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Implement the high level interface to make (de)compression easier.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@17775 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Reid Spencer 2004-11-14 22:04:46 +00:00
parent ad0846bd8b
commit e3c6ad7e76
1 changed files with 181 additions and 9 deletions
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190
lib/Support/Compressor.cpp
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@ -111,13 +111,137 @@ bool NULLCOMP_decompress(NULLCOMP_stream* s) {
void NULLCOMP_end(NULLCOMP_stream* strm) {
}
/// This structure is only used when a bytecode file is compressed.
/// As bytecode is being decompressed, the memory buffer might need
/// to be reallocated. The buffer allocation is handled in a callback
/// and this structure is needed to retain information across calls
/// to the callback.
/// @brief An internal buffer object used for handling decompression
struct BufferContext {
char* buff;
unsigned size;
BufferContext(unsigned compressedSize ) {
// Null to indicate malloc of a new block
buff = 0;
// 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 the callback for an initial allocation of 4x compressedSize. 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.
size = compressedSize*2;
}
/// 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 callback(char*&buff, unsigned& sz, void* ctxt){
// Case the context variable to our BufferContext
BufferContext* bc = reinterpret_cast<BufferContext*>(ctxt);
// Compute the new, doubled, size of the block
unsigned new_size = bc->size * 2;
// Extend or allocate the block (realloc(0,n) == malloc(n))
char* new_buff = (char*) ::realloc(bc->buff, new_size);
// Figure out what to return to the Compressor. If this is the first call,
// then bc->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 BufferContext.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 (bc->buff == 0 ) {
buff = bc->buff = new_buff;
sz = new_size;
} else {
bc->buff = new_buff;
buff = new_buff + bc->size;
sz = bc->size;
}
// Retain the size of the allocated block
bc->size = new_size;
// Make sure we fail (return 1) if we didn't get any memory.
return (bc->buff == 0 ? 1 : 0);
}
};
// This structure retains the context when compressing the bytecode file. The
// WriteCompressedData function below uses it to keep track of the previously
// filled chunk of memory (which it writes) and how many bytes have been
// written.
struct WriterContext {
// Initialize the context
WriterContext(std::ostream*OS, unsigned CS)
: chunk(0), sz(0), written(0), compSize(CS), Out(OS) {}
// Make sure we clean up memory
~WriterContext() {
if (chunk)
delete [] chunk;
}
// Write the chunk
void write(unsigned size = 0) {
unsigned write_size = (size == 0 ? sz : size);
Out->write(chunk,write_size);
written += write_size;
delete [] chunk;
chunk = 0;
sz = 0;
}
// This function is a callback used by the Compressor::compress function to
// allocate memory for the compression buffer. This function fulfills that
// responsibility but also writes the previous (now filled) buffer out to the
// stream.
static unsigned callback(char*& buffer, unsigned& size, void* context) {
// Cast the context to the structure it must point to.
WriterContext* ctxt =
reinterpret_cast<WriterContext*>(context);
// If there's a previously allocated chunk, it must now be filled with
// compressed data, so we write it out and deallocate it.
if (ctxt->chunk != 0 && ctxt->sz > 0 ) {
ctxt->write();
}
// Compute the size of the next chunk to allocate. We attempt to allocate
// enough memory to handle the compression in a single memory allocation. In
// general, the worst we do on compression of bytecode is about 50% so we
// conservatively estimate compSize / 2 as the size needed for the
// compression buffer. compSize is the size of the compressed data, provided
// by WriteBytecodeToFile.
size = ctxt->sz = ctxt->compSize / 2;
// Allocate the chunks
buffer = ctxt->chunk = new char [size];
// We must return 1 if the allocation failed so that the Compressor knows
// not to use the buffer pointer.
return (ctxt->chunk == 0 ? 1 : 0);
}
char* chunk; // pointer to the chunk of memory filled by compression
unsigned sz; // size of chunk
unsigned written; // aggregate total of bytes written in all chunks
unsigned compSize; // size of the uncompressed buffer
std::ostream* Out; // The stream we write the data to.
