• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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) << 3u));
66   if (use_last_distance && inscode < 8u && copycode < 16u) {
67     return (copycode < 8u) ? bits64 : (bits64 | 64u);
68   } else {
69     /* Specification: 5 Encoding of ... (last table) */
70     /* offset = 2 * index, where index is in range [0..8] */
71     uint32_t offset = 2u * ((copycode >> 3u) + 3u * (inscode >> 3u));
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 << 5u) + 0x40u + ((0x520D40u >> offset) & 0xC0u);
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