text: // Copyright 2011 Google Inc. All Rights Reserved.
  //
  // Use of this source code is governed by a BSD-style license
  // that can be found in the COPYING file in the root of the source
  // tree. An additional intellectual property rights grant can be found
  // in the file PATENTS. All contributing project authors may
  // be found in the AUTHORS file in the root of the source tree.
  // -----------------------------------------------------------------------------
  //
  // Bit writing and boolean coder
  //
  // Author: Skal (pascal.massimino@gmail.com)
  //         Vikas Arora (vikaas.arora@gmail.com)
  
  #include <assert.h>
  #include <string.h>   // for memcpy()
  #include <stdlib.h>
  
  #include "utils_bit_writer_utils.h"
  #include "utils_endian_inl_utils.h"
  #include "utils_utils.h"
  
  //------------------------------------------------------------------------------
  // VP8BitWriter
  
  static int BitWriterResize(VP8BitWriter* const bw, size_t extra_size) {
    uint8_t* new_buf;
    size_t new_size;
    const uint64_t needed_size_64b = (uint64_t)bw->pos_ + extra_size;
    const size_t needed_size = (size_t)needed_size_64b;
    if (needed_size_64b != needed_size) {
      bw->error_ = 1;
      return 0;
    }
    if (needed_size <= bw->max_pos_) return 1;
    // If the following line wraps over 32bit, the test just after will catch it.
    new_size = 2 * bw->max_pos_;
    if (new_size < needed_size) new_size = needed_size;
    if (new_size < 1024) new_size = 1024;
    new_buf = (uint8_t*)WebPSafeMalloc(1ULL, new_size);
    if (new_buf == NULL) {
      bw->error_ = 1;
      return 0;
    }
    if (bw->pos_ > 0) {
      assert(bw->buf_ != NULL);
      memcpy(new_buf, bw->buf_, bw->pos_);
    }
    WebPSafeFree(bw->buf_);
    bw->buf_ = new_buf;
    bw->max_pos_ = new_size;
    return 1;
  }
  
  static void Flush(VP8BitWriter* const bw) {
    const int s = 8 + bw->nb_bits_;
    const int32_t bits = bw->value_ >> s;
    assert(bw->nb_bits_ >= 0);
    bw->value_ -= bits << s;
    bw->nb_bits_ -= 8;
    if ((bits & 0xff) != 0xff) {
      size_t pos = bw->pos_;
      if (!BitWriterResize(bw, bw->run_ + 1)) {
        return;
      }
      if (bits & 0x100) {  // overflow -> propagate carry over pending 0xff's
        if (pos > 0) bw->buf_[pos - 1]++;
      }
      if (bw->run_ > 0) {
        const int value = (bits & 0x100) ? 0x00 : 0xff;
        for (; bw->run_ > 0; --bw->run_) bw->buf_[pos++] = value;
      }
      bw->buf_[pos++] = bits & 0xff;
      bw->pos_ = pos;
    } else {
      bw->run_++;   // delay writing of bytes 0xff, pending eventual carry.
    }
  }
  
  //------------------------------------------------------------------------------
  // renormalization
  
  static const uint8_t kNorm[128] = {  // renorm_sizes[i] = 8 - log2(i)
       7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
    3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
    0
  };
  
  // range = ((range + 1) << kVP8Log2Range[range]) - 1
  static const uint8_t kNewRange[128] = {
    127, 127, 191, 127, 159, 191, 223, 127, 143, 159, 175, 191, 207, 223, 239,
    127, 135, 143, 151, 159, 167, 175, 183, 191, 199, 207, 215, 223, 231, 239,
    247, 127, 131, 135, 139, 143, 147, 151, 155, 159, 163, 167, 171, 175, 179,
    183, 187, 191, 195, 199, 203, 207, 211, 215, 219, 223, 227, 231, 235, 239,
    243, 247, 251, 127, 129, 131, 133, 135, 137, 139, 141, 143, 145, 147, 149,
    151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171, 173, 175, 177, 179,
    181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201, 203, 205, 207, 209,
    211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231, 233, 235, 237, 239,
    241, 243, 245, 247, 249, 251, 253, 127
  };
  
  int VP8PutBit(VP8BitWriter* const bw, int bit, int prob) {
    const int split = (bw->range_ * prob) >> 8;
    if (bit) {
      bw->value_ += split + 1;
      bw->range_ -= split + 1;
    } else {
      bw->range_ = split;
    }
    if (bw->range_ < 127) {   // emit 'shift' bits out and renormalize
      const int shift = kNorm[bw->range_];
      bw->range_ = kNewRange[bw->range_];
      bw->value_ <<= shift;
      bw->nb_bits_ += shift;
      if (bw->nb_bits_ > 0) Flush(bw);
    }
    return bit;
  }
  
