/
StringCreate.swift
301 lines (264 loc) · 9.12 KB
/
StringCreate.swift
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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 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
//
//===----------------------------------------------------------------------===//
// String Creation Helpers
//===----------------------------------------------------------------------===//
internal func _allASCII(_ input: UnsafeBufferPointer<UInt8>) -> Bool {
if input.isEmpty { return true }
// NOTE: Avoiding for-in syntax to avoid bounds checks
//
// TODO(String performance): SIMD-ize
//
let ptr = input.baseAddress._unsafelyUnwrappedUnchecked
var i = 0
let count = input.count
let stride = MemoryLayout<UInt>.stride
let address = Int(bitPattern: ptr)
let wordASCIIMask = UInt(truncatingIfNeeded: 0x8080_8080_8080_8080 as UInt64)
let byteASCIIMask = UInt8(truncatingIfNeeded: wordASCIIMask)
while (address &+ i) % stride != 0 && i < count {
guard ptr[i] & byteASCIIMask == 0 else { return false }
i &+= 1
}
while (i &+ stride) <= count {
let word: UInt = UnsafePointer(
bitPattern: address &+ i
)._unsafelyUnwrappedUnchecked.pointee
guard word & wordASCIIMask == 0 else { return false }
i &+= stride
}
while i < count {
guard ptr[i] & byteASCIIMask == 0 else { return false }
i &+= 1
}
return true
}
extension String {
internal static func _uncheckedFromASCII(
_ input: UnsafeBufferPointer<UInt8>
) -> String {
if let smol = _SmallString(input) {
return String(_StringGuts(smol))
}
let storage = __StringStorage.create(initializingFrom: input, isASCII: true)
return storage.asString
}
@usableFromInline
internal static func _fromASCII(
_ input: UnsafeBufferPointer<UInt8>
) -> String {
_internalInvariant(_allASCII(input), "not actually ASCII")
return _uncheckedFromASCII(input)
}
internal static func _fromASCIIValidating(
_ input: UnsafeBufferPointer<UInt8>
) -> String? {
if _fastPath(_allASCII(input)) {
return _uncheckedFromASCII(input)
}
return nil
}
public // SPI(Foundation)
static func _tryFromUTF8(_ input: UnsafeBufferPointer<UInt8>) -> String? {
guard case .success(let extraInfo) = validateUTF8(input) else {
return nil
}
return String._uncheckedFromUTF8(input, isASCII: extraInfo.isASCII)
}
@usableFromInline
internal static func _fromUTF8Repairing(
_ input: UnsafeBufferPointer<UInt8>
) -> (result: String, repairsMade: Bool) {
switch validateUTF8(input) {
case .success(let extraInfo):
return (String._uncheckedFromUTF8(
input, asciiPreScanResult: extraInfo.isASCII
), false)
case .error(let initialRange):
return (repairUTF8(input, firstKnownBrokenRange: initialRange), true)
}
}
internal static func _fromLargeUTF8Repairing(
uninitializedCapacity capacity: Int,
initializingWith initializer: (
_ buffer: UnsafeMutableBufferPointer<UInt8>
) throws -> Int
) rethrows -> String {
let result = try __StringStorage.create(
uninitializedCodeUnitCapacity: capacity,
initializingUncheckedUTF8With: initializer)
switch validateUTF8(result.codeUnits) {
case .success(let info):
result._updateCountAndFlags(
newCount: result.count,
newIsASCII: info.isASCII
)
return result.asString
case .error(let initialRange):
defer { _fixLifetime(result) }
//This could be optimized to use excess tail capacity
return repairUTF8(result.codeUnits, firstKnownBrokenRange: initialRange)
}
}
@usableFromInline
internal static func _uncheckedFromUTF8(
_ input: UnsafeBufferPointer<UInt8>
) -> String {
return _uncheckedFromUTF8(input, isASCII: _allASCII(input))
}
@usableFromInline
internal static func _uncheckedFromUTF8(
_ input: UnsafeBufferPointer<UInt8>,
isASCII: Bool
) -> String {
if let smol = _SmallString(input) {
return String(_StringGuts(smol))
}
let storage = __StringStorage.create(
initializingFrom: input, isASCII: isASCII)
return storage.asString
}
// If we've already pre-scanned for ASCII, just supply the result
@usableFromInline
internal static func _uncheckedFromUTF8(
_ input: UnsafeBufferPointer<UInt8>, asciiPreScanResult: Bool
) -> String {
if let smol = _SmallString(input) {
return String(_StringGuts(smol))
}
let isASCII = asciiPreScanResult
let storage = __StringStorage.create(
initializingFrom: input, isASCII: isASCII)
return storage.asString
}
@usableFromInline
internal static func _uncheckedFromUTF16(
_ input: UnsafeBufferPointer<UInt16>
) -> String {
// TODO(String Performance): Attempt to form smol strings
// TODO(String performance): Skip intermediary array, transcode directly
// into a StringStorage space.
