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//===--- SymbolID.h ----------------------------------------------*- C++-*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/raw_ostream.h"
#include <array>
#include <cstdint>
#include <string>
namespace clang {
namespace clangd {
// The class identifies a particular C++ symbol (class, function, method, etc).
// As USRs (Unified Symbol Resolution) could be large, especially for functions
// with long type arguments, SymbolID is using truncated SHA1(USR) values to
// guarantee the uniqueness of symbols while using a relatively small amount of
// memory (vs storing USRs directly).
// SymbolID can be used as key in the symbol indexes to lookup the symbol.
class SymbolID {
SymbolID() = default;
explicit SymbolID(llvm::StringRef USR);
bool operator==(const SymbolID &Sym) const {
return HashValue == Sym.HashValue;
bool operator!=(const SymbolID &Sym) const {
return !(*this == Sym);
bool operator<(const SymbolID &Sym) const {
return HashValue < Sym.HashValue;
// The stored hash is truncated to RawSize bytes.
// This trades off memory against the number of symbols we can handle.
constexpr static size_t RawSize = 8;
llvm::StringRef raw() const;
static SymbolID fromRaw(llvm::StringRef);
// Returns a hex encoded string.
std::string str() const;
static llvm::Expected<SymbolID> fromStr(llvm::StringRef);
bool isNull() const { return *this == SymbolID(); }
explicit operator bool() const { return !isNull(); }
std::array<uint8_t, RawSize> HashValue{};
llvm::hash_code hash_value(const SymbolID &ID);
// Write SymbolID into the given stream. SymbolID is encoded as ID.str().
llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const SymbolID &ID);
} // namespace clangd
} // namespace clang
namespace llvm {
// Support SymbolIDs as DenseMap keys.
template <> struct DenseMapInfo<clang::clangd::SymbolID> {
static inline clang::clangd::SymbolID getEmptyKey() {
static clang::clangd::SymbolID EmptyKey("EMPTYKEY");
return EmptyKey;
static inline clang::clangd::SymbolID getTombstoneKey() {
static clang::clangd::SymbolID TombstoneKey("TOMBSTONEKEY");
return TombstoneKey;
static unsigned getHashValue(const clang::clangd::SymbolID &Sym) {
return hash_value(Sym);
static bool isEqual(const clang::clangd::SymbolID &LHS,
const clang::clangd::SymbolID &RHS) {
return LHS == RHS;
} // namespace llvm