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July 15, 2024 11:44
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Compression in Swift on Darwin Platforms
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| // | |
| // ZzCompression.swift | |
| // Core/S | |
| // | |
| // Created by Helge Heß on 25.10.19. | |
| // | |
| import Compression | |
| public extension Data { | |
| enum ZzCompressionOperation { | |
| case compress, decompress | |
| } | |
| enum ZzCompressionAlgorithm { | |
| case lz4, zlib, lzma, lz4Raw | |
| case lzfse // Apple specific | |
| } | |
| func zzDecompress(using algorithm: ZzCompressionAlgorithm = .lzfse) -> Data? { | |
| return zzCompress(using: algorithm, operation: .decompress) | |
| } | |
| func zzCompress(using algorithm: ZzCompressionAlgorithm = .lzfse, | |
| operation: ZzCompressionOperation = .compress) | |
| -> Data? | |
| { | |
| return self.withUnsafeBytes { rbp in | |
| return rbp.compress(using: algorithm, operation: operation) | |
| } | |
| } | |
| } | |
| fileprivate extension UnsafeRawBufferPointer { | |
| func compress(using algorithm: Data.ZzCompressionAlgorithm, | |
| operation: Data.ZzCompressionOperation) -> Data? | |
| { | |
| return self.bindMemory(to: UInt8.self).compress(using: algorithm, | |
| operation: operation) | |
| } | |
| } | |
| fileprivate extension UnsafeBufferPointer where Element == UInt8 { | |
| func compress(using algorithm: Data.ZzCompressionAlgorithm, | |
| operation: Data.ZzCompressionOperation) -> Data? | |
| { | |
| guard !isEmpty, let base = baseAddress else { return nil } | |
| let destBufferSize : Int = Swift.min(32768, count) | |
| let destinationBuffer : UnsafeMutablePointer<UInt8> = | |
| UnsafeMutablePointer<UInt8>.allocate(capacity: destBufferSize) | |
| defer { destinationBuffer.deallocate() } | |
| var stream = compression_stream(dst_ptr : destinationBuffer, | |
| dst_size : destBufferSize, | |
| src_ptr : base, | |
| src_size : count, state: nil) | |
| let rc = compression_stream_init(&stream, operation.streamOperation, | |
| algorithm.algorithm) | |
| guard rc != COMPRESSION_STATUS_ERROR else { | |
| console.error("could not create compression stream!") | |
| assertionFailure("could not create compression stream!") | |
| return nil | |
| } | |
| defer { compression_stream_destroy(&stream) } | |
| var destinationData = Data() | |
| destinationData.reserveCapacity(count > 512 ? (count / 3) : count) | |
| // Yup, this is required, the init overrides the ctor fields. | |
| stream.src_ptr = base | |
| stream.src_size = count | |
| repeat { | |
| let flags = COMPRESSION_STREAM_FINALIZE | |
| stream.dst_ptr = destinationBuffer | |
| stream.dst_size = destBufferSize | |
| let rc = compression_stream_process(&stream, Int32(flags.rawValue)) | |
| let encodedCount = stream.dst_ptr - destinationBuffer | |
| if encodedCount > 0 { | |
| destinationData.append(destinationBuffer, count: encodedCount) | |
| } | |
| if rc == COMPRESSION_STATUS_END { | |
| break | |
| } | |
| else if rc == COMPRESSION_STATUS_OK { | |
| continue | |
| } | |
| else { | |
| console.error("compression failed with error:", rc) | |
| return nil | |
| } | |
| } | |
| while true | |
| return destinationData | |
| } | |
| } | |
| public extension Data.ZzCompressionOperation { | |
| var streamOperation: compression_stream_operation { | |
| switch self { | |
| case .compress : return COMPRESSION_STREAM_ENCODE | |
| case .decompress : return COMPRESSION_STREAM_DECODE | |
| } | |
| } | |
| } | |
| public extension Data.ZzCompressionAlgorithm { | |
| var algorithm : compression_algorithm { | |
| switch self { | |
| case .lz4 : return COMPRESSION_LZ4 | |
| case .zlib : return COMPRESSION_ZLIB | |
| case .lzma : return COMPRESSION_LZMA | |
| case .lz4Raw : return COMPRESSION_LZ4_RAW | |
| case .lzfse : return COMPRESSION_LZFSE | |
| } | |
| } | |
| } |
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