427 lines
14 KiB
C++
427 lines
14 KiB
C++
/*
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* Copyright (c) 2020-2021 Samsung Electronics Co., Ltd. All rights reserved.
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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/*
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* Lempel–Ziv–Welch (LZW) encoder/decoder by Guilherme R. Lampert(guilherme.ronaldo.lampert@gmail.com)
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* This is the compression scheme used by the GIF image format and the Unix 'compress' tool.
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* Main differences from this implementation is that End Of Input (EOI) and Clear Codes (CC)
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* are not stored in the output and the max code length in bits is 12, vs 16 in compress.
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*
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* EOI is simply detected by the end of the data stream, while CC happens if the
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* dictionary gets filled. Data is written/read from bit streams, which handle
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* byte-alignment for us in a transparent way.
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* The decoder relies on the hardcoded data layout produced by the encoder, since
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* no additional reconstruction data is added to the output, so they must match.
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* The nice thing about LZW is that we can reconstruct the dictionary directly from
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* the stream of codes generated by the encoder, so this avoids storing additional
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* headers in the bit stream.
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* The output code length is variable. It starts with the minimum number of bits
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* required to store the base byte-sized dictionary and automatically increases
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* as the dictionary gets larger (it starts at 9-bits and grows to 10-bits when
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* code 512 is added, then 11-bits when 1024 is added, and so on). If the dictionary
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* is filled (4096 items for a 12-bits dictionary), the whole thing is cleared and
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* the process starts over. This is the main reason why the encoder and the decoder
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* must match perfectly, since the lengths of the codes will not be specified with
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* the data itself.
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* USEFUL LINKS:
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* https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch
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* http://rosettacode.org/wiki/LZW_compression
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* http://www.cs.duke.edu/csed/curious/compression/lzw.html
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* http://www.cs.cf.ac.uk/Dave/Multimedia/node214.html
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* http://marknelson.us/1989/10/01/lzw-data-compression/
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*/
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#include "config.h"
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#if defined(THORVG_TVG_SAVER_SUPPORT) || defined(THORVG_TVG_LOADER_SUPPORT)
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/************************************************************************/
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/* Internal Class Implementation */
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/************************************************************************/
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#include <string>
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#include <memory.h>
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#include "tvgLzw.h"
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//LZW Dictionary helper:
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constexpr int Nil = -1;
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constexpr int MaxDictBits = 12;
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constexpr int StartBits = 9;
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constexpr int FirstCode = (1 << (StartBits - 1)); // 256
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constexpr int MaxDictEntries = (1 << MaxDictBits); // 4096
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//Round up to the next power-of-two number, e.g. 37 => 64
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static int nextPowerOfTwo(int num)
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{
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--num;
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for (size_t i = 1; i < sizeof(num) * 8; i <<= 1) {
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num = num | num >> i;
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}
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return ++num;
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}
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struct BitStreamWriter
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{
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uint8_t* stream; //Growable buffer to store our bits. Heap allocated & owned by the class instance.
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int bytesAllocated; //Current size of heap-allocated stream buffer *in bytes*.
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int granularity; //Amount bytesAllocated multiplies by when auto-resizing in appendBit().
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int currBytePos; //Current byte being written to, from 0 to bytesAllocated-1.
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int nextBitPos; //Bit position within the current byte to access next. 0 to 7.
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int numBitsWritten; //Number of bits in use from the stream buffer, not including byte-rounding padding.
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void internalInit()
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{
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stream = nullptr;
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bytesAllocated = 0;
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granularity = 2;
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currBytePos = 0;
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nextBitPos = 0;
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numBitsWritten = 0;
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}
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uint8_t* allocBytes(const int bytesWanted, uint8_t * oldPtr, const int oldSize)
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{
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auto newMemory = static_cast<uint8_t *>(malloc(bytesWanted));
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memset(newMemory, 0, bytesWanted);
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if (oldPtr) {
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memcpy(newMemory, oldPtr, oldSize);
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free(oldPtr);
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}
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return newMemory;
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}
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BitStreamWriter()
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{
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/* 8192 bits for a start (1024 bytes). It will resize if needed.
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Default granularity is 2. */
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internalInit();
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allocate(8192);
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}
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BitStreamWriter(const int initialSizeInBits, const int growthGranularity = 2)
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{
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internalInit();
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setGranularity(growthGranularity);
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allocate(initialSizeInBits);
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}
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~BitStreamWriter()
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{
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free(stream);
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}
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void allocate(int bitsWanted)
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{
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//Require at least a byte.
