Update brotli to v1.0.0-snapshot.

third_party/brotli/enc/quality.h

+/* 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>
+
+#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_ENRTOPY_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
+
+/* Encoding parameters */
+typedef struct BrotliEncoderParams {
+  BrotliEncoderMode mode;
+  int quality;
+  int lgwin;
+  int lgblock;
+} 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 int ChooseHasher(const BrotliEncoderParams* params) {
+  if (params->quality > 9) {
+    return 10;
+  } else if (params->quality < 5) {
+    return params->quality;
+  } else if (params->lgwin <= 16) {
+    return params->quality < 7 ? 40 : params->quality < 9 ? 41 : 42;
+  }
+  return params->quality;
+}
+
+#endif  /* BROTLI_ENC_QUALITY_H_ */