+ memset(refs, 0, sizeof(*refs));
+ refs->tail_ = &refs->refs_;
+ refs->block_size_ =
+ (block_size < MIN_BLOCK_SIZE) ? MIN_BLOCK_SIZE : block_size;
+}
+
+VP8LRefsCursor VP8LRefsCursorInit(const VP8LBackwardRefs* const refs) {
+ VP8LRefsCursor c;
+ c.cur_block_ = refs->refs_;
+ if (refs->refs_ != NULL) {
+ c.cur_pos = c.cur_block_->start_;
+ c.last_pos_ = c.cur_pos + c.cur_block_->size_;
+ } else {
+ c.cur_pos = NULL;
+ c.last_pos_ = NULL;
+ }
+ return c;
+}
+
+void VP8LRefsCursorNextBlock(VP8LRefsCursor* const c) {
+ PixOrCopyBlock* const b = c->cur_block_->next_;
+ c->cur_pos = (b == NULL) ? NULL : b->start_;
+ c->last_pos_ = (b == NULL) ? NULL : b->start_ + b->size_;
+ c->cur_block_ = b;
+}
+
+// Create a new block, either from the free list or allocated
+static PixOrCopyBlock* BackwardRefsNewBlock(VP8LBackwardRefs* const refs) {
+ PixOrCopyBlock* b = refs->free_blocks_;
+ if (b == NULL) { // allocate new memory chunk
+ const size_t total_size =
+ sizeof(*b) + refs->block_size_ * sizeof(*b->start_);
+ b = (PixOrCopyBlock*)WebPSafeMalloc(1ULL, total_size);
+ if (b == NULL) {
+ refs->error_ |= 1;
+ return NULL;
+ }
+ b->start_ = (PixOrCopy*)((uint8_t*)b + sizeof(*b)); // not always aligned
+ } else { // recycle from free-list
+ refs->free_blocks_ = b->next_;
+ }
+ *refs->tail_ = b;
+ refs->tail_ = &b->next_;
+ refs->last_block_ = b;
+ b->next_ = NULL;
+ b->size_ = 0;
+ return b;
+}
+
+static WEBP_INLINE void BackwardRefsCursorAdd(VP8LBackwardRefs* const refs,
+ const PixOrCopy v) {
+ PixOrCopyBlock* b = refs->last_block_;
+ if (b == NULL || b->size_ == refs->block_size_) {
+ b = BackwardRefsNewBlock(refs);
+ if (b == NULL) return; // refs->error_ is set
+ }
+ b->start_[b->size_++] = v;
+}
+
+int VP8LBackwardRefsCopy(const VP8LBackwardRefs* const src,
+ VP8LBackwardRefs* const dst) {
+ const PixOrCopyBlock* b = src->refs_;
+ ClearBackwardRefs(dst);
+ assert(src->block_size_ == dst->block_size_);
+ while (b != NULL) {
+ PixOrCopyBlock* const new_b = BackwardRefsNewBlock(dst);
+ if (new_b == NULL) return 0; // dst->error_ is set
+ memcpy(new_b->start_, b->start_, b->size_ * sizeof(*b->start_));
+ new_b->size_ = b->size_;
+ b = b->next_;
+ }