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if (bitsWanted <= 0) bitsWanted = 8;
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//Round upwards if needed:
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if ((bitsWanted % 8) != 0) bitsWanted = nextPowerOfTwo(bitsWanted);
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//We might already have the required count.
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const int sizeInBytes = bitsWanted / 8;
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if (sizeInBytes <= bytesAllocated) return;
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stream = allocBytes(sizeInBytes, stream, bytesAllocated);
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bytesAllocated = sizeInBytes;
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}
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void appendBit(const int bit)
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{
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const uint32_t mask = uint32_t(1) << nextBitPos;
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stream[currBytePos] = (stream[currBytePos] & ~mask) | (-bit & mask);
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++numBitsWritten;
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if (++nextBitPos == 8) {
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nextBitPos = 0;
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if (++currBytePos == bytesAllocated) allocate(bytesAllocated * granularity * 8);
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}
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}
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void appendBitsU64(const uint64_t num, const int bitCount)
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{
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for (int b = 0; b < bitCount; ++b) {
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const uint64_t mask = uint64_t(1) << b;
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const int bit = !!(num & mask);
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appendBit(bit);
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}
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}
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uint8_t* release()
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{
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auto oldPtr = stream;
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internalInit();
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return oldPtr;
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}
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void setGranularity(const int growthGranularity)
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{
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granularity = (growthGranularity >= 2) ? growthGranularity : 2;
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}
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int getByteCount() const
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{
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int usedBytes = numBitsWritten / 8;
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int leftovers = numBitsWritten % 8;
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if (leftovers != 0) ++usedBytes;
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return usedBytes;
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}
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};
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struct BitStreamReader
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{
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const uint8_t* stream; // Pointer to the external bit stream. Not owned by the reader.
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const int sizeInBytes; // Size of the stream *in bytes*. Might include padding.
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const int sizeInBits; // Size of the stream *in bits*, padding *not* include.
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int currBytePos = 0; // Current byte being read in the stream.
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int nextBitPos = 0; // Bit position within the current byte to access next. 0 to 7.
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int numBitsRead = 0; // Total bits read from the stream so far. Never includes byte-rounding padding.
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BitStreamReader(const uint8_t* bitStream, const int byteCount, const int bitCount) : stream(bitStream), sizeInBytes(byteCount), sizeInBits(bitCount)
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{
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}
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bool readNextBit(int& bitOut)
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{
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if (numBitsRead >= sizeInBits) return false; //We are done.
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const uint32_t mask = uint32_t(1) << nextBitPos;
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bitOut = !!(stream[currBytePos] & mask);
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++numBitsRead;
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if (++nextBitPos == 8) {
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nextBitPos = 0;
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++currBytePos;
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}
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return true;
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}
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uint64_t readBitsU64(const int bitCount)
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{
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uint64_t num = 0;
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for (int b = 0; b < bitCount; ++b) {
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int bit;
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if (!readNextBit(bit)) break;
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/* Based on a "Stanford bit-hack":
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http://graphics.stanford.edu/~seander/bithacks.html#ConditionalSetOrClearBitsWithoutBranching */
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const uint64_t mask = uint64_t(1) << b;
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num = (num & ~mask) | (-bit & mask);
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}
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return num;
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}
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bool isEndOfStream() const
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{
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return numBitsRead >= sizeInBits;
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}
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};
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struct Dictionary
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{
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struct Entry
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{
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int code;
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int value;
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};
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//Dictionary entries 0-255 are always reserved to the byte/ASCII range.
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int size;
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Entry entries[MaxDictEntries];
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Dictionary()
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{
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/* First 256 dictionary entries are reserved to the byte/ASCII range.
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Additional entries follow for the character sequences found in the input.
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Up to 4096 - 256 (MaxDictEntries - FirstCode). */
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size = FirstCode;
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for (int i = 0; i < size; ++i) {
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entries[i].code = Nil;
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entries[i].value = i;
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}
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}
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int findIndex(const int code, const int value) const
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{
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if (code == Nil) return value;
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//Linear search for now.
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//TODO: Worth optimizing with a proper hash-table?
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for (int i = 0; i < size; ++i) {
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if (entries[i].code == code && entries[i].value == value) return i;
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}
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return Nil;
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}
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bool add(const int code, const int value)
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{
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if (size == MaxDictEntries) return false;
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entries[size].code = code;
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entries[size].value = value;
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++size;
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return true;
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}
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bool flush(int & codeBitsWidth)
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{
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if (size == (1 << codeBitsWidth)) {
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++codeBitsWidth;
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if (codeBitsWidth > MaxDictBits) {
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//Clear the dictionary (except the first 256 byte entries).
