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OutputStream.swift
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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2017 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
//
//===----------------------------------------------------------------------===//
import SwiftShims
//===----------------------------------------------------------------------===//
// Input/Output interfaces
//===----------------------------------------------------------------------===//
/// A type that can be the target of text-streaming operations.
///
/// You can send the output of the standard library's `print(_:to:)` and
/// `dump(_:to:)` functions to an instance of a type that conforms to the
/// `TextOutputStream` protocol instead of to standard output. Swift's
/// `String` type conforms to `TextOutputStream` already, so you can capture
/// the output from `print(_:to:)` and `dump(_:to:)` in a string instead of
/// logging it to standard output.
///
/// var s = ""
/// for n in 1...5 {
/// print(n, terminator: "", to: &s)
/// }
/// // s == "12345"
///
/// Conforming to the TextOutputStream Protocol
/// ===========================================
///
/// To make your custom type conform to the `TextOutputStream` protocol,
/// implement the required `write(_:)` method. Functions that use a
/// `TextOutputStream` target may call `write(_:)` multiple times per writing
/// operation.
///
/// As an example, here's an implementation of an output stream that converts
/// any input to its plain ASCII representation before sending it to standard
/// output.
///
/// struct ASCIILogger: TextOutputStream {
/// mutating func write(_ string: String) {
/// let ascii = string.unicodeScalars.lazy.map { scalar in
/// scalar == "\n"
/// ? "\n"
/// : scalar.escaped(asASCII: true)
/// }
/// print(ascii.joined(separator: ""), terminator: "")
/// }
/// }
///
/// The `ASCIILogger` type's `write(_:)` method processes its string input by
/// escaping each Unicode scalar, with the exception of `"\n"` line returns.
/// By sending the output of the `print(_:to:)` function to an instance of
/// `ASCIILogger`, you invoke its `write(_:)` method.
///
/// let s = "Hearts ♡ and Diamonds ♢"
/// print(s)
/// // Prints "Hearts ♡ and Diamonds ♢"
///
/// var asciiLogger = ASCIILogger()
/// print(s, to: &asciiLogger)
/// // Prints "Hearts \u{2661} and Diamonds \u{2662}"
public protocol TextOutputStream {
mutating func _lock()
mutating func _unlock()
/// Appends the given string to the stream.
mutating func write(_ string: String)
}
extension TextOutputStream {
@inlinable // FIXME(sil-serialize-all)
public mutating func _lock() {}
@inlinable // FIXME(sil-serialize-all)
public mutating func _unlock() {}
}
/// A source of text-streaming operations.
///
/// Instances of types that conform to the `TextOutputStreamable` protocol can
/// write their value to instances of any type that conforms to the
/// `TextOutputStream` protocol. The Swift standard library's text-related
/// types, `String`, `Character`, and `Unicode.Scalar`, all conform to
/// `TextOutputStreamable`.
///
/// Conforming to the TextOutputStreamable Protocol
/// =====================================
///
/// To add `TextOutputStreamable` conformance to a custom type, implement the
/// required `write(to:)` method. Call the given output stream's `write(_:)`
/// method in your implementation.
public protocol TextOutputStreamable {
/// Writes a textual representation of this instance into the given output
/// stream.
func write<Target : TextOutputStream>(to target: inout Target)
}
/// A type with a customized textual representation.
///
/// Types that conform to the `CustomStringConvertible` protocol can provide
/// their own representation to be used when converting an instance to a
/// string. The `String(describing:)` initializer is the preferred way to
/// convert an instance of *any* type to a string. If the passed instance
/// conforms to `CustomStringConvertible`, the `String(describing:)`
/// initializer and the `print(_:)` function use the instance's custom
/// `description` property.
///
/// Accessing a type's `description` property directly or using
/// `CustomStringConvertible` as a generic constraint is discouraged.
///
/// Conforming to the CustomStringConvertible Protocol
/// ==================================================
///
/// Add `CustomStringConvertible` conformance to your custom types by defining
/// a `description` property.
///
/// For example, this custom `Point` struct uses the default representation
/// supplied by the standard library:
///
/// struct Point {
/// let x: Int, y: Int
/// }
///
/// let p = Point(x: 21, y: 30)
/// print(p)
/// // Prints "Point(x: 21, y: 30)"
///
/// After implementing the `description` property and declaring
/// `CustomStringConvertible` conformance, the `Point` type provides its own
/// custom representation.
///
/// extension Point: CustomStringConvertible {
/// var description: String {
/// return "(\(x), \(y))"
/// }
/// }
///
/// print(p)
/// // Prints "(21, 30)"
public protocol CustomStringConvertible {
/// A textual representation of this instance.
