Add libwebp 0.6.0 to the tree

1 files changed, 223 insertions, 0 deletions

diff --git a/media/libwebp/utils/huffman_utils.c b/media/libwebp/utils/huffman_utils.c
new file mode 100644
index 000000000..008b5d746
--- /dev/null
+++ b/media/libwebp/utils/huffman_utils.c
@@ -0,0 +1,223 @@
+// Copyright 2012 Google Inc. All Rights Reserved.
+//
+// Use of this source code is governed by a BSD-style license
+// that can be found in the COPYING file in the root of the source
+// tree. An additional intellectual property rights grant can be found
+// in the file PATENTS. All contributing project authors may
+// be found in the AUTHORS file in the root of the source tree.
+// -----------------------------------------------------------------------------
+//
+// Utilities for building and looking up Huffman trees.
+//
+// Author: Urvang Joshi (urvang@google.com)
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include "./huffman_utils.h"
+#include "./utils.h"
+#include "../webp/format_constants.h"
+
+// Huffman data read via DecodeImageStream is represented in two (red and green)
+// bytes.
+#define MAX_HTREE_GROUPS    0x10000
+
+HTreeGroup* VP8LHtreeGroupsNew(int num_htree_groups) {
+  HTreeGroup* const htree_groups =
+      (HTreeGroup*)WebPSafeMalloc(num_htree_groups, sizeof(*htree_groups));
+  if (htree_groups == NULL) {
+    return NULL;
+  }
+  assert(num_htree_groups <= MAX_HTREE_GROUPS);
+  return htree_groups;
+}
+
+void VP8LHtreeGroupsFree(HTreeGroup* const htree_groups) {
+  if (htree_groups != NULL) {
+    WebPSafeFree(htree_groups);
+  }
+}
+
+// Returns reverse(reverse(key, len) + 1, len), where reverse(key, len) is the
+// bit-wise reversal of the len least significant bits of key.
+static WEBP_INLINE uint32_t GetNextKey(uint32_t key, int len) {
+  uint32_t step = 1 << (len - 1);
+  while (key & step) {
+    step >>= 1;
+  }
+  return step ? (key & (step - 1)) + step : key;
+}
+
+// Stores code in table[0], table[step], table[2*step], ..., table[end].
+// Assumes that end is an integer multiple of step.
+static WEBP_INLINE void ReplicateValue(HuffmanCode* table,
+                                       int step, int end,
+                                       HuffmanCode code) {
+  assert(end % step == 0);
+  do {
+    end -= step;
+    table[end] = code;
+  } while (end > 0);
+}
+
+// Returns the table width of the next 2nd level table. count is the histogram
+// of bit lengths for the remaining symbols, len is the code length of the next
+// processed symbol
+static WEBP_INLINE int NextTableBitSize(const int* const count,
+                                        int len, int root_bits) {
+  int left = 1 << (len - root_bits);
+  while (len < MAX_ALLOWED_CODE_LENGTH) {
+    left -= count[len];
+    if (left <= 0) break;
+    ++len;
+    left <<= 1;
+  }
+  return len - root_bits;
+}
+
+// sorted[code_lengths_size] is a pre-allocated array for sorting symbols
+// by code length.
+static int BuildHuffmanTable(HuffmanCode* const root_table, int root_bits,
+                             const int code_lengths[], int code_lengths_size,
+                             uint16_t sorted[]) {
+  HuffmanCode* table = root_table;  // next available space in table
+  int total_size = 1 << root_bits;  // total size root table + 2nd level table
+  int len;                          // current code length
+  int symbol;                       // symbol index in original or sorted table
+  // number of codes of each length:
+  int count[MAX_ALLOWED_CODE_LENGTH + 1] = { 0 };
+  // offsets in sorted table for each length:
+  int offset[MAX_ALLOWED_CODE_LENGTH + 1];
+
+  assert(code_lengths_size != 0);
+  assert(code_lengths != NULL);
+  assert(root_table != NULL);
+  assert(root_bits > 0);
+
+  // Build histogram of code lengths.
+  for (symbol = 0; symbol < code_lengths_size; ++symbol) {
+    if (code_lengths[symbol] > MAX_ALLOWED_CODE_LENGTH) {
+      return 0;
+    }
+    ++count[code_lengths[symbol]];
+  }
+
+  // Error, all code lengths are zeros.
+  if (count[0] == code_lengths_size) {
+    return 0;
+  }
+
+  // Generate offsets into sorted symbol table by code length.
