Will continue to return 0xFF when a marker is encountered.
inline uint8 jpeg_decoder::get_octet()
{
    bool padding_flag;
    int c = get_char(&padding_flag);

    if (c == 0xFF) {
        if (padding_flag) {
            return 0xFF;
        }

        c = get_char(&padding_flag);
        if (padding_flag) {
            stuff_char(0xFF);
            return 0xFF;
        }

        if (c == 0x00) {
            return 0xFF;
        } else {
            stuff_char(static_cast<uint8>(c));
            stuff_char(0xFF);
            return 0xFF;
        }
    }

    return static_cast<uint8>(c);
}

// Retrieves a variable number of bits from the input stream. Does not recognize markers.
inline uint jpeg_decoder::get_bits(int num_bits)
{
    if (!num_bits) {
        return 0;
    }

    uint i = m_bit_buf >> (32 - num_bits);

    if ((m_bits_left -= num_bits) <= 0) {
        m_bit_buf <<= (num_bits += m_bits_left);

        uint c1 = get_char();
        uint c2 = get_char();
        m_bit_buf = (m_bit_buf & 0xFFFF0000) | (c1 << 8) | c2;

        m_bit_buf <<= -m_bits_left;

        m_bits_left += 16;

        JPGD_ASSERT(m_bits_left >= 0);
    } else {
        m_bit_buf <<= num_bits;
    }

    return i;
}

// Retrieves a variable number of bits from the input stream. Markers will not be read into the input bit buffer. Instead, an infinite number of all 1's will be returned when a marker is encountered.
inline uint jpeg_decoder::get_bits_no_markers(int num_bits)
{
    if (!num_bits) {
        return 0;
    }

    uint i = m_bit_buf >> (32 - num_bits);

    if ((m_bits_left -= num_bits) <= 0) {
        m_bit_buf <<= (num_bits += m_bits_left);

        if ((m_in_buf_left < 2) || (m_pIn_buf_ofs[0] == 0xFF) || (m_pIn_buf_ofs[1] == 0xFF)) {
            uint c1 = get_octet();
            uint c2 = get_octet();
            m_bit_buf |= (c1 << 8) | c2;
        } else {
            m_bit_buf |= ((uint)m_pIn_buf_ofs[0] << 8) | m_pIn_buf_ofs[1];
            m_in_buf_left -= 2;
            m_pIn_buf_ofs += 2;
        }

        m_bit_buf <<= -m_bits_left;

        m_bits_left += 16;

        JPGD_ASSERT(m_bits_left >= 0);
    } else {
        m_bit_buf <<= num_bits;
    }

    return i;
}

// Decodes a Huffman encoded symbol.
inline int jpeg_decoder::huff_decode(huff_tables *pH)
{
    int symbol;

    // Check first 8-bits: do we have a complete symbol?
    if ((symbol = pH->look_up[m_bit_buf >> 24]) < 0) {
        // Decode more bits, use a tree traversal to find symbol.
        int ofs = 23;
        do {
            symbol = pH->tree[-(int)(symbol + ((m_bit_buf >> ofs) & 1))];
            ofs--;
        } while (symbol < 0);

        get_bits_no_markers(8 + (23 - ofs));
    } else {
        get_bits_no_markers(pH->code_size[symbol]);
    }

    return symbol;
}

// Decodes a Huffman encoded symbol.
inline int jpeg_decoder::huff_decode(huff_tables *pH, int &extra_bits)
{
    int symbol;

    // Check first 8-bits: do we have a complete symbol?
    if ((symbol = pH->look_up2[m_bit_buf >> 24]) < 0) {
        // Use a tree traversal to find symbol.
        int ofs = 23;
        do {
            symbol = pH->tree[-(int)(symbol + ((m_bit_buf >> ofs) & 1))];
            ofs--;
        } while (symbol < 0);

        get_bits_no_markers(8 + (23 - ofs));

        extra_bits = get_bits_no_markers(symbol & 0xF);
    } else {
        JPGD_ASSERT(((symbol >> 8) & 31) == pH->code_size[symbol & 255] + ((symbol & 0x8000) ? (symbol & 15) : 0));

        if (symbol & 0x8000) {
            get_bits_no_markers((symbol >> 8) & 31);
            extra_bits = symbol >> 16;
        } else {
            int code_size = (symbol >> 8) & 31;
            int num_extra_bits = symbol & 0xF;
            int bits = code_size + num_extra_bits;
            if (bits <= (m_bits_left + 16)) {
                extra_bits = get_bits_no_markers(bits) & ((1 << num_extra_bits) - 1);
            } else {
                get_bits_no_markers(code_size);
                extra_bits = get_bits_no_markers(num_extra_bits);
            }
        }

        symbol &= 0xFF;
    }

    return symbol;
}

// Tables and macro used to fully decode the DPCM differences.
static const int s_extend_test[16] = { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080, 0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };
static const int s_extend_offset[16] = { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1, ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1, ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1, ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };
static const int s_extend_mask[] = { 0, (1<<0), (1<<1), (1<<2), (1<<3), (1<<4), (1<<5), (1<<6), (1<<7), (1<<8), (1<<9), (1<<10), (1<<11), (1<<12), (1<<13), (1<<14), (1<<15), (1<<16) };
// The logical AND's in this macro are to shut up static code analysis (aren't really necessary - couldn't find another way to do this)
#define JPGD_HUFF_EXTEND(x, s) (((x) < s_extend_test[s & 15]) ? ((x) + s_extend_offset[s & 15]) : (x))

// Clamps a value between 0-255.
inline uint8 jpeg_decoder::clamp(int i)
{
    if (static_cast<uint>(i) > 255) {
        i = (((~i) >> 31) & 0xFF);
    }

    return static_cast<uint8>(i);
}

namespace DCT_Upsample
{
struct Matrix44 {
    typedef int Element_Type;
    enum { NUM_ROWS = 4, NUM_COLS = 4 };

    Element_Type v[NUM_ROWS][NUM_COLS];

    inline int rows() const
    {
        return NUM_ROWS;
    }
    inline int cols() const
    {
        return NUM_COLS;
    }

    inline const Element_Type &at(int r, int c) const
    {
        return v[r][c];
    }
    inline       Element_Type &at(int r, int c)
    {
        return v[r][c];
    }

    inline Matrix44() { }

    inline Matrix44 &operator += (const Matrix44 &a)
    {
        for (int r = 0; r < NUM_ROWS; r++) {
            at(r, 0) += a.at(r, 0);
            at(r, 1) += a.at(r, 1);
            at(r, 2) += a.at(r, 2);
            at(r, 3) += a.at(r, 3);
        }
        return *this;
    }

    inline Matrix44 &operator -= (const Matrix44 &a)
    {
        for (int r = 0; r < NUM_ROWS; r++) {
            at(r, 0) -= a.at(r, 0);
            at(r, 1) -= a.at(r, 1);
            at(r, 2) -= a.at(r, 2);
            at(r, 3) -= a.at(r, 3);
        }
        return *this;
    }

    friend inline Matrix44 operator + (const Matrix44 &a, const Matrix44 &b)
    {
        Matrix44 ret;
        for (int r = 0; r < NUM_ROWS; r++) {
            ret.at(r, 0) = a.at(r, 0) + b.at(r, 0);
            ret.at(r, 1) = a.at(r, 1) + b.at(r, 1);
            ret.at(r, 2) = a.at(r, 2) + b.at(r, 2);
            ret.at(r, 3) = a.at(r, 3) + b.at(r, 3);
        }
        return ret;
    }

    friend inline Matrix44 operator - (const Matrix44 &a, const Matrix44 &b)
    {
        Matrix44 ret;
        for (int r = 0; r < NUM_ROWS; r++) {
            ret.at(r, 0) = a.at(r, 0) - b.at(r, 0);
            ret.at(r, 1) = a.at(r, 1) - b.at(r, 1);
            ret.at(r, 2) = a.at(r, 2) - b.at(r, 2);
            ret.at(r, 3) = a.at(r, 3) - b.at(r, 3);
        }
        return ret;
    }

    static inline void add_and_store(jpgd_block_t *pDst, const Matrix44 &a, const Matrix44 &b)
    {
        for (int r = 0; r < 4; r++) {
            pDst[0*8 + r] = static_cast<jpgd_block_t>(a.at(r, 0) + b.at(r, 0));
            pDst[1*8 + r] = static_cast<jpgd_block_t>(a.at(r, 1) + b.at(r, 1));
            pDst[2*8 + r] = static_cast<jpgd_block_t>(a.at(r, 2) + b.at(r, 2));
            pDst[3*8 + r] = static_cast<jpgd_block_t>(a.at(r, 3) + b.at(r, 3));
        }
    }

    static inline void sub_and_store(jpgd_block_t *pDst, const Matrix44 &a, const Matrix44 &b)
    {
        for (int r = 0; r < 4; r++) {
            pDst[0*8 + r] = static_cast<jpgd_block_t>(a.at(r, 0) - b.at(r, 0));
            pDst[1*8 + r] = static_cast<jpgd_block_t>(a.at(r, 1) - b.at(r, 1));
            pDst[2*8 + r] = static_cast<jpgd_block_t>(a.at(r, 2) - b.at(r, 2));
            pDst[3*8 + r] = static_cast<jpgd_block_t>(a.at(r, 3) - b.at(r, 3));
        }
    }
};

const int FRACT_BITS = 10;
const int SCALE = 1 << FRACT_BITS;

typedef int Temp_Type;
#define D(i) (((i) + (SCALE >> 1)) >> FRACT_BITS)
#define F(i) ((int)((i) * SCALE + .5f))

// Any decent C++ compiler will optimize this at compile time to a 0, or an array access.
#define AT(c, r) ((((c)>=NUM_COLS)||((r)>=NUM_ROWS)) ? 0 : pSrc[(c)+(r)*8])

