text: /*
   * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  /**
   * @file
   * bitstream reader API header.
   */
  
  #ifndef AVCODEC_GET_BITS_H
  #define AVCODEC_GET_BITS_H
  
  #include <stdint.h>
  
  #include "libavutil/common.h"
  #include "libavutil/intreadwrite.h"
  #include "libavutil/log.h"
  #include "libavutil/avassert.h"
  #include "mathops.h"
  
  /*
   * Safe bitstream reading:
   * optionally, the get_bits API can check to ensure that we
   * don't read past input buffer boundaries. This is protected
   * with CONFIG_SAFE_BITSTREAM_READER at the global level, and
   * then below that with UNCHECKED_BITSTREAM_READER at the per-
   * decoder level. This means that decoders that check internally
   * can "#define UNCHECKED_BITSTREAM_READER 1" to disable
   * overread checks.
   * Boundary checking causes a minor performance penalty so for
   * applications that won't want/need this, it can be disabled
   * globally using "#define CONFIG_SAFE_BITSTREAM_READER 0".
   */
  #ifndef UNCHECKED_BITSTREAM_READER
  #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
  #endif
  
  typedef struct GetBitContext {
      const uint8_t *buffer, *buffer_end;
      int index;
      int size_in_bits;
      int size_in_bits_plus8;
  } GetBitContext;
  
  #define VLC_TYPE int16_t
  
  typedef struct VLC {
      int bits;
      VLC_TYPE (*table)[2]; ///< code, bits
      int table_size, table_allocated;
      void * volatile init_state;
  } VLC;
  
  typedef struct RL_VLC_ELEM {
      int16_t level;
      int8_t len;
      uint8_t run;
  } RL_VLC_ELEM;
  
  /* Bitstream reader API docs:
   * name
   *   arbitrary name which is used as prefix for the internal variables
   *
   * gb
   *   getbitcontext
   *
   * OPEN_READER(name, gb)
   *   load gb into local variables
   *
   * CLOSE_READER(name, gb)
   *   store local vars in gb
   *
   * UPDATE_CACHE(name, gb)
   *   Refill the internal cache from the bitstream.
   *   After this call at least MIN_CACHE_BITS will be available.
   *
   * GET_CACHE(name, gb)
   *   Will output the contents of the internal cache,
   *   next bit is MSB of 32 or 64 bit (FIXME 64bit).
   *
   * SHOW_UBITS(name, gb, num)
   *   Will return the next num bits.
   *
   * SHOW_SBITS(name, gb, num)
   *   Will return the next num bits and do sign extension.
   *
   * SKIP_BITS(name, gb, num)
   *   Will skip over the next num bits.
   *   Note, this is equivalent to SKIP_CACHE; SKIP_COUNTER.
   *
   * SKIP_CACHE(name, gb, num)
   *   Will remove the next num bits from the cache (note SKIP_COUNTER
   *   MUST be called before UPDATE_CACHE / CLOSE_READER).
   *
   * SKIP_COUNTER(name, gb, num)
   *   Will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS).
   *
   * LAST_SKIP_BITS(name, gb, num)
   *   Like SKIP_BITS, to be used if next call is UPDATE_CACHE or CLOSE_READER.
   *
   * For examples see get_bits, show_bits, skip_bits, get_vlc.
   */
  
  #ifdef LONG_BITSTREAM_READER
  #   define MIN_CACHE_BITS 32
  #else
  #   define MIN_CACHE_BITS 25
  #endif
  
  #if UNCHECKED_BITSTREAM_READER
  #define OPEN_READER(name, gb)                   \
      unsigned int name ## _index = (gb)->index;  \
      unsigned int av_unused name ## _cache
  
  #define HAVE_BITS_REMAINING(name, gb) 1
  #else
  #define OPEN_READER(name, gb)                   \
      unsigned int name ## _index = (gb)->index;  \
      unsigned int av_unused name ## _cache = 0;  \
      unsigned int av_unused name ## _size_plus8 = (gb)->size_in_bits_plus8
  
  #define HAVE_BITS_REMAINING(name, gb) name ## _index < name ## _size_plus8
  #endif
  
  #define CLOSE_READER(name, gb) (gb)->index = name ## _index
  
  # ifdef LONG_BITSTREAM_READER
  
  # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
        AV_RL64((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
  
  # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
        AV_RB64((gb)->buffer + (name ## _index >> 3)) >> (32 - (name ## _index & 7))
  
  #else
  
  # define UPDATE_CACHE_LE(name, gb) name ## _cache = \
        AV_RL32((gb)->buffer + (name ## _index >> 3)) >> (name ## _index & 7)
  
  # define UPDATE_CACHE_BE(name, gb) name ## _cache = \
        AV_RB32((gb)->buffer + (name ## _index >> 3)) << (name ## _index & 7)
  
  #endif
  
  
  #ifdef BITSTREAM_READER_LE
  
  # define UPDATE_CACHE(name, gb) UPDATE_CACHE_LE(name, gb)
  
  # define SKIP_CACHE(name, gb, num) name ## _cache >>= (num)
  
  #else
  
  # define UPDATE_CACHE(name, gb) UPDATE_CACHE_BE(name, gb)
  
  # define SKIP_CACHE(name, gb, num) name ## _cache <<= (num)
  
  #endif
  
  #if UNCHECKED_BITSTREAM_READER
  #   define SKIP_COUNTER(name, gb, num) name ## _index += (num)
  #else
  #   define SKIP_COUNTER(name, gb, num) \
      name ## _index = FFMIN(name ## _size_plus8, name ## _index + (num))
  #endif
  
  #define SKIP_BITS(name, gb, num)                \
      do {                                        \
          SKIP_CACHE(name, gb, num);              \
          SKIP_COUNTER(name, gb, num);            \
      } while (0)
  
  #define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
  
  #define SHOW_UBITS_LE(name, gb, num) zero_extend(name ## _cache, num)
  #define SHOW_SBITS_LE(name, gb, num) sign_extend(name ## _cache, num)
  
  #define SHOW_UBITS_BE(name, gb, num) NEG_USR32(name ## _cache, num)
  #define SHOW_SBITS_BE(name, gb, num) NEG_SSR32(name ## _cache, num)
  
  #ifdef BITSTREAM_READER_LE
  #   define SHOW_UBITS(name, gb, num) SHOW_UBITS_LE(name, gb, num)
  #   define SHOW_SBITS(name, gb, num) SHOW_SBITS_LE(name, gb, num)
  #else
  #   define SHOW_UBITS(name, gb, num) SHOW_UBITS_BE(name, gb, num)
  #   define SHOW_SBITS(name, gb, num) SHOW_SBITS_BE(name, gb, num)
  #endif
  
  #define GET_CACHE(name, gb) ((uint32_t) name ## _cache)
  
  static inline int get_bits_count(const GetBitContext *s)
  {
      return s->index;
  }
  
  static inline void skip_bits_long(GetBitContext *s, int n)
  {
  #if UNCHECKED_BITSTREAM_READER
      s->index += n;
  #else
      s->index += av_clip(n, -s->index, s->size_in_bits_plus8 - s->index);
  #endif
  }
  
  /**
   * read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
   * if MSB not set it is negative
   * @param n length in bits
   */
  static inline int get_xbits(GetBitContext *s, int n)
  {
      register int sign;
      register int32_t cache;
      OPEN_READER(re, s);
      av_assert2(n>0 && n<=25);
      UPDATE_CACHE(re, s);
      cache = GET_CACHE(re, s);
      sign  = ~cache >> 31;
      LAST_SKIP_BITS(re, s, n);
      CLOSE_READER(re, s);
      return (NEG_USR32(sign ^ cache, n) ^ sign) - sign;
  }
  
  static inline int get_sbits(GetBitContext *s, int n)
  {
      register int tmp;
      OPEN_READER(re, s);
      av_assert2(n>0 && n<=25);
      UPDATE_CACHE(re, s);
      tmp = SHOW_SBITS(re, s, n);
      LAST_SKIP_BITS(re, s, n);
      CLOSE_READER(re, s);
      return tmp;
  }
  
  /**
   * Read 1-25 bits.
   */
  static inline unsigned int get_bits(GetBitContext *s, int n)
  {
      register int tmp;
      OPEN_READER(re, s);
      av_assert2(n>0 && n<=25);
      UPDATE_CACHE(re, s);
      tmp = SHOW_UBITS(re, s, n);
      LAST_SKIP_BITS(re, s, n);
      CLOSE_READER(re, s);
      return tmp;
  }
  
  static inline unsigned int get_bits_le(GetBitContext *s, int n)
  {
      register int tmp;
      OPEN_READER(re, s);
      av_assert2(n>0 && n<=25);
      UPDATE_CACHE_LE(re, s);
      tmp = SHOW_UBITS_LE(re, s, n);
      LAST_SKIP_BITS(re, s, n);
      CLOSE_READER(re, s);
      return tmp;
  }
  