+  offset[1] = 0;
+  for (len = 1; len < MAX_ALLOWED_CODE_LENGTH; ++len) {
+    if (count[len] > (1 << len)) {
+      return 0;
+    }
+    offset[len + 1] = offset[len] + count[len];
+  }
+
+  // Sort symbols by length, by symbol order within each length.
+  for (symbol = 0; symbol < code_lengths_size; ++symbol) {
+    const int symbol_code_length = code_lengths[symbol];
+    if (code_lengths[symbol] > 0) {
+      sorted[offset[symbol_code_length]++] = symbol;
+    }
+  }
+
+  // Special case code with only one value.
+  if (offset[MAX_ALLOWED_CODE_LENGTH] == 1) {
+    HuffmanCode code;
+    code.bits = 0;
+    code.value = (uint16_t)sorted[0];
+    ReplicateValue(table, 1, total_size, code);
+    return total_size;
+  }
+
+  {
+    int step;              // step size to replicate values in current table
+    uint32_t low = -1;     // low bits for current root entry
+    uint32_t mask = total_size - 1;    // mask for low bits
+    uint32_t key = 0;      // reversed prefix code
+    int num_nodes = 1;     // number of Huffman tree nodes
+    int num_open = 1;      // number of open branches in current tree level
+    int table_bits = root_bits;        // key length of current table
+    int table_size = 1 << table_bits;  // size of current table
+    symbol = 0;
+    // Fill in root table.
+    for (len = 1, step = 2; len <= root_bits; ++len, step <<= 1) {
+      num_open <<= 1;
+      num_nodes += num_open;
+      num_open -= count[len];
+      if (num_open < 0) {
+        return 0;
+      }
+      for (; count[len] > 0; --count[len]) {
+        HuffmanCode code;
+        code.bits = (uint8_t)len;
+        code.value = (uint16_t)sorted[symbol++];
+        ReplicateValue(&table[key], step, table_size, code);
+        key = GetNextKey(key, len);
+      }
+    }
+
+    // Fill in 2nd level tables and add pointers to root table.
+    for (len = root_bits + 1, step = 2; len <= MAX_ALLOWED_CODE_LENGTH;
+         ++len, step <<= 1) {
+      num_open <<= 1;
+      num_nodes += num_open;
+      num_open -= count[len];
+      if (num_open < 0) {
+        return 0;
+      }
+      for (; count[len] > 0; --count[len]) {
+        HuffmanCode code;
+        if ((key & mask) != low) {
+          table += table_size;
+          table_bits = NextTableBitSize(count, len, root_bits);
+          table_size = 1 << table_bits;
+          total_size += table_size;
+          low = key & mask;
+          root_table[low].bits = (uint8_t)(table_bits + root_bits);
+          root_table[low].value = (uint16_t)((table - root_table) - low);
+        }
+        code.bits = (uint8_t)(len - root_bits);
+        code.value = (uint16_t)sorted[symbol++];
+        ReplicateValue(&table[key >> root_bits], step, table_size, code);
+        key = GetNextKey(key, len);
+      }
+    }
+
+    // Check if tree is full.
+    if (num_nodes != 2 * offset[MAX_ALLOWED_CODE_LENGTH] - 1) {
+      return 0;
+    }
+  }
+
+  return total_size;
+}
+
+// Maximum code_lengths_size is 2328 (reached for 11-bit color_cache_bits).
+// More commonly, the value is around ~280.
+#define MAX_CODE_LENGTHS_SIZE \
+  ((1 << MAX_CACHE_BITS) + NUM_LITERAL_CODES + NUM_LENGTH_CODES)
+// Cut-off value for switching between heap and stack allocation.
+#define SORTED_SIZE_CUTOFF 512
+int VP8LBuildHuffmanTable(HuffmanCode* const root_table, int root_bits,
+                          const int code_lengths[], int code_lengths_size) {
+  int total_size;
+  assert(code_lengths_size <= MAX_CODE_LENGTHS_SIZE);
+  if (code_lengths_size <= SORTED_SIZE_CUTOFF) {
+    // use local stack-allocated array.
+    uint16_t sorted[SORTED_SIZE_CUTOFF];
+    total_size = BuildHuffmanTable(root_table, root_bits,
+                                   code_lengths, code_lengths_size, sorted);
+  } else {   // rare case. Use heap allocation.
+    uint16_t* const sorted =
+        (uint16_t*)WebPSafeMalloc(code_lengths_size, sizeof(*sorted));
+    if (sorted == NULL) return 0;
+    total_size = BuildHuffmanTable(root_table, root_bits,
+                                   code_lengths, code_lengths_size, sorted);
+    WebPSafeFree(sorted);
+  }
+  return total_size;
+}