Compression.swift

import Foundation
import Compression

/// A convenience class for compressing an NSData object.
///
/// Example:
/// ```
/// let compression = Compression(algorithm: .ZLIB)
/// let compressedData = compression.compressData(data)
/// let decompressedData = compresison.decompressData(compressedData)
/// ```
///
public final class Compression {
    
    public enum Algorithm {
        case LZ4
        case LZFSE
        case LZMA
        case ZLIB
        
        public func algorithm() -> compression_algorithm {
            switch self {
            case .LZ4: return COMPRESSION_LZ4
            case .LZFSE: return COMPRESSION_LZFSE
            case .LZMA: return COMPRESSION_LZMA
            case .ZLIB: return COMPRESSION_ZLIB
            }
        }
    }
    
    private let algorithm: Algorithm
    
    private let bufferSize: Int
    
    public init(algorithm: Algorithm, bufferSize: Int = 0x20000) {
        self.algorithm = algorithm
        self.bufferSize = bufferSize
    }
    
    public func compressData(data: NSData) -> NSData? {
        return processData(data, algorithm: algorithm, bufferSize: bufferSize, compress: true)
    }
    
    public func decompressData(data: NSData) -> NSData? {
        return processData(data, algorithm: algorithm, bufferSize: bufferSize, compress: true)
    }
    
    private func processData(inputData: NSData, algorithm: Algorithm, bufferSize: Int, compress: Bool) -> NSData? {
        guard inputData.length > 0 else { return nil }
        
        var stream = UnsafeMutablePointer<compression_stream>.alloc(1).memory
        
        let initStatus = compression_stream_init(&stream, compress ? COMPRESSION_STREAM_ENCODE : COMPRESSION_STREAM_DECODE, algorithm.algorithm())
        guard initStatus != COMPRESSION_STATUS_ERROR else {
            print("[Compression] \(compress ? "Compression" : "Decompression") with \(algorithm) failed to init stream with status \(initStatus).")
            return nil
        }

        defer {
            compression_stream_destroy(&stream)
        }
        
        stream.src_ptr = UnsafePointer<UInt8>(inputData.bytes)
        stream.src_size = inputData.length
        
        let buffer = UnsafeMutablePointer<UInt8>.alloc(bufferSize)
        stream.dst_ptr = buffer
        stream.dst_size = bufferSize
        let outputData = NSMutableData()
        
        while true {
            let status = compression_stream_process(&stream, Int32(compress ? COMPRESSION_STREAM_FINALIZE.rawValue : 0))
            if status == COMPRESSION_STATUS_OK {
                guard stream.dst_size == 0 else { continue }
                outputData.appendBytes(buffer, length: bufferSize)
                stream.dst_ptr = buffer
                stream.dst_size = bufferSize
            } else if status == COMPRESSION_STATUS_END {
                guard stream.dst_ptr > buffer else { continue }
                outputData.appendBytes(buffer, length: stream.dst_ptr - buffer)
                return outputData
            } else if status == COMPRESSION_STATUS_ERROR {
                print("[Compression] \(compress ? "Compression" : "Decompression") with \(algorithm) failed with status \(status).")
                return nil
            }
        }
    }
}

I guess this should be a compress: false in line 45

Hey @brototyp, yeah you are right as we are decoding stream we have to set them false