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`Substring.UTF8View` began implementing `Collection.withContiguousStorageIfAvailable(_:)` starting in Swift 5.3. Update `ByteBuffer.setSubstring(_:at:)` to use it to avoid a conversion to `String` in the common case. (#1975) 

Co-authored-by: George Barnett <gbarnett@apple.com>
Co-authored-by: Cory Benfield <lukasa@apple.com>
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Gwynne Raskind 2022-02-07 08:24:48 -06:00 committed by GitHub
parent 4ad4c11526
commit 7ec0281c1f
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1 changed files with 15 additions and 9 deletions
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24
Sources/NIOCore/ByteBuffer-aux.swift
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@ -125,9 +125,9 @@ extension ByteBuffer {
@discardableResult
@inlinable
public mutating func setString(_ string: String, at index: Int) -> Int {
// Do not implement setString via setSubstring. As of Swift version 5.1.3,
// Substring.UTF8View does not implement withContiguousStorageIfAvailable
// and therefore has no fast access to the backing storage.
// Do not implement setString via setSubstring. Before Swift version 5.3,
// Substring.UTF8View did not implement withContiguousStorageIfAvailable
// and therefore had no fast access to the backing storage.
if let written = string.utf8.withContiguousStorageIfAvailable({ utf8Bytes in
self.setBytes(utf8Bytes, at: index)
}) {
@ -236,16 +236,22 @@ extension ByteBuffer {
///
/// - parameters:
/// - substring: The substring to write.
/// - index: The index for the first serilized byte.
/// - index: The index for the first serialized byte.
/// - returns: The number of bytes written
@discardableResult
@inlinable
public mutating func setSubstring(_ substring: Substring, at index: Int) -> Int {
// As of Swift 5.1.3, Substring.UTF8View does not implement
// withContiguousStorageIfAvailable and therefore has no fast access
// to the backing storage. For now, convert to a String and call
// setString instead.
return self.setString(String(substring), at: index)
// Substring.UTF8View implements withContiguousStorageIfAvailable starting with
// Swift version 5.3.
if let written = substring.utf8.withContiguousStorageIfAvailable({ utf8Bytes in
self.setBytes(utf8Bytes, at: index)
}) {
// fast path, directly available
return written
} else {
// slow path, convert to string
return self.setString(String(substring), at: index)
}
}
// MARK: DispatchData APIs