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    <p>Following @Zaph &amp; @Brad Larson's posts, below are the 2 methods <code>gzipInflate</code> and <code>gzipDeflate</code> that work just fine to compress/decompress <code>NSData</code>. (code reformatted from <a href="http://cocoadev.com/wiki/NSDataCategory" rel="noreferrer">cocoadev.com/wiki/NSDataCategory</a></p> <pre><code>#import "zlib.h" // don't forget to add libz.1.2.x.dylib into your project - (NSData *)gzipInflate:(NSData*)data { if ([data length] == 0) return data; unsigned full_length = [data length]; unsigned half_length = [data length] / 2; NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length]; BOOL done = NO; int status; z_stream strm; strm.next_in = (Bytef *)[data bytes]; strm.avail_in = [data length]; strm.total_out = 0; strm.zalloc = Z_NULL; strm.zfree = Z_NULL; if (inflateInit2(&amp;strm, (15+32)) != Z_OK) return nil; while (!done) { // Make sure we have enough room and reset the lengths. if (strm.total_out &gt;= [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 (&amp;strm, Z_SYNC_FLUSH); if (status == Z_STREAM_END) done = YES; else if (status != Z_OK) break; } if (inflateEnd (&amp;strm) != Z_OK) return nil; // Set real length. if (done) { [decompressed setLength: strm.total_out]; return [NSData dataWithData: decompressed]; } else return nil; } - (NSData *)gzipDeflate:(NSData*)data { if ([data length] == 0) return data; z_stream strm; strm.zalloc = Z_NULL; strm.zfree = Z_NULL; strm.opaque = Z_NULL; strm.total_out = 0; strm.next_in=(Bytef *)[data bytes]; strm.avail_in = [data length]; // Compresssion Levels: // Z_NO_COMPRESSION // Z_BEST_SPEED // Z_BEST_COMPRESSION // Z_DEFAULT_COMPRESSION if (deflateInit2(&amp;strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY) != Z_OK) return nil; NSMutableData *compressed = [NSMutableData dataWithLength:16384]; // 16K chunks for expansion do { if (strm.total_out &gt;= [compressed length]) [compressed increaseLengthBy: 16384]; strm.next_out = [compressed mutableBytes] + strm.total_out; strm.avail_out = [compressed length] - strm.total_out; deflate(&amp;strm, Z_FINISH); } while (strm.avail_out == 0); deflateEnd(&amp;strm); [compressed setLength: strm.total_out]; return [NSData dataWithData:compressed]; } </code></pre> <p>From the log:</p> <pre><code>[data length] (orig):989631 [data length] (gz): 102757 [data length] (ungz):989631 </code></pre>
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    1. POIs there a practical way to compress NSData?
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    1. USAdriano Lucas
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    1. COWow, this is great! Thanks
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    2. CO@Rickay if wanting to use bzip2 instead of gzip, see [this post](http://stackoverflow.com/questions/9577735/how-compress-data-in-memory-buffer-by-using-libbz2-library-in-c-program/11390277#11390277).
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    3. COLooks very nice, but when compiling, Xcode says _BZ2_bzCompressEnd and friends are undefined symbols for armv7.
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