libwebp-0.6.0-rc1

third_party/libwebp/utils/bit_writer.h

-// 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)
-
-#ifndef WEBP_UTILS_BIT_WRITER_H_
-#define WEBP_UTILS_BIT_WRITER_H_
-
-#include "../webp/types.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-//------------------------------------------------------------------------------
-// Bit-writing
-
-typedef struct VP8BitWriter VP8BitWriter;
-struct VP8BitWriter {
-  int32_t  range_;      // range-1
-  int32_t  value_;
-  int      run_;        // number of outstanding bits
-  int      nb_bits_;    // number of pending bits
-  uint8_t* buf_;        // internal buffer. Re-allocated regularly. Not owned.
-  size_t   pos_;
-  size_t   max_pos_;
-  int      error_;      // true in case of error
-};
-
-// Initialize the object. Allocates some initial memory based on expected_size.
-int VP8BitWriterInit(VP8BitWriter* const bw, size_t expected_size);
-// Finalize the bitstream coding. Returns a pointer to the internal buffer.
-uint8_t* VP8BitWriterFinish(VP8BitWriter* const bw);
-// Release any pending memory and zeroes the object. Not a mandatory call.
-// Only useful in case of error, when the internal buffer hasn't been grabbed!
-void VP8BitWriterWipeOut(VP8BitWriter* const bw);
-
-int VP8PutBit(VP8BitWriter* const bw, int bit, int prob);
-int VP8PutBitUniform(VP8BitWriter* const bw, int bit);
-void VP8PutBits(VP8BitWriter* const bw, uint32_t value, int nb_bits);
-void VP8PutSignedBits(VP8BitWriter* const bw, int value, int nb_bits);
-
-// Appends some bytes to the internal buffer. Data is copied.
-int VP8BitWriterAppend(VP8BitWriter* const bw,
-                       const uint8_t* data, size_t size);
-
-// return approximate write position (in bits)
-static WEBP_INLINE uint64_t VP8BitWriterPos(const VP8BitWriter* const bw) {
-  return (uint64_t)(bw->pos_ + bw->run_) * 8 + 8 + bw->nb_bits_;
-}
-
-// Returns a pointer to the internal buffer.
-static WEBP_INLINE uint8_t* VP8BitWriterBuf(const VP8BitWriter* const bw) {
-  return bw->buf_;
-}
-// Returns the size of the internal buffer.
-static WEBP_INLINE size_t VP8BitWriterSize(const VP8BitWriter* const bw) {
-  return bw->pos_;
-}
-
-//------------------------------------------------------------------------------
-// VP8LBitWriter
-
-#if defined(__x86_64__) || defined(_M_X64)   // 64bit
-typedef uint64_t vp8l_atype_t;   // accumulator type
-typedef uint32_t vp8l_wtype_t;   // writing type
-#define WSWAP HToLE32
-#define VP8L_WRITER_BYTES    4   // sizeof(vp8l_wtype_t)
-#define VP8L_WRITER_BITS     32  // 8 * sizeof(vp8l_wtype_t)
-#define VP8L_WRITER_MAX_BITS 64  // 8 * sizeof(vp8l_atype_t)
-#else
-typedef uint32_t vp8l_atype_t;
-typedef uint16_t vp8l_wtype_t;
-#define WSWAP HToLE16
-#define VP8L_WRITER_BYTES    2
-#define VP8L_WRITER_BITS     16
-#define VP8L_WRITER_MAX_BITS 32
-#endif
-
-typedef struct {
-  vp8l_atype_t bits_;   // bit accumulator
-  int          used_;   // number of bits used in accumulator
-  uint8_t*     buf_;    // start of buffer
-  uint8_t*     cur_;    // current write position
-  uint8_t*     end_;    // end of buffer
-
-  // After all bits are written (VP8LBitWriterFinish()), the caller must observe
-  // the state of error_. A value of 1 indicates that a memory allocation
-  // failure has happened during bit writing. A value of 0 indicates successful
-  // writing of bits.
-  int error_;
-} VP8LBitWriter;
-
-static WEBP_INLINE size_t VP8LBitWriterNumBytes(VP8LBitWriter* const bw) {
-  return (bw->cur_ - bw->buf_) + ((bw->used_ + 7) >> 3);
-}
-
-// Returns false in case of memory allocation error.
-int VP8LBitWriterInit(VP8LBitWriter* const bw, size_t expected_size);
-// Finalize the bitstream coding. Returns a pointer to the internal buffer.
-uint8_t* VP8LBitWriterFinish(VP8LBitWriter* const bw);
-// Release any pending memory and zeroes the object.
-void VP8LBitWriterWipeOut(VP8LBitWriter* const bw);
-
-// Internal function for VP8LPutBits flushing 32 bits from the written state.
-void VP8LPutBitsFlushBits(VP8LBitWriter* const bw);
-
-// PutBits internal function used in the 16 bit vp8l_wtype_t case.
-void VP8LPutBitsInternal(VP8LBitWriter* const bw, uint32_t bits, int n_bits);
-
-// This function writes bits into bytes in increasing addresses (little endian),
-// and within a byte least-significant-bit first.
-// This function can write up to 32 bits in one go, but VP8LBitReader can only
-// read 24 bits max (VP8L_MAX_NUM_BIT_READ).
-// VP8LBitWriter's error_ flag is set in case of  memory allocation error.
-static WEBP_INLINE void VP8LPutBits(VP8LBitWriter* const bw,
-                                    uint32_t bits, int n_bits) {
-  if (sizeof(vp8l_wtype_t) == 4) {
-    if (n_bits > 0) {
-      if (bw->used_ >= 32) {
-        VP8LPutBitsFlushBits(bw);
-      }
-      bw->bits_ |= (vp8l_atype_t)bits << bw->used_;
-      bw->used_ += n_bits;
-    }
-  } else {
-    VP8LPutBitsInternal(bw, bits, n_bits);
-  }
-}
-
-//------------------------------------------------------------------------------
-
-#ifdef __cplusplus
-}    // extern "C"
-#endif
-
-#endif  /* WEBP_UTILS_BIT_WRITER_H_ */