1 files changed, 234 insertions, 0 deletions
diff --git a/thirdparty/libwebp/src/enc/backward_references_enc.h b/thirdparty/libwebp/src/enc/backward_references_enc.h
new file mode 100644
index 0000000000..103ddfdcb7
--- /dev/null
+++ b/thirdparty/libwebp/src/enc/backward_references_enc.h
@@ -0,0 +1,234 @@
+// 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.
+// -----------------------------------------------------------------------------
+//
+// Author: Jyrki Alakuijala (jyrki@google.com)
+//
+
+#ifndef WEBP_ENC_BACKWARD_REFERENCES_ENC_H_
+#define WEBP_ENC_BACKWARD_REFERENCES_ENC_H_
+
+#include <assert.h>
+#include <stdlib.h>
+#include "src/webp/types.h"
+#include "src/webp/format_constants.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// The maximum allowed limit is 11.
+#define MAX_COLOR_CACHE_BITS 10
+
+// -----------------------------------------------------------------------------
+// PixOrCopy
+
+enum Mode {
+  kLiteral,
+  kCacheIdx,
+  kCopy,
+  kNone
+};
+
+typedef struct {
+  // mode as uint8_t to make the memory layout to be exactly 8 bytes.
+  uint8_t mode;
+  uint16_t len;
+  uint32_t argb_or_distance;
+} PixOrCopy;
+
+static WEBP_INLINE PixOrCopy PixOrCopyCreateCopy(uint32_t distance,
+                                                 uint16_t len) {
+  PixOrCopy retval;
+  retval.mode = kCopy;
+  retval.argb_or_distance = distance;
+  retval.len = len;
+  return retval;
+}
+
+static WEBP_INLINE PixOrCopy PixOrCopyCreateCacheIdx(int idx) {
+  PixOrCopy retval;
+  assert(idx >= 0);
+  assert(idx < (1 << MAX_COLOR_CACHE_BITS));
+  retval.mode = kCacheIdx;
+  retval.argb_or_distance = idx;
+  retval.len = 1;
+  return retval;
+}
+
+static WEBP_INLINE PixOrCopy PixOrCopyCreateLiteral(uint32_t argb) {
+  PixOrCopy retval;
+  retval.mode = kLiteral;
+  retval.argb_or_distance = argb;
+  retval.len = 1;
+  return retval;
+}
+
+static WEBP_INLINE int PixOrCopyIsLiteral(const PixOrCopy* const p) {
+  return (p->mode == kLiteral);
+}
+
+static WEBP_INLINE int PixOrCopyIsCacheIdx(const PixOrCopy* const p) {
+  return (p->mode == kCacheIdx);
+}
+
+static WEBP_INLINE int PixOrCopyIsCopy(const PixOrCopy* const p) {
+  return (p->mode == kCopy);
+}
+
+static WEBP_INLINE uint32_t PixOrCopyLiteral(const PixOrCopy* const p,
+                                             int component) {
+  assert(p->mode == kLiteral);
+  return (p->argb_or_distance >> (component * 8)) & 0xff;
+}
+
+static WEBP_INLINE uint32_t PixOrCopyLength(const PixOrCopy* const p) {
+  return p->len;
+}
+
+static WEBP_INLINE uint32_t PixOrCopyCacheIdx(const PixOrCopy* const p) {
+  assert(p->mode == kCacheIdx);
+  assert(p->argb_or_distance < (1U << MAX_COLOR_CACHE_BITS));
+  return p->argb_or_distance;
+}
+
+static WEBP_INLINE uint32_t PixOrCopyDistance(const PixOrCopy* const p) {
+  assert(p->mode == kCopy);
+  return p->argb_or_distance;
+}
+
+// -----------------------------------------------------------------------------
+// VP8LHashChain
+
+#define HASH_BITS 18
+#define HASH_SIZE (1 << HASH_BITS)
+
+// If you change this, you need MAX_LENGTH_BITS + WINDOW_SIZE_BITS <= 32 as it
+// is used in VP8LHashChain.
+#define MAX_LENGTH_BITS 12
+#define WINDOW_SIZE_BITS 20
+// We want the max value to be attainable and stored in MAX_LENGTH_BITS bits.
+#define MAX_LENGTH ((1 << MAX_LENGTH_BITS) - 1)
+#if MAX_LENGTH_BITS + WINDOW_SIZE_BITS > 32
+#error "MAX_LENGTH_BITS + WINDOW_SIZE_BITS > 32"
+#endif
+
+typedef struct VP8LHashChain VP8LHashChain;
+struct VP8LHashChain {
+  // The 20 most significant bits contain the offset at which the best match
+  // is found. These 20 bits are the limit defined by GetWindowSizeForHashChain
+  // (through WINDOW_SIZE = 1<<20).
+  // The lower 12 bits contain the length of the match. The 12 bit limit is
+  // defined in MaxFindCopyLength with MAX_LENGTH=4096.
