Update brotli to v1.0.0-snapshot.

third_party/brotli/enc/histogram.c

 /* Copyright 2013 Google Inc. All Rights Reserved.
 
    Distributed under MIT license.
    See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
 */
 
-// Build per-context histograms of literals, commands and distance codes.
+/* Build per-context histograms of literals, commands and distance codes. */
 
 #include "./histogram.h"
 
-#include <cmath>
-
 #include "./block_splitter.h"
 #include "./command.h"
 #include "./context.h"
-#include "./prefix.h"
 
-namespace brotli {
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
 
-void BuildHistograms(
-    const Command* cmds,
-    const size_t num_commands,
-    const BlockSplit& literal_split,
-    const BlockSplit& insert_and_copy_split,
-    const BlockSplit& dist_split,
-    const uint8_t* ringbuffer,
-    size_t start_pos,
-    size_t mask,
-    uint8_t prev_byte,
-    uint8_t prev_byte2,
-    const std::vector<ContextType>& context_modes,
-    std::vector<HistogramLiteral>* literal_histograms,
-    std::vector<HistogramCommand>* insert_and_copy_histograms,
-    std::vector<HistogramDistance>* copy_dist_histograms) {
+typedef struct BlockSplitIterator {
+  const BlockSplit* split_;  /* Not owned. */
+  size_t idx_;
+  size_t type_;
+  size_t length_;
+} BlockSplitIterator;
+
+static void InitBlockSplitIterator(BlockSplitIterator* self,
+    const BlockSplit* split) {
+  self->split_ = split;
+  self->idx_ = 0;
+  self->type_ = 0;
+  self->length_ = split->lengths ? split->lengths[0] : 0;
+}
+
+static void BlockSplitIteratorNext(BlockSplitIterator* self) {
+  if (self->length_ == 0) {
+    ++self->idx_;
+    self->type_ = self->split_->types[self->idx_];
+    self->length_ = self->split_->lengths[self->idx_];
+  }
+  --self->length_;
+}
+
+void BrotliBuildHistogramsWithContext(
+    const Command* cmds, const size_t num_commands,
+    const BlockSplit* literal_split, const BlockSplit* insert_and_copy_split,
+    const BlockSplit* dist_split, const uint8_t* ringbuffer, size_t start_pos,
+    size_t mask, uint8_t prev_byte, uint8_t prev_byte2,
+    const ContextType* context_modes, HistogramLiteral* literal_histograms,
+    HistogramCommand* insert_and_copy_histograms,
+    HistogramDistance* copy_dist_histograms) {
   size_t pos = start_pos;
-  BlockSplitIterator literal_it(literal_split);
-  BlockSplitIterator insert_and_copy_it(insert_and_copy_split);
-  BlockSplitIterator dist_it(dist_split);
-  for (size_t i = 0; i < num_commands; ++i) {
-    const Command &cmd = cmds[i];
-    insert_and_copy_it.Next();
-    (*insert_and_copy_histograms)[insert_and_copy_it.type_].Add(
-        cmd.cmd_prefix_);
-    for (size_t j = cmd.insert_len_; j != 0; --j) {
-      literal_it.Next();
-      size_t context = (literal_it.type_ << kLiteralContextBits) +
+  BlockSplitIterator literal_it;
+  BlockSplitIterator insert_and_copy_it;
+  BlockSplitIterator dist_it;
+  size_t i;
+
+  InitBlockSplitIterator(&literal_it, literal_split);
+  InitBlockSplitIterator(&insert_and_copy_it, insert_and_copy_split);
+  InitBlockSplitIterator(&dist_it, dist_split);
+  for (i = 0; i < num_commands; ++i) {
+    const Command* cmd = &cmds[i];
+    size_t j;
+    BlockSplitIteratorNext(&insert_and_copy_it);
+    HistogramAddCommand(&insert_and_copy_histograms[insert_and_copy_it.type_],
+        cmd->cmd_prefix_);
+    for (j = cmd->insert_len_; j != 0; --j) {
+      size_t context;
+      BlockSplitIteratorNext(&literal_it);
+      context = (literal_it.type_ << BROTLI_LITERAL_CONTEXT_BITS) +
           Context(prev_byte, prev_byte2, context_modes[literal_it.type_]);
-      (*literal_histograms)[context].Add(ringbuffer[pos & mask]);
+      HistogramAddLiteral(&literal_histograms[context],
+          ringbuffer[pos & mask]);
       prev_byte2 = prev_byte;
       prev_byte = ringbuffer[pos & mask];
       ++pos;
     }
-    pos += cmd.copy_len();
-    if (cmd.copy_len()) {
+    pos += CommandCopyLen(cmd);
+    if (CommandCopyLen(cmd)) {
       prev_byte2 = ringbuffer[(pos - 2) & mask];
       prev_byte = ringbuffer[(pos - 1) & mask];
-      if (cmd.cmd_prefix_ >= 128) {
-        dist_it.Next();
-        size_t context = (dist_it.type_ << kDistanceContextBits) +
-            cmd.DistanceContext();
-        (*copy_dist_histograms)[context].Add(cmd.dist_prefix_);
+      if (cmd->cmd_prefix_ >= 128) {
+        size_t context;
+        BlockSplitIteratorNext(&dist_it);
+        context = (dist_it.type_ << BROTLI_DISTANCE_CONTEXT_BITS) +
+            CommandDistanceContext(cmd);
+        HistogramAddDistance(&copy_dist_histograms[context],
+            cmd->dist_prefix_);
       }
     }
   }
 }
 
-}  // namespace brotli
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif