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Diffstat (limited to 'thirdparty/thorvg/src/lib/tvgLzw.cpp')
| -rw-r--r-- | thirdparty/thorvg/src/lib/tvgLzw.cpp | 428 |
1 files changed, 428 insertions, 0 deletions
diff --git a/thirdparty/thorvg/src/lib/tvgLzw.cpp b/thirdparty/thorvg/src/lib/tvgLzw.cpp new file mode 100644 index 0000000000..0049c89962 --- /dev/null +++ b/thirdparty/thorvg/src/lib/tvgLzw.cpp @@ -0,0 +1,428 @@ +/* + * Copyright (c) 2020-2021 Samsung Electronics Co., Ltd. All rights reserved. + + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + + * The above copyright notice and this permission notice shall be included in all + * copies or substantial portions of the Software. + + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +/* + * Lempel–Ziv–Welch (LZW) encoder/decoder by Guilherme R. Lampert(guilherme.ronaldo.lampert@gmail.com) + + * This is the compression scheme used by the GIF image format and the Unix 'compress' tool. + * Main differences from this implementation is that End Of Input (EOI) and Clear Codes (CC) + * are not stored in the output and the max code length in bits is 12, vs 16 in compress. + * + * EOI is simply detected by the end of the data stream, while CC happens if the + * dictionary gets filled. Data is written/read from bit streams, which handle + * byte-alignment for us in a transparent way. + + * The decoder relies on the hardcoded data layout produced by the encoder, since + * no additional reconstruction data is added to the output, so they must match. + * The nice thing about LZW is that we can reconstruct the dictionary directly from + * the stream of codes generated by the encoder, so this avoids storing additional + * headers in the bit stream. + + * The output code length is variable. It starts with the minimum number of bits + * required to store the base byte-sized dictionary and automatically increases + * as the dictionary gets larger (it starts at 9-bits and grows to 10-bits when + * code 512 is added, then 11-bits when 1024 is added, and so on). If the dictionary + * is filled (4096 items for a 12-bits dictionary), the whole thing is cleared and + * the process starts over. This is the main reason why the encoder and the decoder + * must match perfectly, since the lengths of the codes will not be specified with + * the data itself. + + * USEFUL LINKS: + * https://en.wikipedia.org/wiki/Lempel%E2%80%93Ziv%E2%80%93Welch + * http://rosettacode.org/wiki/LZW_compression + * http://www.cs.duke.edu/csed/curious/compression/lzw.html + * http://www.cs.cf.ac.uk/Dave/Multimedia/node214.html + * http://marknelson.us/1989/10/01/lzw-data-compression/ + */ +#include "config.h" + +#if defined(THORVG_TVG_SAVER_SUPPORT) || defined(THORVG_TVG_LOADER_SUPPORT) + +/************************************************************************/ +/* Internal Class Implementation */ +/************************************************************************/ + +#include <string> +#include <memory.h> +#include "tvgLzw.h" + +namespace { +//LZW Dictionary helper: +constexpr int Nil = -1; +constexpr int MaxDictBits = 12; +constexpr int StartBits = 9; +constexpr int FirstCode = (1 << (StartBits - 1)); // 256 +constexpr int MaxDictEntries = (1 << MaxDictBits); // 4096 + + +//Round up to the next power-of-two number, e.g. 37 => 64 +static int nextPowerOfTwo(int num) +{ + --num; + for (size_t i = 1; i < sizeof(num) * 8; i <<= 1) { + num = num | num >> i; + } + return ++num; +} + + +struct BitStreamWriter +{ + uint8_t* stream; //Growable buffer to store our bits. Heap allocated & owned by the class instance. + int bytesAllocated; //Current size of heap-allocated stream buffer *in bytes*. + int granularity; //Amount bytesAllocated multiplies by when auto-resizing in appendBit(). + int currBytePos; //Current byte being written to, from 0 to bytesAllocated-1. + int nextBitPos; //Bit position within the current byte to access next. 0 to 7. + int numBitsWritten; //Number of bits in use from the stream buffer, not including byte-rounding padding. + + void internalInit() + { + stream = nullptr; + bytesAllocated = 0; + granularity = 2; + currBytePos = 0; + nextBitPos = 0; + numBitsWritten = 0; + } + + uint8_t* allocBytes(const int bytesWanted, uint8_t * oldPtr, const int