1 /* Copyright 2013 Google Inc. All Rights Reserved.
2
3 Distributed under MIT license.
4 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
5 */
6
7 /* This class models a sequence of literals and a backward reference copy. */
8
9 #ifndef BROTLI_ENC_COMMAND_H_
10 #define BROTLI_ENC_COMMAND_H_
11
12 #include "../common/constants.h"
13 #include "../common/platform.h"
14 #include <brotli/types.h>
15 #include "./fast_log.h"
16 #include "./params.h"
17 #include "./prefix.h"
18
19 #if defined(__cplusplus) || defined(c_plusplus)
20 extern "C" {
21 #endif
22
23 static uint32_t kInsBase[] = { 0, 1, 2, 3, 4, 5, 6, 8, 10, 14, 18, 26, 34, 50,
24 66, 98, 130, 194, 322, 578, 1090, 2114, 6210, 22594 };
25 static uint32_t kInsExtra[] = { 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4,
26 5, 5, 6, 7, 8, 9, 10, 12, 14, 24 };
27 static uint32_t kCopyBase[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 18, 22, 30,
28 38, 54, 70, 102, 134, 198, 326, 582, 1094, 2118 };
29 static uint32_t kCopyExtra[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 3, 3,
30 4, 4, 5, 5, 6, 7, 8, 9, 10, 24 };
31
GetInsertLengthCode(size_t insertlen)32 static BROTLI_INLINE uint16_t GetInsertLengthCode(size_t insertlen) {
33 if (insertlen < 6) {
34 return (uint16_t)insertlen;
35 } else if (insertlen < 130) {
36 uint32_t nbits = Log2FloorNonZero(insertlen - 2) - 1u;
37 return (uint16_t)((nbits << 1) + ((insertlen - 2) >> nbits) + 2);
38 } else if (insertlen < 2114) {
39 return (uint16_t)(Log2FloorNonZero(insertlen - 66) + 10);
40 } else if (insertlen < 6210) {
41 return 21u;
42 } else if (insertlen < 22594) {
43 return 22u;
44 } else {
45 return 23u;
46 }
47 }
48
GetCopyLengthCode(size_t copylen)49 static BROTLI_INLINE uint16_t GetCopyLengthCode(size_t copylen) {
50 if (copylen < 10) {
51 return (uint16_t)(copylen - 2);
52 } else if (copylen < 134) {
53 uint32_t nbits = Log2FloorNonZero(copylen - 6) - 1u;
54 return (uint16_t)((nbits << 1) + ((copylen - 6) >> nbits) + 4);
55 } else if (copylen < 2118) {
56 return (uint16_t)(Log2FloorNonZero(copylen - 70) + 12);
57 } else {
58 return 23u;
59 }
60 }
61
CombineLengthCodes(uint16_t inscode,uint16_t copycode,BROTLI_BOOL use_last_distance)62 static BROTLI_INLINE uint16_t CombineLengthCodes(
63 uint16_t inscode, uint16_t copycode, BROTLI_BOOL use_last_distance) {
64 uint16_t bits64 =
65 (uint16_t)((copycode & 0x7u) | ((inscode & 0x7u) << 3));
66 if (use_last_distance && inscode < 8 && copycode < 16) {
67 return (copycode < 8) ? bits64 : (bits64 | 64);
68 } else {
69 /* Specification: 5 Encoding of ... (last table) */
70 /* offset = 2 * index, where index is in range [0..8] */
71 int offset = 2 * ((copycode >> 3) + 3 * (inscode >> 3));
