(Objective-C) Compress and Decompress Hex String

Imagine we have data represented as a hex string. This example demonstrates how to decode, compress, and re-encode to a smaller hex string representing the compressed data. An even better choice is to re-encode to a more compact encoding such as base64.

Note: This example requires Chilkat v9.5.0.66 or greater.

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#import <NSString.h>
#import <CkoCompression.h>
#import <CkoBinData.h>

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

BOOL success;

NSString *strHex = @"54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A";

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

CkoBinData *binDat = [[CkoBinData alloc] init];
// Load the hex string into a BinData object.
// This decodes the hexidecimal. The decoded bytes will be contained in the BinData.
[binDat AppendEncoded: strHex encoding: @"hex"];

// Compress the BinData.
[compress CompressBd: binDat];

// Get the compressed data in hex format:
NSString *compressedHex = [binDat GetEncoded: @"hex"];
NSLog(@"%@",@"compressed hex:");
NSLog(@"%@",compressedHex);

// The compressed hex is: 0BC94855282CCD4CCE56482ACA2FCF5348CBAF50C82ACD2D484D51C82F4B2D522801CAE72456552AA4E4A7EBF172850C61E5BC5C00

// Even better, get the compressed data in base64 format:
// (base64url and modbase64 are other valid choices...)
NSString *compressedBase64 = [binDat GetEncoded: @"base64"];
NSLog(@"%@",@"compressed base64:");
NSLog(@"%@",compressedBase64);

// The compressed base64 is: C8lIVSgszUzOVkgqyi/PU0jLr1DIKs0tSE1RyC9LLVIoAcrnJFZVKqTkp+vxcoUMYeW8XAA=

// Now decompress:
[binDat Clear];
[binDat AppendEncoded: compressedHex encoding: @"hex"];
[compress DecompressBd: binDat];

NSString *decompressedHex = [binDat GetEncoded: @"hex"];
NSLog(@"%@",@"decompressed hex:");
NSLog(@"%@",decompressedHex);

// The output is the original hex string:
// 54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A