1//===- StringMapEntry.h - String Hash table map interface -------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8///
9/// \file
10/// This file defines the StringMapEntry class - it is intended to be a low
11/// dependency implementation detail of StringMap that is more suitable for
12/// inclusion in public headers than StringMap.h itself is.
13///
14//===----------------------------------------------------------------------===//
15
16#ifndef LLVM_ADT_STRINGMAPENTRY_H
17#define LLVM_ADT_STRINGMAPENTRY_H
18
19#include "llvm/ADT/StringRef.h"
20#include <optional>
21
22namespace llvm {
23
24/// StringMapEntryBase - Shared base class of StringMapEntry instances.
25class StringMapEntryBase {
26 size_t keyLength;
27
28public:
29 explicit StringMapEntryBase(size_t keyLength) : keyLength(keyLength) {}
30
31 size_t getKeyLength() const { return keyLength; }
32
33protected:
34 /// Helper to tail-allocate \p Key. It'd be nice to generalize this so it
35 /// could be reused elsewhere, maybe even taking an llvm::function_ref to
36 /// type-erase the allocator and put it in a source file.
37 template <typename AllocatorTy>
38 static void *allocateWithKey(size_t EntrySize, size_t EntryAlign,
39 StringRef Key, AllocatorTy &Allocator);
40};
41
42// Define out-of-line to dissuade inlining.
43template <typename AllocatorTy>
44void *StringMapEntryBase::allocateWithKey(size_t EntrySize, size_t EntryAlign,
45 StringRef Key,
46 AllocatorTy &Allocator) {
47 size_t KeyLength = Key.size();
48
49 // Allocate a new item with space for the string at the end and a null
50 // terminator.
51 size_t AllocSize = EntrySize + KeyLength + 1;
52 void *Allocation = Allocator.Allocate(AllocSize, EntryAlign);
53 assert(Allocation && "Unhandled out-of-memory");
54
55 // Copy the string information.
56 char *Buffer = reinterpret_cast<char *>(Allocation) + EntrySize;
57 if (KeyLength > 0)
58 ::memcpy(dest: Buffer, src: Key.data(), n: KeyLength);
59 Buffer[KeyLength] = 0; // Null terminate for convenience of clients.
60 return Allocation;
61}
62
63/// StringMapEntryStorage - Holds the value in a StringMapEntry.
64///
65/// Factored out into a separate base class to make it easier to specialize.
66/// This is primarily intended to support StringSet, which doesn't need a value
67/// stored at all.
68template <typename ValueTy>
69class StringMapEntryStorage : public StringMapEntryBase {
70public:
71 ValueTy second;
72
73 explicit StringMapEntryStorage(size_t keyLength)
74 : StringMapEntryBase(keyLength), second() {}
75 template <typename... InitTy>
76 StringMapEntryStorage(size_t keyLength, InitTy &&...initVals)
77 : StringMapEntryBase(keyLength),
78 second(std::forward<InitTy>(initVals)...) {}
79 StringMapEntryStorage(StringMapEntryStorage &e) = delete;
80
81 const ValueTy &getValue() const { return second; }
82 ValueTy &getValue() { return second; }
83
84 void setValue(const ValueTy &V) { second = V; }
85};
86
87template <>
88class StringMapEntryStorage<std::nullopt_t> : public StringMapEntryBase {
89public:
90 explicit StringMapEntryStorage(size_t keyLength,
91 std::nullopt_t = std::nullopt)
92 : StringMapEntryBase(keyLength) {}
93 StringMapEntryStorage(StringMapEntryStorage &entry) = delete;
94
95 std::nullopt_t getValue() const { return std::nullopt; }
96};
97
98/// StringMapEntry - This is used to represent one value that is inserted into
99/// a StringMap. It contains the Value itself and the key: the string length
100/// and data.
101template <typename ValueTy>
102class StringMapEntry final : public StringMapEntryStorage<ValueTy> {
103public:
104 using StringMapEntryStorage<ValueTy>::StringMapEntryStorage;
105
106 using ValueType = ValueTy;
107
108 StringRef getKey() const {
109 return StringRef(getKeyData(), this->getKeyLength());
110 }
111
112 /// getKeyData - Return the start of the string data that is the key for this
113 /// value. The string data is always stored immediately after the
114 /// StringMapEntry object.
115 const char *getKeyData() const {
116 return reinterpret_cast<const char *>(this + 1);
117 }
118
119 StringRef first() const {
120 return StringRef(getKeyData(), this->getKeyLength());
121 }
122
123 /// Create a StringMapEntry for the specified key construct the value using
124 /// \p InitiVals.
125 template <typename AllocatorTy, typename... InitTy>
126 static StringMapEntry *create(StringRef key, AllocatorTy &allocator,
127 InitTy &&...initVals) {
128 return new (StringMapEntryBase::allocateWithKey(
129 sizeof(StringMapEntry), alignof(StringMapEntry), key, allocator))
130 StringMapEntry(key.size(), std::forward<InitTy>(initVals)...);
131 }
132
133 /// GetStringMapEntryFromKeyData - Given key data that is known to be embedded
134 /// into a StringMapEntry, return the StringMapEntry itself.
135 static StringMapEntry &GetStringMapEntryFromKeyData(const char *keyData) {
136 char *ptr = const_cast<char *>(keyData) - sizeof(StringMapEntry<ValueTy>);
137 return *reinterpret_cast<StringMapEntry *>(ptr);
138 }
139
140 /// Destroy - Destroy this StringMapEntry, releasing memory back to the
141 /// specified allocator.
142 template <typename AllocatorTy> void Destroy(AllocatorTy &allocator) {
143 // Free memory referenced by the item.
144 size_t AllocSize = sizeof(StringMapEntry) + this->getKeyLength() + 1;
145 this->~StringMapEntry();
146 allocator.Deallocate(static_cast<void *>(this), AllocSize,
147 alignof(StringMapEntry));
148 }
149};
150
151// Allow structured bindings on StringMapEntry.
152template <std::size_t Index, typename ValueTy>
153decltype(auto) get(const StringMapEntry<ValueTy> &E) {
154 static_assert(Index < 2);
155 if constexpr (Index == 0)
156 return E.first();
157 else
158 return E.second;
159}
160
161} // end namespace llvm
162
163namespace std {
164template <typename ValueTy>
165struct tuple_size<llvm::StringMapEntry<ValueTy>>
166 : std::integral_constant<std::size_t, 2> {};
167
168template <std::size_t I, typename ValueTy>
169struct tuple_element<I, llvm::StringMapEntry<ValueTy>>
170 : std::conditional<I == 0, llvm::StringRef, ValueTy> {};
171} // namespace std
172
173#endif // LLVM_ADT_STRINGMAPENTRY_H
174

source code of llvm/include/llvm/ADT/StringMapEntry.h