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+// 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.
+// -----------------------------------------------------------------------------
+//
+// Internal header for constants related to WebP file format.
+//
+// Author: Urvang (urvang@google.com)
+
+#ifndef WEBP_WEBP_FORMAT_CONSTANTS_H_
+#define WEBP_WEBP_FORMAT_CONSTANTS_H_
+
+// Create fourcc of the chunk from the chunk tag characters.
+#define MKFOURCC(a, b, c, d) ((a) | (b) << 8 | (c) << 16 | (uint32_t)(d) << 24)
+
+// VP8 related constants.
+#define VP8_SIGNATURE 0x9d012a // Signature in VP8 data.
+#define VP8_MAX_PARTITION0_SIZE (1 << 19) // max size of mode partition
+#define VP8_MAX_PARTITION_SIZE (1 << 24) // max size for token partition
+#define VP8_FRAME_HEADER_SIZE 10 // Size of the frame header within VP8 data.
+
+// VP8L related constants.
+#define VP8L_SIGNATURE_SIZE 1 // VP8L signature size.
+#define VP8L_MAGIC_BYTE 0x2f // VP8L signature byte.
+#define VP8L_IMAGE_SIZE_BITS 14 // Number of bits used to store
+ // width and height.
+#define VP8L_VERSION_BITS 3 // 3 bits reserved for version.
+#define VP8L_VERSION 0 // version 0
+#define VP8L_FRAME_HEADER_SIZE 5 // Size of the VP8L frame header.
+
+#define MAX_PALETTE_SIZE 256
+#define MAX_CACHE_BITS 11
+#define HUFFMAN_CODES_PER_META_CODE 5
+#define ARGB_BLACK 0xff000000
+
+#define DEFAULT_CODE_LENGTH 8
+#define MAX_ALLOWED_CODE_LENGTH 15
+
+#define NUM_LITERAL_CODES 256
+#define NUM_LENGTH_CODES 24
+#define NUM_DISTANCE_CODES 40
+#define CODE_LENGTH_CODES 19
+
+#define MIN_HUFFMAN_BITS 2 // min number of Huffman bits
+#define MAX_HUFFMAN_BITS 9 // max number of Huffman bits
+
+#define TRANSFORM_PRESENT 1 // The bit to be written when next data
+ // to be read is a transform.
+#define NUM_TRANSFORMS 4 // Maximum number of allowed transform
+ // in a bitstream.
+typedef enum {
+ PREDICTOR_TRANSFORM = 0,
+ CROSS_COLOR_TRANSFORM = 1,
+ SUBTRACT_GREEN = 2,
+ COLOR_INDEXING_TRANSFORM = 3
+} VP8LImageTransformType;
+
+// Alpha related constants.
+#define ALPHA_HEADER_LEN 1
+#define ALPHA_NO_COMPRESSION 0
+#define ALPHA_LOSSLESS_COMPRESSION 1
+#define ALPHA_PREPROCESSED_LEVELS 1
+
+// Mux related constants.
+#define TAG_SIZE 4 // Size of a chunk tag (e.g. "VP8L").
+#define CHUNK_SIZE_BYTES 4 // Size needed to store chunk's size.
+#define CHUNK_HEADER_SIZE 8 // Size of a chunk header.
+#define RIFF_HEADER_SIZE 12 // Size of the RIFF header ("RIFFnnnnWEBP").
+#define ANMF_CHUNK_SIZE 16 // Size of an ANMF chunk.
+#define ANIM_CHUNK_SIZE 6 // Size of an ANIM chunk.
+#define VP8X_CHUNK_SIZE 10 // Size of a VP8X chunk.
+
+#define MAX_CANVAS_SIZE (1 << 24) // 24-bit max for VP8X width/height.
+#define MAX_IMAGE_AREA (1ULL << 32) // 32-bit max for width x height.
+#define MAX_LOOP_COUNT (1 << 16) // maximum value for loop-count
+#define MAX_DURATION (1 << 24) // maximum duration
+#define MAX_POSITION_OFFSET (1 << 24) // maximum frame x/y offset
+
+// Maximum chunk payload is such that adding the header and padding won't
+// overflow a uint32_t.
+#define MAX_CHUNK_PAYLOAD (~0U - CHUNK_HEADER_SIZE - 1)
+
+#endif /* WEBP_WEBP_FORMAT_CONSTANTS_H_ */