vpx_dsp/bitwriter_buffer.c

   1 /*
   2  *  Copyright (c) 2013 The WebM project authors. All Rights Reserved.
   3  *
   4  *  Use of this source code is governed by a BSD-style license
   5  *  that can be found in the LICENSE file in the root of the source
   6  *  tree. An additional intellectual property rights grant can be found
   7  *  in the file PATENTS.  All contributing project authors may
   8  *  be found in the AUTHORS file in the root of the source tree.
   9  */
  10
  11 #include <limits.h>
  12 #include <stdlib.h>
  13
  14 #include "./vpx_config.h"
  15 #include "./bitwriter_buffer.h"
  16
  17 size_t vpx_wb_bytes_written(const struct vpx_write_bit_buffer *wb) {
  18   return wb->bit_offset / CHAR_BIT + (wb->bit_offset % CHAR_BIT > 0);
  19 }
  20
  21 void vpx_wb_write_bit(struct vpx_write_bit_buffer *wb, int bit) {
  22   const int off = (int)wb->bit_offset;
  23   const int p = off / CHAR_BIT;
  24   const int q = CHAR_BIT - 1 - off % CHAR_BIT;
  25   if (q == CHAR_BIT -1) {
  26     wb->bit_buffer[p] = bit << q;
  27   } else {
  28     wb->bit_buffer[p] &= ~(1 << q);
  29     wb->bit_buffer[p] |= bit << q;
  30   }
  31   wb->bit_offset = off + 1;
  32 }
  33
  34 void vpx_wb_write_literal(struct vpx_write_bit_buffer *wb, int data, int bits) {
  35   int bit;
  36   for (bit = bits - 1; bit >= 0; bit--)
  37     vpx_wb_write_bit(wb, (data >> bit) & 1);
  38 }
  39
  40 void vpx_wb_write_inv_signed_literal(struct vpx_write_bit_buffer *wb,
  41                                      int data, int bits) {
  42 #if CONFIG_MISC_FIXES
  43   vpx_wb_write_literal(wb, data, bits + 1);
  44 #else
  45   vpx_wb_write_literal(wb, abs(data), bits);
  46   vpx_wb_write_bit(wb, data < 0);
  47 #endif
  48 }