};
}
namespace llvm {
// Compress in one of three ways
uint64_t Compressor::compress(char* in, unsigned size, OutputDataCallback* cb,
Algorithm hint, void* context ) {
uint64_t Compressor::compress(const char* in, unsigned size,
OutputDataCallback* cb, Algorithm hint, void* context ) {
assert(in && "Can't compress null buffer");
assert(size && "Can't compress empty buffer");
assert(cb && "Can't compress without a callback function");
@ -132,7 +256,7 @@ uint64_t Compressor::compress(char* in, unsigned size, OutputDataCallback* cb,
bzdata.bzalloc = 0;
bzdata.bzfree = 0;
bzdata.opaque = 0;
bzdata.next_in = in;
bzdata.next_in = (char*)in;
bzdata.avail_in = size;
bzdata.next_out = 0;
bzdata.avail_out = 0;
@ -188,7 +312,7 @@ uint64_t Compressor::compress(char* in, unsigned size, OutputDataCallback* cb,
zdata.zalloc = Z_NULL;
zdata.zfree = Z_NULL;
zdata.opaque = Z_NULL;
zdata.next_in = reinterpret_cast<Bytef*>(in);
zdata.next_in = (Bytef*)in;
zdata.avail_in = size;
if (Z_OK != deflateInit(&zdata,6))
throw std::string(zdata.msg ? zdata.msg : "zlib error");
@ -227,7 +351,7 @@ uint64_t Compressor::compress(char* in, unsigned size, OutputDataCallback* cb,
case COMP_TYPE_SIMPLE: {
NULLCOMP_stream sdata;
sdata.next_in = in;
sdata.next_in = (char*)in;
sdata.avail_in = size;
NULLCOMP_init(&sdata);
@ -254,8 +378,33 @@ uint64_t Compressor::compress(char* in, unsigned size, OutputDataCallback* cb,
return result;
}
uint64_t
Compressor::compressToNewBuffer(const char* in, unsigned size, char*&out,
Algorithm hint) {
BufferContext bc(size);
unsigned result = compress(in,size,BufferContext::callback,hint,(void*)&bc);
out = bc.buff;
return result;
}
uint64_t
Compressor::compressToStream(const char*in, unsigned size, std::ostream& out,
Algorithm hint) {
// Set up the context and writer
WriterContext ctxt(&out,size / 2);
// Compress everything after the magic number (which we'll alter)
uint64_t zipSize = Compressor::compress(in,size,
WriterContext::callback, hint, (void*)&ctxt);
if (ctxt.chunk) {
ctxt.write(zipSize - ctxt.written);
}
return zipSize;
}
// Decompress in one of three ways
uint64_t Compressor::decompress(char *in, unsigned size,
uint64_t Compressor::decompress(const char *in, unsigned size,
OutputDataCallback* cb, void* context) {
assert(in && "Can't decompress null buffer");
assert(size > 1 && "Can't decompress empty buffer");
@ -273,7 +422,7 @@ uint64_t Compressor::decompress(char *in, unsigned size,
bzdata.bzalloc = 0;
bzdata.bzfree = 0;
bzdata.opaque = 0;
bzdata.next_in = in;
bzdata.next_in = (char*)in;
bzdata.avail_in = size - 1;
bzdata.next_out = 0;
bzdata.avail_out = 0;
@ -327,7 +476,7 @@ uint64_t Compressor::decompress(char *in, unsigned size,
zdata.zalloc = Z_NULL;
zdata.zfree = Z_NULL;
zdata.opaque = Z_NULL;
zdata.next_in = reinterpret_cast<Bytef*>(in);
zdata.next_in = (Bytef*)(in);
zdata.avail_in = size - 1;
if ( Z_OK != inflateInit(&zdata))
throw std::string(zdata.msg ? zdata.msg : "zlib error");
@ -356,7 +505,7 @@ uint64_t Compressor::decompress(char *in, unsigned size,
case COMP_TYPE_SIMPLE: {
NULLCOMP_stream sdata;
sdata.next_in = in;
sdata.next_in = (char*)in;
sdata.avail_in = size - 1;
NULLCOMP_init(&sdata);
@ -382,6 +531,29 @@ uint64_t Compressor::decompress(char *in, unsigned size,
return result;
}
uint64_t
Compressor::decompressToNewBuffer(const char* in, unsigned size, char*&out) {
BufferContext bc(size);
unsigned result = decompress(in,size,BufferContext::callback,(void*)&bc);
out = bc.buff;
return result;
}
uint64_t
Compressor::decompressToStream(const char*in, unsigned size, std::ostream& out){
// Set up the context and writer
WriterContext ctxt(&out,size / 2);
// Compress everything after the magic number (which we'll alter)
uint64_t zipSize = Compressor::decompress(in,size,
WriterContext::callback, (void*)&ctxt);
if (ctxt.chunk) {
ctxt.write(zipSize - ctxt.written);
}
return zipSize;
}
}
// vim: sw=2 ai