  int VP8PutBitUniform(VP8BitWriter* const bw, int bit) {
    const int split = bw->range_ >> 1;
    if (bit) {
      bw->value_ += split + 1;
      bw->range_ -= split + 1;
    } else {
      bw->range_ = split;
    }
    if (bw->range_ < 127) {
      bw->range_ = kNewRange[bw->range_];
      bw->value_ <<= 1;
      bw->nb_bits_ += 1;
      if (bw->nb_bits_ > 0) Flush(bw);
    }
    return bit;
  }
  
  void VP8PutBits(VP8BitWriter* const bw, uint32_t value, int nb_bits) {
    uint32_t mask;
    assert(nb_bits > 0 && nb_bits < 32);
    for (mask = 1u << (nb_bits - 1); mask; mask >>= 1) {
      VP8PutBitUniform(bw, value & mask);
    }
  }
  
  void VP8PutSignedBits(VP8BitWriter* const bw, int value, int nb_bits) {
    if (!VP8PutBitUniform(bw, value != 0)) return;
    if (value < 0) {
      VP8PutBits(bw, ((-value) << 1) | 1, nb_bits + 1);
    } else {
      VP8PutBits(bw, value << 1, nb_bits + 1);
    }
  }
  
  //------------------------------------------------------------------------------
  
  int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size) {
    bw->range_   = 255 - 1;
    bw->value_   = 0;
    bw->run_     = 0;
    bw->nb_bits_ = -8;
    bw->pos_     = 0;
    bw->max_pos_ = 0;
    bw->error_   = 0;
    bw->buf_     = NULL;
    return (expected_size > 0) ? BitWriterResize(bw, expected_size) : 1;
  }
  
  uint8_t* VP8BitWriterFinish(VP8BitWriter* const bw) {
    VP8PutBits(bw, 0, 9 - bw->nb_bits_);
    bw->nb_bits_ = 0;   // pad with zeroes
    Flush(bw);
    return bw->buf_;
  }
  
  int VP8BitWriterAppend(VP8BitWriter* const bw,
                         const uint8_t* data, size_t size) {
    assert(data != NULL);
    if (bw->nb_bits_ != -8) return 0;   // Flush() must have been called
    if (!BitWriterResize(bw, size)) return 0;
    memcpy(bw->buf_ + bw->pos_, data, size);
    bw->pos_ += size;
    return 1;
  }
  
  void VP8BitWriterWipeOut(VP8BitWriter* const bw) {
    if (bw != NULL) {
      WebPSafeFree(bw->buf_);
      memset(bw, 0, sizeof(*bw));
    }
  }
  
  //------------------------------------------------------------------------------
  // VP8LBitWriter
  
  // This is the minimum amount of size the memory buffer is guaranteed to grow
  // when extra space is needed.
  #define MIN_EXTRA_SIZE  (32768ULL)
  
  // Returns 1 on success.
  static int VP8LBitWriterResize(VP8LBitWriter* const bw, size_t extra_size) {
    uint8_t* allocated_buf;
    size_t allocated_size;
    const size_t max_bytes = bw->end_ - bw->buf_;
    const size_t current_size = bw->cur_ - bw->buf_;
    const uint64_t size_required_64b = (uint64_t)current_size + extra_size;
    const size_t size_required = (size_t)size_required_64b;
    if (size_required != size_required_64b) {
      bw->error_ = 1;
      return 0;
    }
    if (max_bytes > 0 && size_required <= max_bytes) return 1;
    allocated_size = (3 * max_bytes) >> 1;
    if (allocated_size < size_required) allocated_size = size_required;
    // make allocated size multiple of 1k
    allocated_size = (((allocated_size >> 10) + 1) << 10);
    allocated_buf = (uint8_t*)WebPSafeMalloc(1ULL, allocated_size);
    if (allocated_buf == NULL) {
      bw->error_ = 1;
      return 0;
    }
    if (current_size > 0) {
      memcpy(allocated_buf, bw->buf_, current_size);
    }
    WebPSafeFree(bw->buf_);
    bw->buf_ = allocated_buf;
    bw->cur_ = bw->buf_ + current_size;
    bw->end_ = bw->buf_ + allocated_size;
    return 1;
  }
  
  int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size) {
    memset(bw, 0, sizeof(*bw));
    return VP8LBitWriterResize(bw, expected_size);
  }
  