  /**
   * Show 1-25 bits.
   */
  static inline unsigned int show_bits(GetBitContext *s, int n)
  {
      register int tmp;
      OPEN_READER(re, s);
      av_assert2(n>0 && n<=25);
      UPDATE_CACHE(re, s);
      tmp = SHOW_UBITS(re, s, n);
      return tmp;
  }
  
  static inline void skip_bits(GetBitContext *s, int n)
  {
      OPEN_READER(re, s);
      LAST_SKIP_BITS(re, s, n);
      CLOSE_READER(re, s);
  }
  
  static inline unsigned int get_bits1(GetBitContext *s)
  {
      unsigned int index = s->index;
      uint8_t result     = s->buffer[index >> 3];
  #ifdef BITSTREAM_READER_LE
      result >>= index & 7;
      result  &= 1;
  #else
      result <<= index & 7;
      result >>= 8 - 1;
  #endif
  #if !UNCHECKED_BITSTREAM_READER
      if (s->index < s->size_in_bits_plus8)
  #endif
          index++;
      s->index = index;
  
      return result;
  }
  
  static inline unsigned int show_bits1(GetBitContext *s)
  {
      return show_bits(s, 1);
  }
  
  static inline void skip_bits1(GetBitContext *s)
  {
      skip_bits(s, 1);
  }
  
  /**
   * Read 0-32 bits.
   */
  static inline unsigned int get_bits_long(GetBitContext *s, int n)
  {
      if (!n) {
          return 0;
      } else if (n <= MIN_CACHE_BITS) {
          return get_bits(s, n);
      } else {
  #ifdef BITSTREAM_READER_LE
          unsigned ret = get_bits(s, 16);
          return ret | (get_bits(s, n - 16) << 16);
  #else
          unsigned ret = get_bits(s, 16) << (n - 16);
          return ret | get_bits(s, n - 16);
  #endif
      }
  }
  
  /**
   * Read 0-64 bits.
   */
  static inline uint64_t get_bits64(GetBitContext *s, int n)
  {
      if (n <= 32) {
          return get_bits_long(s, n);
      } else {
  #ifdef BITSTREAM_READER_LE
          uint64_t ret = get_bits_long(s, 32);
          return ret | (uint64_t) get_bits_long(s, n - 32) << 32;
  #else
          uint64_t ret = (uint64_t) get_bits_long(s, n - 32) << 32;
          return ret | get_bits_long(s, 32);
  #endif
      }
  }
  
  /**
   * Read 0-32 bits as a signed integer.
   */
  static inline int get_sbits_long(GetBitContext *s, int n)
  {
      return sign_extend(get_bits_long(s, n), n);
  }
  
  /**
   * Show 0-32 bits.
   */
  static inline unsigned int show_bits_long(GetBitContext *s, int n)
  {
      if (n <= MIN_CACHE_BITS) {
          return show_bits(s, n);
      } else {
          GetBitContext gb = *s;
          return get_bits_long(&gb, n);
      }
  }
  
  static inline int check_marker(GetBitContext *s, const char *msg)
  {
      int bit = get_bits1(s);
      if (!bit)
          av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
  
      return bit;
  }
  
  /**
   * Initialize GetBitContext.
   * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
   *        larger than the actual read bits because some optimized bitstream
   *        readers read 32 or 64 bit at once and could read over the end
   * @param bit_size the size of the buffer in bits
   * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
   */
  static inline int init_get_bits(GetBitContext *s, const uint8_t *buffer,
                                  int bit_size)
  {
      int buffer_size;
      int ret = 0;
  
      if (bit_size >= INT_MAX - 7 || bit_size < 0 || !buffer) {
          buffer_size = bit_size = 0;
          buffer      = NULL;
          ret         = AVERROR_INVALIDDATA;
      }
  
      buffer_size = (bit_size + 7) >> 3;
  
