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+/*
+ * Copyright (c) 2020 - 2023 the ThorVG project. 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"
+
+
+
+#include <string>
+#include <memory.h>
+#include "tvgCompressor.h"
+
+namespace tvg {
+
+
+/************************************************************************/
+/* LZW Implementation */
+/************************************************************************/
+
+
+//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;
+}
+
+
+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();
+}
+
+
+/************************************************************************/
+/* B64 Implementation */
+/************************************************************************/
+
+
+size_t b64Decode(const char* encoded, const size_t len, char** decoded)
+{
+ static constexpr const char B64_INDEX[256] =
+ {
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+ 0, 0, 0, 0, 0, 0, 0, 62, 63, 62, 62, 63, 52, 53, 54, 55, 56, 57,
+ 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6,
+ 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
+ 25, 0, 0, 0, 0, 63, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
+ 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51
+ };
+
+
+ if (!decoded || !encoded || len == 0) return 0;
+
+ auto reserved = 3 * (1 + (len >> 2)) + 1;
+ auto output = static_cast<char*>(malloc(reserved * sizeof(char)));
+ if (!output) return 0;
+ output[reserved - 1] = '\0';
+
+ size_t idx = 0;
+
+ while (*encoded && *(encoded + 1)) {
+ if (*encoded <= 0x20) {
+ ++encoded;
+ continue;
+ }
+
+ auto value1 = B64_INDEX[(size_t)encoded[0]];
+ auto value2 = B64_INDEX[(size_t)encoded[1]];
+ output[idx++] = (value1 << 2) + ((value2 & 0x30) >> 4);
+
+ if (!encoded[2] || encoded[2] == '=' || encoded[2] == '.') break;
+ auto value3 = B64_INDEX[(size_t)encoded[2]];
+ output[idx++] = ((value2 & 0x0f) << 4) + ((value3 & 0x3c) >> 2);
+
+ if (!encoded[3] || encoded[3] == '=' || encoded[3] == '.') break;
+ auto value4 = B64_INDEX[(size_t)encoded[3]];
+ output[idx++] = ((value3 & 0x03) << 6) + value4;
+ encoded += 4;
+ }
+ *decoded = output;
+ return reserved;
+}
+
+
+}