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//===- StringMapEntry.h - String Hash table map interface -------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// This file defines the StringMapEntry class - it is intended to be a low
/// dependency implementation detail of StringMap that is more suitable for
/// inclusion in public headers than StringMap.h itself is.
///
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_STRINGMAPENTRY_H
#define LLVM_ADT_STRINGMAPENTRY_H
#include "llvm/ADT/StringRef.h"
#include <optional>
namespace llvm {
/// StringMapEntryBase - Shared base class of StringMapEntry instances.
class StringMapEntryBase {
size_t keyLength;
public:
explicit StringMapEntryBase(size_t keyLength) : keyLength(keyLength) {}
size_t getKeyLength() const { return keyLength; }
protected:
/// Helper to tail-allocate \p Key. It'd be nice to generalize this so it
/// could be reused elsewhere, maybe even taking an llvm::function_ref to
/// type-erase the allocator and put it in a source file.
template <typename AllocatorTy>
static void *allocateWithKey(size_t EntrySize, size_t EntryAlign,
StringRef Key, AllocatorTy &Allocator);
};
// Define out-of-line to dissuade inlining.
template <typename AllocatorTy>
void *StringMapEntryBase::allocateWithKey(size_t EntrySize, size_t EntryAlign,
StringRef Key,
AllocatorTy &Allocator) {
size_t KeyLength = Key.size();
// Allocate a new item with space for the string at the end and a null
// terminator.
size_t AllocSize = EntrySize + KeyLength + 1;
void *Allocation = Allocator.Allocate(AllocSize, EntryAlign);
assert(Allocation && "Unhandled out-of-memory");
// Copy the string information.
char *Buffer = reinterpret_cast<char *>(Allocation) + EntrySize;
if (KeyLength > 0)
::memcpy(Buffer, Key.data(), KeyLength);
Buffer[KeyLength] = 0; // Null terminate for convenience of clients.
return Allocation;
}
/// StringMapEntryStorage - Holds the value in a StringMapEntry.
///
/// Factored out into a separate base class to make it easier to specialize.
/// This is primarily intended to support StringSet, which doesn't need a value
/// stored at all.
template <typename ValueTy>
class StringMapEntryStorage : public StringMapEntryBase {
public:
ValueTy second;
explicit StringMapEntryStorage(size_t keyLength)
: StringMapEntryBase(keyLength), second() {}
template <typename... InitTy>
StringMapEntryStorage(size_t keyLength, InitTy &&...initVals)
: StringMapEntryBase(keyLength),
second(std::forward<InitTy>(initVals)...) {}
StringMapEntryStorage(StringMapEntryStorage &e) = delete;
const ValueTy &getValue() const { return second; }
ValueTy &getValue() { return second; }
void setValue(const ValueTy &V) { second = V; }
};
template <>
class StringMapEntryStorage<std::nullopt_t> : public StringMapEntryBase {
public:
explicit StringMapEntryStorage(size_t keyLength,
std::nullopt_t = std::nullopt)
: StringMapEntryBase(keyLength) {}
StringMapEntryStorage(StringMapEntryStorage &entry) = delete;
std::nullopt_t getValue() const { return std::nullopt; }
};
/// StringMapEntry - This is used to represent one value that is inserted into
/// a StringMap. It contains the Value itself and the key: the string length
/// and data.
template <typename ValueTy>
class StringMapEntry final : public StringMapEntryStorage<ValueTy> {
public:
using StringMapEntryStorage<ValueTy>::StringMapEntryStorage;
using ValueType = ValueTy;
StringRef getKey() const {
return StringRef(getKeyData(), this->getKeyLength());
}
/// getKeyData - Return the start of the string data that is the key for this
/// value. The string data is always stored immediately after the
/// StringMapEntry object.
const char *getKeyData() const {
return reinterpret_cast<const char *>(this + 1);
}
StringRef first() const {
return StringRef(getKeyData(), this->getKeyLength());
}
/// Create a StringMapEntry for the specified key construct the value using
/// \p InitiVals.
template <typename AllocatorTy, typename... InitTy>
static StringMapEntry *create(StringRef key, AllocatorTy &allocator,
InitTy &&...initVals) {
return new (StringMapEntryBase::allocateWithKey(
sizeof(StringMapEntry), alignof(StringMapEntry), key, allocator))
StringMapEntry(key.size(), std::forward<InitTy>(initVals)...);
}
/// GetStringMapEntryFromKeyData - Given key data that is known to be embedded
/// into a StringMapEntry, return the StringMapEntry itself.
static StringMapEntry &GetStringMapEntryFromKeyData(const char *keyData) {
char *ptr = const_cast<char *>(keyData) - sizeof(StringMapEntry<ValueTy>);
return *reinterpret_cast<StringMapEntry *>(ptr);
}
/// Destroy - Destroy this StringMapEntry, releasing memory back to the
/// specified allocator.
template <typename AllocatorTy> void Destroy(AllocatorTy &allocator) {
// Free memory referenced by the item.
size_t AllocSize = sizeof(StringMapEntry) + this->getKeyLength() + 1;
this->~StringMapEntry();
allocator.Deallocate(static_cast<void *>(this), AllocSize,
alignof(StringMapEntry));
}
};
// Allow structured bindings on StringMapEntry.
template <std::size_t Index, typename ValueTy>
decltype(auto) get(const StringMapEntry<ValueTy> &E) {
static_assert(Index < 2);
if constexpr (Index == 0)
return E.first();
else
return E.second;
}
} // end namespace llvm
namespace std {
template <typename ValueTy>
struct tuple_size<llvm::StringMapEntry<ValueTy>>
: std::integral_constant<std::size_t, 2> {};
template <std::size_t I, typename ValueTy>
struct tuple_element<I, llvm::StringMapEntry<ValueTy>>
: std::conditional<I == 0, llvm::StringRef, ValueTy> {};
} // namespace std
#endif // LLVM_ADT_STRINGMAPENTRY_H
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