// NUM_ROWS/NUM_COLS = # of non-zero rows/cols in input matrix
template<int NUM_ROWS, int NUM_COLS>
struct P_Q {
    static void calc(Matrix44 &P, Matrix44 &Q, const jpgd_block_t *pSrc)
    {
        // 4x8 = 4x8 times 8x8, matrix 0 is constant
        const Temp_Type X000 = AT(0, 0);
        const Temp_Type X001 = AT(0, 1);
        const Temp_Type X002 = AT(0, 2);
        const Temp_Type X003 = AT(0, 3);
        const Temp_Type X004 = AT(0, 4);
        const Temp_Type X005 = AT(0, 5);
        const Temp_Type X006 = AT(0, 6);
        const Temp_Type X007 = AT(0, 7);
        const Temp_Type X010 = D(F(0.415735f) * AT(1, 0) + F(0.791065f) * AT(3, 0) + F(-0.352443f) * AT(5, 0) + F(0.277785f) * AT(7, 0));
        const Temp_Type X011 = D(F(0.415735f) * AT(1, 1) + F(0.791065f) * AT(3, 1) + F(-0.352443f) * AT(5, 1) + F(0.277785f) * AT(7, 1));
        const Temp_Type X012 = D(F(0.415735f) * AT(1, 2) + F(0.791065f) * AT(3, 2) + F(-0.352443f) * AT(5, 2) + F(0.277785f) * AT(7, 2));
        const Temp_Type X013 = D(F(0.415735f) * AT(1, 3) + F(0.791065f) * AT(3, 3) + F(-0.352443f) * AT(5, 3) + F(0.277785f) * AT(7, 3));
        const Temp_Type X014 = D(F(0.415735f) * AT(1, 4) + F(0.791065f) * AT(3, 4) + F(-0.352443f) * AT(5, 4) + F(0.277785f) * AT(7, 4));
        const Temp_Type X015 = D(F(0.415735f) * AT(1, 5) + F(0.791065f) * AT(3, 5) + F(-0.352443f) * AT(5, 5) + F(0.277785f) * AT(7, 5));
        const Temp_Type X016 = D(F(0.415735f) * AT(1, 6) + F(0.791065f) * AT(3, 6) + F(-0.352443f) * AT(5, 6) + F(0.277785f) * AT(7, 6));
        const Temp_Type X017 = D(F(0.415735f) * AT(1, 7) + F(0.791065f) * AT(3, 7) + F(-0.352443f) * AT(5, 7) + F(0.277785f) * AT(7, 7));
        const Temp_Type X020 = AT(4, 0);
        const Temp_Type X021 = AT(4, 1);
        const Temp_Type X022 = AT(4, 2);
        const Temp_Type X023 = AT(4, 3);
        const Temp_Type X024 = AT(4, 4);
        const Temp_Type X025 = AT(4, 5);
        const Temp_Type X026 = AT(4, 6);
        const Temp_Type X027 = AT(4, 7);
        const Temp_Type X030 = D(F(0.022887f) * AT(1, 0) + F(-0.097545f) * AT(3, 0) + F(0.490393f) * AT(5, 0) + F(0.865723f) * AT(7, 0));
        const Temp_Type X031 = D(F(0.022887f) * AT(1, 1) + F(-0.097545f) * AT(3, 1) + F(0.490393f) * AT(5, 1) + F(0.865723f) * AT(7, 1));
        const Temp_Type X032 = D(F(0.022887f) * AT(1, 2) + F(-0.097545f) * AT(3, 2) + F(0.490393f) * AT(5, 2) + F(0.865723f) * AT(7, 2));
        const Temp_Type X033 = D(F(0.022887f) * AT(1, 3) + F(-0.097545f) * AT(3, 3) + F(0.490393f) * AT(5, 3) + F(0.865723f) * AT(7, 3));
        const Temp_Type X034 = D(F(0.022887f) * AT(1, 4) + F(-0.097545f) * AT(3, 4) + F(0.490393f) * AT(5, 4) + F(0.865723f) * AT(7, 4));
        const Temp_Type X035 = D(F(0.022887f) * AT(1, 5) + F(-0.097545f) * AT(3, 5) + F(0.490393f) * AT(5, 5) + F(0.865723f) * AT(7, 5));
        const Temp_Type X036 = D(F(0.022887f) * AT(1, 6) + F(-0.097545f) * AT(3, 6) + F(0.490393f) * AT(5, 6) + F(0.865723f) * AT(7, 6));
        const Temp_Type X037 = D(F(0.022887f) * AT(1, 7) + F(-0.097545f) * AT(3, 7) + F(0.490393f) * AT(5, 7) + F(0.865723f) * AT(7, 7));

        // 4x4 = 4x8 times 8x4, matrix 1 is constant
        P.at(0, 0) = X000;
        P.at(0, 1) = D(X001 * F(0.415735f) + X003 * F(0.791065f) + X005 * F(-0.352443f) + X007 * F(0.277785f));
        P.at(0, 2) = X004;
        P.at(0, 3) = D(X001 * F(0.022887f) + X003 * F(-0.097545f) + X005 * F(0.490393f) + X007 * F(0.865723f));
        P.at(1, 0) = X010;
        P.at(1, 1) = D(X011 * F(0.415735f) + X013 * F(0.791065f) + X015 * F(-0.352443f) + X017 * F(0.277785f));
        P.at(1, 2) = X014;
        P.at(1, 3) = D(X011 * F(0.022887f) + X013 * F(-0.097545f) + X015 * F(0.490393f) + X017 * F(0.865723f));
        P.at(2, 0) = X020;
        P.at(2, 1) = D(X021 * F(0.415735f) + X023 * F(0.791065f) + X025 * F(-0.352443f) + X027 * F(0.277785f));
        P.at(2, 2) = X024;
        P.at(2, 3) = D(X021 * F(0.022887f) + X023 * F(-0.097545f) + X025 * F(0.490393f) + X027 * F(0.865723f));
        P.at(3, 0) = X030;
        P.at(3, 1) = D(X031 * F(0.415735f) + X033 * F(0.791065f) + X035 * F(-0.352443f) + X037 * F(0.277785f));
        P.at(3, 2) = X034;
        P.at(3, 3) = D(X031 * F(0.022887f) + X033 * F(-0.097545f) + X035 * F(0.490393f) + X037 * F(0.865723f));
        // 40 muls 24 adds

        // 4x4 = 4x8 times 8x4, matrix 1 is constant
        Q.at(0, 0) = D(X001 * F(0.906127f) + X003 * F(-0.318190f) + X005 * F(0.212608f) + X007 * F(-0.180240f));
        Q.at(0, 1) = X002;
        Q.at(0, 2) = D(X001 * F(-0.074658f) + X003 * F(0.513280f) + X005 * F(0.768178f) + X007 * F(-0.375330f));
        Q.at(0, 3) = X006;
        Q.at(1, 0) = D(X011 * F(0.906127f) + X013 * F(-0.318190f) + X015 * F(0.212608f) + X017 * F(-0.180240f));
        Q.at(1, 1) = X012;
        Q.at(1, 2) = D(X011 * F(-0.074658f) + X013 * F(0.513280f) + X015 * F(0.768178f) + X017 * F(-0.375330f));
        Q.at(1, 3) = X016;
        Q.at(2, 0) = D(X021 * F(0.906127f) + X023 * F(-0.318190f) + X025 * F(0.212608f) + X027 * F(-0.180240f));
        Q.at(2, 1) = X022;
        Q.at(2, 2) = D(X021 * F(-0.074658f) + X023 * F(0.513280f) + X025 * F(0.768178f) + X027 * F(-0.375330f));
        Q.at(2, 3) = X026;
        Q.at(3, 0) = D(X031 * F(0.906127f) + X033 * F(-0.318190f) + X035 * F(0.212608f) + X037 * F(-0.180240f));
        Q.at(3, 1) = X032;
        Q.at(3, 2) = D(X031 * F(-0.074658f) + X033 * F(0.513280f) + X035 * F(0.768178f) + X037 * F(-0.375330f));
        Q.at(3, 3) = X036;
        // 40 muls 24 adds
    }
};

template<int NUM_ROWS, int NUM_COLS>
struct R_S {
    static void calc(Matrix44 &R, Matrix44 &S, const jpgd_block_t *pSrc)
    {
        // 4x8 = 4x8 times 8x8, matrix 0 is constant
        const Temp_Type X100 = D(F(0.906127f) * AT(1, 0) + F(-0.318190f) * AT(3, 0) + F(0.212608f) * AT(5, 0) + F(-0.180240f) * AT(7, 0));
        const Temp_Type X101 = D(F(0.906127f) * AT(1, 1) + F(-0.318190f) * AT(3, 1) + F(0.212608f) * AT(5, 1) + F(-0.180240f) * AT(7, 1));
        const Temp_Type X102 = D(F(0.906127f) * AT(1, 2) + F(-0.318190f) * AT(3, 2) + F(0.212608f) * AT(5, 2) + F(-0.180240f) * AT(7, 2));
        const Temp_Type X103 = D(F(0.906127f) * AT(1, 3) + F(-0.318190f) * AT(3, 3) + F(0.212608f) * AT(5, 3) + F(-0.180240f) * AT(7, 3));
        const Temp_Type X104 = D(F(0.906127f) * AT(1, 4) + F(-0.318190f) * AT(3, 4) + F(0.212608f) * AT(5, 4) + F(-0.180240f) * AT(7, 4));
        const Temp_Type X105 = D(F(0.906127f) * AT(1, 5) + F(-0.318190f) * AT(3, 5) + F(0.212608f) * AT(5, 5) + F(-0.180240f) * AT(7, 5));
        const Temp_Type X106 = D(F(0.906127f) * AT(1, 6) + F(-0.318190f) * AT(3, 6) + F(0.212608f) * AT(5, 6) + F(-0.180240f) * AT(7, 6));
        const Temp_Type X107 = D(F(0.906127f) * AT(1, 7) + F(-0.318190f) * AT(3, 7) + F(0.212608f) * AT(5, 7) + F(-0.180240f) * AT(7, 7));
        const Temp_Type X110 = AT(2, 0);
        const Temp_Type X111 = AT(2, 1);
        const Temp_Type X112 = AT(2, 2);
        const Temp_Type X113 = AT(2, 3);
        const Temp_Type X114 = AT(2, 4);
        const Temp_Type X115 = AT(2, 5);
        const Temp_Type X116 = AT(2, 6);
        const Temp_Type X117 = AT(2, 7);
        const Temp_Type X120 = D(F(-0.074658f) * AT(1, 0) + F(0.513280f) * AT(3, 0) + F(0.768178f) * AT(5, 0) + F(-0.375330f) * AT(7, 0));
        const Temp_Type X121 = D(F(-0.074658f) * AT(1, 1) + F(0.513280f) * AT(3, 1) + F(0.768178f) * AT(5, 1) + F(-0.375330f) * AT(7, 1));
        const Temp_Type X122 = D(F(-0.074658f) * AT(1, 2) + F(0.513280f) * AT(3, 2) + F(0.768178f) * AT(5, 2) + F(-0.375330f) * AT(7, 2));
        const Temp_Type X123 = D(F(-0.074658f) * AT(1, 3) + F(0.513280f) * AT(3, 3) + F(0.768178f) * AT(5, 3) + F(-0.375330f) * AT(7, 3));
        const Temp_Type X124 = D(F(-0.074658f) * AT(1, 4) + F(0.513280f) * AT(3, 4) + F(0.768178f) * AT(5, 4) + F(-0.375330f) * AT(7, 4));
        const Temp_Type X125 = D(F(-0.074658f) * AT(1, 5) + F(0.513280f) * AT(3, 5) + F(0.768178f) * AT(5, 5) + F(-0.375330f) * AT(7, 5));
        const Temp_Type X126 = D(F(-0.074658f) * AT(1, 6) + F(0.513280f) * AT(3, 6) + F(0.768178f) * AT(5, 6) + F(-0.375330f) * AT(7, 6));
        const Temp_Type X127 = D(F(-0.074658f) * AT(1, 7) + F(0.513280f) * AT(3, 7) + F(0.768178f) * AT(5, 7) + F(-0.375330f) * AT(7, 7));
        const Temp_Type X130 = AT(6, 0);
        const Temp_Type X131 = AT(6, 1);
        const Temp_Type X132 = AT(6, 2);
        const Temp_Type X133 = AT(6, 3);
        const Temp_Type X134 = AT(6, 4);
        const Temp_Type X135 = AT(6, 5);
        const Temp_Type X136 = AT(6, 6);
        const Temp_Type X137 = AT(6, 7);
        // 80 muls 48 adds

