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msagent.js/core: Clean up C++/WASM decompression code

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mostly just removing C-style casts and replacing the win32 LO* macros with constexpr functions, because they suck

(also, add a gitignore scoped to msagent.js to ignore the obj/ of building the WASM decompression code)
This commit is contained in:
Lily Tsuru 2024-11-26 23:57:23 -05:00
parent 95708da8cc
commit d9faea4c1c
3 changed files with 32 additions and 24 deletions
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1
msagent.js/.gitignore vendored Normal file
View file

@ -0,0 +1 @@
core/obj

50
msagent.js/core/src/decompress.cpp
View file

@ -2,17 +2,25 @@
// Integer types from WASI-libc
using usize = unsigned int;
using u32 = unsigned int;
using u16 = unsigned short;
using u8 = unsigned char;
#define LOWORD(x) (x & 0xffff)
#define LOBYTE(x) (x & 0xff)
template<class T>
constexpr auto LowOrderShortOf(T item) {
return static_cast<u16>(item & 0xffff);
}
#define PUBLIC __attribute__((visibility("default"))) extern "C"
template<class T>
constexpr auto LowOrderByteOf(T item) {
return static_cast<u8>(item & 0xff);
}
PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTrgData, usize pTrgSize) {
const u8* lSrcPtr = (const u8*)pSrcData;
#define PUBLIC extern "C" __attribute__((visibility("default")))
PUBLIC usize agentDecompressWASM(const u8* pSrcData, usize pSrcSize, u8* pTrgData, usize pTrgSize) {
const u8* lSrcPtr = pSrcData;
const u8* lSrcEnd = lSrcPtr + pSrcSize;
u8* lTrgPtr = (u8*)pTrgData;
u8* lTrgPtr = pTrgData;
u8* lTrgEnd = lTrgPtr + pTrgSize;
u32 lSrcQuad;
u8 lTrgByte;
@ -38,15 +46,15 @@ PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTr
lSrcPtr += 5;
while((lSrcPtr < lSrcEnd) && (lTrgPtr < lTrgEnd)) {
lSrcQuad = *(const u32*)(lSrcPtr - sizeof(u32));
lSrcQuad = *reinterpret_cast<const u32*>(lSrcPtr - sizeof(u32));
if(lSrcQuad & (1 << LOWORD(lBitCount))) {
if(lSrcQuad & (1 << LowOrderShortOf(lBitCount))) {
lSrcOffset = 1;
if(lSrcQuad & (1 << LOWORD(lBitCount + 1))) {
if(lSrcQuad & (1 << LOWORD(lBitCount + 2))) {
if(lSrcQuad & (1 << LOWORD(lBitCount + 3))) {
lSrcQuad >>= LOWORD(lBitCount + 4);
if(lSrcQuad & (1 << LowOrderShortOf(lBitCount + 1))) {
if(lSrcQuad & (1 << LowOrderShortOf(lBitCount + 2))) {
if(lSrcQuad & (1 << LowOrderShortOf(lBitCount + 3))) {
lSrcQuad >>= LowOrderShortOf(lBitCount + 4);
lSrcQuad &= 0x000FFFFF;
if(lSrcQuad == 0x000FFFFF) {
break;
@ -56,19 +64,19 @@ PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTr
lSrcOffset = 2;
} else {
lSrcQuad >>= LOWORD(lBitCount + 4);
lSrcQuad >>= LowOrderShortOf(lBitCount + 4);
lSrcQuad &= 0x00000FFF;
lSrcQuad += 577;
lBitCount += 16;
}
} else {
lSrcQuad >>= LOWORD(lBitCount + 3);
lSrcQuad >>= LowOrderShortOf(lBitCount + 3);
lSrcQuad &= 0x000001FF;
lSrcQuad += 65;
lBitCount += 12;
}
} else {
lSrcQuad >>= LOWORD(lBitCount + 2);
lSrcQuad >>= LowOrderShortOf(lBitCount + 2);
lSrcQuad &= 0x0000003F;
lSrcQuad += 1;
lBitCount += 8;
@ -76,16 +84,16 @@ PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTr
lSrcPtr += (lBitCount / 8);
lBitCount &= 7;
lRunLgth = *(const u32*)(lSrcPtr - sizeof(u32));
lRunLgth = *reinterpret_cast<const u32*>(lSrcPtr - sizeof(u32));
lRunCount = 0;
while(lRunLgth & (1 << LOWORD(lBitCount + lRunCount))) {
while(lRunLgth & (1 << LowOrderShortOf(lBitCount + lRunCount))) {
lRunCount++;
if(lRunCount > 11) {
break;
}
}
lRunLgth >>= LOWORD(lBitCount + lRunCount + 1);
lRunLgth >>= LowOrderShortOf(lBitCount + lRunCount + 1);
lRunLgth &= (1 << lRunCount) - 1;
lRunLgth += 1 << lRunCount;
lRunLgth += lSrcOffset;
@ -103,10 +111,10 @@ PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTr
lRunLgth--;
}
} else {
lSrcQuad >>= LOWORD(lBitCount + 1);
lSrcQuad >>= LowOrderShortOf(lBitCount + 1);
lBitCount += 9;
lTrgByte = LOBYTE(lSrcQuad);
lTrgByte = LowOrderByteOf(lSrcQuad);
*(lTrgPtr++) = lTrgByte;
}
@ -114,5 +122,5 @@ PUBLIC usize agentDecompressWASM(const void* pSrcData, usize pSrcSize, void* pTr
lBitCount &= 7;
}
return (usize)(lTrgPtr - (u8*)pTrgData);
return static_cast<usize>(lTrgPtr - pTrgData);
}

5
msagent.js/core/src/decompress.ts
View file

@ -28,8 +28,7 @@ function compressWASMGetMemory(): WebAssembly.Memory {
// Decompress Agent compressed data. This compression algorithm sucks.
// [dest] is to be preallocated to the decompressed data size.
export function compressDecompress(src: Uint8Array, dest: Uint8Array) {
// Grow the WASM heap if needed. Funnily enough, this code is never hit in most
// ACSes, so IDK if it's even needed
// Grow the WASM heap if needed.
compressWasm.growHeapTo(src.length + dest.length);
let memory = compressWASMGetMemory();
@ -41,7 +40,7 @@ export function compressDecompress(src: Uint8Array, dest: Uint8Array) {
// Call the WASM compression routine
let nrBytesDecompressed = compressWasmGetExports().agentDecompressWASM(0, src.length, src.length, dest.length);
if (nrBytesDecompressed != dest.length) throw new Error(`decompression failed: ${nrBytesDecompressed} != ${dest.length}`);
if (nrBytesDecompressed != dest.length) throw new Error(`Decompression failed: Output ${nrBytesDecompressed} != expected ${dest.length}`);
// The uncompressed data is located at memory[src.length..dest.length].
// Copy it into the destination buffer.