oldSize) + { + auto newMemory = static_cast<uint8_t *>(malloc(bytesWanted)); + memset(newMemory, 0, bytesWanted); + + if (oldPtr) { + memcpy(newMemory, oldPtr, oldSize); + free(oldPtr); + } + return newMemory; + } + + BitStreamWriter() + { + /* 8192 bits for a start (1024 bytes). It will resize if needed. + Default granularity is 2. */ + internalInit(); + allocate(8192); + } + + BitStreamWriter(const int initialSizeInBits, const int growthGranularity = 2) + { + internalInit(); + setGranularity(growthGranularity); + allocate(initialSizeInBits); + } + + ~BitStreamWriter() + { + free(stream); + } + + void allocate(int bitsWanted) + { + //Require at least a byte. + if (bitsWanted <= 0) bitsWanted = 8; + + //Round upwards if needed: + if ((bitsWanted % 8) != 0) bitsWanted = nextPowerOfTwo(bitsWanted); + + //We might already have the required count. + const int sizeInBytes = bitsWanted / 8; + if (sizeInBytes <= bytesAllocated) return; + + stream = allocBytes(sizeInBytes, stream, bytesAllocated); + bytesAllocated = sizeInBytes; + } + + void appendBit(const int bit) + { + const uint32_t mask = uint32_t(1) << nextBitPos; + stream[currBytePos] = (stream[currBytePos] & ~mask) | (-bit & mask); + ++numBitsWritten; + + if (++nextBitPos == 8) { + nextBitPos = 0; + if (++currBytePos == bytesAllocated) allocate(bytesAllocated * granularity * 8); + } + } + + void appendBitsU64(const uint64_t num, const int bitCount) + { + for (int b = 0; b < bitCount; ++b) { + const uint64_t mask = uint64_t(1) << b; + const int bit = !!(num & mask); + appendBit(bit); + } + } + + uint8_t* release() + { + auto oldPtr = stream; + internalInit(); + return oldPtr; + } + + void setGranularity(const int growthGranularity) + { + granularity = (growthGranularity >= 2) ? growthGranularity : 2; + } + + int getByteCount() const + { + int usedBytes = numBitsWritten / 8; + int leftovers = numBitsWritten % 8; + if (leftovers != 0) ++usedBytes; + return usedBytes; + } +}; + + +struct BitStreamReader +{ + const uint8_t* stream; // Pointer to the external bit stream. Not owned by the reader. + const int sizeInBytes; // Size of the stream *in bytes*. Might include padding. + const int sizeInBits; // Size of the stream *in bits*, padding *not* include. + int currBytePos = 0; // Current byte being read in the stream. + int nextBitPos = 0; // Bit position within the current byte to access next. 0 to 7. + int numBitsRead = 0; // Total bits read from the stream so far. Never includes byte-rounding padding. + + BitStreamReader(const uint8_t* bitStream, const int byteCount, const int bitCount) : stream(bitStream), sizeInBytes(byteCount), sizeInBits(bitCount) + { + } + + bool readNextBit(int& bitOut) + { + if (numBitsRead >= sizeInBits) return false; //We are done. + + const uint32_t mask = uint32_t(1) << nextBitPos; + bitOut = !!(stream[currBytePos] & mask); + ++numBitsRead; + + if (++nextBitPos == 8) { + nextBitPos = 0; + ++currBytePos; + } + return true; + } + + uint64_t readBitsU64(const int bitCount) + { + uint64_t num = 0; + for (int b = 0; b < bitCount; ++b) { + int bit; + if (!readNextBit(bit)) break; + /* Based on a "Stanford bit-hack": + http://graphics.stanford.edu/~seander/bithacks.html#ConditionalSetOrClearBitsWithoutBranching */ + const uint64_t mask = uint64_t(1) << b; + num = (num & ~mask) | (-bit & mask); + } + return num; + } + + bool isEndOfStream() const + { + return numBitsRead >= sizeInBits; + } +}; + + +struct Dictionary +{ + struct Entry + { + int code; + int value; + }; + + //Dictionary entries 0-255 are always reserved to the byte/ASCII range. + int size; + Entry entries[MaxDictEntries]; + + Dictionary() + { + /* First 256 dictionary entries are reserved to the byte/ASCII range. + Additional entries follow for the character sequences found in the input. + Up to 4096 - 256 (MaxDictEntries - FirstCode). */ + size = FirstCode; + + for (int i = 0; i < size; ++i) { + entries[i].code = Nil; + entries[i].value = i; + } + } + + int findIndex(const int code, const int value) const + { + if (code == Nil) return value; + + //Linear search for now. + //TODO: Worth optimizing with a proper hash-table? + for (int i = 0; i < size; ++i) { + if (entries[i].code == code && entries[i].value == value) return i; + } + return Nil; + } + + bool add(const int code, const