72 /* All values in specification are K * 64,
73 where K = [2, 3, 6, 4, 5, 8, 7, 9, 10],
74 i + 1 = [1, 2, 3, 4, 5, 6, 7, 8, 9],
75 K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1, 2] = D.
76 All values in D require only 2 bits to encode.
77 Magic constant is shifted 6 bits left, to avoid final multiplication. */
78 offset = (offset << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0);
79 return (uint16_t)offset | bits64;
80 }
81 }
82
GetLengthCode(size_t insertlen,size_t copylen,BROTLI_BOOL use_last_distance,uint16_t * code)83 static BROTLI_INLINE void GetLengthCode(size_t insertlen, size_t copylen,
84 BROTLI_BOOL use_last_distance,
85 uint16_t* code) {
86 uint16_t inscode = GetInsertLengthCode(insertlen);
87 uint16_t copycode = GetCopyLengthCode(copylen);
88 *code = CombineLengthCodes(inscode, copycode, use_last_distance);
89 }
90
GetInsertBase(uint16_t inscode)91 static BROTLI_INLINE uint32_t GetInsertBase(uint16_t inscode) {
92 return kInsBase[inscode];
93 }
94
GetInsertExtra(uint16_t inscode)95 static BROTLI_INLINE uint32_t GetInsertExtra(uint16_t inscode) {
96 return kInsExtra[inscode];
97 }
98
GetCopyBase(uint16_t copycode)99 static BROTLI_INLINE uint32_t GetCopyBase(uint16_t copycode) {
100 return kCopyBase[copycode];
101 }
102
GetCopyExtra(uint16_t copycode)103 static BROTLI_INLINE uint32_t GetCopyExtra(uint16_t copycode) {
104 return kCopyExtra[copycode];
105 }
106
107 typedef struct Command {
108 uint32_t insert_len_;
109 /* Stores copy_len in low 25 bits and copy_code - copy_len in high 7 bit. */
110 uint32_t copy_len_;
111 /* Stores distance extra bits. */
112 uint32_t dist_extra_;
113 uint16_t cmd_prefix_;
114 /* Stores distance code in low 10 bits
115 and number of extra bits in high 6 bits. */
116 uint16_t dist_prefix_;
117 } Command;
118
119 /* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */
InitCommand(Command * self,const BrotliDistanceParams * dist,size_t insertlen,size_t copylen,int copylen_code_delta,size_t distance_code)120 static BROTLI_INLINE void InitCommand(Command* self,
121 const BrotliDistanceParams* dist, size_t insertlen,
122 size_t copylen, int copylen_code_delta, size_t distance_code) {
123 /* Don't rely on signed int representation, use honest casts. */
124 uint32_t delta = (uint8_t)((int8_t)copylen_code_delta);
125 self->insert_len_ = (uint32_t)insertlen;
126 self->copy_len_ = (uint32_t)(copylen | (delta << 25));
127 /* The distance prefix and extra bits are stored in this Command as if
128 npostfix and ndirect were 0, they are only recomputed later after the
129 clustering if needed. */
130 PrefixEncodeCopyDistance(
131 distance_code, dist->num_direct_distance_codes,
132 dist->distance_postfix_bits, &self->dist_prefix_, &self->dist_extra_);
133 GetLengthCode(
134 insertlen, (size_t)((int)copylen + copylen_code_delta),
135 TO_BROTLI_BOOL((self->dist_prefix_ & 0x3FF) == 0), &self->cmd_prefix_);
136 }
137
InitInsertCommand(Command * self,size_t insertlen)138 static BROTLI_INLINE void InitInsertCommand(Command* self, size_t insertlen) {
139 self->insert_len_ = (uint32_t)insertlen;
140 self->copy_len_ = 4 << 25;
141 self->dist_extra_ = 0;
142 self->dist_prefix_ = BROTLI_NUM_DISTANCE_SHORT_CODES;
143 GetLengthCode(insertlen, 4, BROTLI_FALSE, &self->cmd_prefix_);
144 }
145
CommandRestoreDistanceCode(const Command * self,const BrotliDistanceParams * dist)146 static BROTLI_INLINE uint32_t CommandRestoreDistanceCode(
147 const Command* self, const BrotliDistanceParams* dist) {
148 if ((self->dist_prefix_ & 0x3FFu) <
149 BROTLI_NUM_DISTANCE_SHORT_CODES + dist->num_direct_distance_codes) {
150 return self->dist_prefix_ & 0x3FFu;
151 } else {
152 uint32_t dcode = self->dist_prefix_ & 0x3FFu;
153 uint32_t nbits = self->dist_prefix_ >> 10;
154 uint32_t extra = self->dist_extra_;
155 uint32_t postfix_mask = (1U << dist->distance_postfix_bits) - 1U;
156 uint32_t hcode = (dcode - dist->num_direct_distance_codes -
157 BROTLI_NUM_DISTANCE_SHORT_CODES) >>
158 dist->distance_postfix_bits;
159 uint32_t lcode = (dcode - dist->num_direct_distance_codes -
160 BROTLI_NUM_DISTANCE_SHORT_CODES) & postfix_mask;
161 uint32_t offset = ((2U + (hcode & 1U)) << nbits) - 4U;
162 return ((offset + extra) << dist->distance_postfix_bits) + lcode +
163 dist->num_direct_distance_codes + BROTLI_NUM_DISTANCE_SHORT_CODES;
164 }
165 }
166
CommandDistanceContext(const Command * self)167 static BROTLI_INLINE uint32_t CommandDistanceContext(const Command* self) {
168 uint32_t r = self->cmd_prefix_ >> 6;
169 uint32_t c = self->cmd_prefix_ & 7;
170 if ((r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2)) {
171 return c;
172 }
173 return 3;
174 }
175
CommandCopyLen(const Command * self)176 static BROTLI_INLINE uint32_t CommandCopyLen(const Command* self) {
177 return self->copy_len_ & 0x1FFFFFF;
178 }
179
CommandCopyLenCode(const Command * self)180 static BROTLI_INLINE uint32_t CommandCopyLenCode(const Command* self) {
181 uint32_t modifier = self->copy_len_ >> 25;
182 int32_t delta = (int8_t)((uint8_t)(modifier | ((modifier & 0x40) << 1)));
183 return (uint32_t)((int32_t)(self->copy_len_ & 0x1FFFFFF) + delta);
184 }
185
186 #if defined(__cplusplus) || defined(c_plusplus)
187 } /* extern "C" */
188 #endif
189
190 #endif /* BROTLI_ENC_COMMAND_H_ */
191