+  uint32_t* offset_length_;
+  // This is the maximum size of the hash_chain that can be constructed.
+  // Typically this is the pixel count (width x height) for a given image.
+  int size_;
+};
+
+// Must be called first, to set size.
+int VP8LHashChainInit(VP8LHashChain* const p, int size);
+// Pre-compute the best matches for argb.
+int VP8LHashChainFill(VP8LHashChain* const p, int quality,
+                      const uint32_t* const argb, int xsize, int ysize,
+                      int low_effort);
+void VP8LHashChainClear(VP8LHashChain* const p);  // release memory
+
+static WEBP_INLINE int VP8LHashChainFindOffset(const VP8LHashChain* const p,
+                                               const int base_position) {
+  return p->offset_length_[base_position] >> MAX_LENGTH_BITS;
+}
+
+static WEBP_INLINE int VP8LHashChainFindLength(const VP8LHashChain* const p,
+                                               const int base_position) {
+  return p->offset_length_[base_position] & ((1U << MAX_LENGTH_BITS) - 1);
+}
+
+static WEBP_INLINE void VP8LHashChainFindCopy(const VP8LHashChain* const p,
+                                              int base_position,
+                                              int* const offset_ptr,
+                                              int* const length_ptr) {
+  *offset_ptr = VP8LHashChainFindOffset(p, base_position);
+  *length_ptr = VP8LHashChainFindLength(p, base_position);
+}
+
+// -----------------------------------------------------------------------------
+// VP8LBackwardRefs (block-based backward-references storage)
+
+// maximum number of reference blocks the image will be segmented into
+#define MAX_REFS_BLOCK_PER_IMAGE 16
+
+typedef struct PixOrCopyBlock PixOrCopyBlock;   // forward declaration
+typedef struct VP8LBackwardRefs VP8LBackwardRefs;
+
+// Container for blocks chain
+struct VP8LBackwardRefs {
+  int block_size_;               // common block-size
+  int error_;                    // set to true if some memory error occurred
+  PixOrCopyBlock* refs_;         // list of currently used blocks
+  PixOrCopyBlock** tail_;        // for list recycling
+  PixOrCopyBlock* free_blocks_;  // free-list
+  PixOrCopyBlock* last_block_;   // used for adding new refs (internal)
+};
+
+// Initialize the object. 'block_size' is the common block size to store
+// references (typically, width * height / MAX_REFS_BLOCK_PER_IMAGE).
+void VP8LBackwardRefsInit(VP8LBackwardRefs* const refs, int block_size);
+// Release memory for backward references.
+void VP8LBackwardRefsClear(VP8LBackwardRefs* const refs);
+
+// Cursor for iterating on references content
+typedef struct {
+  // public:
+  PixOrCopy* cur_pos;           // current position
+  // private:
+  PixOrCopyBlock* cur_block_;   // current block in the refs list
+  const PixOrCopy* last_pos_;   // sentinel for switching to next block
+} VP8LRefsCursor;
+
+// Returns a cursor positioned at the beginning of the references list.
+VP8LRefsCursor VP8LRefsCursorInit(const VP8LBackwardRefs* const refs);
+// Returns true if cursor is pointing at a valid position.
+static WEBP_INLINE int VP8LRefsCursorOk(const VP8LRefsCursor* const c) {
+  return (c->cur_pos != NULL);
+}
+// Move to next block of references. Internal, not to be called directly.
+void VP8LRefsCursorNextBlock(VP8LRefsCursor* const c);
+// Move to next position, or NULL. Should not be called if !VP8LRefsCursorOk().
+static WEBP_INLINE void VP8LRefsCursorNext(VP8LRefsCursor* const c) {
+  assert(c != NULL);
+  assert(VP8LRefsCursorOk(c));
+  if (++c->cur_pos == c->last_pos_) VP8LRefsCursorNextBlock(c);
+}
+
+// -----------------------------------------------------------------------------
+// Main entry points
+
+enum VP8LLZ77Type {
+  kLZ77Standard = 1,
+  kLZ77RLE = 2,
+  kLZ77Box = 4
+};
+
+// Evaluates best possible backward references for specified quality.
+// The input cache_bits to 'VP8LGetBackwardReferences' sets the maximum cache
+// bits to use (passing 0 implies disabling the local color cache).
+// The optimal cache bits is evaluated and set for the *cache_bits parameter.
+// The return value is the pointer to the best of the two backward refs viz,
+// refs[0] or refs[1].
+VP8LBackwardRefs* VP8LGetBackwardReferences(
+    int width, int height, const uint32_t* const argb, int quality,
+    int low_effort, int lz77_types_to_try, int* const cache_bits,
+    const VP8LHashChain* const hash_chain, VP8LBackwardRefs* const refs_tmp1,
+    VP8LBackwardRefs* const refs_tmp2);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // WEBP_ENC_BACKWARD_REFERENCES_ENC_H_