        // 4x4 = 4x8 times 8x4, matrix 1 is constant
        R.at(0, 0) = X100;
        R.at(0, 1) = D(X101 * F(0.415735f) + X103 * F(0.791065f) + X105 * F(-0.352443f) + X107 * F(0.277785f));
        R.at(0, 2) = X104;
        R.at(0, 3) = D(X101 * F(0.022887f) + X103 * F(-0.097545f) + X105 * F(0.490393f) + X107 * F(0.865723f));
        R.at(1, 0) = X110;
        R.at(1, 1) = D(X111 * F(0.415735f) + X113 * F(0.791065f) + X115 * F(-0.352443f) + X117 * F(0.277785f));
        R.at(1, 2) = X114;
        R.at(1, 3) = D(X111 * F(0.022887f) + X113 * F(-0.097545f) + X115 * F(0.490393f) + X117 * F(0.865723f));
        R.at(2, 0) = X120;
        R.at(2, 1) = D(X121 * F(0.415735f) + X123 * F(0.791065f) + X125 * F(-0.352443f) + X127 * F(0.277785f));
        R.at(2, 2) = X124;
        R.at(2, 3) = D(X121 * F(0.022887f) + X123 * F(-0.097545f) + X125 * F(0.490393f) + X127 * F(0.865723f));
        R.at(3, 0) = X130;
        R.at(3, 1) = D(X131 * F(0.415735f) + X133 * F(0.791065f) + X135 * F(-0.352443f) + X137 * F(0.277785f));
        R.at(3, 2) = X134;
        R.at(3, 3) = D(X131 * F(0.022887f) + X133 * F(-0.097545f) + X135 * F(0.490393f) + X137 * F(0.865723f));
        // 40 muls 24 adds
        // 4x4 = 4x8 times 8x4, matrix 1 is constant
        S.at(0, 0) = D(X101 * F(0.906127f) + X103 * F(-0.318190f) + X105 * F(0.212608f) + X107 * F(-0.180240f));
        S.at(0, 1) = X102;
        S.at(0, 2) = D(X101 * F(-0.074658f) + X103 * F(0.513280f) + X105 * F(0.768178f) + X107 * F(-0.375330f));
        S.at(0, 3) = X106;
        S.at(1, 0) = D(X111 * F(0.906127f) + X113 * F(-0.318190f) + X115 * F(0.212608f) + X117 * F(-0.180240f));
        S.at(1, 1) = X112;
        S.at(1, 2) = D(X111 * F(-0.074658f) + X113 * F(0.513280f) + X115 * F(0.768178f) + X117 * F(-0.375330f));
        S.at(1, 3) = X116;
        S.at(2, 0) = D(X121 * F(0.906127f) + X123 * F(-0.318190f) + X125 * F(0.212608f) + X127 * F(-0.180240f));
        S.at(2, 1) = X122;
        S.at(2, 2) = D(X121 * F(-0.074658f) + X123 * F(0.513280f) + X125 * F(0.768178f) + X127 * F(-0.375330f));
        S.at(2, 3) = X126;
        S.at(3, 0) = D(X131 * F(0.906127f) + X133 * F(-0.318190f) + X135 * F(0.212608f) + X137 * F(-0.180240f));
        S.at(3, 1) = X132;
        S.at(3, 2) = D(X131 * F(-0.074658f) + X133 * F(0.513280f) + X135 * F(0.768178f) + X137 * F(-0.375330f));
        S.at(3, 3) = X136;
        // 40 muls 24 adds
    }
};
} // end namespace DCT_Upsample

// Unconditionally frees all allocated m_blocks.
void jpeg_decoder::free_all_blocks()
{
    m_pStream = NULL;
    for (mem_block *b = m_pMem_blocks; b; ) {
        mem_block *n = b->m_pNext;
        jpgd_free(b);
        b = n;
    }
    m_pMem_blocks = NULL;
}

// This method handles all errors. It will never return.
// It could easily be changed to use C++ exceptions.
JPGD_NORETURN void jpeg_decoder::stop_decoding(jpgd_status status)
{
    m_error_code = status;
    free_all_blocks();
    longjmp(m_jmp_state, status);
}

void *jpeg_decoder::alloc(size_t nSize, bool zero)
{
    nSize = (JPGD_MAX(nSize, 1) + 3) & ~3;
    char *rv = NULL;
    for (mem_block *b = m_pMem_blocks; b; b = b->m_pNext) {
        if ((b->m_used_count + nSize) <= b->m_size) {
            rv = b->m_data + b->m_used_count;
            b->m_used_count += nSize;
            break;
        }
    }
    if (!rv) {
        size_t capacity = JPGD_MAX(32768 - 256, (nSize + 2047) & ~2047);
        mem_block *b = (mem_block *)jpgd_malloc(sizeof(mem_block) + capacity);
        if (!b) {
            stop_decoding(JPGD_NOTENOUGHMEM);
        }
        b->m_pNext = m_pMem_blocks;
        m_pMem_blocks = b;
        b->m_used_count = nSize;
        b->m_size = capacity;
        rv = b->m_data;
    }
    if (zero) {
        memset(rv, 0, nSize);
    }
    return rv;
}

void jpeg_decoder::word_clear(void *p, uint16 c, uint n)
{
    uint8 *pD = (uint8 *)p;
    const uint8 l = c & 0xFF, h = (c >> 8) & 0xFF;
    while (n) {
        pD[0] = l; pD[1] = h; pD += 2;
        n--;
    }
}

// Refill the input buffer.
// This method will sit in a loop until (A) the buffer is full or (B)
// the stream's read() method reports and end of file condition.
void jpeg_decoder::prep_in_buffer()
{
    m_in_buf_left = 0;
    m_pIn_buf_ofs = m_in_buf;

    if (m_eof_flag) {
        return;
    }

    do {
        int bytes_read = m_pStream->read(m_in_buf + m_in_buf_left, JPGD_IN_BUF_SIZE - m_in_buf_left, &m_eof_flag);
        if (bytes_read == -1) {
            stop_decoding(JPGD_STREAM_READ);
        }

        m_in_buf_left += bytes_read;
    } while ((m_in_buf_left < JPGD_IN_BUF_SIZE) && (!m_eof_flag));

    m_total_bytes_read += m_in_buf_left;

    // Pad the end of the block with M_EOI (prevents the decompressor from going off the rails if the stream is invalid).
    // (This dates way back to when this decompressor was written in C/asm, and the all-asm Huffman decoder did some fancy things to increase perf.)
    word_clear(m_pIn_buf_ofs + m_in_buf_left, 0xD9FF, 64);
}

// Read a Huffman code table.
void jpeg_decoder::read_dht_marker()
{
    int i, index, count;
    uint8 huff_num[17];
    uint8 huff_val[256];

    uint num_left = get_bits(16);

    if (num_left < 2) {
        stop_decoding(JPGD_BAD_DHT_MARKER);
    }

    num_left -= 2;

    while (num_left) {
        index = get_bits(8);

        huff_num[0] = 0;

        count = 0;

        for (i = 1; i <= 16; i++) {
            huff_num[i] = static_cast<uint8>(get_bits(8));
            count += huff_num[i];
        }

        if (count > 255) {
            stop_decoding(JPGD_BAD_DHT_COUNTS);
        }

        for (i = 0; i < count; i++) {
            huff_val[i] = static_cast<uint8>(get_bits(8));
        }

        i = 1 + 16 + count;

        if (num_left < (uint)i) {
            stop_decoding(JPGD_BAD_DHT_MARKER);
        }

        num_left -= i;

        if ((index & 0x10) > 0x10) {
            stop_decoding(JPGD_BAD_DHT_INDEX);
        }

        index = (index & 0x0F) + ((index & 0x10) >> 4) * (JPGD_MAX_HUFF_TABLES >> 1);

        if (index >= JPGD_MAX_HUFF_TABLES) {
            stop_decoding(JPGD_BAD_DHT_INDEX);
        }

        if (!m_huff_num[index]) {
            m_huff_num[index] = (uint8 *)alloc(17);
        }

        if (!m_huff_val[index]) {
            m_huff_val[index] = (uint8 *)alloc(256);
        }

        m_huff_ac[index] = (index & 0x10) != 0;
        memcpy(m_huff_num[index], huff_num, 17);
        memcpy(m_huff_val[index], huff_val, 256);
    }
}

// Read a quantization table.
void jpeg_decoder::read_dqt_marker()
{
    int n, i, prec;
    uint num_left;
    uint temp;

    num_left = get_bits(16);

    if (num_left < 2) {
        stop_decoding(JPGD_BAD_DQT_MARKER);
    }

    num_left -= 2;

    while (num_left) {
        n = get_bits(8);
        prec = n >> 4;
        n &= 0x0F;

        if (n >= JPGD_MAX_QUANT_TABLES) {
            stop_decoding(JPGD_BAD_DQT_TABLE);
        }

        if (!m_quant[n]) {
            m_quant[n] = (jpgd_quant_t *)alloc(64 * sizeof(jpgd_quant_t));
        }

        // read quantization entries, in zag order
        for (i = 0; i < 64; i++) {
            temp = get_bits(8);

            if (prec) {
                temp = (temp << 8) + get_bits(8);
            }

            m_quant[n][i] = static_cast<jpgd_quant_t>(temp);
        }

        i = 64 + 1;

        if (prec) {
            i += 64;
        }

        if (num_left < (uint)i) {
            stop_decoding(JPGD_BAD_DQT_LENGTH);
        }

        num_left -= i;
    }
}

// Read the start of frame (SOF) marker.
void jpeg_decoder::read_sof_marker()
{
    int i;
    uint num_left;

    num_left = get_bits(16);

    if (get_bits(8) != 8) { /* precision: sorry, only 8-bit precision is supported right now */
        stop_decoding(JPGD_BAD_PRECISION);
    }

    m_image_y_size = get_bits(16);

    if ((m_image_y_size < 1) || (m_image_y_size > JPGD_MAX_HEIGHT)) {
        stop_decoding(JPGD_BAD_HEIGHT);
    }

    m_image_x_size = get_bits(16);

    if ((m_image_x_size < 1) || (m_image_x_size > JPGD_MAX_WIDTH)) {
        stop_decoding(JPGD_BAD_WIDTH);
    }

    m_comps_in_frame = get_bits(8);

    if (m_comps_in_frame > JPGD_MAX_COMPONENTS) {
        stop_decoding(JPGD_TOO_MANY_COMPONENTS);
    }

    if (num_left != (uint)(m_comps_in_frame * 3 + 8)) {
        stop_decoding(JPGD_BAD_SOF_LENGTH);
    }

    for (i = 0; i < m_comps_in_frame; i++) {
        m_comp_ident[i]  = get_bits(8);
        m_comp_h_samp[i] = get_bits(4);
        m_comp_v_samp[i] = get_bits(4);
        m_comp_quant[i]  = get_bits(8);
    }
}

// Used to skip unrecognized markers.
void jpeg_decoder::skip_variable_marker()
{
    uint num_left;

    num_left = get_bits(16);

    if (num_left < 2) {
        stop_decoding(JPGD_BAD_VARIABLE_MARKER);
    }

    num_left -= 2;

    while (num_left) {
        get_bits(8);
        num_left--;
    }
}

// Read a define restart interval (DRI) marker.
void jpeg_decoder::read_dri_marker()
{
    if (get_bits(16) != 4) {
        stop_decoding(JPGD_BAD_DRI_LENGTH);
    }

    m_restart_interval = get_bits(16);
}

// Read a start of scan (SOS) marker.
void jpeg_decoder::read_sos_marker()
{
    uint num_left;
    int i, ci, n, c, cc;

    num_left = get_bits(16);

    n = get_bits(8);

    m_comps_in_scan = n;

    num_left -= 3;

    if ( (num_left != (uint)(n * 2 + 3)) || (n < 1) || (n > JPGD_MAX_COMPS_IN_SCAN) ) {
        stop_decoding(JPGD_BAD_SOS_LENGTH);
    }

    for (i = 0; i < n; i++) {
        cc = get_bits(8);
        c = get_bits(8);
        num_left -= 2;

        for (ci = 0; ci < m_comps_in_frame; ci++)
            if (cc == m_comp_ident[ci]) {
                break;
            }

        if (ci >= m_comps_in_frame) {
            stop_decoding(JPGD_BAD_SOS_COMP_ID);
        }

        m_comp_list[i]    = ci;
        m_comp_dc_tab[ci] = (c >> 4) & 15;
        m_comp_ac_tab[ci] = (c & 15) + (JPGD_MAX_HUFF_TABLES >> 1);
    }

    m_spectral_start  = get_bits(8);
    m_spectral_end    = get_bits(8);
    m_successive_high = get_bits(4);
    m_successive_low  = get_bits(4);

    if (!m_progressive_flag) {
        m_spectral_start = 0;
        m_spectral_end = 63;
    }

    num_left -= 3;

    while (num_left) {                /* read past whatever is num_left */
        get_bits(8);
        num_left--;
    }
}

// Finds the next marker.
int jpeg_decoder::next_marker()
{
    uint c, bytes;

    bytes = 0;

    do {
        do {
            bytes++;
            c = get_bits(8);
        } while (c != 0xFF);

        do {
            c = get_bits(8);
        } while (c == 0xFF);

    } while (c == 0);

    // If bytes > 0 here, there where extra bytes before the marker (not good).

