feat: dump t6 xbox fastfile data

src/ZoneCommon/Zone/XChunk/XChunkProcessorLzxDecompress.cpp

@@ -1,12 +1,132 @@
 #include "XChunkProcessorLzxDecompress.h"
 
 #include <cstring>
+#include <format>
+#include <iostream>
+#include <lzx.h>
 
-size_t
-    XChunkProcessorLzxDecompress::Process(unsigned streamNumber, const uint8_t* input, const size_t inputLength, uint8_t* output, const size_t outputBufferSize)
+namespace
 {
-    // TODO: Implement
+    uint8_t NextByte(const uint8_t* input, size_t& offset, size_t& remainingSize)
+    {
+        const auto value = input[offset];
+        offset++;
+        remainingSize--;
+        return value;
+    }
 
-    memcpy(output, input, inputLength);
-    return inputLength;
+    uint16_t CombineHighLow(const uint8_t highByte, const uint8_t lowByte)
+    {
+        return static_cast<uint16_t>(static_cast<uint16_t>(static_cast<uint16_t>(highByte) << 8u) | static_cast<uint16_t>(lowByte));
+    }
+
+    void LogErrorHeaderSpace(size_t remainingInputSize)
+    {
+        std::cerr << std::format("XMemCompress: Not enough data for header: {}\n", remainingInputSize);
+    }
+} // namespace
+
+XChunkProcessorLzxDecompress::XChunkProcessorLzxDecompress(const unsigned streamCount)
+    : m_lzx_states(streamCount)
+{
+    // T6 uses 17 for window bits
+    for (auto& lzxState : m_lzx_states)
+        lzxState = lzx_init(17);
+}
+
+XChunkProcessorLzxDecompress::~XChunkProcessorLzxDecompress()
+{
+    for (auto* lzxState : m_lzx_states)
+        lzx_teardown(static_cast<lzx_state*>(lzxState));
+}
+
+size_t XChunkProcessorLzxDecompress::Process(
+    const unsigned streamNumber, const uint8_t* input, const size_t inputLength, uint8_t* output, const size_t outputBufferSize)
+{
+    auto* state = static_cast<lzx_state*>(m_lzx_states[streamNumber]);
+
+    // lzx state is reset before each chunk
+    lzx_reset(state);
+
+    size_t curInputOffset = 0uz;
+    size_t curInputSize = inputLength;
+
+    size_t curOutputOffset = 0uz;
+    size_t curOutputSize = outputBufferSize;
+
+    uint8_t lowByte;
+    uint16_t dstSize, srcSize;
+
+    while (curInputSize > 0)
+    {
+        uint8_t highByte = NextByte(input, curInputOffset, curInputSize);
+
+        uint8_t suffixSize;
+        if (highByte == 0xFF) // magic number: output is smaller than 0x8000
+        {
+            if (curInputSize < 4)
+            {
+                LogErrorHeaderSpace(curInputSize);
+                return curOutputOffset;
+            }
+
+            highByte = NextByte(input, curInputOffset, curInputSize);
+            lowByte = NextByte(input, curInputOffset, curInputSize);
+            dstSize = CombineHighLow(highByte, lowByte);
+
+            highByte = NextByte(input, curInputOffset, curInputSize);
+            lowByte = NextByte(input, curInputOffset, curInputSize);
+            srcSize = CombineHighLow(highByte, lowByte);
+
+            // The game seems to skip a 5 byte suffix after these blocks, not sure why.
+            suffixSize = 5u;
+        }
+        else
+        {
+            if (curInputSize < 1)
+            {
+                LogErrorHeaderSpace(curInputSize);
+                return curOutputOffset;
+            }
+
+            dstSize = 0x8000u;
+            lowByte = NextByte(input, curInputOffset, curInputSize);
+            srcSize = CombineHighLow(highByte, lowByte);
+
+            suffixSize = 0u;
+        }
+
+        if (srcSize == 0 || dstSize == 0)
+        {
+            // Other implementations do not handle this as a failure, game code suggests otherwise though
+            std::cerr << std::format("XMemCompress: EOF: {} {}, {}\n", srcSize, dstSize, curInputSize);
+            return curOutputOffset;
+        }
+
+        if (static_cast<size_t>(srcSize) + suffixSize > curInputSize)
+        {
+            std::cerr << std::format("XMemCompress: block size bigger than remaining data: {} > {}\n", srcSize, curInputSize);
+            return curOutputOffset;
+        }
+
+        if (dstSize > curOutputSize)
+        {
+            std::cerr << std::format("XMemCompress: output size bigger than remaining data: {} > {}\n", dstSize, curOutputSize);
+            return curOutputOffset;
+        }
+
+        auto ret = lzx_decompress(state, &input[curInputOffset], &output[curOutputOffset], srcSize, dstSize);
+        curInputOffset += srcSize + suffixSize;
+        curInputSize -= (srcSize + suffixSize);
+        curOutputOffset += dstSize;
+        curOutputSize -= srcSize;
+
+        if (ret != DECR_OK)
+        {
+            std::cerr << std::format("XMemCompress: lzx decompression failed: {}\n", ret);
+            return curOutputOffset;
+        }
+    }
+
+    return curOutputOffset;
 }

src/ZoneCommon/Zone/XChunk/XChunkProcessorLzxDecompress.h

@@ -1,8 +1,16 @@
 #pragma once
+
 #include "IXChunkProcessor.h"
 
+#include <vector>
+
 class XChunkProcessorLzxDecompress final : public IXChunkProcessor
 {
 public:
+    explicit XChunkProcessorLzxDecompress(unsigned streamCount);
+    ~XChunkProcessorLzxDecompress();
     size_t Process(unsigned streamNumber, const uint8_t* input, size_t inputLength, uint8_t* output, size_t outputBufferSize) override;
+
+private:
+    std::vector<void*> m_lzx_states;
 };