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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2025 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
//
//===----------------------------------------------------------------------===//
extension String {
/// Convert to NFC and percent-escape.
func normalizedAddingPercentEncoding(
withAllowedCharacters allowed: URL.Template.Expression.Operator.AllowedCharacters
) -> String {
return withContiguousNFCAndOutputBuffer(allowed: allowed) { input -> String in
switch input {
case .noConversionNorEncodedNeeded: return self
case .needsEncoding(input: let inputBuffer, outputCount: let outputCount):
switch allowed {
case .unreserved:
return addingPercentEncodingToNFC(
input: inputBuffer,
outputCount: outputCount,
allowed: allowed
)
case .unreservedReserved:
return withUnsafeTemporaryAllocation(of: UInt8.self, capacity: outputCount + 1) { outputBuffer -> String in
addPercentEscapesForUnreservedReserved(
inputBuffer: inputBuffer,
outputBuffer: outputBuffer
)
}
}
}
}
}
}
/// For the `unreserved / reserved / pct-encoded` case, create a String by percent encoding the NFC input as needed.
private func addPercentEscapesForUnreservedReserved(
inputBuffer: UnsafeBufferPointer<UTF8.CodeUnit>,
outputBuffer: UnsafeMutableBufferPointer<UTF8.CodeUnit>
) -> String {
let allowed = URL.Template.Expression.Operator.AllowedCharacters.unreservedReserved
var remainingInput = inputBuffer[...]
var outputIndex = 0
func write(_ a: UInt8) {
outputBuffer[outputIndex] = a
outputIndex += 1
}
while let next = remainingInput.popFirst() {
// Any (valid) existing escape sequences need to be copied to the output verbatim.
// But any `%` that are not part of a valid escape sequence, need to be encoded.
guard next != UInt8(ascii: "%") || remainingInput.count < 2 else {
// Is this a valid escape sequence?
if remainingInput[remainingInput.startIndex].isValidHexDigit && remainingInput[remainingInput.startIndex + 1].isValidHexDigit {
write(next)
} else {
write(UInt8(ascii: "%"))
write(UInt8(ascii: "2"))
write(UInt8(ascii: "5"))
}
continue
}
if allowed.isAllowedCodeUnit(next) {
write(next)
} else {
write(UInt8(ascii: "%"))
write(hexToAscii(next >> 4))
write(hexToAscii(next & 0xf))
}
}
return String(decoding: outputBuffer[..<outputIndex], as: UTF8.self)
}
private func addingPercentEncodingToNFC(
input inputBuffer: UnsafeBufferPointer<String.UTF8View.Element>,
outputCount: Int,
allowed: URL.Template.Expression.Operator.AllowedCharacters
) -> String {
return withUnsafeTemporaryAllocation(of: UInt8.self, capacity: outputCount + 1) { outputBuffer -> String in
var index = 0
for v in inputBuffer {
if allowed.isAllowedCodeUnit(v) {
outputBuffer[index] = v
index += 1
} else {
outputBuffer[index + 0] = UInt8(ascii: "%")
outputBuffer[index + 1] = hexToAscii(v >> 4)
outputBuffer[index + 2] = hexToAscii(v & 0xF)
index += 3
}
}
return String(decoding: outputBuffer[..<index], as: UTF8.self)
}
}
fileprivate enum NeededConversion: Comparable {
case none
case encodeOnly(outputCount: Int)
case convertAndEncode
}
fileprivate enum AllowedNFCResult {
case noConversionNorEncodedNeeded
case needsEncoding(input: UnsafeBufferPointer<String.UTF8View.Element>, outputCount: Int)
}
extension String {
/// Runs the given closure with a UTF-8 buffer that is the NFC normalized version of the string.
///
/// If the input is already NFC _and_ it only contains allowed characters, the given closure will
/// be called with ``NeededConversion.noConversionNorEncodedNeeded`.
fileprivate func withContiguousNFCAndOutputBuffer<R>(
allowed: URL.Template.Expression.Operator.AllowedCharacters,
_ body: (AllowedNFCResult) -> R
) -> R {
// We’ll do a quick check. If the input is valid UTF-8 and bytes are less than
// 0xcc, then it’s NFC. Since most input will be ASCII, this allows us to
// be more efficient in those common cases.
// At the same, we’ll do a check if there are any characters that need
// encoding. If the input (is likely) already NFC, and nothing needs
// percent encoding, we can just use the original input.
func cheapCheck(utf8Buffer: some Collection<UInt8>) -> NeededConversion {
// The number of code units that need percent encoding:
var needsEncoding = 0
var count = 0
for v in utf8Buffer {
count += 1
switch (v < 0xcc, allowed.isAllowedCodeUnit(v)) {
case (false, _):
// Input might not be NFC. Need to convert.
return .convertAndEncode
case (true, false):
needsEncoding += 1
case (true, true):
break
}
}
return (needsEncoding == 0) ? .none : .encodeOnly(outputCount: count + 2 * needsEncoding)
}
let fastResult: R?? = utf8.withContiguousStorageIfAvailable {
switch cheapCheck(utf8Buffer: $0) {
case .none:
return body(.noConversionNorEncodedNeeded)
case .encodeOnly(outputCount: let c):
return body(.needsEncoding(input: $0, outputCount: c))
case .convertAndEncode:
return nil
}
}
switch fastResult {
case .some(.some(let r)):
return r
case .some(.none):
// We have a continguous UTF-8 buffer, but it’s (probably) not NFC
break
case .none:
// Contiguous UTF-8 storage is not available:
switch cheapCheck(utf8Buffer: utf8) {
case .none:
return body(.noConversionNorEncodedNeeded)
case .encodeOnly(outputCount: let c):
return withUnsafeTemporaryAllocation(of: UInt8.self, capacity: utf8.count) { buffer in
_ = buffer.initialize(from: utf8)
return body(.needsEncoding(input: UnsafeBufferPointer(buffer), outputCount: c))
}
case .convertAndEncode:
break
}
}
// Convert to NFC:
return _nfcCodeUnits.withUnsafeBufferPointer { input in
let outputCount = input.reduce(into: 0) {
$0 += allowed.isAllowedCodeUnit($1) ? 1 : 3
}
return body(.needsEncoding(input: input, outputCount: outputCount))
}
}
}
extension URL.Template.Expression.Operator.AllowedCharacters {
func isAllowedCodeUnit(_ unit: UTF8.CodeUnit) -> Bool {
switch self {
case .unreserved:
return unit.isUnreservedURLCharacter
case .unreservedReserved:
return unit.isValidURLCharacter
}
}
}
private func hexToAscii(_ hex: UInt8) -> UInt8 {
switch hex {
case 0x0: UInt8(ascii: "0")
case 0x1: UInt8(ascii: "1")
case 0x2: UInt8(ascii: "2")
case 0x3: UInt8(ascii: "3")
case 0x4: UInt8(ascii: "4")
case 0x5: UInt8(ascii: "5")
case 0x6: UInt8(ascii: "6")
case 0x7: UInt8(ascii: "7")
case 0x8: UInt8(ascii: "8")
case 0x9: UInt8(ascii: "9")
case 0xA: UInt8(ascii: "A")
case 0xB: UInt8(ascii: "B")
case 0xC: UInt8(ascii: "C")
case 0xD: UInt8(ascii: "D")
case 0xE: UInt8(ascii: "E")
case 0xF: UInt8(ascii: "F")
default: fatalError("Invalid hex digit: \(hex)")
}
}
|
