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Improve ByteBuffer.setSubstring(_:at:) performance #1975

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merged 3 commits into from
Feb 7, 2022
Merged

Improve ByteBuffer.setSubstring(_:at:) performance #1975

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c8b6e50
`Substring.UTF8View` began implementing `Collection.withContiguousSto…
gwynne Oct 13, 2021
b90d3fe
Merge branch 'main' into improve-setsubstring-performance
glbrntt Feb 4, 2022
8e7e489
Merge branch 'main' into improve-setsubstring-performance
Lukasa Feb 7, 2022
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24 changes: 15 additions & 9 deletions Sources/NIOCore/ByteBuffer-aux.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -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)
}) {
Expand Down Expand Up @@ -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
Expand Down