/src/h2o/deps/brotli/c/enc/quality.h

Source (jump to first uncovered line)
/* Copyright 2016 Google Inc. All Rights Reserved.

   Distributed under MIT license.
   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/

/* Constants and formulas that affect speed-ratio trade-offs and thus define
   quality levels. */

#ifndef BROTLI_ENC_QUALITY_H_
#define BROTLI_ENC_QUALITY_H_

#include <brotli/encode.h>
#include "./port.h"

#define FAST_ONE_PASS_COMPRESSION_QUALITY 0
#define FAST_TWO_PASS_COMPRESSION_QUALITY 1
#define ZOPFLIFICATION_QUALITY 10
#define HQ_ZOPFLIFICATION_QUALITY 11

#define MAX_QUALITY_FOR_STATIC_ENTROPY_CODES 2
#define MIN_QUALITY_FOR_BLOCK_SPLIT 4
#define MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS 4
#define MIN_QUALITY_FOR_EXTENSIVE_REFERENCE_SEARCH 5
#define MIN_QUALITY_FOR_CONTEXT_MODELING 5
#define MIN_QUALITY_FOR_HQ_CONTEXT_MODELING 7
#define MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING 10
/* Only for "font" mode. */
#define MIN_QUALITY_FOR_RECOMPUTE_DISTANCE_PREFIXES 10

/* For quality below MIN_QUALITY_FOR_BLOCK_SPLIT there is no block splitting,
   so we buffer at most this much literals and commands. */
#define MAX_NUM_DELAYED_SYMBOLS 0x2fff

typedef struct BrotliHasherParams {
  int type;
  int bucket_bits;
  int block_bits;
  int hash_len;
  int num_last_distances_to_check;
} BrotliHasherParams;

/* Encoding parameters */
typedef struct BrotliEncoderParams {
  BrotliEncoderMode mode;
  int quality;
  int lgwin;
  int lgblock;
  size_t size_hint;
  BROTLI_BOOL disable_literal_context_modeling;
  BrotliHasherParams hasher;
} BrotliEncoderParams;

/* Returns hash-table size for quality levels 0 and 1. */
static BROTLI_INLINE size_t MaxHashTableSize(int quality) {
  return quality == FAST_ONE_PASS_COMPRESSION_QUALITY ? 1 << 15 : 1 << 17;
}

/* The maximum length for which the zopflification uses distinct distances. */
#define MAX_ZOPFLI_LEN_QUALITY_10 150
#define MAX_ZOPFLI_LEN_QUALITY_11 325

/* Do not thoroughly search when a long copy is found. */
#define BROTLI_LONG_COPY_QUICK_STEP 16384

static BROTLI_INLINE size_t MaxZopfliLen(const BrotliEncoderParams* params) {
  return params->quality <= 10 ?
      MAX_ZOPFLI_LEN_QUALITY_10 :
      MAX_ZOPFLI_LEN_QUALITY_11;
}

/* Number of best candidates to evaluate to expand Zopfli chain. */
static BROTLI_INLINE size_t MaxZopfliCandidates(
  const BrotliEncoderParams* params) {
  return params->quality <= 10 ? 1 : 5;
}

static BROTLI_INLINE void SanitizeParams(BrotliEncoderParams* params) {
  params->quality = BROTLI_MIN(int, BROTLI_MAX_QUALITY,
      BROTLI_MAX(int, BROTLI_MIN_QUALITY, params->quality));
  if (params->lgwin < BROTLI_MIN_WINDOW_BITS) {
    params->lgwin = BROTLI_MIN_WINDOW_BITS;
  } else if (params->lgwin > BROTLI_MAX_WINDOW_BITS) {
    params->lgwin = BROTLI_MAX_WINDOW_BITS;
  }
}

/* Returns optimized lg_block value. */
static BROTLI_INLINE int ComputeLgBlock(const BrotliEncoderParams* params) {
  int lgblock = params->lgblock;
  if (params->quality == FAST_ONE_PASS_COMPRESSION_QUALITY ||
      params->quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
    lgblock = params->lgwin;
  } else if (params->quality < MIN_QUALITY_FOR_BLOCK_SPLIT) {
    lgblock = 14;
  } else if (lgblock == 0) {
    lgblock = 16;
    if (params->quality >= 9 && params->lgwin > lgblock) {
      lgblock = BROTLI_MIN(int, 18, params->lgwin);
    }
  } else {
    lgblock = BROTLI_MIN(int, BROTLI_MAX_INPUT_BLOCK_BITS,
        BROTLI_MAX(int, BROTLI_MIN_INPUT_BLOCK_BITS, lgblock));
  }
  return lgblock;
}