    return c;
}

// Process markers. Returns when an SOFx, SOI, EOI, or SOS marker is
// encountered.
int jpeg_decoder::process_markers()
{
    int c;

    for ( ; ; ) {
        c = next_marker();

        switch (c) {
        case M_SOF0:
        case M_SOF1:
        case M_SOF2:
        case M_SOF3:
        case M_SOF5:
        case M_SOF6:
        case M_SOF7:
            //      case M_JPG:
        case M_SOF9:
        case M_SOF10:
        case M_SOF11:
        case M_SOF13:
        case M_SOF14:
        case M_SOF15:
        case M_SOI:
        case M_EOI:
        case M_SOS: {
            return c;
        }
        case M_DHT: {
            read_dht_marker();
            break;
        }
        // No arithmitic support - dumb patents!
        case M_DAC: {
            stop_decoding(JPGD_NO_ARITHMITIC_SUPPORT);
            break;
        }
        case M_DQT: {
            read_dqt_marker();
            break;
        }
        case M_DRI: {
            read_dri_marker();
            break;
        }
        //case M_APP0:  /* no need to read the JFIF marker */

        case M_JPG:
        case M_RST0:    /* no parameters */
        case M_RST1:
        case M_RST2:
        case M_RST3:
        case M_RST4:
        case M_RST5:
        case M_RST6:
        case M_RST7:
        case M_TEM: {
            stop_decoding(JPGD_UNEXPECTED_MARKER);
            break;
        }
        default: {  /* must be DNL, DHP, EXP, APPn, JPGn, COM, or RESn or APP0 */
            skip_variable_marker();
            break;
        }
        }
    }
}

// Finds the start of image (SOI) marker.
// This code is rather defensive: it only checks the first 512 bytes to avoid
// false positives.
void jpeg_decoder::locate_soi_marker()
{
    uint lastchar, thischar;
    uint bytesleft;

    lastchar = get_bits(8);

    thischar = get_bits(8);

    /* ok if it's a normal JPEG file without a special header */

    if ((lastchar == 0xFF) && (thischar == M_SOI)) {
        return;
    }

    bytesleft = 4096; //512;

    for ( ; ; ) {
        if (--bytesleft == 0) {
            stop_decoding(JPGD_NOT_JPEG);
        }

        lastchar = thischar;

        thischar = get_bits(8);

        if (lastchar == 0xFF) {
            if (thischar == M_SOI) {
                break;
            } else if (thischar == M_EOI) { // get_bits will keep returning M_EOI if we read past the end
                stop_decoding(JPGD_NOT_JPEG);
            }
        }
    }

    // Check the next character after marker: if it's not 0xFF, it can't be the start of the next marker, so the file is bad.
    thischar = (m_bit_buf >> 24) & 0xFF;

    if (thischar != 0xFF) {
        stop_decoding(JPGD_NOT_JPEG);
    }
}

// Find a start of frame (SOF) marker.
void jpeg_decoder::locate_sof_marker()
{
    locate_soi_marker();

    int c = process_markers();

    switch (c) {
    case M_SOF2:
        m_progressive_flag = JPGD_TRUE;
    case M_SOF0:  /* baseline DCT */
    case M_SOF1: { /* extended sequential DCT */
        read_sof_marker();
        break;
    }
    case M_SOF9: { /* Arithmitic coding */
        stop_decoding(JPGD_NO_ARITHMITIC_SUPPORT);
        break;
    }
    default: {
        stop_decoding(JPGD_UNSUPPORTED_MARKER);
        break;
    }
    }
}

// Find a start of scan (SOS) marker.
int jpeg_decoder::locate_sos_marker()
{
    int c;

    c = process_markers();

    if (c == M_EOI) {
        return JPGD_FALSE;
    } else if (c != M_SOS) {
        stop_decoding(JPGD_UNEXPECTED_MARKER);
    }

    read_sos_marker();

    return JPGD_TRUE;
}

// Reset everything to default/uninitialized state.
void jpeg_decoder::init(jpeg_decoder_stream *pStream)
{
    m_pMem_blocks = NULL;
    m_error_code = JPGD_SUCCESS;
    m_ready_flag = false;
    m_image_x_size = m_image_y_size = 0;
    m_pStream = pStream;
    m_progressive_flag = JPGD_FALSE;

    memset(m_huff_ac, 0, sizeof(m_huff_ac));
    memset(m_huff_num, 0, sizeof(m_huff_num));
    memset(m_huff_val, 0, sizeof(m_huff_val));
    memset(m_quant, 0, sizeof(m_quant));

    m_scan_type = 0;
    m_comps_in_frame = 0;

    memset(m_comp_h_samp, 0, sizeof(m_comp_h_samp));
    memset(m_comp_v_samp, 0, sizeof(m_comp_v_samp));
    memset(m_comp_quant, 0, sizeof(m_comp_quant));
    memset(m_comp_ident, 0, sizeof(m_comp_ident));
    memset(m_comp_h_blocks, 0, sizeof(m_comp_h_blocks));
    memset(m_comp_v_blocks, 0, sizeof(m_comp_v_blocks));

    m_comps_in_scan = 0;
    memset(m_comp_list, 0, sizeof(m_comp_list));
    memset(m_comp_dc_tab, 0, sizeof(m_comp_dc_tab));
    memset(m_comp_ac_tab, 0, sizeof(m_comp_ac_tab));

    m_spectral_start = 0;
    m_spectral_end = 0;
    m_successive_low = 0;
    m_successive_high = 0;
    m_max_mcu_x_size = 0;
    m_max_mcu_y_size = 0;
    m_blocks_per_mcu = 0;
    m_max_blocks_per_row = 0;
    m_mcus_per_row = 0;
    m_mcus_per_col = 0;
    m_expanded_blocks_per_component = 0;
    m_expanded_blocks_per_mcu = 0;
    m_expanded_blocks_per_row = 0;
    m_freq_domain_chroma_upsample = false;

    memset(m_mcu_org, 0, sizeof(m_mcu_org));

    m_total_lines_left = 0;
    m_mcu_lines_left = 0;
    m_real_dest_bytes_per_scan_line = 0;
    m_dest_bytes_per_scan_line = 0;
    m_dest_bytes_per_pixel = 0;

    memset(m_pHuff_tabs, 0, sizeof(m_pHuff_tabs));

    memset(m_dc_coeffs, 0, sizeof(m_dc_coeffs));
    memset(m_ac_coeffs, 0, sizeof(m_ac_coeffs));
    memset(m_block_y_mcu, 0, sizeof(m_block_y_mcu));

    m_eob_run = 0;

    memset(m_block_y_mcu, 0, sizeof(m_block_y_mcu));

    m_pIn_buf_ofs = m_in_buf;
    m_in_buf_left = 0;
    m_eof_flag = false;
    m_tem_flag = 0;

    memset(m_in_buf_pad_start, 0, sizeof(m_in_buf_pad_start));
    memset(m_in_buf, 0, sizeof(m_in_buf));
    memset(m_in_buf_pad_end, 0, sizeof(m_in_buf_pad_end));

    m_restart_interval = 0;
    m_restarts_left    = 0;
    m_next_restart_num = 0;

    m_max_mcus_per_row = 0;
    m_max_blocks_per_mcu = 0;
    m_max_mcus_per_col = 0;

    memset(m_last_dc_val, 0, sizeof(m_last_dc_val));
    m_pMCU_coefficients = NULL;
    m_pSample_buf = NULL;

    m_total_bytes_read = 0;

    m_pScan_line_0 = NULL;
    m_pScan_line_1 = NULL;

    // Ready the input buffer.
    prep_in_buffer();

    // Prime the bit buffer.
    m_bits_left = 16;
    m_bit_buf = 0;

    get_bits(16);
    get_bits(16);

    for (int i = 0; i < JPGD_MAX_BLOCKS_PER_MCU; i++) {
        m_mcu_block_max_zag[i] = 64;
    }
}

#define SCALEBITS 16
#define ONE_HALF  ((int) 1 << (SCALEBITS-1))
#define FIX(x)    ((int) ((x) * (1L<<SCALEBITS) + 0.5f))

// Create a few tables that allow us to quickly convert YCbCr to RGB.
void jpeg_decoder::create_look_ups()
{
    for (int i = 0; i <= 255; i++) {
        int k = i - 128;
        m_crr[i] = ( FIX(1.40200f)  * k + ONE_HALF) >> SCALEBITS;
        m_cbb[i] = ( FIX(1.77200f)  * k + ONE_HALF) >> SCALEBITS;
        m_crg[i] = (-FIX(0.71414f)) * k;
        m_cbg[i] = (-FIX(0.34414f)) * k + ONE_HALF;
    }
}

// This method throws back into the stream any bytes that where read
// into the bit buffer during initial marker scanning.
void jpeg_decoder::fix_in_buffer()
{
    // In case any 0xFF's where pulled into the buffer during marker scanning.
    JPGD_ASSERT((m_bits_left & 7) == 0);

    if (m_bits_left == 16) {
        stuff_char( (uint8)(m_bit_buf & 0xFF));
    }

    if (m_bits_left >= 8) {
        stuff_char( (uint8)((m_bit_buf >> 8) & 0xFF));
    }

    stuff_char((uint8)((m_bit_buf >> 16) & 0xFF));
    stuff_char((uint8)((m_bit_buf >> 24) & 0xFF));

    m_bits_left = 16;
    get_bits_no_markers(16);
    get_bits_no_markers(16);
}

void jpeg_decoder::transform_mcu(int mcu_row)
{
    jpgd_block_t *pSrc_ptr = m_pMCU_coefficients;
    uint8 *pDst_ptr = m_pSample_buf + mcu_row * m_blocks_per_mcu * 64;

    for (int mcu_block = 0; mcu_block < m_blocks_per_mcu; mcu_block++) {
        idct(pSrc_ptr, pDst_ptr, m_mcu_block_max_zag[mcu_block]);
        pSrc_ptr += 64;
        pDst_ptr += 64;
    }
}

static const uint8 s_max_rc[64] = {
    17, 18, 34, 50, 50, 51, 52, 52, 52, 68, 84, 84, 84, 84, 85, 86, 86, 86, 86, 86,
    102, 118, 118, 118, 118, 118, 118, 119, 120, 120, 120, 120, 120, 120, 120, 136,
    136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136,
    136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136, 136
};

void jpeg_decoder::transform_mcu_expand(int mcu_row)
{
    jpgd_block_t *pSrc_ptr = m_pMCU_coefficients;
    uint8 *pDst_ptr = m_pSample_buf + mcu_row * m_expanded_blocks_per_mcu * 64;

    // Y IDCT
    int mcu_block;
    for (mcu_block = 0; mcu_block < m_expanded_blocks_per_component; mcu_block++) {
        idct(pSrc_ptr, pDst_ptr, m_mcu_block_max_zag[mcu_block]);
        pSrc_ptr += 64;
        pDst_ptr += 64;
    }

    // Chroma IDCT, with upsampling
    jpgd_block_t temp_block[64];

    for (int i = 0; i < 2; i++) {
        DCT_Upsample::Matrix44 P, Q, R, S;

