(Objective-C) Decompress Large Binary File in Blocks

Decompresses a large binary file in blocks.

Note: This example requires Chilkat v11.0.0 or greater.

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#import <CkoFileAccess.h>
#import <CkoCompression.h>

BOOL success = NO;

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

CkoFileAccess *facSrc = [[CkoFileAccess alloc] init];
CkoFileAccess *facDest = [[CkoFileAccess alloc] init];

// Open a previously compressed file for decompressing.
// See Compress Large File in Blocks

success = [facSrc OpenForRead: @"c:/temp/qa_output/compressedBmp.dat"];
if (success == NO) {
    NSLog(@"%@",facSrc.LastErrorText);
    return;
}

// If we compress in 32K chunks, find out how many blocks there will be.
int blockSize = 32768;
int numBlocks = [[facSrc GetNumBlocks: [NSNumber numberWithInt: blockSize]] intValue];

// Open an output file for the decompressed data.
success = [facDest OpenForWrite: @"c:/temp/qa_output/decompressed.bmp"];
if (success == NO) {
    NSLog(@"%@",facDest.LastErrorText);
    return;
}

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

NSData decompressedBytes;
NSData compressedBytes;

// Assuming numBlocks > 1
compress.FirstChunk = YES;
compress.LastChunk = NO;

int i = 0;
while (i < numBlocks) {
    compressedBytes = [facSrc ReadBlock: [NSNumber numberWithInt: i] blockSize: [NSNumber numberWithInt: blockSize]];

    decompressedBytes = [compress DecompressBytes: compressedBytes];
    [facDest FileWrite: decompressedBytes];

    i = i + 1;

    compress.FirstChunk = NO;
    if (i == (numBlocks - 1)) {
        compress.LastChunk = YES;
    }

}

[facSrc FileClose];
[facDest FileClose];

NSLog(@"%@",@"Finished decompressing file.");