///
/// Calling this property directly is discouraged. Instead, convert an
/// instance of any type to a string by using the `String(describing:)`
/// initializer. This initializer works with any type, and uses the custom
/// `description` property for types that conform to
/// `CustomStringConvertible`:
///
/// struct Point: CustomStringConvertible {
/// let x: Int, y: Int
///
/// var description: String {
/// return "(\(x), \(y))"
/// }
/// }
///
/// let p = Point(x: 21, y: 30)
/// let s = String(describing: p)
/// print(s)
/// // Prints "(21, 30)"
///
/// The conversion of `p` to a string in the assignment to `s` uses the
/// `Point` type's `description` property.
var description: String { get }
}
/// A type that can be represented as a string in a lossless, unambiguous way.
///
/// For example, the integer value 1050 can be represented in its entirety as
/// the string "1050".
///
/// The description property of a conforming type must be a value-preserving
/// representation of the original value. As such, it should be possible to
/// re-create an instance from its string representation.
public protocol LosslessStringConvertible : CustomStringConvertible {
/// Instantiates an instance of the conforming type from a string
/// representation.
init?(_ description: String)
}
/// A type with a customized textual representation suitable for debugging
/// purposes.
///
/// Swift provides a default debugging textual representation for any type.
/// That default representation is used by the `String(reflecting:)`
/// initializer and the `debugPrint(_:)` function for types that don't provide
/// their own. To customize that representation, make your type conform to the
/// `CustomDebugStringConvertible` protocol.
///
/// Because the `String(reflecting:)` initializer works for instances of *any*
/// type, returning an instance's `debugDescription` if the value passed
/// conforms to `CustomDebugStringConvertible`, accessing a type's
/// `debugDescription` property directly or using
/// `CustomDebugStringConvertible` as a generic constraint is discouraged.
///
/// - Note: Calling the `dump(_:_:_:_:)` function and printing in the debugger
/// uses both `String(reflecting:)` and `Mirror(reflecting:)` to collect
/// information about an instance. If you implement
/// `CustomDebugStringConvertible` conformance for your custom type, you may
/// want to consider providing a custom mirror by implementing
/// `CustomReflectable` conformance, as well.
///
/// Conforming to the CustomDebugStringConvertible Protocol
/// =======================================================
///
/// Add `CustomDebugStringConvertible` conformance to your custom types by
/// defining a `debugDescription` property.
///
/// For example, this custom `Point` struct uses the default representation
/// supplied by the standard library:
///
/// struct Point {
/// let x: Int, y: Int
/// }
///
/// let p = Point(x: 21, y: 30)
/// print(String(reflecting: p))
/// // Prints "p: Point = {
/// // x = 21
/// // y = 30
/// // }"
///
/// After adding `CustomDebugStringConvertible` conformance by implementing the
/// `debugDescription` property, `Point` provides its own custom debugging
/// representation.
///
/// extension Point: CustomDebugStringConvertible {
/// var debugDescription: String {
/// return "Point(x: \(x), y: \(y))"
/// }
/// }
///
/// print(String(reflecting: p))
/// // Prints "Point(x: 21, y: 30)"
public protocol CustomDebugStringConvertible {
/// A textual representation of this instance, suitable for debugging.
///
/// Calling this property directly is discouraged. Instead, convert an
/// instance of any type to a string by using the `String(reflecting:)`
/// initializer. This initializer works with any type, and uses the custom
/// `debugDescription` property for types that conform to
/// `CustomDebugStringConvertible`:
///
/// struct Point: CustomDebugStringConvertible {
/// let x: Int, y: Int
///
/// var debugDescription: String {
/// return "(\(x), \(y))"
/// }
/// }
///
/// let p = Point(x: 21, y: 30)
/// let s = String(reflecting: p)
/// print(s)
/// // Prints "(21, 30)"
///
/// The conversion of `p` to a string in the assignment to `s` uses the
/// `Point` type's `debugDescription` property.
var debugDescription: String { get }
}
//===----------------------------------------------------------------------===//
// Default (ad-hoc) printing
//===----------------------------------------------------------------------===//
@usableFromInline // FIXME(sil-serialize-all)
@_silgen_name("swift_EnumCaseName")
internal func _getEnumCaseName<T>(_ value: T) -> UnsafePointer<CChar>?
@usableFromInline // FIXME(sil-serialize-all)
@_silgen_name("swift_OpaqueSummary")
internal func _opaqueSummary(_ metadata: Any.Type) -> UnsafePointer<CChar>?
/// Do our best to print a value that cannot be printed directly.
