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4cd1e812b7
Fixes a general category (pun intended) of scalar-alignment bugs surrounding exchanging non-scalar-aligned indices between views and for slicing. SE-0180 unifies the Index type of String and all its views and allows non-scalar-aligned indices to be used across views. In order to guarantee behavior, we often have to check and perform scalar alignment. To speed up these checks, we allocate a bit denoting known-to-be-aligned, so that the alignment check can skip the load. The below shows what views need to check for alignment before they can operate, and whether the indices they produce are aligned. ┌───────────────╥────────────────────┬──────────────────────────┐ │ View ║ Requires Alignment │ Produces Aligned Indices │ ╞═══════════════╬════════════════════╪══════════════════════════╡ │ Native UTF8 ║ no │ no │ ├───────────────╫────────────────────┼──────────────────────────┤ │ Native UTF16 ║ yes │ no │ ╞═══════════════╬════════════════════╪══════════════════════════╡ │ Foreign UTF8 ║ yes │ no │ ├───────────────╫────────────────────┼──────────────────────────┤ │ Foreign UTF16 ║ no │ no │ ╞═══════════════╬════════════════════╪══════════════════════════╡ │ UnicodeScalar ║ yes │ yes │ ├───────────────╫────────────────────┼──────────────────────────┤ │ Character ║ yes │ yes │ └───────────────╨────────────────────┴──────────────────────────┘ The "requires alignment" applies to any operation taking a String.Index that's not defined entirely in terms of other operations taking a String.Index. These include: * index(after:) * index(before:) * subscript * distance(from:to:) (since `to` is compared against directly) * UTF16View._nativeGetOffset(for:)
82 lines
2.5 KiB
Swift
82 lines
2.5 KiB
Swift
//===----------------------------------------------------------------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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// This file contains non-API (or underscored) declarations that are needed to
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// be kept around for ABI compatibility
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extension Unicode.UTF16 {
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@available(*, unavailable, renamed: "Unicode.UTF16.isASCII")
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@inlinable
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public static func _isASCII(_ x: CodeUnit) -> Bool {
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return Unicode.UTF16.isASCII(x)
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}
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}
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@available(*, unavailable, renamed: "Unicode.UTF8.isASCII")
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@inlinable
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internal func _isASCII(_ x: UInt8) -> Bool {
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return Unicode.UTF8.isASCII(x)
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}
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@available(*, unavailable, renamed: "Unicode.UTF8.isContinuation")
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@inlinable
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internal func _isContinuation(_ x: UInt8) -> Bool {
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return UTF8.isContinuation(x)
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}
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extension Substring {
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@available(*, unavailable, renamed: "Substring.base")
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@inlinable
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internal var _wholeString: String { return base }
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}
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extension String {
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@available(*, unavailable, renamed: "String.withUTF8")
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@inlinable
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internal func _withUTF8<R>(
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_ body: (UnsafeBufferPointer<UInt8>) throws -> R
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) rethrows -> R {
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var copy = self
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return try copy.withUTF8(body)
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}
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}
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extension Substring {
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@available(*, unavailable, renamed: "Substring.withUTF8")
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@inlinable
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internal func _withUTF8<R>(
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_ body: (UnsafeBufferPointer<UInt8>) throws -> R
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) rethrows -> R {
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var copy = self
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return try copy.withUTF8(body)
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}
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}
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// This function is no longer used but must be kept for ABI compatibility
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// because references to it may have been inlined.
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@usableFromInline
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internal func _branchHint(_ actual: Bool, expected: Bool) -> Bool {
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// The LLVM intrinsic underlying int_expect_Int1 now requires an immediate
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// argument for the expected value so we cannot call it here. This should
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// never be called in cases where performance matters, so just return the
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// value without any branch hint.
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return actual
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}
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extension String {
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@usableFromInline // Never actually used in inlinable code...
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internal func _nativeCopyUTF16CodeUnits(
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into buffer: UnsafeMutableBufferPointer<UInt16>,
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range: Range<String.Index>
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) { fatalError() }
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}
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