media/libvpx/vp9/decoder/vp9_dboolhuff.h@ac0c01689b40 (annotated)
media/libvpx/vp9/decoder/vp9_dboolhuff.h
Thu, 15 Jan 2015 15:59:08 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Thu, 15 Jan 2015 15:59:08 +0100
- branch
- TOR_BUG_9701
- changeset 10
- ac0c01689b40
- permissions
- -rw-r--r--
Implement a real Private Browsing Mode condition by changing the API/ABI;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.
| michael@0 | 1 | /* |
| michael@0 | 2 | * Copyright (c) 2010 The WebM project authors. All Rights Reserved. |
| michael@0 | 3 | * |
| michael@0 | 4 | * Use of this source code is governed by a BSD-style license |
| michael@0 | 5 | * that can be found in the LICENSE file in the root of the source |
| michael@0 | 6 | * tree. An additional intellectual property rights grant can be found |
| michael@0 | 7 | * in the file PATENTS. All contributing project authors may |
| michael@0 | 8 | * be found in the AUTHORS file in the root of the source tree. |
| michael@0 | 9 | */ |
| michael@0 | 10 | |
| michael@0 | 11 | #ifndef VP9_DECODER_VP9_DBOOLHUFF_H_ |
| michael@0 | 12 | #define VP9_DECODER_VP9_DBOOLHUFF_H_ |
| michael@0 | 13 | |
| michael@0 | 14 | #include <stddef.h> |
| michael@0 | 15 | #include <limits.h> |
| michael@0 | 16 | |
| michael@0 | 17 | #include "./vpx_config.h" |
| michael@0 | 18 | #include "vpx_ports/mem.h" |
| michael@0 | 19 | #include "vpx/vpx_integer.h" |
| michael@0 | 20 | |
| michael@0 | 21 | typedef size_t VP9_BD_VALUE; |
| michael@0 | 22 | |
| michael@0 | 23 | #define BD_VALUE_SIZE ((int)sizeof(VP9_BD_VALUE)*CHAR_BIT) |
| michael@0 | 24 | |
| michael@0 | 25 | typedef struct { |
| michael@0 | 26 | const uint8_t *buffer_end; |
| michael@0 | 27 | const uint8_t *buffer; |
| michael@0 | 28 | VP9_BD_VALUE value; |
| michael@0 | 29 | int count; |
| michael@0 | 30 | unsigned int range; |
| michael@0 | 31 | } vp9_reader; |
| michael@0 | 32 | |
| michael@0 | 33 | DECLARE_ALIGNED(16, extern const uint8_t, vp9_norm[256]); |
| michael@0 | 34 | |
| michael@0 | 35 | int vp9_reader_init(vp9_reader *r, const uint8_t *buffer, size_t size); |
| michael@0 | 36 | |
| michael@0 | 37 | void vp9_reader_fill(vp9_reader *r); |
| michael@0 | 38 | |
| michael@0 | 39 | const uint8_t *vp9_reader_find_end(vp9_reader *r); |
| michael@0 | 40 | |
| michael@0 | 41 | static int vp9_read(vp9_reader *br, int probability) { |
| michael@0 | 42 | unsigned int bit = 0; |
| michael@0 | 43 | VP9_BD_VALUE value; |
| michael@0 | 44 | VP9_BD_VALUE bigsplit; |
| michael@0 | 45 | int count; |
| michael@0 | 46 | unsigned int range; |
| michael@0 | 47 | unsigned int split = ((br->range * probability) + (256 - probability)) >> 8; |
| michael@0 | 48 | |
| michael@0 | 49 | if (br->count < 0) |
| michael@0 | 50 | vp9_reader_fill(br); |
| michael@0 | 51 | |
| michael@0 | 52 | value = br->value; |
| michael@0 | 53 | count = br->count; |
| michael@0 | 54 | |
| michael@0 | 55 | bigsplit = (VP9_BD_VALUE)split << (BD_VALUE_SIZE - 8); |
| michael@0 | 56 | |
| michael@0 | 57 | range = split; |
| michael@0 | 58 | |
| michael@0 | 59 | if (value >= bigsplit) { |
| michael@0 | 60 | range = br->range - split; |
| michael@0 | 61 | value = value - bigsplit; |
| michael@0 | 62 | bit = 1; |
| michael@0 | 63 | } |
| michael@0 | 64 | |
| michael@0 | 65 | { |
| michael@0 | 66 | register unsigned int shift = vp9_norm[range]; |
| michael@0 | 67 | range <<= shift; |
| michael@0 | 68 | value <<= shift; |
| michael@0 | 69 | count -= shift; |
| michael@0 | 70 | } |
| michael@0 | 71 | br->value = value; |
| michael@0 | 72 | br->count = count; |
| michael@0 | 73 | br->range = range; |
| michael@0 | 74 | |
| michael@0 | 75 | return bit; |
| michael@0 | 76 | } |
| michael@0 | 77 | |
| michael@0 | 78 | static int vp9_read_bit(vp9_reader *r) { |
| michael@0 | 79 | return vp9_read(r, 128); // vp9_prob_half |
| michael@0 | 80 | } |
| michael@0 | 81 | |
| michael@0 | 82 | static int vp9_read_literal(vp9_reader *br, int bits) { |
| michael@0 | 83 | int z = 0, bit; |
| michael@0 | 84 | |
| michael@0 | 85 | for (bit = bits - 1; bit >= 0; bit--) |
| michael@0 | 86 | z |= vp9_read_bit(br) << bit; |
| michael@0 | 87 | |
| michael@0 | 88 | return z; |
| michael@0 | 89 | } |
| michael@0 | 90 | |
| michael@0 | 91 | int vp9_reader_has_error(vp9_reader *r); |
| michael@0 | 92 | |
| michael@0 | 93 | #endif // VP9_DECODER_VP9_DBOOLHUFF_H_ |