@inlinable // FIXME(sil-serialize-all)
@_semantics("optimize.sil.specialize.generic.never")
internal func _adHocPrint_unlocked<T, TargetStream : TextOutputStream>(
_ value: T, _ mirror: Mirror, _ target: inout TargetStream,
isDebugPrint: Bool
) {
func printTypeName(_ type: Any.Type) {
// Print type names without qualification, unless we're debugPrint'ing.
target.write(_typeName(type, qualified: isDebugPrint))
}
if let displayStyle = mirror.displayStyle {
switch displayStyle {
case .optional:
if let child = mirror.children.first {
_debugPrint_unlocked(child.1, &target)
} else {
_debugPrint_unlocked("nil", &target)
}
case .tuple:
target.write("(")
var first = true
for (label, value) in mirror.children {
if first {
first = false
} else {
target.write(", ")
}
if let label = label {
if !label.isEmpty && label[label.startIndex] != "." {
target.write(label)
target.write(": ")
}
}
_debugPrint_unlocked(value, &target)
}
target.write(")")
case .struct:
printTypeName(mirror.subjectType)
target.write("(")
var first = true
for (label, value) in mirror.children {
if let label = label {
if first {
first = false
} else {
target.write(", ")
}
target.write(label)
target.write(": ")
_debugPrint_unlocked(value, &target)
}
}
target.write(")")
case .enum:
if let cString = _getEnumCaseName(value),
let caseName = String(validatingUTF8: cString) {
// Write the qualified type name in debugPrint.
if isDebugPrint {
printTypeName(mirror.subjectType)
target.write(".")
}
target.write(caseName)
} else {
// If the case name is garbage, just print the type name.
printTypeName(mirror.subjectType)
}
if let (_, value) = mirror.children.first {
if Mirror(reflecting: value).displayStyle == .tuple {
_debugPrint_unlocked(value, &target)
} else {
target.write("(")
_debugPrint_unlocked(value, &target)
target.write(")")
}
}
default:
target.write(_typeName(mirror.subjectType))
}
} else if let metatypeValue = value as? Any.Type {
// Metatype
printTypeName(metatypeValue)
} else {
// Fall back to the type or an opaque summary of the kind
if let cString = _opaqueSummary(mirror.subjectType),
let opaqueSummary = String(validatingUTF8: cString) {
target.write(opaqueSummary)
} else {
target.write(_typeName(mirror.subjectType, qualified: true))
}
}
}
@usableFromInline
@_semantics("optimize.sil.specialize.generic.never")
internal func _print_unlocked<T, TargetStream : TextOutputStream>(
_ value: T, _ target: inout TargetStream
) {
// Optional has no representation suitable for display; therefore,
// values of optional type should be printed as a debug
// string. Check for Optional first, before checking protocol
// conformance below, because an Optional value is convertible to a
// protocol if its wrapped type conforms to that protocol.
if _isOptional(type(of: value)) {
let debugPrintable = value as! CustomDebugStringConvertible
debugPrintable.debugDescription.write(to: &target)
return
}
if case let streamableObject as TextOutputStreamable = value {
streamableObject.write(to: &target)
return
}
if case let printableObject as CustomStringConvertible = value {
printableObject.description.write(to: &target)
return
}
if case let debugPrintableObject as CustomDebugStringConvertible = value {
debugPrintableObject.debugDescription.write(to: &target)
return
}
let mirror = Mirror(reflecting: value)
_adHocPrint_unlocked(value, mirror, &target, isDebugPrint: false)
}
/// Returns the result of `print`'ing `x` into a `String`.
///
/// Exactly the same as `String`, but annotated 'readonly' to allow
/// the optimizer to remove calls where results are unused.
///
/// This function is forbidden from being inlined because when building the
/// standard library inlining makes us drop the special semantics.
