Compress & decompress of NSData in Iphone

- (NSData *) compressedData
{
NSData *result = nil;
unsigned int srcLength = [self length];
if (srcLength > 0) {
uLong buffLength = srcLength * 1.001 + 12;
NSMutableData *compData = [[NSMutableData alloc] initWithCapacity:buffLength];
[compData increaseLengthBy:buffLength];
int error = compress([compData mutableBytes], &buffLength, [self bytes], srcLength);
switch( error ) {
case Z_OK:
[compData setLength: buffLength];
COPY(result, compData);
break;
default:
NSAssert(NO, @"Error compressing: Memory Error!");
break;
}
RELEASE(compData);
}
AUTORELEASE(result);
return result;
}

- (NSData *) decompressedData
{
if ([self length] == 0) return self;
unsigned full_length = [self length];
unsigned half_length = [self length] / 2;
NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length];
BOOL done = NO;
int status;
z_stream strm;
strm.next_in = (Bytef *)[self bytes];
strm.avail_in = [self length];
strm.total_out = 0;
strm.zalloc = Z_NULL;
strm.zfree = Z_NULL;
strm.opaque = Z_NULL;
if (inflateInit(&strm) != Z_OK) {
return nil;
}
while (!done) {
// Make sure we have enough room and reset the lengths.
if (strm.total_out >= [decompressed length]) {
[decompressed increaseLengthBy: half_length];
}
strm.next_out = [decompressed mutableBytes] + strm.total_out;
strm.avail_out = [decompressed length] - strm.total_out;
// Inflate another chunk.
status = inflate (&strm, Z_SYNC_FLUSH);
if (status == Z_STREAM_END) {
done = YES;
} else if (status != Z_OK) {
break;
}
}
if (inflateEnd (&strm) != Z_OK) {
return nil;
}
// Set real length.
if (done) {
[decompressed setLength: strm.total_out];
return [NSData dataWithData: decompressed];
} else {
return nil;
}
}