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1//===--- SymbolID.h ----------------------------------------------*- 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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_SYMBOLID_H10#define LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_SYMBOLID_H11 12#include "llvm/ADT/Hashing.h"13#include "llvm/ADT/StringRef.h"14#include "llvm/Support/Error.h"15#include "llvm/Support/raw_ostream.h"16#include <array>17#include <cstddef>18#include <cstdint>19#include <string>20 21namespace clang {22namespace clangd {23 24// The class identifies a particular C++ symbol (class, function, method, etc).25//26// As USRs (Unified Symbol Resolution) could be large, especially for functions27// with long type arguments, SymbolID is using truncated SHA1(USR) values to28// guarantee the uniqueness of symbols while using a relatively small amount of29// memory (vs storing USRs directly).30//31// SymbolID can be used as key in the symbol indexes to lookup the symbol.32class SymbolID {33public:34 SymbolID() = default;35 explicit SymbolID(llvm::StringRef USR);36 37 bool operator==(const SymbolID &Sym) const {38 return HashValue == Sym.HashValue;39 }40 bool operator!=(const SymbolID &Sym) const { return !(*this == Sym); }41 bool operator<(const SymbolID &Sym) const {42 // Avoid lexicographic compare which requires swapping bytes or even memcmp!43 return llvm::bit_cast<IntTy>(HashValue) <44 llvm::bit_cast<IntTy>(Sym.HashValue);45 }46 47 // The stored hash is truncated to RawSize bytes.48 // This trades off memory against the number of symbols we can handle.49 constexpr static size_t RawSize = 8;50 llvm::StringRef raw() const;51 static SymbolID fromRaw(llvm::StringRef);52 53 // Returns a hex encoded string.54 std::string str() const;55 static llvm::Expected<SymbolID> fromStr(llvm::StringRef);56 57 bool isNull() const { return *this == SymbolID(); }58 explicit operator bool() const { return !isNull(); }59 60private:61 using IntTy = uint64_t;62 static_assert(sizeof(IntTy) == RawSize);63 std::array<uint8_t, RawSize> HashValue{};64};65 66inline llvm::hash_code hash_value(const SymbolID &ID) {67 // We already have a good hash, just return the first bytes.68 static_assert(sizeof(size_t) <= SymbolID::RawSize,69 "size_t longer than SHA1!");70 size_t Result;71 memcpy(&Result, ID.raw().data(), sizeof(size_t));72 return llvm::hash_code(Result);73}74 75// Write SymbolID into the given stream. SymbolID is encoded as ID.str().76llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const SymbolID &ID);77 78} // namespace clangd79} // namespace clang80 81namespace llvm {82// Support SymbolIDs as DenseMap keys.83template <> struct DenseMapInfo<clang::clangd::SymbolID> {84 static inline clang::clangd::SymbolID getEmptyKey() {85 static clang::clangd::SymbolID EmptyKey("EMPTYKEY");86 return EmptyKey;87 }88 static inline clang::clangd::SymbolID getTombstoneKey() {89 static clang::clangd::SymbolID TombstoneKey("TOMBSTONEKEY");90 return TombstoneKey;91 }92 static unsigned getHashValue(const clang::clangd::SymbolID &Sym) {93 return hash_value(Sym);94 }95 static bool isEqual(const clang::clangd::SymbolID &LHS,96 const clang::clangd::SymbolID &RHS) {97 return LHS == RHS;98 }99};100} // namespace llvm101 102#endif // LLVM_CLANG_TOOLS_EXTRA_CLANGD_INDEX_SYMBOLID_H103