As a (small) return to the community, here’s a category that adds bzip2 compression to NSData. It requires adding libbz2.a to the project and uses Objective-C’s modern exception style.

I’ll be adding an NSValueTransformer soon. Done. See BzipValueTransformer � BryanWoods

// NSData+Bzip2.h @interface NSData (Bzip2)

• (NSData *) bzip2;
• (NSData *) bzip2WithCompressionSetting:(int)OneToNine;
• (NSData *) bunzip2;

@end

// NSData+Bzip2.m #import “NSData+Bzip2.h” #import “bzlib.h”

@implementation NSData (Bzip2)

• (NSData *) bzip2WithCompressionSetting:(int)compression { int bzret, buffer_size = 1000000; bz_stream stream = { 0 }; stream.next_in = [self bytes]; stream.avail_in = [self length];

  NSMutableData * buffer = [NSMutableData dataWithLength:buffer_size]; stream.next_out = [buffer mutableBytes]; stream.avail_out = buffer_size;

  NSMutableData * compressed = [NSMutableData data];

  BZ2_bzCompressInit(&stream, compression, 0, 0); @try { do { bzret = BZ2_bzCompress(&stream, (stream.avail_in) ? BZ_RUN : BZ_FINISH); if (bzret != BZ_RUN_OK && bzret != BZ_STREAM_END) @throw [NSException exceptionWithName:@”bzip2” reason:@”BZ2_bzCompress failed” userInfo:nil];

        [compressed appendBytes:[buffer bytes] length:(buffer_size - stream.avail_out)];
        stream.next_out = [buffer mutableBytes];
        stream.avail_out = buffer_size;
    } while(bzret != BZ_STREAM_END);   }   @finally {
    BZ2_bzCompressEnd(&stream);   }
  

  return compressed; }

• (NSData *) bunzip2 { int bzret; bz_stream stream = { 0 }; stream.next_in = [self bytes]; stream.avail_in = [self length];

  const int buffer_size = 10000; NSMutableData * buffer = [NSMutableData dataWithLength:buffer_size]; stream.next_out = [buffer mutableBytes]; stream.avail_out = buffer_size;

  NSMutableData * decompressed = [NSMutableData data];

  BZ2_bzDecompressInit(&stream, 0, NO); @try { do { bzret = BZ2_bzDecompress(&stream); if (bzret != BZ_OK && bzret != BZ_STREAM_END) @throw [NSException exceptionWithName:@”bzip2” reason:@”BZ2_bzDecompress failed” userInfo:nil];

        [decompressed appendBytes:[buffer bytes] length:(buffer_size - stream.avail_out)];
        stream.next_out = [buffer mutableBytes];
        stream.avail_out = buffer_size;
    } while(bzret != BZ_STREAM_END);   }   @finally {
    BZ2_bzDecompressEnd(&stream);   }
  

  return decompressed; } @end