        JPGD_ASSERT(m_mcu_block_max_zag[mcu_block] >= 1);
        JPGD_ASSERT(m_mcu_block_max_zag[mcu_block] <= 64);

        int max_zag = m_mcu_block_max_zag[mcu_block++] - 1;
        if (max_zag <= 0) {
            max_zag = 0;    // should never happen, only here to shut up static analysis
        }
        switch (s_max_rc[max_zag]) {
        case 1*16+1:
            DCT_Upsample::P_Q<1, 1>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<1, 1>::calc(R, S, pSrc_ptr);
            break;
        case 1*16+2:
            DCT_Upsample::P_Q<1, 2>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<1, 2>::calc(R, S, pSrc_ptr);
            break;
        case 2*16+2:
            DCT_Upsample::P_Q<2, 2>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<2, 2>::calc(R, S, pSrc_ptr);
            break;
        case 3*16+2:
            DCT_Upsample::P_Q<3, 2>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<3, 2>::calc(R, S, pSrc_ptr);
            break;
        case 3*16+3:
            DCT_Upsample::P_Q<3, 3>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<3, 3>::calc(R, S, pSrc_ptr);
            break;
        case 3*16+4:
            DCT_Upsample::P_Q<3, 4>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<3, 4>::calc(R, S, pSrc_ptr);
            break;
        case 4*16+4:
            DCT_Upsample::P_Q<4, 4>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<4, 4>::calc(R, S, pSrc_ptr);
            break;
        case 5*16+4:
            DCT_Upsample::P_Q<5, 4>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<5, 4>::calc(R, S, pSrc_ptr);
            break;
        case 5*16+5:
            DCT_Upsample::P_Q<5, 5>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<5, 5>::calc(R, S, pSrc_ptr);
            break;
        case 5*16+6:
            DCT_Upsample::P_Q<5, 6>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<5, 6>::calc(R, S, pSrc_ptr);
            break;
        case 6*16+6:
            DCT_Upsample::P_Q<6, 6>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<6, 6>::calc(R, S, pSrc_ptr);
            break;
        case 7*16+6:
            DCT_Upsample::P_Q<7, 6>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<7, 6>::calc(R, S, pSrc_ptr);
            break;
        case 7*16+7:
            DCT_Upsample::P_Q<7, 7>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<7, 7>::calc(R, S, pSrc_ptr);
            break;
        case 7*16+8:
            DCT_Upsample::P_Q<7, 8>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<7, 8>::calc(R, S, pSrc_ptr);
            break;
        case 8*16+8:
            DCT_Upsample::P_Q<8, 8>::calc(P, Q, pSrc_ptr);
            DCT_Upsample::R_S<8, 8>::calc(R, S, pSrc_ptr);
            break;
        default:
            JPGD_ASSERT(false);
        }

        DCT_Upsample::Matrix44 a(P + Q); P -= Q;
        DCT_Upsample::Matrix44 &b = P;
        DCT_Upsample::Matrix44 c(R + S); R -= S;
        DCT_Upsample::Matrix44 &d = R;

        DCT_Upsample::Matrix44::add_and_store(temp_block, a, c);
        idct_4x4(temp_block, pDst_ptr);
        pDst_ptr += 64;

        DCT_Upsample::Matrix44::sub_and_store(temp_block, a, c);
        idct_4x4(temp_block, pDst_ptr);
        pDst_ptr += 64;

        DCT_Upsample::Matrix44::add_and_store(temp_block, b, d);
        idct_4x4(temp_block, pDst_ptr);
        pDst_ptr += 64;

        DCT_Upsample::Matrix44::sub_and_store(temp_block, b, d);
        idct_4x4(temp_block, pDst_ptr);
        pDst_ptr += 64;

        pSrc_ptr += 64;
    }
}

// Loads and dequantizes the next row of (already decoded) coefficients.
// Progressive images only.
void jpeg_decoder::load_next_row()
{
    int i;
    jpgd_block_t *p;
    jpgd_quant_t *q;
    int mcu_row, mcu_block, row_block = 0;
    int component_num, component_id;
    int block_x_mcu[JPGD_MAX_COMPONENTS];

    memset(block_x_mcu, 0, JPGD_MAX_COMPONENTS * sizeof(int));

    for (mcu_row = 0; mcu_row < m_mcus_per_row; mcu_row++) {
        int block_x_mcu_ofs = 0, block_y_mcu_ofs = 0;

        for (mcu_block = 0; mcu_block < m_blocks_per_mcu; mcu_block++) {
            component_id = m_mcu_org[mcu_block];
            q = m_quant[m_comp_quant[component_id]];

            p = m_pMCU_coefficients + 64 * mcu_block;

            jpgd_block_t *pAC = coeff_buf_getp(m_ac_coeffs[component_id], block_x_mcu[component_id] + block_x_mcu_ofs, m_block_y_mcu[component_id] + block_y_mcu_ofs);
            jpgd_block_t *pDC = coeff_buf_getp(m_dc_coeffs[component_id], block_x_mcu[component_id] + block_x_mcu_ofs, m_block_y_mcu[component_id] + block_y_mcu_ofs);
            p[0] = pDC[0];
            memcpy(&p[1], &pAC[1], 63 * sizeof(jpgd_block_t));

            for (i = 63; i > 0; i--)
                if (p[g_ZAG[i]]) {
                    break;
                }

            m_mcu_block_max_zag[mcu_block] = i + 1;

            for ( ; i >= 0; i--)
                if (p[g_ZAG[i]]) {
                    p[g_ZAG[i]] = static_cast<jpgd_block_t>(p[g_ZAG[i]] * q[i]);
                }

            row_block++;

            if (m_comps_in_scan == 1) {
                block_x_mcu[component_id]++;
            } else {
                if (++block_x_mcu_ofs == m_comp_h_samp[component_id]) {
                    block_x_mcu_ofs = 0;

                    if (++block_y_mcu_ofs == m_comp_v_samp[component_id]) {
                        block_y_mcu_ofs = 0;

                        block_x_mcu[component_id] += m_comp_h_samp[component_id];
                    }
                }
            }
        }

        if (m_freq_domain_chroma_upsample) {
            transform_mcu_expand(mcu_row);
        } else {
            transform_mcu(mcu_row);
        }
    }

    if (m_comps_in_scan == 1) {
        m_block_y_mcu[m_comp_list[0]]++;
    } else {
        for (component_num = 0; component_num < m_comps_in_scan; component_num++) {
            component_id = m_comp_list[component_num];

            m_block_y_mcu[component_id] += m_comp_v_samp[component_id];
        }
    }
}

// Restart interval processing.
void jpeg_decoder::process_restart()
{
    int i;
    int c = 0;

    // Align to a byte boundry
    // FIXME: Is this really necessary? get_bits_no_markers() never reads in markers!
    //get_bits_no_markers(m_bits_left & 7);

    // Let's scan a little bit to find the marker, but not _too_ far.
    // 1536 is a "fudge factor" that determines how much to scan.
    for (i = 1536; i > 0; i--)
        if (get_char() == 0xFF) {
            break;
        }

    if (i == 0) {
        stop_decoding(JPGD_BAD_RESTART_MARKER);
    }

    for ( ; i > 0; i--)
        if ((c = get_char()) != 0xFF) {
            break;
        }

    if (i == 0) {
        stop_decoding(JPGD_BAD_RESTART_MARKER);
    }

    // Is it the expected marker? If not, something bad happened.
    if (c != (m_next_restart_num + M_RST0)) {
        stop_decoding(JPGD_BAD_RESTART_MARKER);
    }

    // Reset each component's DC prediction values.
    memset(&m_last_dc_val, 0, m_comps_in_frame * sizeof(uint));

    m_eob_run = 0;

    m_restarts_left = m_restart_interval;

    m_next_restart_num = (m_next_restart_num + 1) & 7;

    // Get the bit buffer going again...

    m_bits_left = 16;
    get_bits_no_markers(16);
    get_bits_no_markers(16);
}

static inline int dequantize_ac(int c, int q)
{
    c *= q;
    return c;
}

// Decodes and dequantizes the next row of coefficients.
void jpeg_decoder::decode_next_row()
{
    int row_block = 0;

    for (int mcu_row = 0; mcu_row < m_mcus_per_row; mcu_row++) {
        if ((m_restart_interval) && (m_restarts_left == 0)) {
            process_restart();
        }

        jpgd_block_t *p = m_pMCU_coefficients;
        for (int mcu_block = 0; mcu_block < m_blocks_per_mcu; mcu_block++, p += 64) {
            int component_id = m_mcu_org[mcu_block];
            jpgd_quant_t *q = m_quant[m_comp_quant[component_id]];

            int r, s;
            s = huff_decode(m_pHuff_tabs[m_comp_dc_tab[component_id]], r);
            s = JPGD_HUFF_EXTEND(r, s);

            m_last_dc_val[component_id] = (s += m_last_dc_val[component_id]);

            p[0] = static_cast<jpgd_block_t>(s * q[0]);

            int prev_num_set = m_mcu_block_max_zag[mcu_block];

            huff_tables *pH = m_pHuff_tabs[m_comp_ac_tab[component_id]];

            int k;
            for (k = 1; k < 64; k++) {
                int extra_bits;
                s = huff_decode(pH, extra_bits);

                r = s >> 4;
                s &= 15;

                if (s) {
                    if (r) {
                        if ((k + r) > 63) {
                            stop_decoding(JPGD_DECODE_ERROR);
                        }

                        if (k < prev_num_set) {
                            int n = JPGD_MIN(r, prev_num_set - k);
                            int kt = k;
                            while (n--) {
                                p[g_ZAG[kt++]] = 0;
                            }
                        }

                        k += r;
                    }

                    s = JPGD_HUFF_EXTEND(extra_bits, s);

                    JPGD_ASSERT(k < 64);

                    p[g_ZAG[k]] = static_cast<jpgd_block_t>(dequantize_ac(s, q[k])); //s * q[k];
                } else {
                    if (r == 15) {
                        if ((k + 16) > 64) {
                            stop_decoding(JPGD_DECODE_ERROR);
                        }

                        if (k < prev_num_set) {
                            int n = JPGD_MIN(16, prev_num_set - k);
                            int kt = k;
                            while (n--) {
                                JPGD_ASSERT(kt <= 63);
                                p[g_ZAG[kt++]] = 0;
                            }
                        }

                        k += 16 - 1; // - 1 because the loop counter is k
                        JPGD_ASSERT(p[g_ZAG[k]] == 0);
                    } else {
                        break;
                    }
                }
            }

            if (k < prev_num_set) {
                int kt = k;
                while (kt < prev_num_set) {
                    p[g_ZAG[kt++]] = 0;
                }
            }

            m_mcu_block_max_zag[mcu_block] = k;

            row_block++;
        }

        if (m_freq_domain_chroma_upsample) {
            transform_mcu_expand(mcu_row);
        } else {
            transform_mcu(mcu_row);
        }

        m_restarts_left--;
    }
}

// YCbCr H1V1 (1x1:1:1, 3 m_blocks per MCU) to RGB
void jpeg_decoder::H1V1Convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;
    uint8 *d = m_pScan_line_0;
    uint8 *s = m_pSample_buf + row * 8;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        for (int j = 0; j < 8; j++) {
            int y = s[j];
            int cb = s[64+j];
            int cr = s[128+j];

            d[0] = clamp(y + m_crr[cr]);
            d[1] = clamp(y + ((m_crg[cr] + m_cbg[cb]) >> 16));
            d[2] = clamp(y + m_cbb[cb]);
            d[3] = 255;

            d += 4;
        }

        s += 64*3;
    }
}

// YCbCr H2V1 (2x1:1:1, 4 m_blocks per MCU) to RGB
void jpeg_decoder::H2V1Convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;
    uint8 *d0 = m_pScan_line_0;
    uint8 *y = m_pSample_buf + row * 8;
    uint8 *c = m_pSample_buf + 2*64 + row * 8;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        for (int l = 0; l < 2; l++) {
            for (int j = 0; j < 4; j++) {
                int cb = c[0];
                int cr = c[64];

                int rc = m_crr[cr];
                int gc = ((m_crg[cr] + m_cbg[cb]) >> 16);
                int bc = m_cbb[cb];

                int yy = y[j<<1];
                d0[0] = clamp(yy+rc);
                d0[1] = clamp(yy+gc);
                d0[2] = clamp(yy+bc);
                d0[3] = 255;

                yy = y[(j<<1)+1];
                d0[4] = clamp(yy+rc);
                d0[5] = clamp(yy+gc);
                d0[6] = clamp(yy+bc);
                d0[7] = 255;

                d0 += 8;

                c++;
            }
            y += 64;
        }

        y += 64*4 - 64*2;
        c += 64*4 - 8;
    }
}

// YCbCr H2V1 (1x2:1:1, 4 m_blocks per MCU) to RGB
void jpeg_decoder::H1V2Convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;
    uint8 *d0 = m_pScan_line_0;
    uint8 *d1 = m_pScan_line_1;
    uint8 *y;
    uint8 *c;

    if (row < 8) {
        y = m_pSample_buf + row * 8;
    } else {
        y = m_pSample_buf + 64*1 + (row & 7) * 8;
    }

    c = m_pSample_buf + 64*2 + (row >> 1) * 8;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        for (int j = 0; j < 8; j++) {
            int cb = c[0+j];
            int cr = c[64+j];

