Objective-C

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. Objective-C

#import <CkoFileAccess.h>
#import <CkoCompression.h>
#import <CkoStream.h>
#import <CkoTask.h>
#import <NSString.h>

BOOL success = NO;

//  This example assumes the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

CkoFileAccess *fac = [[CkoFileAccess alloc] init];
CkoCompression *compress = [[CkoCompression alloc] init];
compress.Algorithm = @"deflate";

CkoStream *streamC = [[CkoStream alloc] init];

//  This example sets the source and sink of the stream to files.
//  A stream can have use other streams as a source or sink,
//  or the application can itself be the source/sink by directly
//  reading or writing a stream.  (See below for an example of this..)
streamC.SourceFile = @"qa_data/hamlet.xml";
streamC.SinkFile = @"qa_output/hamlet_compressed.dat";

//  Compress from source to sink.
success = [compress CompressStream: streamC];
if (success != YES) {
    NSLog(@"%@",compress.LastErrorText);
    return;
}

NSLog(@"%@",@"File-to-file deflate compression successful.");
//  Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
//  the size of the file as a string, then convert to an integer value.
NSLog(@"%@%d",@"Original size = ",[[fac FileSize: streamC.SourceFile] intValue]);
NSLog(@"%@%d",@"Compressed size = ",[[fac FileSize: streamC.SinkFile] intValue]);

//  Now do file-to-file decompression
CkoStream *streamD = [[CkoStream alloc] init];
streamD.SourceFile = @"qa_output/hamlet_compressed.dat";
streamD.SinkFile = @"qa_output/hamlet_restored.xml";

//  Decompress from source to sink.
success = [compress DecompressStream: streamD];
if (success != YES) {
    NSLog(@"%@",compress.LastErrorText);
    return;
}

NSLog(@"%@",@"File-to-file deflate decompression successful.");

//  Let's double-check to see that the files are equal in size and content:

BOOL bFilesEqual = [fac FileContentsEqual: streamC.SourceFile path2: streamD.SinkFile];
if (bFilesEqual != YES) {
    NSLog(@"%@",@"The output file is not equal to the input file!");
}
else {
    NSLog(@"%@",@"The file was successfully compressed and decompressed.");
}

//  ---------------------------------------------------------------------
//  Now let's decompress again, but this time w/ the application reading
//  the decompressed data directly from a stream.
CkoStream *streamA = [[CkoStream alloc] init];

streamA.SourceFile = @"qa_output/hamlet_compressed.dat";

//  Start decompressing in a background thread.
CkoTask *task = [compress DecompressStreamAsync: streamA];
success = [task Run];

//  Read decompressed data from streamA:
NSString *decompressedText = 0;
while ((streamA.EndOfStream != YES)) {
    if (streamA.DataAvailable == YES) {
        decompressedText = [streamA ReadString];
        NSLog(@"%@",decompressedText);
    }

}

//  Let's make sure the background task finished and that the decompress was successful.
//  It should already be the case that the task is finished.
while ((task.Finished != YES)) {
    [task SleepMs: [NSNumber numberWithInt: 20]];
}

//  The decompressor may have finished, but it is possible that data
//  remains to be flushed.  
if (streamA.DataAvailable == YES) {
    decompressedText = [streamA ReadString];
    NSLog(@"%@",decompressedText);
}

//  Did streamA succeed in reading the entire file?
if (task.TaskSuccess != YES) {
    NSLog(@"%@",@"async decompress failed:");
    NSLog(@"%@",task.ResultErrorText);
    success = NO;
}

NSLog(@"%@",@"The async decompress was successful.");