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Simplify decompression code by using the high level interface to the Compressor

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llvm-svn: 17768
This commit is contained in:
Reid Spencer 2004-11-14 21:59:21 +00:00
parent 2917639a35
commit 115f252d2a
1 changed files with 11 additions and 57 deletions
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68
lib/Bytecode/Reader/Reader.cpp
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@ -2157,43 +2157,6 @@ void BytecodeReader::ParseModule() {
error("Function declared, but bytecode stream ended before definition");
}
/// This function handles allocation of the buffer used for decompression of
/// compressed bytecode files. It is called by Compressor::decompress which is
/// called by BytecodeReader::ParseBytecode.
static unsigned GetDecompressionBuffer(char*&buff, unsigned& sz, void* ctxt){
// Case the context variable to our BufferInfo
BytecodeReader::BufferInfo* bi =
reinterpret_cast<BytecodeReader::BufferInfo*>(ctxt);
// Compute the new, doubled, size of the block
unsigned new_size = bi->size * 2;
// Extend or allocate the block (realloc(0,n) == malloc(n))
char* new_buff = (char*) ::realloc(bi->buff, new_size);
// Figure out what to return to the Compressor. If this is the first call,
// then bi->buff will be null. In this case we want to return the entire
// buffer because there was no previous allocation. Otherwise, when the
// buffer is reallocated, we save the new base pointer in the BufferInfo.buff
// field but return the address of only the extension, mid-way through the
// buffer (since its size was doubled). Furthermore, the sz result must be
// 1/2 the total size of the buffer.
if (bi->buff == 0 ) {
buff = bi->buff = new_buff;
sz = new_size;
} else {
bi->buff = new_buff;
buff = new_buff + bi->size;
sz = bi->size;
}
// Retain the size of the allocated block
bi->size = new_size;
// Make sure we fail (return 1) if we didn't get any memory.
return (bi->buff == 0 ? 1 : 0);
}
/// This function completely parses a bytecode buffer given by the \p Buf
/// and \p Length parameters.
void BytecodeReader::ParseBytecode(BufPtr Buf, unsigned Length,
@ -2214,27 +2177,18 @@ void BytecodeReader::ParseBytecode(BufPtr Buf, unsigned Length,
// If this is a compressed file
if (Sig == ('l' | ('l' << 8) | ('v' << 16) | ('c' << 24))) {
// Compute the initial length of the uncompression buffer. Note that this
// is twice the length of the compressed buffer and will be doubled again
// in GetDecompressionBuffer for an initial allocation of 4xLength. This
// calculation is based on the typical compression ratio of bzip2 on LLVM
// bytecode files which typically ranges in the 50%-75% range. Since we
// tyipcally get at least 50%, doubling is insufficient. By using a 4x
// multiplier on the first allocation, we minimize the impact of having to
// copy the buffer on reallocation.
bi.size = Length * 2;
// Invoke the decompression of the bytecode. Note that we have to skip the
// file's magic number which is not part of the compressed block. Hence,
// the Buf+4 and Length-4.
unsigned decompressedLength = Compressor::decompress((char*)Buf+4,Length-4,
GetDecompressionBuffer, (void*) &bi);
// the Buf+4 and Length-4. The result goes into decompressedBlock, a data
// member for retention until BytecodeReader is destructed.
unsigned decompressedLength = Compressor::decompressToNewBuffer(
(char*)Buf+4,Length-4,decompressedBlock);
// We must adjust the buffer pointers used by the bytecode reader to point
// into the new decompressed block. After decompression, the BufferInfo
// structure (member bi), will point to a contiguous memory area that has
// into the new decompressed block. After decompression, the
// decompressedBlock will point to a contiguous memory area that has
// the decompressed data.
At = MemStart = BlockStart = Buf = (BufPtr) bi.buff;
At = MemStart = BlockStart = Buf = (BufPtr) decompressedBlock;
MemEnd = BlockEnd = Buf + decompressedLength;
// else if this isn't a regular (uncompressed) bytecode file, then its
@ -2286,8 +2240,8 @@ void BytecodeReader::ParseBytecode(BufPtr Buf, unsigned Length,
freeState();
delete TheModule;
TheModule = 0;
if (bi.buff != 0 )
::free(bi.buff);
if (decompressedBlock != 0 )
::free(decompressedBlock);
throw;
} catch (...) {
std::string msg("Unknown Exception Occurred");
@ -2295,8 +2249,8 @@ void BytecodeReader::ParseBytecode(BufPtr Buf, unsigned Length,
freeState();
delete TheModule;
TheModule = 0;
if (bi.buff != 0 )
::free(bi.buff);
if (decompressedBlock != 0 )
::free(decompressedBlock);
throw msg;
}
}