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107 lines
3.5 KiB
Swift
107 lines
3.5 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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// This file contains compiler intrinsics for optimized string switch
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// implementations. All functions and types declared in this file are not
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// intended to be used by switch source directly.
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/// The compiler intrinsic which is called to lookup a string in a table
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/// of static string case values.
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@_semantics("findStringSwitchCase")
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public // COMPILER_INTRINSIC
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func _findStringSwitchCase(
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cases: [StaticString],
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string: String) -> Int {
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for (idx, s) in cases.enumerated() {
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if String(_builtinStringLiteral: s.utf8Start._rawValue,
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utf8CodeUnitCount: s._utf8CodeUnitCount,
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isASCII: s.isASCII._value) == string {
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return idx
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}
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}
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return -1
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}
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@frozen // needs known size for static allocation
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public // used by COMPILER_INTRINSIC
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struct _OpaqueStringSwitchCache {
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var a: Builtin.Word
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var b: Builtin.Word
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}
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internal typealias _StringSwitchCache = Dictionary<String, Int>
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internal struct _StringSwitchContext {
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internal let cases: [StaticString]
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internal let cachePtr: UnsafeMutablePointer<_StringSwitchCache>
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internal init(
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cases: [StaticString],
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cachePtr: UnsafeMutablePointer<_StringSwitchCache>
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){
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self.cases = cases
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self.cachePtr = cachePtr
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}
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}
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/// The compiler intrinsic which is called to lookup a string in a table
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/// of static string case values.
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///
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/// The first time this function is called, a cache is built and stored
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/// in \p cache. Consecutive calls use the cache for faster lookup.
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/// The \p cases array must not change between subsequent calls with the
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/// same \p cache.
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@_semantics("findStringSwitchCaseWithCache")
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public // COMPILER_INTRINSIC
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func _findStringSwitchCaseWithCache(
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cases: [StaticString],
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string: String,
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cache: inout _OpaqueStringSwitchCache) -> Int {
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return withUnsafeMutableBytes(of: &cache) {
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(bufPtr: UnsafeMutableRawBufferPointer) -> Int in
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let oncePtr = bufPtr.baseAddress!
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let cacheRawPtr = oncePtr + MemoryLayout<Builtin.Word>.stride
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let cachePtr = cacheRawPtr.bindMemory(to: _StringSwitchCache.self, capacity: 1)
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var context = _StringSwitchContext(cases: cases, cachePtr: cachePtr)
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withUnsafeMutablePointer(to: &context) { (context) -> () in
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Builtin.onceWithContext(oncePtr._rawValue, _createStringTableCache,
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context._rawValue)
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}
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let cache = cachePtr.pointee;
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if let idx = cache[string] {
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return idx
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}
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return -1
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}
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}
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/// Builds the string switch case.
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internal func _createStringTableCache(_ cacheRawPtr: Builtin.RawPointer) {
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let context = UnsafePointer<_StringSwitchContext>(cacheRawPtr).pointee
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var cache = _StringSwitchCache()
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cache.reserveCapacity(context.cases.count)
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_internalInvariant(
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MemoryLayout<_StringSwitchCache>.size <= MemoryLayout<Builtin.Word>.size)
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for (idx, s) in context.cases.enumerated() {
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let key = String(_builtinStringLiteral: s.utf8Start._rawValue,
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utf8CodeUnitCount: s._utf8CodeUnitCount,
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isASCII: s.isASCII._value)
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cache[key] = idx
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}
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context.cachePtr.initialize(to: cache)
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}
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