Added brotli enc/ and tools/ directories.

third_party/brotli/enc/prefix.h

+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+// Functions for encoding of integers into prefix codes the amount of extra
+// bits, and the actual values of the extra bits.
+
+#ifndef BROTLI_ENC_PREFIX_H_
+#define BROTLI_ENC_PREFIX_H_
+
+#include "./fast_log.h"
+#include "./types.h"
+
+namespace brotli {
+
+static const uint32_t kNumInsertLenPrefixes = 24;
+static const uint32_t kNumCopyLenPrefixes = 24;
+static const uint32_t kNumCommandPrefixes = 704;
+static const uint32_t kNumBlockLenPrefixes = 26;
+static const uint32_t kNumDistanceShortCodes = 16;
+static const uint32_t kNumDistancePrefixes = 520;
+
+// Represents the range of values belonging to a prefix code:
+// [offset, offset + 2^nbits)
+struct PrefixCodeRange {
+  uint32_t offset;
+  uint32_t nbits;
+};
+
+static const PrefixCodeRange kBlockLengthPrefixCode[kNumBlockLenPrefixes] = {
+  {   1,  2}, {    5,  2}, {  9,   2}, {  13,  2},
+  {  17,  3}, {   25,  3}, {  33,  3}, {  41,  3},
+  {  49,  4}, {   65,  4}, {  81,  4}, {  97,  4},
+  { 113,  5}, {  145,  5}, { 177,  5}, { 209,  5},
+  { 241,  6}, {  305,  6}, { 369,  7}, { 497,  8},
+  { 753,  9}, { 1265, 10}, {2289, 11}, {4337, 12},
+  {8433, 13}, {16625, 24}
+};
+
+inline void GetBlockLengthPrefixCode(uint32_t len, uint32_t* code,
+                                     uint32_t* n_extra, uint32_t* extra) {
+  *code = 0;
+  while (*code < 25 && len >= kBlockLengthPrefixCode[*code + 1].offset) {
+    ++(*code);
+  }
+  *n_extra = kBlockLengthPrefixCode[*code].nbits;
+  *extra = len - kBlockLengthPrefixCode[*code].offset;
+}
+
+inline void PrefixEncodeCopyDistance(size_t distance_code,
+                                     size_t num_direct_codes,
+                                     size_t postfix_bits,
+                                     uint16_t* code,
+                                     uint32_t* extra_bits) {
+  if (distance_code < kNumDistanceShortCodes + num_direct_codes) {
+    *code = static_cast<uint16_t>(distance_code);
+    *extra_bits = 0;
+    return;
+  }
+  distance_code -= kNumDistanceShortCodes + num_direct_codes;  /* >= 0 */
+  distance_code += (1u << (postfix_bits + 2u));  /* > 0 */
+  size_t bucket = Log2FloorNonZero(distance_code) - 1;
+  size_t postfix_mask = (1 << postfix_bits) - 1;
+  size_t postfix = distance_code & postfix_mask;
+  size_t prefix = (distance_code >> bucket) & 1;
+  size_t offset = (2 + prefix) << bucket;
+  size_t nbits = bucket - postfix_bits;
+  *code = static_cast<uint16_t>(
+      (kNumDistanceShortCodes + num_direct_codes +
+       ((2 * (nbits - 1) + prefix) << postfix_bits) + postfix));
+  *extra_bits = static_cast<uint32_t>(
+      (nbits << 24) | ((distance_code - offset) >> postfix_bits));
+}
+
+}  // namespace brotli
+
+#endif  // BROTLI_ENC_PREFIX_H_