/* Returns log2 of the size of main ring buffer area.
   Allocate at least lgwin + 1 bits for the ring buffer so that the newly
   added block fits there completely and we still get lgwin bits and at least
   read_block_size_bits + 1 bits because the copy tail length needs to be
   smaller than ring-buffer size. */
static BROTLI_INLINE int ComputeRbBits(const BrotliEncoderParams* params) {
  return 1 + BROTLI_MAX(int, params->lgwin, params->lgblock);
}

static BROTLI_INLINE size_t MaxMetablockSize(
    const BrotliEncoderParams* params) {
  int bits =
      BROTLI_MIN(int, ComputeRbBits(params), BROTLI_MAX_INPUT_BLOCK_BITS);
  return (size_t)1 << bits;
}

/* When searching for backward references and have not seen matches for a long
   time, we can skip some match lookups. Unsuccessful match lookups are very
   expensive and this kind of a heuristic speeds up compression quite a lot.
   At first 8 byte strides are taken and every second byte is put to hasher.
   After 4x more literals stride by 16 bytes, every put 4-th byte to hasher.
   Applied only to qualities 2 to 9. */
static BROTLI_INLINE size_t LiteralSpreeLengthForSparseSearch(
    const BrotliEncoderParams* params) {
  return params->quality < 9 ? 64 : 512;
}

static BROTLI_INLINE void ChooseHasher(const BrotliEncoderParams* params,
                                       BrotliHasherParams* hparams) {
  if (params->quality > 9) {
    hparams->type = 10;
  } else if (params->quality == 4 && params->size_hint >= (1 << 20)) {
    hparams->type = 54;
  } else if (params->quality < 5) {
    hparams->type = params->quality;
  } else if (params->lgwin <= 16) {
    hparams->type = params->quality < 7 ? 40 : params->quality < 9 ? 41 : 42;
  } else if (params->size_hint >= (1 << 20) && params->lgwin >= 19) {
    hparams->type = 6;
    hparams->block_bits = params->quality - 1;
    hparams->bucket_bits = 15;
    hparams->hash_len = 5;
    hparams->num_last_distances_to_check =
        params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
  } else {
    hparams->type = 5;
    hparams->block_bits = params->quality - 1;
    hparams->bucket_bits = params->quality < 7 ? 14 : 15;
    hparams->num_last_distances_to_check =
        params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
  }
}