int value) + { + if (size == MaxDictEntries) return false; + entries[size].code = code; + entries[size].value = value; + ++size; + return true; + } + + bool flush(int & codeBitsWidth) + { + if (size == (1 << codeBitsWidth)) { + ++codeBitsWidth; + if (codeBitsWidth > MaxDictBits) { + //Clear the dictionary (except the first 256 byte entries). + codeBitsWidth = StartBits; + size = FirstCode; + return true; + } + } + return false; + } +}; + + +static bool outputByte(int code, uint8_t*& output, int outputSizeBytes, int& bytesDecodedSoFar) +{ + if (bytesDecodedSoFar >= outputSizeBytes) return false; + *output++ = static_cast<uint8_t>(code); + ++bytesDecodedSoFar; + return true; +} + + +static bool outputSequence(const Dictionary& dict, int code, uint8_t*& output, int outputSizeBytes, int& bytesDecodedSoFar, int& firstByte) +{ + /* A sequence is stored backwards, so we have to write + it to a temp then output the buffer in reverse. */ + int i = 0; + uint8_t sequence[MaxDictEntries]; + + do { + sequence[i++] = dict.entries[code].value; + code = dict.entries[code].code; + } while (code >= 0); + + firstByte = sequence[--i]; + + for (; i >= 0; --i) { + if (!outputByte(sequence[i], output, outputSizeBytes, bytesDecodedSoFar)) return false; + } + return true; +} +} + + +/************************************************************************/ +/* External Class Implementation */ +/************************************************************************/ + +namespace tvg { + +uint8_t* lzwDecode(const uint8_t* compressed, uint32_t compressedSizeBytes, uint32_t compressedSizeBits, uint32_t uncompressedSizeBytes) +{ + int code = Nil; + int prevCode = Nil; + int firstByte = 0; + int bytesDecoded = 0; + int codeBitsWidth = StartBits; + auto uncompressed = (uint8_t*) malloc(sizeof(uint8_t) * uncompressedSizeBytes); + auto ptr = uncompressed; + + /* We'll reconstruct the dictionary based on the bit stream codes. + Unlike Huffman encoding, we don't store the dictionary as a prefix to the data. */ + Dictionary dictionary; + BitStreamReader bitStream(compressed, compressedSizeBytes, compressedSizeBits); + + /* We check to avoid an overflow of the user buffer. + If the buffer is smaller than the decompressed size, we break the loop and return the current decompression count. */ + while (!bitStream.isEndOfStream()) { + code = static_cast<int>(bitStream.readBitsU64(codeBitsWidth)); + + if (prevCode == Nil) { + if (!outputByte(code, ptr, uncompressedSizeBytes, bytesDecoded)) break; + firstByte = code; + prevCode = code; + continue; + } + if (code >= dictionary.size) { + if (!outputSequence(dictionary, prevCode, ptr, uncompressedSizeBytes, bytesDecoded, firstByte)) break; + if (!outputByte(firstByte, ptr, uncompressedSizeBytes, bytesDecoded)) break; + } else if (!outputSequence(dictionary, code, ptr, uncompressedSizeBytes, bytesDecoded, firstByte)) break; + + dictionary.add(prevCode, firstByte); + if (dictionary.flush(codeBitsWidth)) prevCode = Nil; + else prevCode = code; + } + + return uncompressed; +} + + +uint8_t* lzwEncode(const uint8_t* uncompressed, uint32_t uncompressedSizeBytes, uint32_t* compressedSizeBytes, uint32_t* compressedSizeBits) +{ + //LZW encoding context: + int code = Nil; + int codeBitsWidth = StartBits; + Dictionary dictionary; + + //Output bit stream we write to. This will allocate memory as needed to accommodate the encoded data. + BitStreamWriter bitStream; + + for (; uncompressedSizeBytes > 0; --uncompressedSizeBytes, ++uncompressed) { + const int value = *uncompressed; + const int index = dictionary.findIndex(code, value); + + if (index != Nil) { + code = index; + continue; + } + + //Write the dictionary code using the minimum bit-with: + bitStream.appendBitsU64(code, codeBitsWidth); + + //Flush it when full so we can restart the sequences. + if (!dictionary.flush(codeBitsWidth)) { + //There's still space for this sequence. + dictionary.add(code, value); + } + code = value; + } + + //Residual code at the end: + if (code != Nil) bitStream.appendBitsU64(code, codeBitsWidth); + + //Pass ownership of the compressed data buffer to the user pointer: + *compressedSizeBytes = bitStream.getByteCount(); + *compressedSizeBits = bitStream.numBitsWritten; + + return bitStream.release(); +} + +} + +#endif |