      s->buffer             = buffer;
      s->size_in_bits       = bit_size;
      s->size_in_bits_plus8 = bit_size + 8;
      s->buffer_end         = buffer + buffer_size;
      s->index              = 0;
  
      return ret;
  }
  
  /**
   * Initialize GetBitContext.
   * @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes
   *        larger than the actual read bits because some optimized bitstream
   *        readers read 32 or 64 bit at once and could read over the end
   * @param byte_size the size of the buffer in bytes
   * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow.
   */
  static inline int init_get_bits8(GetBitContext *s, const uint8_t *buffer,
                                   int byte_size)
  {
      if (byte_size > INT_MAX / 8 || byte_size < 0)
          byte_size = -1;
      return init_get_bits(s, buffer, byte_size * 8);
  }
  
  static inline const uint8_t *align_get_bits(GetBitContext *s)
  {
      int n = -get_bits_count(s) & 7;
      if (n)
          skip_bits(s, n);
      return s->buffer + (s->index >> 3);
  }
  
  #define init_vlc(vlc, nb_bits, nb_codes,                \
                   bits, bits_wrap, bits_size,            \
                   codes, codes_wrap, codes_size,         \
                   flags)                                 \
      ff_init_vlc_sparse(vlc, nb_bits, nb_codes,          \
                         bits, bits_wrap, bits_size,      \
                         codes, codes_wrap, codes_size,   \
                         NULL, 0, 0, flags)
  
  int ff_init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
                         const void *bits, int bits_wrap, int bits_size,
                         const void *codes, int codes_wrap, int codes_size,
                         const void *symbols, int symbols_wrap, int symbols_size,
                         int flags);
  void ff_free_vlc(VLC *vlc);
  
  #define INIT_VLC_LE             2
  #define INIT_VLC_USE_NEW_STATIC 4
  
  #define INIT_VLC_STATIC(vlc, bits, a, b, c, d, e, f, g, static_size)       \
      do {                                                                   \
          static VLC_TYPE table[static_size][2];                             \
          (vlc)->table           = table;                                    \
          (vlc)->table_allocated = static_size;                              \
          init_vlc(vlc, bits, a, b, c, d, e, f, g, INIT_VLC_USE_NEW_STATIC); \
      } while (0)
  
  /**
   * If the vlc code is invalid and max_depth=1, then no bits will be removed.
   * If the vlc code is invalid and max_depth>1, then the number of bits removed
   * is undefined.
   */
  #define GET_VLC(code, name, gb, table, bits, max_depth)         \
      do {                                                        \
          int n, nb_bits;                                         \
          unsigned int index;                                     \
                                                                  \
          index = SHOW_UBITS(name, gb, bits);                     \
          code  = table[index][0];                                \
          n     = table[index][1];                                \
                                                                  \
          if (max_depth > 1 && n < 0) {                           \
              LAST_SKIP_BITS(name, gb, bits);                     \
              UPDATE_CACHE(name, gb);                             \
                                                                  \
              nb_bits = -n;                                       \
                                                                  \
              index = SHOW_UBITS(name, gb, nb_bits) + code;       \
              code  = table[index][0];                            \
              n     = table[index][1];                            \
              if (max_depth > 2 && n < 0) {                       \
                  LAST_SKIP_BITS(name, gb, nb_bits);              \
                  UPDATE_CACHE(name, gb);                         \
                                                                  \
                  nb_bits = -n;                                   \
                                                                  \
                  index = SHOW_UBITS(name, gb, nb_bits) + code;   \
                  code  = table[index][0];                        \
                  n     = table[index][1];                        \
              }                                                   \
          }                                                       \
          SKIP_BITS(name, gb, n);                                 \
      } while (0)
  
  #define GET_RL_VLC(level, run, name, gb, table, bits,           \
                     max_depth, need_update)                      \
      do {                                                        \
          int n, nb_bits;                                         \
          unsigned int index;                                     \
                                                                  \
          index = SHOW_UBITS(name, gb, bits);                     \
          level = table[index].level;                             \
          n     = table[index].len;                               \
                                                                  \
          if (max_depth > 1 && n < 0) {                           \
              SKIP_BITS(name, gb, bits);                          \
              if (need_update) {                                  \
                  UPDATE_CACHE(name, gb);                         \
              }                                                   \
                                                                  \
              nb_bits = -n;                                       \
                                                                  \
              index = SHOW_UBITS(name, gb, nb_bits) + level;      \
              level = table[index].level;                         \
              n     = table[index].len;                           \
          }                                                       \
          run = table[index].run;                                 \
          SKIP_BITS(name, gb, n);                                 \
      } while (0)
  
