1 | //===------------------------ __refstring ---------------------------------===// |
---|---|
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 _LIBCPP_REFSTRING_H |
10 | #define _LIBCPP_REFSTRING_H |
11 | |
12 | #include <__config> |
13 | #include <stdexcept> |
14 | #include <cstddef> |
15 | #include <cstring> |
16 | #ifdef __APPLE__ |
17 | #include <dlfcn.h> |
18 | #include <mach-o/dyld.h> |
19 | #endif |
20 | #include "atomic_support.h" |
21 | |
22 | _LIBCPP_BEGIN_NAMESPACE_STD |
23 | |
24 | namespace __refstring_imp { namespace { |
25 | typedef int count_t; |
26 | |
27 | struct _Rep_base { |
28 | std::size_t len; |
29 | std::size_t cap; |
30 | count_t count; |
31 | }; |
32 | |
33 | inline _Rep_base* rep_from_data(const char *data_) noexcept { |
34 | char *data = const_cast<char *>(data_); |
35 | return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base)); |
36 | } |
37 | |
38 | inline char * data_from_rep(_Rep_base *rep) noexcept { |
39 | char *data = reinterpret_cast<char *>(rep); |
40 | return data + sizeof(*rep); |
41 | } |
42 | |
43 | #if defined(__APPLE__) |
44 | inline |
45 | const char* compute_gcc_empty_string_storage() _NOEXCEPT |
46 | { |
47 | void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD); |
48 | if (handle == nullptr) |
49 | return nullptr; |
50 | void* sym = dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE"); |
51 | if (sym == nullptr) |
52 | return nullptr; |
53 | return data_from_rep(reinterpret_cast<_Rep_base *>(sym)); |
54 | } |
55 | |
56 | inline |
57 | const char* |
58 | get_gcc_empty_string_storage() _NOEXCEPT |
59 | { |
60 | static const char* p = compute_gcc_empty_string_storage(); |
61 | return p; |
62 | } |
63 | #endif |
64 | |
65 | }} // namespace __refstring_imp |
66 | |
67 | using namespace __refstring_imp; |
68 | |
69 | inline |
70 | __libcpp_refstring::__libcpp_refstring(const char* msg) { |
71 | std::size_t len = strlen(msg); |
72 | _Rep_base* rep = static_cast<_Rep_base *>(::operator new(sizeof(*rep) + len + 1)); |
73 | rep->len = len; |
74 | rep->cap = len; |
75 | rep->count = 0; |
76 | char *data = data_from_rep(rep); |
77 | std::memcpy(data, msg, len + 1); |
78 | __imp_ = data; |
79 | } |
80 | |
81 | inline |
82 | __libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) _NOEXCEPT |
83 | : __imp_(s.__imp_) |
84 | { |
85 | if (__uses_refcount()) |
86 | __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1); |
87 | } |
88 | |
89 | inline |
90 | __libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _NOEXCEPT { |
91 | bool adjust_old_count = __uses_refcount(); |
92 | struct _Rep_base *old_rep = rep_from_data(__imp_); |
93 | __imp_ = s.__imp_; |
94 | if (__uses_refcount()) |
95 | __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1); |
96 | if (adjust_old_count) |
97 | { |
98 | if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0) |
99 | { |
100 | ::operator delete(old_rep); |
101 | } |
102 | } |
103 | return *this; |
104 | } |
105 | |
106 | inline |
107 | __libcpp_refstring::~__libcpp_refstring() { |
108 | if (__uses_refcount()) { |
109 | _Rep_base* rep = rep_from_data(__imp_); |
110 | if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) { |
111 | ::operator delete(rep); |
112 | } |
113 | } |
114 | } |
115 | |
116 | inline |
117 | bool __libcpp_refstring::__uses_refcount() const { |
118 | #ifdef __APPLE__ |
119 | return __imp_ != get_gcc_empty_string_storage(); |
120 | #else |
121 | return true; |
122 | #endif |
123 | } |
124 | |
125 | _LIBCPP_END_NAMESPACE_STD |
126 | |
127 | #endif //_LIBCPP_REFSTRING_H |
128 |