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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import Foundation
extension Data {
/// Writes the contents of the data to `url` if it is different than the existing contents, or if
/// the URL does not exist.
///
/// Checking if the contents have changed and writing the new contents are not done atomically,
/// so there is no guarantee that there are no spurious writes if this API is used concurrently.
///
/// * parameters:
/// * url: The location to write the data into.
/// * options: Options for writing the data. Default value is [].
/// * returns: `true` if the data was written.
@discardableResult
public func writeIfChanged(to url: URL, options: Data.WritingOptions = []) throws -> Bool {
let prev: Data?
do {
prev = try Data(contentsOf: url)
} catch CocoaError.fileReadNoSuchFile {
prev = nil
} catch let error as NSError where error.code == POSIXError.ENOENT.rawValue {
prev = nil
}
if prev != self {
try write(to: url, options: options)
return true
} else {
return false
}
}
}
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