71 lines
1.7 KiB
C++
71 lines
1.7 KiB
C++
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#include "MemoryRead.h"
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#include "il2cpp-config.h"
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namespace il2cpp
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{
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namespace utils
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{
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uint32_t ReadCompressedUInt32(const char** p)
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{
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uint32_t val = 0;
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uint8_t read = Read8(p);
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if ((read & 0x80) == 0)
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{
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// 1 byte written
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val = read;
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}
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else if ((read & 0xC0) == 0x80)
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{
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// 2 bytes written
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val = (read & ~0x80) << 8;
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val |= Read8(p);
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}
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else if ((read & 0xE0) == 0xC0)
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{
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// 4 bytes written
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val = (read & ~0xC0) << 24;
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val |= ((uint32_t)Read8(p) << 16);
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val |= ((uint32_t)Read8(p) << 8);
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val |= Read8(p);
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}
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else if (read == 0xF0)
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{
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// 5 bytes written, we had a really large int32!
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val = Read32(p);
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}
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else if (read == 0xFE)
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{
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// Special encoding for Int32.MaxValue
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val = UINT32_MAX - 1;
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}
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else if (read == 0xFF)
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{
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// Yes we treat UInt32.MaxValue (and Int32.MinValue, see ReadCompressedInt32) specially
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val = UINT32_MAX;
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}
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else
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{
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IL2CPP_ASSERT(false && "Invalid compressed integer format");
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}
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return val;
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}
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int32_t ReadCompressedInt32(const char** p)
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{
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uint32_t encoded = ReadCompressedUInt32(p);
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// -UINT32_MAX can't be represted safely in an int32_t, so we treat it specially
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if (encoded == UINT32_MAX)
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return INT32_MIN;
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bool isNegative = encoded & 1;
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encoded >>= 1;
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if (isNegative)
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return -(int32_t)(encoded + 1);
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return encoded;
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}
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} /* utils */
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} /* il2cpp */
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