#endif  /* BROTLI_ENC_QUALITY_H_ */

Coverage Report

Created: 2025-07-11 06:26

Line	Count	Source (jump to first uncovered line)
1		/* Copyright 2016 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		/* Constants and formulas that affect speed-ratio trade-offs and thus define
8		quality levels. */
9
10		#ifndef BROTLI_ENC_QUALITY_H_
11		#define BROTLI_ENC_QUALITY_H_
12
13		#include <brotli/encode.h>
14		#include "./port.h"
15
16	0	#define FAST_ONE_PASS_COMPRESSION_QUALITY 0
17	0	#define FAST_TWO_PASS_COMPRESSION_QUALITY 1
18	0	#define ZOPFLIFICATION_QUALITY 10
19	0	#define HQ_ZOPFLIFICATION_QUALITY 11
20
21	0	#define MAX_QUALITY_FOR_STATIC_ENTROPY_CODES 2
22	0	#define MIN_QUALITY_FOR_BLOCK_SPLIT 4
23	0	#define MIN_QUALITY_FOR_OPTIMIZE_HISTOGRAMS 4
24	0	#define MIN_QUALITY_FOR_EXTENSIVE_REFERENCE_SEARCH 5
25	0	#define MIN_QUALITY_FOR_CONTEXT_MODELING 5
26	0	#define MIN_QUALITY_FOR_HQ_CONTEXT_MODELING 7
27	0	#define MIN_QUALITY_FOR_HQ_BLOCK_SPLITTING 10
28		/* Only for "font" mode. */
29	0	#define MIN_QUALITY_FOR_RECOMPUTE_DISTANCE_PREFIXES 10
30
31		/* For quality below MIN_QUALITY_FOR_BLOCK_SPLIT there is no block splitting,
32		so we buffer at most this much literals and commands. */
33		#define MAX_NUM_DELAYED_SYMBOLS 0x2fff
34
35		typedef struct BrotliHasherParams {
36		int type;
37		int bucket_bits;
38		int block_bits;
39		int hash_len;
40		int num_last_distances_to_check;
41		} BrotliHasherParams;
42
43		/* Encoding parameters */
44		typedef struct BrotliEncoderParams {
45		BrotliEncoderMode mode;
46		int quality;
47		int lgwin;
48		int lgblock;
49		size_t size_hint;
50		BROTLI_BOOL disable_literal_context_modeling;
51		BrotliHasherParams hasher;
52		} BrotliEncoderParams;
53
54		/* Returns hash-table size for quality levels 0 and 1. */
55	0	static BROTLI_INLINE size_t MaxHashTableSize(int quality) {
56	0	return quality == FAST_ONE_PASS_COMPRESSION_QUALITY ? 1 << 15 : 1 << 17;
57	0	} Unexecuted instantiation: backward_references.c:MaxHashTableSize Unexecuted instantiation: backward_references_hq.c:MaxHashTableSize Unexecuted instantiation: bit_cost.c:MaxHashTableSize Unexecuted instantiation: block_splitter.c:MaxHashTableSize Unexecuted instantiation: brotli_bit_stream.c:MaxHashTableSize Unexecuted instantiation: cluster.c:MaxHashTableSize Unexecuted instantiation: compress_fragment.c:MaxHashTableSize Unexecuted instantiation: compress_fragment_two_pass.c:MaxHashTableSize Unexecuted instantiation: encode.c:MaxHashTableSize Unexecuted instantiation: histogram.c:MaxHashTableSize Unexecuted instantiation: metablock.c:MaxHashTableSize
58
59		/* The maximum length for which the zopflification uses distinct distances. */
60	0	#define MAX_ZOPFLI_LEN_QUALITY_10 150
61	0	#define MAX_ZOPFLI_LEN_QUALITY_11 325
62
63		/* Do not thoroughly search when a long copy is found. */
64	0	#define BROTLI_LONG_COPY_QUICK_STEP 16384
65
66	0	static BROTLI_INLINE size_t MaxZopfliLen(const BrotliEncoderParams* params) {
67	0	return params->quality <= 10 ?
68	0	MAX_ZOPFLI_LEN_QUALITY_10 :
69	0	MAX_ZOPFLI_LEN_QUALITY_11;
70	0	} Unexecuted instantiation: backward_references.c:MaxZopfliLen Unexecuted instantiation: backward_references_hq.c:MaxZopfliLen Unexecuted instantiation: bit_cost.c:MaxZopfliLen Unexecuted instantiation: block_splitter.c:MaxZopfliLen Unexecuted instantiation: brotli_bit_stream.c:MaxZopfliLen Unexecuted instantiation: cluster.c:MaxZopfliLen Unexecuted instantiation: compress_fragment.c:MaxZopfliLen Unexecuted instantiation: compress_fragment_two_pass.c:MaxZopfliLen Unexecuted instantiation: encode.c:MaxZopfliLen Unexecuted instantiation: histogram.c:MaxZopfliLen Unexecuted instantiation: metablock.c:MaxZopfliLen
71
72		/* Number of best candidates to evaluate to expand Zopfli chain. */
73		static BROTLI_INLINE size_t MaxZopfliCandidates(
74	0	const BrotliEncoderParams* params) {
75	0	return params->quality <= 10 ? 1 : 5;
