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cdfeb88cfe
Streamline internal String creation. Previously, everything funneled into a single generic function, however, every single call of the generic funnel had relevant specific information that could be used for a more efficient algorithm. In preparation for efficiently forming small strings, refactor this logic into a handful of more specialized subroutines to preserve more specific information from the callers.
74 lines
2.5 KiB
Swift
74 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 - 2017 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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import SwiftShims
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/// Returns a string read from standard input through the end of the current
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/// line or until EOF is reached.
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///
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/// Standard input is interpreted as `UTF-8`. Invalid bytes are replaced by
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/// Unicode [replacement characters][rc].
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///
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/// [rc]:
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/// http://en.wikipedia.org/wiki/Specials_(Unicode_block)#Replacement_character
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///
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/// - Parameter strippingNewline: If `true`, newline characters and character
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/// combinations are stripped from the result; otherwise, newline characters
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/// or character combinations are preserved. The default is `true`.
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/// - Returns: The string of characters read from standard input. If EOF has
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/// already been reached when `readLine()` is called, the result is `nil`.
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@_inlineable // FIXME(sil-serialize-all)
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public func readLine(strippingNewline: Bool = true) -> String? {
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var linePtrVar: UnsafeMutablePointer<UInt8>?
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var readBytes = swift_stdlib_readLine_stdin(&linePtrVar)
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if readBytes == -1 {
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return nil
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}
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_sanityCheck(readBytes >= 0,
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"unexpected return value from swift_stdlib_readLine_stdin")
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if readBytes == 0 {
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return ""
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}
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let linePtr = linePtrVar!
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if strippingNewline {
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// FIXME: Unicode conformance. To fix this, we need to reimplement the
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// code we call above to get a line, since it will only stop on LF.
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//
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// <rdar://problem/20013999> Recognize Unicode newlines in readLine()
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//
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// Recognize only LF and CR+LF combinations for now.
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let cr = UInt8(ascii: "\r")
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let lf = UInt8(ascii: "\n")
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if readBytes == 1 && linePtr[0] == lf {
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return ""
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}
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if readBytes >= 2 {
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switch (linePtr[readBytes - 2], linePtr[readBytes - 1]) {
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case (cr, lf):
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readBytes -= 2
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break
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case (_, lf):
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readBytes -= 1
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break
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default:
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()
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}
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}
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}
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let result = String._fromUTF8CodeUnitSequence(
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UnsafeMutableBufferPointer(start: linePtr, count: readBytes),
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repair: true)!
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_stdlib_free(linePtr)
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return result
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}
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