            int rc = m_crr[cr];
            int gc = ((m_crg[cr] + m_cbg[cb]) >> 16);
            int bc = m_cbb[cb];

            int yy = y[j];
            d0[0] = clamp(yy+rc);
            d0[1] = clamp(yy+gc);
            d0[2] = clamp(yy+bc);
            d0[3] = 255;

            yy = y[8+j];
            d1[0] = clamp(yy+rc);
            d1[1] = clamp(yy+gc);
            d1[2] = clamp(yy+bc);
            d1[3] = 255;

            d0 += 4;
            d1 += 4;
        }

        y += 64*4;
        c += 64*4;
    }
}

// YCbCr H2V2 (2x2:1:1, 6 m_blocks per MCU) to RGB
void jpeg_decoder::H2V2Convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;
    uint8 *d0 = m_pScan_line_0;
    uint8 *d1 = m_pScan_line_1;
    uint8 *y;
    uint8 *c;

    if (row < 8) {
        y = m_pSample_buf + row * 8;
    } else {
        y = m_pSample_buf + 64*2 + (row & 7) * 8;
    }

    c = m_pSample_buf + 64*4 + (row >> 1) * 8;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        for (int l = 0; l < 2; l++) {
            for (int j = 0; j < 8; j += 2) {
                int cb = c[0];
                int cr = c[64];

                int rc = m_crr[cr];
                int gc = ((m_crg[cr] + m_cbg[cb]) >> 16);
                int bc = m_cbb[cb];

                int yy = y[j];
                d0[0] = clamp(yy+rc);
                d0[1] = clamp(yy+gc);
                d0[2] = clamp(yy+bc);
                d0[3] = 255;

                yy = y[j+1];
                d0[4] = clamp(yy+rc);
                d0[5] = clamp(yy+gc);
                d0[6] = clamp(yy+bc);
                d0[7] = 255;

                yy = y[j+8];
                d1[0] = clamp(yy+rc);
                d1[1] = clamp(yy+gc);
                d1[2] = clamp(yy+bc);
                d1[3] = 255;

                yy = y[j+8+1];
                d1[4] = clamp(yy+rc);
                d1[5] = clamp(yy+gc);
                d1[6] = clamp(yy+bc);
                d1[7] = 255;

                d0 += 8;
                d1 += 8;

                c++;
            }
            y += 64;
        }

        y += 64*6 - 64*2;
        c += 64*6 - 8;
    }
}

// Y (1 block per MCU) to 8-bit grayscale
void jpeg_decoder::gray_convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;
    uint8 *d = m_pScan_line_0;
    uint8 *s = m_pSample_buf + row * 8;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        *(uint *)d = *(uint *)s;
        *(uint *)(&d[4]) = *(uint *)(&s[4]);

        s += 64;
        d += 8;
    }
}

void jpeg_decoder::expanded_convert()
{
    int row = m_max_mcu_y_size - m_mcu_lines_left;

    uint8 *Py = m_pSample_buf + (row / 8) * 64 * m_comp_h_samp[0] + (row & 7) * 8;

    uint8 *d = m_pScan_line_0;

    for (int i = m_max_mcus_per_row; i > 0; i--) {
        for (int k = 0; k < m_max_mcu_x_size; k += 8) {
            const int Y_ofs = k * 8;
            const int Cb_ofs = Y_ofs + 64 * m_expanded_blocks_per_component;
            const int Cr_ofs = Y_ofs + 64 * m_expanded_blocks_per_component * 2;
            for (int j = 0; j < 8; j++) {
                int y = Py[Y_ofs + j];
                int cb = Py[Cb_ofs + j];
                int cr = Py[Cr_ofs + j];

                d[0] = clamp(y + m_crr[cr]);
                d[1] = clamp(y + ((m_crg[cr] + m_cbg[cb]) >> 16));
                d[2] = clamp(y + m_cbb[cb]);
                d[3] = 255;

                d += 4;
            }
        }

        Py += 64 * m_expanded_blocks_per_mcu;
    }
}

// Find end of image (EOI) marker, so we can return to the user the exact size of the input stream.
void jpeg_decoder::find_eoi()
{
    if (!m_progressive_flag) {
        // Attempt to read the EOI marker.
        //get_bits_no_markers(m_bits_left & 7);

        // Prime the bit buffer
        m_bits_left = 16;
        get_bits(16);
        get_bits(16);

        // The next marker _should_ be EOI
        process_markers();
    }

    m_total_bytes_read -= m_in_buf_left;
}

int jpeg_decoder::decode(const void **pScan_line, uint *pScan_line_len)
{
    if ((m_error_code) || (!m_ready_flag)) {
        return JPGD_FAILED;
    }

    if (m_total_lines_left == 0) {
        return JPGD_DONE;
    }

    if (m_mcu_lines_left == 0) {
        if (setjmp(m_jmp_state)) {
            return JPGD_FAILED;
        }

        if (m_progressive_flag) {
            load_next_row();
        } else {
            decode_next_row();
        }

        // Find the EOI marker if that was the last row.
        if (m_total_lines_left <= m_max_mcu_y_size) {
            find_eoi();
        }

        m_mcu_lines_left = m_max_mcu_y_size;
    }

    if (m_freq_domain_chroma_upsample) {
        expanded_convert();
        *pScan_line = m_pScan_line_0;
    } else {
        switch (m_scan_type) {
        case JPGD_YH2V2: {
            if ((m_mcu_lines_left & 1) == 0) {
                H2V2Convert();
                *pScan_line = m_pScan_line_0;
            } else {
                *pScan_line = m_pScan_line_1;
            }

            break;
        }
        case JPGD_YH2V1: {
            H2V1Convert();
            *pScan_line = m_pScan_line_0;
            break;
        }
        case JPGD_YH1V2: {
            if ((m_mcu_lines_left & 1) == 0) {
                H1V2Convert();
                *pScan_line = m_pScan_line_0;
            } else {
                *pScan_line = m_pScan_line_1;
            }

            break;
        }
        case JPGD_YH1V1: {
            H1V1Convert();
            *pScan_line = m_pScan_line_0;
            break;
        }
        case JPGD_GRAYSCALE: {
            gray_convert();
            *pScan_line = m_pScan_line_0;

            break;
        }
        }
    }

    *pScan_line_len = m_real_dest_bytes_per_scan_line;

    m_mcu_lines_left--;
    m_total_lines_left--;

    return JPGD_SUCCESS;
}

// Creates the tables needed for efficient Huffman decoding.
void jpeg_decoder::make_huff_table(int index, huff_tables *pH)
{
    int p, i, l, si;
    uint8 huffsize[257];
    uint huffcode[257];
    uint code;
    uint subtree;
    int code_size;
    int lastp;
    int nextfreeentry;
    int currententry;

    pH->ac_table = m_huff_ac[index] != 0;

    p = 0;

    for (l = 1; l <= 16; l++) {
        for (i = 1; i <= m_huff_num[index][l]; i++) {
            huffsize[p++] = static_cast<uint8>(l);
        }
    }

    huffsize[p] = 0;

    lastp = p;

    code = 0;
    si = huffsize[0];
    p = 0;

    while (huffsize[p]) {
        while (huffsize[p] == si) {
            huffcode[p++] = code;
            code++;
        }

        code <<= 1;
        si++;
    }

    memset(pH->look_up, 0, sizeof(pH->look_up));
    memset(pH->look_up2, 0, sizeof(pH->look_up2));
    memset(pH->tree, 0, sizeof(pH->tree));
    memset(pH->code_size, 0, sizeof(pH->code_size));

    nextfreeentry = -1;

    p = 0;

    while (p < lastp) {
        i = m_huff_val[index][p];
        code = huffcode[p];
        code_size = huffsize[p];

        pH->code_size[i] = static_cast<uint8>(code_size);

        if (code_size <= 8) {
            code <<= (8 - code_size);

            for (l = 1 << (8 - code_size); l > 0; l--) {
                JPGD_ASSERT(i < 256);

                pH->look_up[code] = i;

                bool has_extrabits = false;
                int extra_bits = 0;
                int num_extra_bits = i & 15;

                int bits_to_fetch = code_size;
                if (num_extra_bits) {
                    int total_codesize = code_size + num_extra_bits;
                    if (total_codesize <= 8) {
                        has_extrabits = true;
                        extra_bits = ((1 << num_extra_bits) - 1) & (code >> (8 - total_codesize));
                        JPGD_ASSERT(extra_bits <= 0x7FFF);
                        bits_to_fetch += num_extra_bits;
                    }
                }

                if (!has_extrabits) {
                    pH->look_up2[code] = i | (bits_to_fetch << 8);
                } else {
                    pH->look_up2[code] = i | 0x8000 | (extra_bits << 16) | (bits_to_fetch << 8);
                }

                code++;
            }
        } else {
            subtree = (code >> (code_size - 8)) & 0xFF;

            currententry = pH->look_up[subtree];

            if (currententry == 0) {
                pH->look_up[subtree] = currententry = nextfreeentry;
                pH->look_up2[subtree] = currententry = nextfreeentry;

                nextfreeentry -= 2;
            }

            code <<= (16 - (code_size - 8));

            for (l = code_size; l > 9; l--) {
                if ((code & 0x8000) == 0) {
                    currententry--;
                }

                if (pH->tree[-currententry - 1] == 0) {
                    pH->tree[-currententry - 1] = nextfreeentry;

                    currententry = nextfreeentry;

                    nextfreeentry -= 2;
                } else {
                    currententry = pH->tree[-currententry - 1];
                }

                code <<= 1;
            }

            if ((code & 0x8000) == 0) {
                currententry--;
            }

            pH->tree[-currententry - 1] = i;
        }

        p++;
    }
}

// Verifies the quantization tables needed for this scan are available.
void jpeg_decoder::check_quant_tables()
{
    for (int i = 0; i < m_comps_in_scan; i++)
        if (m_quant[m_comp_quant[m_comp_list[i]]] == NULL) {
            stop_decoding(JPGD_UNDEFINED_QUANT_TABLE);
        }
}

// Verifies that all the Huffman tables needed for this scan are available.
void jpeg_decoder::check_huff_tables()
{
    for (int i = 0; i < m_comps_in_scan; i++) {
        if ((m_spectral_start == 0) && (m_huff_num[m_comp_dc_tab[m_comp_list[i]]] == NULL)) {
            stop_decoding(JPGD_UNDEFINED_HUFF_TABLE);
        }

        if ((m_spectral_end > 0) && (m_huff_num[m_comp_ac_tab[m_comp_list[i]]] == NULL)) {
            stop_decoding(JPGD_UNDEFINED_HUFF_TABLE);
        }
    }

    for (int i = 0; i < JPGD_MAX_HUFF_TABLES; i++)
        if (m_huff_num[i]) {
            if (!m_pHuff_tabs[i]) {
                m_pHuff_tabs[i] = (huff_tables *)alloc(sizeof(huff_tables));
            }

            make_huff_table(i, m_pHuff_tabs[i]);
        }
}

// Determines the component order inside each MCU.
// Also calcs how many MCU's are on each row, etc.
void jpeg_decoder::calc_mcu_block_order()
{
    int component_num, component_id;
    int max_h_samp = 0, max_v_samp = 0;

    for (component_id = 0; component_id < m_comps_in_frame; component_id++) {
        if (m_comp_h_samp[component_id] > max_h_samp) {
            max_h_samp = m_comp_h_samp[component_id];
        }

        if (m_comp_v_samp[component_id] > max_v_samp) {
            max_v_samp = m_comp_v_samp[component_id];
        }
    }

    for (component_id = 0; component_id < m_comps_in_frame; component_id++) {
        m_comp_h_blocks[component_id] = ((((m_image_x_size * m_comp_h_samp[component_id]) + (max_h_samp - 1)) / max_h_samp) + 7) / 8;
        m_comp_v_blocks[component_id] = ((((m_image_y_size * m_comp_v_samp[component_id]) + (max_v_samp - 1)) / max_v_samp) + 7) / 8;
    }

    if (m_comps_in_scan == 1) {
        m_mcus_per_row = m_comp_h_blocks[m_comp_list[0]];
        m_mcus_per_col = m_comp_v_blocks[m_comp_list[0]];
    } else {
        m_mcus_per_row = (((m_image_x_size + 7) / 8) + (max_h_samp - 1)) / max_h_samp;
        m_mcus_per_col = (((m_image_y_size + 7) / 8) + (max_v_samp - 1)) / max_v_samp;
    }

    if (m_comps_in_scan == 1) {
        m_mcu_org[0] = m_comp_list[0];

        m_blocks_per_mcu = 1;
    } else {
        m_blocks_per_mcu = 0;

        for (component_num = 0; component_num < m_comps_in_scan; component_num++) {
            int num_blocks;

            component_id = m_comp_list[component_num];

            num_blocks = m_comp_h_samp[component_id] * m_comp_v_samp[component_id];

            while (num_blocks--) {
                m_mcu_org[m_blocks_per_mcu++] = component_id;
            }
        }
    }
}

