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   BumpPtrAllocator &getAllocator() const { return Alloc; }
28 
29   // All returned strings are null-terminated: *save(S).end() == 0.
30   StringRef save(const char *S) { return save(StringRef(S)); }
31   StringRef save(StringRef S);
32   StringRef save(const Twine &S) { return save(StringRef(S.str())); }
33   StringRef save(const std::string &S) { return save(StringRef(S)); }
34 };
35 
36 /// Saves strings in the provided stable storage and returns a StringRef with a
37 /// stable character pointer. Saving the same string yields the same StringRef.
38 ///
39 /// Compared to StringSaver, it does more work but avoids saving the same string
40 /// multiple times.
41 ///
42 /// Compared to StringPool, it performs fewer allocations but doesn't support
43 /// refcounting/deletion.
44 class UniqueStringSaver final {
45   StringSaver Strings;
46   llvm::DenseSet<llvm::StringRef> Unique;
47 
48 public:
49   UniqueStringSaver(BumpPtrAllocator &Alloc) : Strings(Alloc) {}
50 
51   // All returned strings are null-terminated: *save(S).end() == 0.
52   StringRef save(const char *S) { return save(StringRef(S)); }
53   StringRef save(StringRef S);
54   StringRef save(const Twine &S) { return save(StringRef(S.str())); }
55   StringRef save(const std::string &S) { return save(StringRef(S)); }
56 };
57 
58 } // namespace llvm
59 #endif
60