  /**
   * Parse a vlc code.
   * @param bits is the number of bits which will be read at once, must be
   *             identical to nb_bits in init_vlc()
   * @param max_depth is the number of times bits bits must be read to completely
   *                  read the longest vlc code
   *                  = (max_vlc_length + bits - 1) / bits
   */
  static av_always_inline int get_vlc2(GetBitContext *s, VLC_TYPE (*table)[2],
                                       int bits, int max_depth)
  {
      int code;
  
      OPEN_READER(re, s);
      UPDATE_CACHE(re, s);
  
      GET_VLC(code, re, s, table, bits, max_depth);
  
      CLOSE_READER(re, s);
  
      return code;
  }
  
  static inline int decode012(GetBitContext *gb)
  {
      int n;
      n = get_bits1(gb);
      if (n == 0)
          return 0;
      else
          return get_bits1(gb) + 1;
  }
  
  static inline int decode210(GetBitContext *gb)
  {
      if (get_bits1(gb))
          return 0;
      else
          return 2 - get_bits1(gb);
  }
  
  static inline int get_bits_left(GetBitContext *gb)
  {
      return gb->size_in_bits - get_bits_count(gb);
  }
  
  static inline int skip_1stop_8data_bits(GetBitContext *gb)
  {
      if (get_bits_left(gb) <= 0)
          return AVERROR_INVALIDDATA;
  
      while (get_bits1(gb)) {
          skip_bits(gb, 8);
          if (get_bits_left(gb) <= 0)
              return AVERROR_INVALIDDATA;
      }
  
      return 0;
  }
  
  //#define TRACE
  
  #ifdef TRACE
  static inline void print_bin(int bits, int n)
  {
      int i;
  
      for (i = n - 1; i >= 0; i--)
          av_log(NULL, AV_LOG_DEBUG, "%d", (bits >> i) & 1);
      for (i = n; i < 24; i++)
          av_log(NULL, AV_LOG_DEBUG, " ");
  }
  
  static inline int get_bits_trace(GetBitContext *s, int n, const char *file,
                                   const char *func, int line)
  {
      int r = get_bits(s, n);
  
      print_bin(r, n);
      av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d bit @%5d in %s %s:%d\n",
             r, n, r, get_bits_count(s) - n, file, func, line);
  
      return r;
  }
  
  static inline int get_vlc_trace(GetBitContext *s, VLC_TYPE (*table)[2],
                                  int bits, int max_depth, const char *file,
                                  const char *func, int line)
  {
      int show  = show_bits(s, 24);
      int pos   = get_bits_count(s);
      int r     = get_vlc2(s, table, bits, max_depth);
      int len   = get_bits_count(s) - pos;
      int bits2 = show >> (24 - len);
  
      print_bin(bits2, len);
  
      av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d vlc @%5d in %s %s:%d\n",
             bits2, len, r, pos, file, func, line);
  
      return r;
  }
  
  static inline int get_xbits_trace(GetBitContext *s, int n, const char *file,
                                    const char *func, int line)
  {
      int show = show_bits(s, n);
      int r    = get_xbits(s, n);
  
      print_bin(show, n);
      av_log(NULL, AV_LOG_DEBUG, "%5d %2d %3d xbt @%5d in %s %s:%d\n",
             show, n, r, get_bits_count(s) - n, file, func, line);
  
      return r;
  }
  
  #define get_bits(s, n)  get_bits_trace(s , n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  #define get_bits1(s)    get_bits_trace(s,  1, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  #define get_xbits(s, n) get_xbits_trace(s, n, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  
  #define get_vlc(s, vlc)             get_vlc_trace(s, (vlc)->table, (vlc)->bits,   3, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  #define get_vlc2(s, tab, bits, max) get_vlc_trace(s,          tab,        bits, max, __FILE__, __PRETTY_FUNCTION__, __LINE__)
  
  #define tprintf(p, ...) av_log(p, AV_LOG_DEBUG, __VA_ARGS__)
  
  #else //TRACE
  #define tprintf(p, ...) { }
  #endif
  
  #endif /* AVCODEC_GET_BITS_H */
  