// Starts a new scan.
int jpeg_decoder::init_scan()
{
    if (!locate_sos_marker()) {
        return JPGD_FALSE;
    }

    calc_mcu_block_order();

    check_huff_tables();

    check_quant_tables();

    memset(m_last_dc_val, 0, m_comps_in_frame * sizeof(uint));

    m_eob_run = 0;

    if (m_restart_interval) {
        m_restarts_left = m_restart_interval;
        m_next_restart_num = 0;
    }

    fix_in_buffer();

    return JPGD_TRUE;
}

// Starts a frame. Determines if the number of components or sampling factors
// are supported.
void jpeg_decoder::init_frame()
{
    int i;

    if (m_comps_in_frame == 1) {
        if ((m_comp_h_samp[0] != 1) || (m_comp_v_samp[0] != 1)) {
            stop_decoding(JPGD_UNSUPPORTED_SAMP_FACTORS);
        }

        m_scan_type = JPGD_GRAYSCALE;
        m_max_blocks_per_mcu = 1;
        m_max_mcu_x_size = 8;
        m_max_mcu_y_size = 8;
    } else if (m_comps_in_frame == 3) {
        if ( ((m_comp_h_samp[1] != 1) || (m_comp_v_samp[1] != 1)) ||
                ((m_comp_h_samp[2] != 1) || (m_comp_v_samp[2] != 1)) ) {
            stop_decoding(JPGD_UNSUPPORTED_SAMP_FACTORS);
        }

        if ((m_comp_h_samp[0] == 1) && (m_comp_v_samp[0] == 1)) {
            m_scan_type = JPGD_YH1V1;

            m_max_blocks_per_mcu = 3;
            m_max_mcu_x_size = 8;
            m_max_mcu_y_size = 8;
        } else if ((m_comp_h_samp[0] == 2) && (m_comp_v_samp[0] == 1)) {
            m_scan_type = JPGD_YH2V1;
            m_max_blocks_per_mcu = 4;
            m_max_mcu_x_size = 16;
            m_max_mcu_y_size = 8;
        } else if ((m_comp_h_samp[0] == 1) && (m_comp_v_samp[0] == 2)) {
            m_scan_type = JPGD_YH1V2;
            m_max_blocks_per_mcu = 4;
            m_max_mcu_x_size = 8;
            m_max_mcu_y_size = 16;
        } else if ((m_comp_h_samp[0] == 2) && (m_comp_v_samp[0] == 2)) {
            m_scan_type = JPGD_YH2V2;
            m_max_blocks_per_mcu = 6;
            m_max_mcu_x_size = 16;
            m_max_mcu_y_size = 16;
        } else {
            stop_decoding(JPGD_UNSUPPORTED_SAMP_FACTORS);
        }
    } else {
        stop_decoding(JPGD_UNSUPPORTED_COLORSPACE);
    }

    m_max_mcus_per_row = (m_image_x_size + (m_max_mcu_x_size - 1)) / m_max_mcu_x_size;
    m_max_mcus_per_col = (m_image_y_size + (m_max_mcu_y_size - 1)) / m_max_mcu_y_size;

    // These values are for the *destination* pixels: after conversion.
    if (m_scan_type == JPGD_GRAYSCALE) {
        m_dest_bytes_per_pixel = 1;
    } else {
        m_dest_bytes_per_pixel = 4;
    }

    m_dest_bytes_per_scan_line = ((m_image_x_size + 15) & 0xFFF0) * m_dest_bytes_per_pixel;

    m_real_dest_bytes_per_scan_line = (m_image_x_size * m_dest_bytes_per_pixel);

    // Initialize two scan line buffers.
    m_pScan_line_0 = (uint8 *)alloc(m_dest_bytes_per_scan_line, true);
    if ((m_scan_type == JPGD_YH1V2) || (m_scan_type == JPGD_YH2V2)) {
        m_pScan_line_1 = (uint8 *)alloc(m_dest_bytes_per_scan_line, true);
    }

    m_max_blocks_per_row = m_max_mcus_per_row * m_max_blocks_per_mcu;

    // Should never happen
    if (m_max_blocks_per_row > JPGD_MAX_BLOCKS_PER_ROW) {
        stop_decoding(JPGD_ASSERTION_ERROR);
    }

    // Allocate the coefficient buffer, enough for one MCU
    m_pMCU_coefficients = (jpgd_block_t *)alloc(m_max_blocks_per_mcu * 64 * sizeof(jpgd_block_t));

    for (i = 0; i < m_max_blocks_per_mcu; i++) {
        m_mcu_block_max_zag[i] = 64;
    }

    m_expanded_blocks_per_component = m_comp_h_samp[0] * m_comp_v_samp[0];
    m_expanded_blocks_per_mcu = m_expanded_blocks_per_component * m_comps_in_frame;
    m_expanded_blocks_per_row = m_max_mcus_per_row * m_expanded_blocks_per_mcu;
    // Freq. domain chroma upsampling is only supported for H2V2 subsampling factor (the most common one I've seen).
    m_freq_domain_chroma_upsample = false;
#if JPGD_SUPPORT_FREQ_DOMAIN_UPSAMPLING
    m_freq_domain_chroma_upsample = (m_expanded_blocks_per_mcu == 4*3);
#endif

    if (m_freq_domain_chroma_upsample) {
        m_pSample_buf = (uint8 *)alloc(m_expanded_blocks_per_row * 64);
    } else {
        m_pSample_buf = (uint8 *)alloc(m_max_blocks_per_row * 64);
    }

    m_total_lines_left = m_image_y_size;

    m_mcu_lines_left = 0;

    create_look_ups();
}

// The coeff_buf series of methods originally stored the coefficients
// into a "virtual" file which was located in EMS, XMS, or a disk file. A cache
// was used to make this process more efficient. Now, we can store the entire
// thing in RAM.
jpeg_decoder::coeff_buf *jpeg_decoder::coeff_buf_open(int block_num_x, int block_num_y, int block_len_x, int block_len_y)
{
    coeff_buf *cb = (coeff_buf *)alloc(sizeof(coeff_buf));

    cb->block_num_x = block_num_x;
    cb->block_num_y = block_num_y;
    cb->block_len_x = block_len_x;
    cb->block_len_y = block_len_y;
    cb->block_size = (block_len_x * block_len_y) * sizeof(jpgd_block_t);
    cb->pData = (uint8 *)alloc(cb->block_size * block_num_x * block_num_y, true);
    return cb;
}

inline jpgd_block_t *jpeg_decoder::coeff_buf_getp(coeff_buf *cb, int block_x, int block_y)
{
    JPGD_ASSERT((block_x < cb->block_num_x) && (block_y < cb->block_num_y));
    return (jpgd_block_t *)(cb->pData + block_x * cb->block_size + block_y * (cb->block_size * cb->block_num_x));
}

// The following methods decode the various types of m_blocks encountered
// in progressively encoded images.
void jpeg_decoder::decode_block_dc_first(jpeg_decoder *pD, int component_id, int block_x, int block_y)
{
    int s, r;
    jpgd_block_t *p = pD->coeff_buf_getp(pD->m_dc_coeffs[component_id], block_x, block_y);

    if ((s = pD->huff_decode(pD->m_pHuff_tabs[pD->m_comp_dc_tab[component_id]])) != 0) {
        r = pD->get_bits_no_markers(s);
        s = JPGD_HUFF_EXTEND(r, s);
    }

    pD->m_last_dc_val[component_id] = (s += pD->m_last_dc_val[component_id]);

    p[0] = static_cast<jpgd_block_t>(s << pD->m_successive_low);
}

void jpeg_decoder::decode_block_dc_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y)
{
    if (pD->get_bits_no_markers(1)) {
        jpgd_block_t *p = pD->coeff_buf_getp(pD->m_dc_coeffs[component_id], block_x, block_y);

        p[0] |= (1 << pD->m_successive_low);
    }
}

void jpeg_decoder::decode_block_ac_first(jpeg_decoder *pD, int component_id, int block_x, int block_y)
{
    int k, s, r;

    if (pD->m_eob_run) {
        pD->m_eob_run--;
        return;
    }

    jpgd_block_t *p = pD->coeff_buf_getp(pD->m_ac_coeffs[component_id], block_x, block_y);

    for (k = pD->m_spectral_start; k <= pD->m_spectral_end; k++) {
        s = pD->huff_decode(pD->m_pHuff_tabs[pD->m_comp_ac_tab[component_id]]);

        r = s >> 4;
        s &= 15;

        if (s) {
            if ((k += r) > 63) {
                pD->stop_decoding(JPGD_DECODE_ERROR);
            }

            r = pD->get_bits_no_markers(s);
            s = JPGD_HUFF_EXTEND(r, s);

            p[g_ZAG[k]] = static_cast<jpgd_block_t>(s << pD->m_successive_low);
        } else {
            if (r == 15) {
                if ((k += 15) > 63) {
                    pD->stop_decoding(JPGD_DECODE_ERROR);
                }
            } else {
                pD->m_eob_run = 1 << r;

                if (r) {
                    pD->m_eob_run += pD->get_bits_no_markers(r);
                }

                pD->m_eob_run--;

                break;
            }
        }
    }
}

void jpeg_decoder::decode_block_ac_refine(jpeg_decoder *pD, int component_id, int block_x, int block_y)
{
    int s, k, r;
    int p1 = 1 << pD->m_successive_low;
    int m1 = (-1) << pD->m_successive_low;
    jpgd_block_t *p = pD->coeff_buf_getp(pD->m_ac_coeffs[component_id], block_x, block_y);

    JPGD_ASSERT(pD->m_spectral_end <= 63);

    k = pD->m_spectral_start;

    if (pD->m_eob_run == 0) {
        for ( ; k <= pD->m_spectral_end; k++) {
            s = pD->huff_decode(pD->m_pHuff_tabs[pD->m_comp_ac_tab[component_id]]);

            r = s >> 4;
            s &= 15;

            if (s) {
                if (s != 1) {
                    pD->stop_decoding(JPGD_DECODE_ERROR);
                }

                if (pD->get_bits_no_markers(1)) {
                    s = p1;
                } else {
                    s = m1;
                }
            } else {
                if (r != 15) {
                    pD->m_eob_run = 1 << r;

                    if (r) {
                        pD->m_eob_run += pD->get_bits_no_markers(r);
                    }

                    break;
                }
            }

            do {
                jpgd_block_t *this_coef = p + g_ZAG[k & 63];

                if (*this_coef != 0) {
                    if (pD->get_bits_no_markers(1)) {
                        if ((*this_coef & p1) == 0) {
                            if (*this_coef >= 0) {
                                *this_coef = static_cast<jpgd_block_t>(*this_coef + p1);
                            } else {
                                *this_coef = static_cast<jpgd_block_t>(*this_coef + m1);
                            }
                        }
                    }
                } else {
                    if (--r < 0) {
                        break;
                    }
                }

                k++;

