Contents

compressed(using:)

Returns a new data object by compressing the data object’s bytes.

Declaration

func compressed(using algorithm: NSData.CompressionAlgorithm) throws -> Self

Parameters

  • algorithm:

    An algorithm used to compress the data. For a list of available algorithms, see Compressionalgorithm.

Return Value

An NSData instance that contains the compressed buffer data.

Discussion

Use this method to compress in-memory data when you want to reduce memory usage and can afford the time to compress and decompress it. If your data object is already in a compressed format, such as media formats like JPEG images or AAC audio, additional compression may provide minimal or no reduction in memory usage.

To restore this data, use decompressed(using:), and specify the algorithm originally used to compress the data.

The following example shows how to compress the data from a string and prints the sizes of the data instances to illustrate the amount of compression:

var string = "NSData and its mutable subclass NSMutableData provide data objects, or object-oriented wrappers for byte buffers. Data objects let simple allocated buffers (that is, data with no embedded pointers) take on the behavior of Foundation objects."
let data = Data(string.utf8) as NSData
print ("original data size: \(data.count) bytes")
do {
    let compressedData = try data.compressed(using: .zlib)
    print("zlib compressed size: \(compressedData.count) bytes")
} catch {
    print ("Compression error: \(error)")
}
// Prints:
//  original data size: 241 bytes
//  zlib compressed size: 158 bytes

See Also

Compressing and Decompressing Data