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      1 //===- llvm/Support/StringSaver.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-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 
      9 #ifndef LLVM_SUPPORT_STRINGSAVER_H
     10 #define LLVM_SUPPORT_STRINGSAVER_H
     11 
     12 #include "llvm/ADT/DenseSet.h"
     13 #include "llvm/ADT/StringRef.h"
     14 #include "llvm/ADT/Twine.h"
     15 #include "llvm/Support/Allocator.h"
     16 
     17 namespace llvm {
     18 
     19 /// Saves strings in the provided stable storage and returns a
     20 /// StringRef with a stable character pointer.
     21 class StringSaver final {
     22   BumpPtrAllocator &Alloc;
     23 
     24 public:
     25   StringSaver(BumpPtrAllocator &Alloc) : Alloc(Alloc) {}
     26 
     27   // All returned strings are null-terminated: *save(S).end() == 0.
     28   StringRef save(const char *S) { return save(StringRef(S)); }
     29   StringRef save(StringRef S);
     30   StringRef save(const Twine &S) { return save(StringRef(S.str())); }
     31   StringRef save(const std::string &S) { return save(StringRef(S)); }
     32 };
     33 
     34 /// Saves strings in the provided stable storage and returns a StringRef with a
     35 /// stable character pointer. Saving the same string yields the same StringRef.
     36 ///
     37 /// Compared to StringSaver, it does more work but avoids saving the same string
     38 /// multiple times.
     39 ///
     40 /// Compared to StringPool, it performs fewer allocations but doesn't support
     41 /// refcounting/deletion.
     42 class UniqueStringSaver final {
     43   StringSaver Strings;
     44   llvm::DenseSet<llvm::StringRef> Unique;
     45 
     46 public:
     47   UniqueStringSaver(BumpPtrAllocator &Alloc) : Strings(Alloc) {}
     48 
     49   // All returned strings are null-terminated: *save(S).end() == 0.
     50   StringRef save(const char *S) { return save(StringRef(S)); }
     51   StringRef save(StringRef S);
     52   StringRef save(const Twine &S) { return save(StringRef(S.str())); }
     53   StringRef save(const std::string &S) { return save(StringRef(S)); }
     54 };
     55 
     56 }
     57 #endif
     58