var contents: [UInt8] = []
contents.reserveCapacity(input.count)
let repaired = transcode(
input.makeIterator(),
from: UTF16.self,
to: UTF8.self,
stoppingOnError: false,
into: { contents.append($0) })
_internalInvariant(!repaired, "Error present")
return contents.withUnsafeBufferPointer { String._uncheckedFromUTF8($0) }
}
@inline(never) // slow path
private static func _slowFromCodeUnits<
Input: Collection,
Encoding: Unicode.Encoding
>(
_ input: Input,
encoding: Encoding.Type,
repair: Bool
) -> (String, repairsMade: Bool)?
where Input.Element == Encoding.CodeUnit {
// TODO(String Performance): Attempt to form smol strings
// TODO(String performance): Skip intermediary array, transcode directly
// into a StringStorage space.
var contents: [UInt8] = []
contents.reserveCapacity(input.underestimatedCount)
let repaired = transcode(
input.makeIterator(),
from: Encoding.self,
to: UTF8.self,
stoppingOnError: false,
into: { contents.append($0) })
guard repair || !repaired else { return nil }
let str = contents.withUnsafeBufferPointer { String._uncheckedFromUTF8($0) }
return (str, repaired)
}
@usableFromInline @inline(never) // can't be inlined w/out breaking ABI
@_specialize(
where Input == UnsafeBufferPointer<UInt8>, Encoding == Unicode.ASCII)
@_specialize(
where Input == Array<UInt8>, Encoding == Unicode.ASCII)
internal static func _fromCodeUnits<
Input: Collection,
Encoding: Unicode.Encoding
>(
_ input: Input,
encoding: Encoding.Type,
repair: Bool
) -> (String, repairsMade: Bool)?
where Input.Element == Encoding.CodeUnit {
guard _fastPath(encoding == Unicode.ASCII.self) else {
return _slowFromCodeUnits(input, encoding: encoding, repair: repair)
}
// Helper to simplify early returns
func resultOrSlow(_ resultOpt: String?) -> (String, repairsMade: Bool)? {
guard let result = resultOpt else {
return _slowFromCodeUnits(input, encoding: encoding, repair: repair)
}
return (result, repairsMade: false)
}
// Fast path for untyped raw storage and known stdlib types
if let contigBytes = input as? _HasContiguousBytes,
contigBytes._providesContiguousBytesNoCopy {
return resultOrSlow(contigBytes.withUnsafeBytes { rawBufPtr in
let buffer = UnsafeBufferPointer(
start: rawBufPtr.baseAddress?.assumingMemoryBound(to: UInt8.self),
count: rawBufPtr.count)
return String._fromASCIIValidating(buffer)
})
}
// Fast path for user-defined Collections
if let strOpt = input.withContiguousStorageIfAvailable({
(buffer: UnsafeBufferPointer<Input.Element>) -> String? in
return String._fromASCIIValidating(
UnsafeRawBufferPointer(buffer).bindMemory(to: UInt8.self))
}) {
return resultOrSlow(strOpt)
}
return resultOrSlow(Array(input).withUnsafeBufferPointer {
let buffer = UnsafeRawBufferPointer($0).bindMemory(to: UInt8.self)
return String._fromASCIIValidating(buffer)
})
}
public // @testable
static func _fromInvalidUTF16(
_ utf16: UnsafeBufferPointer<UInt16>
) -> String {
return String._fromCodeUnits(utf16, encoding: UTF16.self, repair: true)!.0
}
@usableFromInline
internal static func _fromSubstring(
_ substring: __shared Substring
) -> String {
if substring._offsetRange == substring.base._offsetRange {
return substring.base
}
return String._copying(substring)
}
@_alwaysEmitIntoClient
@inline(never) // slow-path
internal static func _copying(_ str: String) -> String {
return String._copying(str[...])
}
@_alwaysEmitIntoClient
@inline(never) // slow-path
internal static func _copying(_ str: Substring) -> String {
if _fastPath(str._wholeGuts.isFastUTF8) {
return str._wholeGuts.withFastUTF8(range: str._offsetRange) {
String._uncheckedFromUTF8($0)
}
}
return Array(str.utf8).withUnsafeBufferPointer {
String._uncheckedFromUTF8($0)
}
}
}