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//
// ASIDataCompressor.m
// Part of ASIHTTPRequest -> http://allseeing-i.com/ASIHTTPRequest
//
// Created by Ben Copsey on 17/08/2010.
// Copyright 2010 All-Seeing Interactive. All rights reserved.
//

#import "ASIDataCompressor.h"
#import "ASIHTTPRequest.h"

#define DATA_CHUNK_SIZE 262144 // Deal with gzipped data in 256KB chunks
#define COMPRESSION_AMOUNT Z_DEFAULT_COMPRESSION

@interface ASIDataCompressor ()
+ (NSError *)deflateErrorWithCode:(int)code;
@end

@implementation ASIDataCompressor

+ (id)compressor
{
ASIDataCompressor *compressor = [[[self alloc] init] autorelease];
[compressor setupStream];
return compressor;
}

- (void)dealloc
{
if (streamReady) {
[self closeStream];
}
[super dealloc];
}

- (NSError *)setupStream
{
if (streamReady) {
return nil;
}
// Setup the inflate stream
zStream.zalloc = Z_NULL;
zStream.zfree = Z_NULL;
zStream.opaque = Z_NULL;
zStream.avail_in = 0;
zStream.next_in = 0;
int status = deflateInit2(&zStream, COMPRESSION_AMOUNT, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY);
if (status != Z_OK) {
return [[self class] deflateErrorWithCode:status];
}
streamReady = YES;
return nil;
}

- (NSError *)closeStream
{
if (!streamReady) {
return nil;
}
// Close the deflate stream
streamReady = NO;
int status = deflateEnd(&zStream);
if (status != Z_OK) {
return [[self class] deflateErrorWithCode:status];
}
return nil;
}

- (NSData *)compressBytes:(Bytef *)bytes length:(NSUInteger)length error:(NSError **)err shouldFinish:(BOOL)shouldFinish
{
if (length == 0) return nil;

NSUInteger halfLength = length/2;

// We'll take a guess that the compressed data will fit in half the size of the original (ie the max to compress at once is half DATA_CHUNK_SIZE), if not, we'll increase it below
NSMutableData *outputData = [NSMutableData dataWithLength:length/2];

int status;

zStream.next_in = bytes;
zStream.avail_in = (unsigned int)length;
zStream.avail_out = 0;

NSInteger bytesProcessedAlready = zStream.total_out;
while (zStream.avail_out == 0) {

if (zStream.total_out-bytesProcessedAlready >= [outputData length]) {
[outputData increaseLengthBy:halfLength];
}

zStream.next_out = (Bytef*)[outputData mutableBytes] + zStream.total_out-bytesProcessedAlready;
zStream.avail_out = (unsigned int)([outputData length] - (zStream.total_out-bytesProcessedAlready));
status = deflate(&zStream, shouldFinish ? Z_FINISH : Z_NO_FLUSH);

if (status == Z_STREAM_END) {
break;
} else if (status != Z_OK) {
if (err) {
*err = [[self class] deflateErrorWithCode:status];
}
return NO;
}
}

// Set real length
[outputData setLength: zStream.total_out-bytesProcessedAlready];
return outputData;
}


+ (NSData *)compressData:(NSData*)uncompressedData error:(NSError **)err
{
NSError *theError = nil;
NSData *outputData = [[ASIDataCompressor compressor] compressBytes:(Bytef *)[uncompressedData bytes] length:[uncompressedData length] error:&theError shouldFinish:YES];
if (theError) {
if (err) {
*err = theError;
}
return nil;
}
return outputData;
}



+ (BOOL)compressDataFromFile:(NSString *)sourcePath toFile:(NSString *)destinationPath error:(NSError **)err
{
NSFileManager *fileManager = [[[NSFileManager alloc] init] autorelease];

// Create an empty file at the destination path
if (![fileManager createFileAtPath:destinationPath contents:[NSData data] attributes:nil]) {
if (err) {
*err = [NSError errorWithDomain:NetworkRequestErrorDomain code:ASICompressionError userInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"Compression of %@ failed because we were to create a file at %@",sourcePath,destinationPath],NSLocalizedDescriptionKey,nil]];
}
return NO;
}

// Ensure the source file exists
if (![fileManager fileExistsAtPath:sourcePath]) {
if (err) {
*err = [NSError errorWithDomain:NetworkRequestErrorDomain code:ASICompressionError userInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"Compression of %@ failed the file does not exist",sourcePath],NSLocalizedDescriptionKey,nil]];
}
return NO;
}

UInt8 inputData[DATA_CHUNK_SIZE];
NSData *outputData;
NSInteger readLength;
NSError *theError = nil;

ASIDataCompressor *compressor = [ASIDataCompressor compressor];

NSInputStream *inputStream = [NSInputStream inputStreamWithFileAtPath:sourcePath];
[inputStream open];
NSOutputStream *outputStream = [NSOutputStream outputStreamToFileAtPath:destinationPath append:NO];
[outputStream open];

    while ([compressor streamReady]) {

// Read some data from the file
readLength = [inputStream read:inputData maxLength:DATA_CHUNK_SIZE];

// Make sure nothing went wrong
if ([inputStream streamStatus] == NSStreamEventErrorOccurred) {
if (err) {
*err = [NSError errorWithDomain:NetworkRequestErrorDomain code:ASICompressionError userInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"Compression of %@ failed because we were unable to read from the source data file",sourcePath],NSLocalizedDescriptionKey,[inputStream streamError],NSUnderlyingErrorKey,nil]];
}
[compressor closeStream];
return NO;
}
// Have we reached the end of the input data?
if (!readLength) {
break;
}

// Attempt to deflate the chunk of data
outputData = [compressor compressBytes:inputData length:readLength error:&theError shouldFinish:readLength < DATA_CHUNK_SIZE ];
if (theError) {
if (err) {
*err = theError;
}
[compressor closeStream];
return NO;
}

// Write the deflated data out to the destination file
[outputStream write:(const uint8_t *)[outputData bytes] maxLength:[outputData length]];

// Make sure nothing went wrong
if ([inputStream streamStatus] == NSStreamEventErrorOccurred) {
if (err) {
*err = [NSError errorWithDomain:NetworkRequestErrorDomain code:ASICompressionError userInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"Compression of %@ failed because we were unable to write to the destination data file at %@",sourcePath,destinationPath],NSLocalizedDescriptionKey,[outputStream streamError],NSUnderlyingErrorKey,nil]];
            }
[compressor closeStream];
return NO;
}

    }
[inputStream close];
[outputStream close];

NSError *error = [compressor closeStream];
if (error) {
if (err) {
*err = error;
}
return NO;
}

return YES;
}

+ (NSError *)deflateErrorWithCode:(int)code
{
return [NSError errorWithDomain:NetworkRequestErrorDomain code:ASICompressionError userInfo:[NSDictionary dictionaryWithObjectsAndKeys:[NSString stringWithFormat:@"Compression of data failed with code %hi",code],NSLocalizedDescriptionKey,nil]];
}

@synthesize streamReady;
@end
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