diff options
Diffstat (limited to 'web/server/h2o/libh2o/deps/brotli/enc/literal_cost.cc')
-rw-r--r-- | web/server/h2o/libh2o/deps/brotli/enc/literal_cost.cc | 165 |
1 files changed, 0 insertions, 165 deletions
diff --git a/web/server/h2o/libh2o/deps/brotli/enc/literal_cost.cc b/web/server/h2o/libh2o/deps/brotli/enc/literal_cost.cc deleted file mode 100644 index e13eedc9d..000000000 --- a/web/server/h2o/libh2o/deps/brotli/enc/literal_cost.cc +++ /dev/null @@ -1,165 +0,0 @@ -/* Copyright 2013 Google Inc. All Rights Reserved. - - Distributed under MIT license. - See file LICENSE for detail or copy at https://opensource.org/licenses/MIT -*/ - -// Literal cost model to allow backward reference replacement to be efficient. - -#include "./literal_cost.h" - -#include <math.h> -#include <algorithm> - -#include "./fast_log.h" -#include "./types.h" -#include "./utf8_util.h" - -namespace brotli { - -static size_t UTF8Position(size_t last, size_t c, size_t clamp) { - if (c < 128) { - return 0; // Next one is the 'Byte 1' again. - } else if (c >= 192) { // Next one is the 'Byte 2' of utf-8 encoding. - return std::min<size_t>(1, clamp); - } else { - // Let's decide over the last byte if this ends the sequence. - if (last < 0xe0) { - return 0; // Completed two or three byte coding. - } else { // Next one is the 'Byte 3' of utf-8 encoding. - return std::min<size_t>(2, clamp); - } - } -} - -static size_t DecideMultiByteStatsLevel(size_t pos, size_t len, size_t mask, - const uint8_t *data) { - size_t counts[3] = { 0 }; - size_t max_utf8 = 1; // should be 2, but 1 compresses better. - size_t last_c = 0; - size_t utf8_pos = 0; - for (size_t i = 0; i < len; ++i) { - size_t c = data[(pos + i) & mask]; - utf8_pos = UTF8Position(last_c, c, 2); - ++counts[utf8_pos]; - last_c = c; - } - if (counts[2] < 500) { - max_utf8 = 1; - } - if (counts[1] + counts[2] < 25) { - max_utf8 = 0; - } - return max_utf8; -} - -void EstimateBitCostsForLiteralsUTF8(size_t pos, size_t len, size_t mask, - const uint8_t *data, float *cost) { - - // max_utf8 is 0 (normal ascii single byte modeling), - // 1 (for 2-byte utf-8 modeling), or 2 (for 3-byte utf-8 modeling). - const size_t max_utf8 = DecideMultiByteStatsLevel(pos, len, mask, data); - size_t histogram[3][256] = { { 0 } }; - size_t window_half = 495; - size_t in_window = std::min(window_half, len); - size_t in_window_utf8[3] = { 0 }; - - // Bootstrap histograms. - size_t last_c = 0; - size_t utf8_pos = 0; - for (size_t i = 0; i < in_window; ++i) { - size_t c = data[(pos + i) & mask]; - ++histogram[utf8_pos][c]; - ++in_window_utf8[utf8_pos]; - utf8_pos = UTF8Position(last_c, c, max_utf8); - last_c = c; - } - - // Compute bit costs with sliding window. - for (size_t i = 0; i < len; ++i) { - if (i >= window_half) { - // Remove a byte in the past. - size_t c = i < window_half + 1 ? - 0 : data[(pos + i - window_half - 1) & mask]; - size_t last_c = i < window_half + 2 ? - 0 : data[(pos + i - window_half - 2) & mask]; - size_t utf8_pos2 = UTF8Position(last_c, c, max_utf8); - --histogram[utf8_pos2][data[(pos + i - window_half) & mask]]; - --in_window_utf8[utf8_pos2]; - } - if (i + window_half < len) { - // Add a byte in the future. - size_t c = data[(pos + i + window_half - 1) & mask]; - size_t last_c = data[(pos + i + window_half - 2) & mask]; - size_t utf8_pos2 = UTF8Position(last_c, c, max_utf8); - ++histogram[utf8_pos2][data[(pos + i + window_half) & mask]]; - ++in_window_utf8[utf8_pos2]; - } - size_t c = i < 1 ? 0 : data[(pos + i - 1) & mask]; - size_t last_c = i < 2 ? 0 : data[(pos + i - 2) & mask]; - size_t utf8_pos = UTF8Position(last_c, c, max_utf8); - size_t masked_pos = (pos + i) & mask; - size_t histo = histogram[utf8_pos][data[masked_pos]]; - if (histo == 0) { - histo = 1; - } - double lit_cost = FastLog2(in_window_utf8[utf8_pos]) - FastLog2(histo); - lit_cost += 0.02905; - if (lit_cost < 1.0) { - lit_cost *= 0.5; - lit_cost += 0.5; - } - // Make the first bytes more expensive -- seems to help, not sure why. - // Perhaps because the entropy source is changing its properties - // rapidly in the beginning of the file, perhaps because the beginning - // of the data is a statistical "anomaly". - if (i < 2000) { - lit_cost += 0.7 - (static_cast<double>(2000 - i) / 2000.0 * 0.35); - } - cost[i] = static_cast<float>(lit_cost); - } -} - -void EstimateBitCostsForLiterals(size_t pos, size_t len, size_t mask, - const uint8_t *data, float *cost) { - if (IsMostlyUTF8(data, pos, mask, len, kMinUTF8Ratio)) { - EstimateBitCostsForLiteralsUTF8(pos, len, mask, data, cost); - return; - } - size_t histogram[256] = { 0 }; - size_t window_half = 2000; - size_t in_window = std::min(window_half, len); - - // Bootstrap histogram. - for (size_t i = 0; i < in_window; ++i) { - ++histogram[data[(pos + i) & mask]]; - } - - // Compute bit costs with sliding window. - for (size_t i = 0; i < len; ++i) { - if (i >= window_half) { - // Remove a byte in the past. - --histogram[data[(pos + i - window_half) & mask]]; - --in_window; - } - if (i + window_half < len) { - // Add a byte in the future. - ++histogram[data[(pos + i + window_half) & mask]]; - ++in_window; - } - size_t histo = histogram[data[(pos + i) & mask]]; - if (histo == 0) { - histo = 1; - } - double lit_cost = FastLog2(in_window) - FastLog2(histo); - lit_cost += 0.029; - if (lit_cost < 1.0) { - lit_cost *= 0.5; - lit_cost += 0.5; - } - cost[i] = static_cast<float>(lit_cost); - } -} - - -} // namespace brotli |