76	0	} Unexecuted instantiation: backward_references.c:MaxZopfliCandidates Unexecuted instantiation: backward_references_hq.c:MaxZopfliCandidates Unexecuted instantiation: bit_cost.c:MaxZopfliCandidates Unexecuted instantiation: block_splitter.c:MaxZopfliCandidates Unexecuted instantiation: brotli_bit_stream.c:MaxZopfliCandidates Unexecuted instantiation: cluster.c:MaxZopfliCandidates Unexecuted instantiation: compress_fragment.c:MaxZopfliCandidates Unexecuted instantiation: compress_fragment_two_pass.c:MaxZopfliCandidates Unexecuted instantiation: encode.c:MaxZopfliCandidates Unexecuted instantiation: histogram.c:MaxZopfliCandidates Unexecuted instantiation: metablock.c:MaxZopfliCandidates
77
78	0	static BROTLI_INLINE void SanitizeParams(BrotliEncoderParams* params) {
79	0	params->quality = BROTLI_MIN(int, BROTLI_MAX_QUALITY,
80	0	BROTLI_MAX(int, BROTLI_MIN_QUALITY, params->quality));
81	0	if (params->lgwin < BROTLI_MIN_WINDOW_BITS) {
82	0	params->lgwin = BROTLI_MIN_WINDOW_BITS;
83	0	} else if (params->lgwin > BROTLI_MAX_WINDOW_BITS) {
84	0	params->lgwin = BROTLI_MAX_WINDOW_BITS;
85	0	}
86	0	} Unexecuted instantiation: backward_references.c:SanitizeParams Unexecuted instantiation: backward_references_hq.c:SanitizeParams Unexecuted instantiation: bit_cost.c:SanitizeParams Unexecuted instantiation: block_splitter.c:SanitizeParams Unexecuted instantiation: brotli_bit_stream.c:SanitizeParams Unexecuted instantiation: cluster.c:SanitizeParams Unexecuted instantiation: compress_fragment.c:SanitizeParams Unexecuted instantiation: compress_fragment_two_pass.c:SanitizeParams Unexecuted instantiation: encode.c:SanitizeParams Unexecuted instantiation: histogram.c:SanitizeParams Unexecuted instantiation: metablock.c:SanitizeParams
87
88		/* Returns optimized lg_block value. */
89	0	static BROTLI_INLINE int ComputeLgBlock(const BrotliEncoderParams* params) {
90	0	int lgblock = params->lgblock;
91	0	if (params->quality == FAST_ONE_PASS_COMPRESSION_QUALITY \|\|
92	0	params->quality == FAST_TWO_PASS_COMPRESSION_QUALITY) {
93	0	lgblock = params->lgwin;
94	0	} else if (params->quality < MIN_QUALITY_FOR_BLOCK_SPLIT) {
95	0	lgblock = 14;
96	0	} else if (lgblock == 0) {
97	0	lgblock = 16;
98	0	if (params->quality >= 9 && params->lgwin > lgblock) {
99	0	lgblock = BROTLI_MIN(int, 18, params->lgwin);
100	0	}
101	0	} else {
102	0	lgblock = BROTLI_MIN(int, BROTLI_MAX_INPUT_BLOCK_BITS,
103	0	BROTLI_MAX(int, BROTLI_MIN_INPUT_BLOCK_BITS, lgblock));
104	0	}
105	0	return lgblock;
106	0	} Unexecuted instantiation: backward_references.c:ComputeLgBlock Unexecuted instantiation: backward_references_hq.c:ComputeLgBlock Unexecuted instantiation: bit_cost.c:ComputeLgBlock Unexecuted instantiation: block_splitter.c:ComputeLgBlock Unexecuted instantiation: brotli_bit_stream.c:ComputeLgBlock Unexecuted instantiation: cluster.c:ComputeLgBlock Unexecuted instantiation: compress_fragment.c:ComputeLgBlock Unexecuted instantiation: compress_fragment_two_pass.c:ComputeLgBlock Unexecuted instantiation: encode.c:ComputeLgBlock Unexecuted instantiation: histogram.c:ComputeLgBlock Unexecuted instantiation: metablock.c:ComputeLgBlock
107
108		/* Returns log2 of the size of main ring buffer area.
109		Allocate at least lgwin + 1 bits for the ring buffer so that the newly
110		added block fits there completely and we still get lgwin bits and at least
111		read_block_size_bits + 1 bits because the copy tail length needs to be
112		smaller than ring-buffer size. */
113	0	static BROTLI_INLINE int ComputeRbBits(const BrotliEncoderParams* params) {
114	0	return 1 + BROTLI_MAX(int, params->lgwin, params->lgblock);
115	0	} Unexecuted instantiation: backward_references.c:ComputeRbBits Unexecuted instantiation: backward_references_hq.c:ComputeRbBits Unexecuted instantiation: bit_cost.c:ComputeRbBits Unexecuted instantiation: block_splitter.c:ComputeRbBits Unexecuted instantiation: brotli_bit_stream.c:ComputeRbBits Unexecuted instantiation: cluster.c:ComputeRbBits Unexecuted instantiation: compress_fragment.c:ComputeRbBits Unexecuted instantiation: compress_fragment_two_pass.c:ComputeRbBits Unexecuted instantiation: encode.c:ComputeRbBits Unexecuted instantiation: histogram.c:ComputeRbBits Unexecuted instantiation: metablock.c:ComputeRbBits