@_effects(readonly)
@usableFromInline
internal func _toStringReadOnlyStreamable<
T : TextOutputStreamable
>(_ x: T) -> String {
var result = ""
x.write(to: &result)
return result
}
@inline(never) @_effects(readonly)
@usableFromInline
internal func _toStringReadOnlyPrintable<
T : CustomStringConvertible
>(_ x: T) -> String {
return x.description
}
//===----------------------------------------------------------------------===//
// `debugPrint`
//===----------------------------------------------------------------------===//
@_semantics("optimize.sil.specialize.generic.never")
@inline(never)
public func _debugPrint_unlocked<T, TargetStream : TextOutputStream>(
_ value: T, _ target: inout TargetStream
) {
if let debugPrintableObject = value as? CustomDebugStringConvertible {
debugPrintableObject.debugDescription.write(to: &target)
return
}
if let printableObject = value as? CustomStringConvertible {
printableObject.description.write(to: &target)
return
}
if let streamableObject = value as? TextOutputStreamable {
streamableObject.write(to: &target)
return
}
let mirror = Mirror(reflecting: value)
_adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
}
@inlinable // FIXME(sil-serialize-all)
@_semantics("optimize.sil.specialize.generic.never")
internal func _dumpPrint_unlocked<T, TargetStream : TextOutputStream>(
_ value: T, _ mirror: Mirror, _ target: inout TargetStream
) {
if let displayStyle = mirror.displayStyle {
// Containers and tuples are always displayed in terms of their element
// count
switch displayStyle {
case .tuple:
let count = mirror.children.count
target.write(count == 1 ? "(1 element)" : "(\(count) elements)")
return
case .collection:
let count = mirror.children.count
target.write(count == 1 ? "1 element" : "\(count) elements")
return
case .dictionary:
let count = mirror.children.count
target.write(count == 1 ? "1 key/value pair" : "\(count) key/value pairs")
return
case .`set`:
let count = mirror.children.count
target.write(count == 1 ? "1 member" : "\(count) members")
return
default:
break
}
}
if let debugPrintableObject = value as? CustomDebugStringConvertible {
debugPrintableObject.debugDescription.write(to: &target)
return
}
if let printableObject = value as? CustomStringConvertible {
printableObject.description.write(to: &target)
return
}
if let streamableObject = value as? TextOutputStreamable {
streamableObject.write(to: &target)
return
}
if let displayStyle = mirror.displayStyle {
switch displayStyle {
case .`class`, .`struct`:
// Classes and structs without custom representations are displayed as
// their fully qualified type name
target.write(_typeName(mirror.subjectType, qualified: true))
return
case .`enum`:
target.write(_typeName(mirror.subjectType, qualified: true))
if let cString = _getEnumCaseName(value),
let caseName = String(validatingUTF8: cString) {
target.write(".")
target.write(caseName)
}
return
default:
break
}
}
_adHocPrint_unlocked(value, mirror, &target, isDebugPrint: true)
}
//===----------------------------------------------------------------------===//
// OutputStreams
//===----------------------------------------------------------------------===//
internal struct _Stdout : TextOutputStream {
internal init() {}
internal mutating func _lock() {
_swift_stdlib_flockfile_stdout()
}
internal mutating func _unlock() {
_swift_stdlib_funlockfile_stdout()
}
internal mutating func write(_ string: String) {
if string.isEmpty { return }
if _fastPath(string._guts.isASCII) {
defer { _fixLifetime(string) }
let ascii = string._guts._unmanagedASCIIView
_stdlib_fwrite_stdout(ascii.start, ascii.count, 1)
return
}
for c in string.utf8 {
_stdlib_putchar_unlocked(Int32(c))
}
}
}
extension String : TextOutputStream {
/// Appends the given string to this string.
///
/// - Parameter other: A string to append.
@inlinable // FIXME(sil-serialize-all)
public mutating func write(_ other: String) {
self += other
}
}
//===----------------------------------------------------------------------===//
// Streamables
//===----------------------------------------------------------------------===//
extension String : TextOutputStreamable {
/// Writes the string into the given output stream.
///
/// - Parameter target: An output stream.
@inlinable // FIXME(sil-serialize-all)
public func write<Target : TextOutputStream>(to target: inout Target) {
target.write(self)
}
}
extension Character : TextOutputStreamable {
/// Writes the character into the given output stream.
///
/// - Parameter target: An output stream.
@inlinable // FIXME(sil-serialize-all)
public func write<Target : TextOutputStream>(to target: inout Target) {
target.write(String(self))
}
}
extension Unicode.Scalar : TextOutputStreamable {
/// Writes the textual representation of the Unicode scalar into the given
/// output stream.
///
/// - Parameter target: An output stream.
@inlinable // FIXME(sil-serialize-all)
public func write<Target : TextOutputStream>(to target: inout Target) {
target.write(String(Character(self)))
}
}
/// A hook for playgrounds to print through.
public var _playgroundPrintHook : ((String) -> Void)? = nil
internal struct _TeeStream<
L : TextOutputStream,
R : TextOutputStream
> : TextOutputStream {
internal init(left: L, right: R) {
self.left = left
self.right = right
}
internal var left: L
internal var right: R
/// Append the given `string` to this stream.
internal mutating func write(_ string: String) {
left.write(string); right.write(string)
}
internal mutating func _lock() { left._lock(); right._lock() }
internal mutating func _unlock() { right._unlock(); left._unlock() }
}