  int VP8LBitWriterClone(const VP8LBitWriter* const src,
                         VP8LBitWriter* const dst) {
    const size_t current_size = src->cur_ - src->buf_;
    assert(src->cur_ >= src->buf_ && src->cur_ <= src->end_);
    if (!VP8LBitWriterResize(dst, current_size)) return 0;
    memcpy(dst->buf_, src->buf_, current_size);
    dst->bits_ = src->bits_;
    dst->used_ = src->used_;
    dst->error_ = src->error_;
    dst->cur_ = dst->buf_ + current_size;
    return 1;
  }
  
  void VP8LBitWriterWipeOut(VP8LBitWriter* const bw) {
    if (bw != NULL) {
      WebPSafeFree(bw->buf_);
      memset(bw, 0, sizeof(*bw));
    }
  }
  
  void VP8LBitWriterReset(const VP8LBitWriter* const bw_init,
                          VP8LBitWriter* const bw) {
    bw->bits_ = bw_init->bits_;
    bw->used_ = bw_init->used_;
    bw->cur_ = bw->buf_ + (bw_init->cur_ - bw_init->buf_);
    assert(bw->cur_ <= bw->end_);
    bw->error_ = bw_init->error_;
  }
  
  void VP8LBitWriterSwap(VP8LBitWriter* const src, VP8LBitWriter* const dst) {
    const VP8LBitWriter tmp = *src;
    *src = *dst;
    *dst = tmp;
  }
  
  void VP8LPutBitsFlushBits(VP8LBitWriter* const bw) {
    // If needed, make some room by flushing some bits out.
    if (bw->cur_ + VP8L_WRITER_BYTES > bw->end_) {
      const uint64_t extra_size = (bw->end_ - bw->buf_) + MIN_EXTRA_SIZE;
      if (extra_size != (size_t)extra_size ||
          !VP8LBitWriterResize(bw, (size_t)extra_size)) {
        bw->cur_ = bw->buf_;
        bw->error_ = 1;
        return;
      }
    }
    *(vp8l_wtype_t*)bw->cur_ = (vp8l_wtype_t)WSWAP((vp8l_wtype_t)bw->bits_);
    bw->cur_ += VP8L_WRITER_BYTES;
    bw->bits_ >>= VP8L_WRITER_BITS;
    bw->used_ -= VP8L_WRITER_BITS;
  }
  
  void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits) {
    assert(n_bits <= 32);
    // That's the max we can handle:
    assert(sizeof(vp8l_wtype_t) == 2);
    if (n_bits > 0) {
      vp8l_atype_t lbits = bw->bits_;
      int used = bw->used_;
      // Special case of overflow handling for 32bit accumulator (2-steps flush).
  #if VP8L_WRITER_BITS == 16
      if (used + n_bits >= VP8L_WRITER_MAX_BITS) {
        // Fill up all the VP8L_WRITER_MAX_BITS so it can be flushed out below.
        const int shift = VP8L_WRITER_MAX_BITS - used;
        lbits |= (vp8l_atype_t)bits << used;
        used = VP8L_WRITER_MAX_BITS;
        n_bits -= shift;
        bits >>= shift;
        assert(n_bits <= VP8L_WRITER_MAX_BITS);
      }
  #endif
      // If needed, make some room by flushing some bits out.
      while (used >= VP8L_WRITER_BITS) {
        if (bw->cur_ + VP8L_WRITER_BYTES > bw->end_) {
          const uint64_t extra_size = (bw->end_ - bw->buf_) + MIN_EXTRA_SIZE;
          if (extra_size != (size_t)extra_size ||
              !VP8LBitWriterResize(bw, (size_t)extra_size)) {
            bw->cur_ = bw->buf_;
            bw->error_ = 1;
            return;
          }
        }
        *(vp8l_wtype_t*)bw->cur_ = (vp8l_wtype_t)WSWAP((vp8l_wtype_t)lbits);
        bw->cur_ += VP8L_WRITER_BYTES;
        lbits >>= VP8L_WRITER_BITS;
        used -= VP8L_WRITER_BITS;
      }
      bw->bits_ = lbits | ((vp8l_atype_t)bits << used);
      bw->used_ = used + n_bits;
    }
  }
  
  uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw) {
    // flush leftover bits
    if (VP8LBitWriterResize(bw, (bw->used_ + 7) >> 3)) {
      while (bw->used_ > 0) {
        *bw->cur_++ = (uint8_t)bw->bits_;
        bw->bits_ >>= 8;
        bw->used_ -= 8;
      }
      bw->used_ = 0;
    }
    return bw->buf_;
  }
  
  //------------------------------------------------------------------------------
  