116
117		static BROTLI_INLINE size_t MaxMetablockSize(
118	0	const BrotliEncoderParams* params) {
119	0	int bits =
120	0	BROTLI_MIN(int, ComputeRbBits(params), BROTLI_MAX_INPUT_BLOCK_BITS);
121	0	return (size_t)1 << bits;
122	0	} Unexecuted instantiation: backward_references.c:MaxMetablockSize Unexecuted instantiation: backward_references_hq.c:MaxMetablockSize Unexecuted instantiation: bit_cost.c:MaxMetablockSize Unexecuted instantiation: block_splitter.c:MaxMetablockSize Unexecuted instantiation: brotli_bit_stream.c:MaxMetablockSize Unexecuted instantiation: cluster.c:MaxMetablockSize Unexecuted instantiation: compress_fragment.c:MaxMetablockSize Unexecuted instantiation: compress_fragment_two_pass.c:MaxMetablockSize Unexecuted instantiation: encode.c:MaxMetablockSize Unexecuted instantiation: histogram.c:MaxMetablockSize Unexecuted instantiation: metablock.c:MaxMetablockSize
123
124		/* When searching for backward references and have not seen matches for a long
125		time, we can skip some match lookups. Unsuccessful match lookups are very
126		expensive and this kind of a heuristic speeds up compression quite a lot.
127		At first 8 byte strides are taken and every second byte is put to hasher.
128		After 4x more literals stride by 16 bytes, every put 4-th byte to hasher.
129		Applied only to qualities 2 to 9. */
130		static BROTLI_INLINE size_t LiteralSpreeLengthForSparseSearch(
131	0	const BrotliEncoderParams* params) {
132	0	return params->quality < 9 ? 64 : 512;
133	0	} Unexecuted instantiation: backward_references.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: backward_references_hq.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: bit_cost.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: block_splitter.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: brotli_bit_stream.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: cluster.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: compress_fragment.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: compress_fragment_two_pass.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: encode.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: histogram.c:LiteralSpreeLengthForSparseSearch Unexecuted instantiation: metablock.c:LiteralSpreeLengthForSparseSearch
134
135		static BROTLI_INLINE void ChooseHasher(const BrotliEncoderParams* params,
136	0	BrotliHasherParams* hparams) {
137	0	if (params->quality > 9) {
138	0	hparams->type = 10;
139	0	} else if (params->quality == 4 && params->size_hint >= (1 << 20)) {
140	0	hparams->type = 54;
141	0	} else if (params->quality < 5) {
142	0	hparams->type = params->quality;
143	0	} else if (params->lgwin <= 16) {
144	0	hparams->type = params->quality < 7 ? 40 : params->quality < 9 ? 41 : 42;
145	0	} else if (params->size_hint >= (1 << 20) && params->lgwin >= 19) {
146	0	hparams->type = 6;
147	0	hparams->block_bits = params->quality - 1;
148	0	hparams->bucket_bits = 15;
149	0	hparams->hash_len = 5;
150	0	hparams->num_last_distances_to_check =
151	0	params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
152	0	} else {
153	0	hparams->type = 5;
154	0	hparams->block_bits = params->quality - 1;
155	0	hparams->bucket_bits = params->quality < 7 ? 14 : 15;
156	0	hparams->num_last_distances_to_check =
157	0	params->quality < 7 ? 4 : params->quality < 9 ? 10 : 16;
158	0	}
159	0	} Unexecuted instantiation: backward_references.c:ChooseHasher Unexecuted instantiation: backward_references_hq.c:ChooseHasher Unexecuted instantiation: bit_cost.c:ChooseHasher Unexecuted instantiation: block_splitter.c:ChooseHasher Unexecuted instantiation: brotli_bit_stream.c:ChooseHasher Unexecuted instantiation: cluster.c:ChooseHasher Unexecuted instantiation: compress_fragment.c:ChooseHasher Unexecuted instantiation: compress_fragment_two_pass.c:ChooseHasher Unexecuted instantiation: encode.c:ChooseHasher Unexecuted instantiation: histogram.c:ChooseHasher Unexecuted instantiation: metablock.c:ChooseHasher
160
161		#endif /* BROTLI_ENC_QUALITY_H_ */