            } while (k <= pD->m_spectral_end);

            if ((s) && (k < 64)) {
                p[g_ZAG[k]] = static_cast<jpgd_block_t>(s);
            }
        }
    }

    if (pD->m_eob_run > 0) {
        for ( ; k <= pD->m_spectral_end; k++) {
            jpgd_block_t *this_coef = p + g_ZAG[k & 63]; // logical AND to shut up static code analysis

            if (*this_coef != 0) {
                if (pD->get_bits_no_markers(1)) {
                    if ((*this_coef & p1) == 0) {
                        if (*this_coef >= 0) {
                            *this_coef = static_cast<jpgd_block_t>(*this_coef + p1);
                        } else {
                            *this_coef = static_cast<jpgd_block_t>(*this_coef + m1);
                        }
                    }
                }
            }
        }

        pD->m_eob_run--;
    }
}

// Decode a scan in a progressively encoded image.
void jpeg_decoder::decode_scan(pDecode_block_func decode_block_func)
{
    int mcu_row, mcu_col, mcu_block;
    int block_x_mcu[JPGD_MAX_COMPONENTS], m_block_y_mcu[JPGD_MAX_COMPONENTS];

    memset(m_block_y_mcu, 0, sizeof(m_block_y_mcu));

    for (mcu_col = 0; mcu_col < m_mcus_per_col; mcu_col++) {
        int component_num, component_id;

        memset(block_x_mcu, 0, sizeof(block_x_mcu));

        for (mcu_row = 0; mcu_row < m_mcus_per_row; mcu_row++) {
            int block_x_mcu_ofs = 0, block_y_mcu_ofs = 0;

            if ((m_restart_interval) && (m_restarts_left == 0)) {
                process_restart();
            }

            for (mcu_block = 0; mcu_block < m_blocks_per_mcu; mcu_block++) {
                component_id = m_mcu_org[mcu_block];

                decode_block_func(this, component_id, block_x_mcu[component_id] + block_x_mcu_ofs, m_block_y_mcu[component_id] + block_y_mcu_ofs);

                if (m_comps_in_scan == 1) {
                    block_x_mcu[component_id]++;
                } else {
                    if (++block_x_mcu_ofs == m_comp_h_samp[component_id]) {
                        block_x_mcu_ofs = 0;

                        if (++block_y_mcu_ofs == m_comp_v_samp[component_id]) {
                            block_y_mcu_ofs = 0;
                            block_x_mcu[component_id] += m_comp_h_samp[component_id];
                        }
                    }
                }
            }

            m_restarts_left--;
        }

        if (m_comps_in_scan == 1) {
            m_block_y_mcu[m_comp_list[0]]++;
        } else {
            for (component_num = 0; component_num < m_comps_in_scan; component_num++) {
                component_id = m_comp_list[component_num];
                m_block_y_mcu[component_id] += m_comp_v_samp[component_id];
            }
        }
    }
}

// Decode a progressively encoded image.
void jpeg_decoder::init_progressive()
{
    int i;

    if (m_comps_in_frame == 4) {
        stop_decoding(JPGD_UNSUPPORTED_COLORSPACE);
    }

    // Allocate the coefficient buffers.
    for (i = 0; i < m_comps_in_frame; i++) {
        m_dc_coeffs[i] = coeff_buf_open(m_max_mcus_per_row * m_comp_h_samp[i], m_max_mcus_per_col * m_comp_v_samp[i], 1, 1);
        m_ac_coeffs[i] = coeff_buf_open(m_max_mcus_per_row * m_comp_h_samp[i], m_max_mcus_per_col * m_comp_v_samp[i], 8, 8);
    }

    for ( ; ; ) {
        int dc_only_scan, refinement_scan;
        pDecode_block_func decode_block_func;

        if (!init_scan()) {
            break;
        }

        dc_only_scan = (m_spectral_start == 0);
        refinement_scan = (m_successive_high != 0);

        if ((m_spectral_start > m_spectral_end) || (m_spectral_end > 63)) {
            stop_decoding(JPGD_BAD_SOS_SPECTRAL);
        }

        if (dc_only_scan) {
            if (m_spectral_end) {
                stop_decoding(JPGD_BAD_SOS_SPECTRAL);
            }
        } else if (m_comps_in_scan != 1) { /* AC scans can only contain one component */
            stop_decoding(JPGD_BAD_SOS_SPECTRAL);
        }

        if ((refinement_scan) && (m_successive_low != m_successive_high - 1)) {
            stop_decoding(JPGD_BAD_SOS_SUCCESSIVE);
        }

        if (dc_only_scan) {
            if (refinement_scan) {
                decode_block_func = decode_block_dc_refine;
            } else {
                decode_block_func = decode_block_dc_first;
            }
        } else {
            if (refinement_scan) {
                decode_block_func = decode_block_ac_refine;
            } else {
                decode_block_func = decode_block_ac_first;
            }
        }

        decode_scan(decode_block_func);

        m_bits_left = 16;
        get_bits(16);
        get_bits(16);
    }

    m_comps_in_scan = m_comps_in_frame;

    for (i = 0; i < m_comps_in_frame; i++) {
        m_comp_list[i] = i;
    }

    calc_mcu_block_order();
}

void jpeg_decoder::init_sequential()
{
    if (!init_scan()) {
        stop_decoding(JPGD_UNEXPECTED_MARKER);
    }
}

void jpeg_decoder::decode_start()
{
    init_frame();

    if (m_progressive_flag) {
        init_progressive();
    } else {
        init_sequential();
    }
}

void jpeg_decoder::decode_init(jpeg_decoder_stream *pStream)
{
    init(pStream);
    locate_sof_marker();
}

jpeg_decoder::jpeg_decoder(jpeg_decoder_stream *pStream)
{
    if (setjmp(m_jmp_state)) {
        return;
    }
    decode_init(pStream);
}

int jpeg_decoder::begin_decoding()
{
    if (m_ready_flag) {
        return JPGD_SUCCESS;
    }

    if (m_error_code) {
        return JPGD_FAILED;
    }

    if (setjmp(m_jmp_state)) {
        return JPGD_FAILED;
    }

    decode_start();

    m_ready_flag = true;

    return JPGD_SUCCESS;
}

jpeg_decoder::~jpeg_decoder()
{
    free_all_blocks();
}

jpeg_decoder_file_stream::jpeg_decoder_file_stream()
{
    m_pFile = NULL;
    m_eof_flag = false;
    m_error_flag = false;
}

void jpeg_decoder_file_stream::close()
{
    if (m_pFile) {
        fclose(m_pFile);
        m_pFile = NULL;
    }

    m_eof_flag = false;
    m_error_flag = false;
}

jpeg_decoder_file_stream::~jpeg_decoder_file_stream()
{
    close();
}

bool jpeg_decoder_file_stream::open(const char *Pfilename)
{
    close();

    m_eof_flag = false;
    m_error_flag = false;

#if defined(_MSC_VER)
    m_pFile = NULL;
    fopen_s(&m_pFile, Pfilename, "rb");
#else
    m_pFile = fopen(Pfilename, "rb");
#endif
    return m_pFile != NULL;
}

int jpeg_decoder_file_stream::read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag)
{
    if (!m_pFile) {
        return -1;
    }

    if (m_eof_flag) {
        *pEOF_flag = true;
        return 0;
    }

    if (m_error_flag) {
        return -1;
    }

    int bytes_read = static_cast<int>(fread(pBuf, 1, max_bytes_to_read, m_pFile));
    if (bytes_read < max_bytes_to_read) {
        if (ferror(m_pFile)) {
            m_error_flag = true;
            return -1;
        }

        m_eof_flag = true;
        *pEOF_flag = true;
    }

    return bytes_read;
}

bool jpeg_decoder_mem_stream::open(const uint8 *pSrc_data, uint size)
{
    close();
    m_pSrc_data = pSrc_data;
    m_ofs = 0;
    m_size = size;
    return true;
}

int jpeg_decoder_mem_stream::read(uint8 *pBuf, int max_bytes_to_read, bool *pEOF_flag)
{
    *pEOF_flag = false;

    if (!m_pSrc_data) {
        return -1;
    }

    uint bytes_remaining = m_size - m_ofs;
    if ((uint)max_bytes_to_read > bytes_remaining) {
        max_bytes_to_read = bytes_remaining;
        *pEOF_flag = true;
    }

    memcpy(pBuf, m_pSrc_data + m_ofs, max_bytes_to_read);
    m_ofs += max_bytes_to_read;

    return max_bytes_to_read;
}

unsigned char *decompress_jpeg_image_from_stream(jpeg_decoder_stream *pStream, int *width, int *height, int *actual_comps, int req_comps)
{
    if (!actual_comps) {
        return NULL;
    }
    *actual_comps = 0;

    if ((!pStream) || (!width) || (!height) || (!req_comps)) {
        return NULL;
    }

    if ((req_comps != 1) && (req_comps != 3) && (req_comps != 4)) {
        return NULL;
    }

    jpeg_decoder decoder(pStream);
    if (decoder.get_error_code() != JPGD_SUCCESS) {
        return NULL;
    }

    const int image_width = decoder.get_width(), image_height = decoder.get_height();
    *width = image_width;
    *height = image_height;
    *actual_comps = decoder.get_num_components();

    if (decoder.begin_decoding() != JPGD_SUCCESS) {
        return NULL;
    }

    const int dst_bpl = image_width * req_comps;

    uint8 *pImage_data = (uint8 *)jpgd_malloc(dst_bpl * image_height);
    if (!pImage_data) {
        return NULL;
    }

    for (int y = 0; y < image_height; y++) {
        const uint8 *pScan_line=0;
        uint scan_line_len;
        if (decoder.decode((const void **)&pScan_line, &scan_line_len) != JPGD_SUCCESS) {
            jpgd_free(pImage_data);
            return NULL;
        }
        JPGD_ASSERT(pScan_line);

        uint8 *pDst = pImage_data + y * dst_bpl;

        if (((req_comps == 1) && (decoder.get_num_components() == 1)) || ((req_comps == 4) && (decoder.get_num_components() == 3))) {
            memcpy(pDst, pScan_line, dst_bpl);
        } else if (decoder.get_num_components() == 1) {
            if (req_comps == 3) {
                for (int x = 0; x < image_width; x++) {
                    uint8 luma = pScan_line[x];
                    pDst[0] = luma;
                    pDst[1] = luma;
                    pDst[2] = luma;
                    pDst += 3;
                }
            } else {
                for (int x = 0; x < image_width; x++) {
                    uint8 luma = pScan_line[x];
                    pDst[0] = luma;
                    pDst[1] = luma;
                    pDst[2] = luma;
                    pDst[3] = 255;
                    pDst += 4;
                }
            }
        } else if (decoder.get_num_components() == 3) {
            if (req_comps == 1) {
                const int YR = 19595, YG = 38470, YB = 7471;
                for (int x = 0; x < image_width; x++) {
                    int r = pScan_line[x*4+0];
                    int g = pScan_line[x*4+1];
                    int b = pScan_line[x*4+2];
                    *pDst++ = static_cast<uint8>((r * YR + g * YG + b * YB + 32768) >> 16);
                }
            } else {
                for (int x = 0; x < image_width; x++) {
                    pDst[0] = pScan_line[x*4+0];
                    pDst[1] = pScan_line[x*4+1];
                    pDst[2] = pScan_line[x*4+2];
                    pDst += 3;
                }
            }
        }
    }

    return pImage_data;
}

unsigned char *decompress_jpeg_image_from_memory(const unsigned char *pSrc_data, int src_data_size, int *width, int *height, int *actual_comps, int req_comps)
{
    jpgd::jpeg_decoder_mem_stream mem_stream(pSrc_data, src_data_size);
    return decompress_jpeg_image_from_stream(&mem_stream, width, height, actual_comps, req_comps);
}

unsigned char *decompress_jpeg_image_from_file(const char *pSrc_filename, int *width, int *height, int *actual_comps, int req_comps)
{
    jpgd::jpeg_decoder_file_stream file_stream;
    if (!file_stream.open(pSrc_filename)) {
        return NULL;
    }
    return decompress_jpeg_image_from_stream(&file_stream, width, height, actual_comps, req_comps);
}

} // namespace jpgd