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//===------------------ InteredStrings.swift ------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2020 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 class Dispatch.DispatchQueue
public protocol InternedStringTableHolder {
var internedStringTable: InternedStringTable {get}
}
public struct InternedString: CustomStringConvertible, Equatable, Hashable {
let index: Int
fileprivate init(_ s: String, _ table: InternedStringTable) {
self.init(index: s.isEmpty ? 0 : table.intern(s))
}
private init(index: Int) {
self.index = index
}
public var isEmpty: Bool { index == 0 }
public static var empty: Self {
let r = Self(index: 0)
assert(r.isEmpty)
return r
}
public func lookup(in holder: InternedStringTableHolder) -> String {
holder.internedStringTable.strings[index]
}
public var description: String { "<<\(index)>>" }
public func description(in holder: InternedStringTableHolder) -> String {
"\(lookup(in: holder))\(description)"
}
}
/// Like `<`, but refers to the looked-up strings.
public func isInIncreasingOrder(
_ lhs: InternedString, _ rhs: InternedString,
in holder: InternedStringTableHolder
) -> Bool {
lhs.lookup(in: holder) < rhs.lookup(in: holder)
}
/// Hardcode empty as 0
public class InternedStringTable: IncrementalCompilationSynchronizer {
/// Ensure accesses & mutations are thread-safe
public let incrementalCompilationQueue: DispatchQueue
var strings = [""]
fileprivate var indices = ["": 0]
public init(_ incrementalCompilationQueue: DispatchQueue) {
self.incrementalCompilationQueue = incrementalCompilationQueue
}
fileprivate func intern(_ s: String) -> Int {
mutationSafetyPrecondition()
if let i = indices[s] { return i }
let i = strings.count
strings.append(s)
indices[s] = i
return i
}
var count: Int {
accessSafetyPrecondition()
return strings.count
}
func reserveCapacity(_ minimumCapacity: Int) {
mutationSafetyPrecondition()
strings.reserveCapacity(minimumCapacity)
indices.reserveCapacity(minimumCapacity)
}
}
extension InternedStringTable: InternedStringTableHolder {
public var internedStringTable: InternedStringTable {self}
}
public extension StringProtocol {
func intern(in holder: InternedStringTableHolder) -> InternedString {
InternedString(String(self), holder.internedStringTable)
}
}
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