The Tor Browser: media/libvpx/vp8/decoder/dboolhuff.c@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 /*

     2  *  Copyright (c) 2010 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  */

    12 #include "dboolhuff.h"

    14 int vp8dx_start_decode(BOOL_DECODER *br,

    15                        const unsigned char *source,

    16                        unsigned int source_sz,

    17                        vp8_decrypt_cb *decrypt_cb,

    18                        void *decrypt_state)

    19 {

    20     br->user_buffer_end = source+source_sz;

    21     br->user_buffer     = source;

    22     br->value    = 0;

    23     br->count    = -8;

    24     br->range    = 255;

    25     br->decrypt_cb = decrypt_cb;

    26     br->decrypt_state = decrypt_state;

    28     if (source_sz && !source)

    29         return 1;

    31     /* Populate the buffer */

    32     vp8dx_bool_decoder_fill(br);

    34     return 0;

    35 }

    37 void vp8dx_bool_decoder_fill(BOOL_DECODER *br)

    38 {

    39     const unsigned char *bufptr = br->user_buffer;

    40     VP8_BD_VALUE value = br->value;

    41     int count = br->count;

    42     int shift = VP8_BD_VALUE_SIZE - 8 - (count + 8);

    43     size_t bytes_left = br->user_buffer_end - bufptr;

    44     size_t bits_left = bytes_left * CHAR_BIT;

    45     int x = (int)(shift + CHAR_BIT - bits_left);

    46     int loop_end = 0;

    47     unsigned char decrypted[sizeof(VP8_BD_VALUE) + 1];

    49     if (br->decrypt_cb) {

    50         size_t n = bytes_left > sizeof(decrypted) ? sizeof(decrypted) : bytes_left;

    51         br->decrypt_cb(br->decrypt_state, bufptr, decrypted, (int)n);

    52         bufptr = decrypted;

    53     }

    55     if(x >= 0)

    56     {

    57         count += VP8_LOTS_OF_BITS;

    58         loop_end = x;

    59     }

    61     if (x < 0 || bits_left)

    62     {

    63         while(shift >= loop_end)

    64         {

    65             count += CHAR_BIT;

    66             value |= (VP8_BD_VALUE)*bufptr << shift;

    67             ++bufptr;

    68             ++br->user_buffer;

    69             shift -= CHAR_BIT;

    70         }

    71     }

    73     br->value = value;

    74     br->count = count;

    75 }

The Tor Browser / file revision