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codeBitsWidth = StartBits;
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size = FirstCode;
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return true;
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}
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}
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return false;
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}
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};
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static bool outputByte(int code, uint8_t*& output, int outputSizeBytes, int& bytesDecodedSoFar)
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{
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if (bytesDecodedSoFar >= outputSizeBytes) return false;
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*output++ = static_cast<uint8_t>(code);
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++bytesDecodedSoFar;
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return true;
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}
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static bool outputSequence(const Dictionary& dict, int code, uint8_t*& output, int outputSizeBytes, int& bytesDecodedSoFar, int& firstByte)
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{
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/* A sequence is stored backwards, so we have to write
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it to a temp then output the buffer in reverse. */
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int i = 0;
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uint8_t sequence[MaxDictEntries];
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do {
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sequence[i++] = dict.entries[code].value;
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code = dict.entries[code].code;
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} while (code >= 0);
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firstByte = sequence[--i];
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for (; i >= 0; --i) {
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if (!outputByte(sequence[i], output, outputSizeBytes, bytesDecodedSoFar)) return false;
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}
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return true;
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}
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/************************************************************************/
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/* External Class Implementation */
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/************************************************************************/
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namespace tvg {
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uint8_t* lzwDecode(const uint8_t* compressed, uint32_t compressedSizeBytes, uint32_t compressedSizeBits, uint32_t uncompressedSizeBytes)
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{
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int code = Nil;
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int prevCode = Nil;
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int firstByte = 0;
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int bytesDecoded = 0;
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int codeBitsWidth = StartBits;
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auto uncompressed = (uint8_t*) malloc(sizeof(uint8_t) * uncompressedSizeBytes);
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auto ptr = uncompressed;
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/* We'll reconstruct the dictionary based on the bit stream codes.
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Unlike Huffman encoding, we don't store the dictionary as a prefix to the data. */
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Dictionary dictionary;
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BitStreamReader bitStream(compressed, compressedSizeBytes, compressedSizeBits);
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/* We check to avoid an overflow of the user buffer.
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If the buffer is smaller than the decompressed size, we break the loop and return the current decompression count. */
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while (!bitStream.isEndOfStream()) {
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code = static_cast<int>(bitStream.readBitsU64(codeBitsWidth));
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if (prevCode == Nil) {
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if (!outputByte(code, ptr, uncompressedSizeBytes, bytesDecoded)) break;
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firstByte = code;
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prevCode = code;
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continue;
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}
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if (code >= dictionary.size) {
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if (!outputSequence(dictionary, prevCode, ptr, uncompressedSizeBytes, bytesDecoded, firstByte)) break;
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if (!outputByte(firstByte, ptr, uncompressedSizeBytes, bytesDecoded)) break;
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} else if (!outputSequence(dictionary, code, ptr, uncompressedSizeBytes, bytesDecoded, firstByte)) break;
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dictionary.add(prevCode, firstByte);
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if (dictionary.flush(codeBitsWidth)) prevCode = Nil;
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else prevCode = code;
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}
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return uncompressed;
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}
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uint8_t* lzwEncode(const uint8_t* uncompressed, uint32_t uncompressedSizeBytes, uint32_t* compressedSizeBytes, uint32_t* compressedSizeBits)
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{
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//LZW encoding context:
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int code = Nil;
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int codeBitsWidth = StartBits;
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Dictionary dictionary;
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//Output bit stream we write to. This will allocate memory as needed to accommodate the encoded data.
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BitStreamWriter bitStream;
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for (; uncompressedSizeBytes > 0; --uncompressedSizeBytes, ++uncompressed) {
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const int value = *uncompressed;
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const int index = dictionary.findIndex(code, value);
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if (index != Nil) {
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code = index;
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continue;
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}
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//Write the dictionary code using the minimum bit-with:
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bitStream.appendBitsU64(code, codeBitsWidth);
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//Flush it when full so we can restart the sequences.
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if (!dictionary.flush(codeBitsWidth)) {
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//There's still space for this sequence.
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dictionary.add(code, value);
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}
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code = value;
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}
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//Residual code at the end:
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if (code != Nil) bitStream.appendBitsU64(code, codeBitsWidth);
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//Pass ownership of the compressed data buffer to the user pointer:
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*compressedSizeBytes = bitStream.getByteCount();
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*compressedSizeBits = bitStream.numBitsWritten;
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return bitStream.release();
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}
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}
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#endif |