1868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// Copyright 2013 The Chromium Authors. All rights reserved.
2868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// Use of this source code is governed by a BSD-style license that can be
3868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// found in the LICENSE file.
4868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
5868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#ifndef BASE_STRINGS_STRING16_H_
6868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#define BASE_STRINGS_STRING16_H_
7868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
8868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// WHAT:
9868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// A version of std::basic_string that provides 2-byte characters even when
10868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// wchar_t is not implemented as a 2-byte type. You can access this class as
11868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// string16. We also define char16, which string16 is based upon.
12868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
13868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// WHY:
14868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// On Windows, wchar_t is 2 bytes, and it can conveniently handle UTF-16/UCS-2
15868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// data. Plenty of existing code operates on strings encoded as UTF-16.
16868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
17868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// On many other platforms, sizeof(wchar_t) is 4 bytes by default. We can make
18868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// it 2 bytes by using the GCC flag -fshort-wchar. But then std::wstring fails
19868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// at run time, because it calls some functions (like wcslen) that come from
20868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// the system's native C library -- which was built with a 4-byte wchar_t!
21868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// It's wasteful to use 4-byte wchar_t strings to carry UTF-16 data, and it's
22868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// entirely improper on those systems where the encoding of wchar_t is defined
23868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// as UTF-32.
24868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
25868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// Here, we define string16, which is similar to std::wstring but replaces all
26868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// libc functions with custom, 2-byte-char compatible routines. It is capable
27868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// of carrying UTF-16-encoded data.
28868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
29868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#include <stdio.h>
30868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#include <string>
31868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
32868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#include "base/base_export.h"
33868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#include "base/basictypes.h"
34868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
35868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#if defined(WCHAR_T_IS_UTF16)
36868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
37868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)namespace base {
38868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
39868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)typedef wchar_t char16;
40868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)typedef std::wstring string16;
41868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)typedef std::char_traits<wchar_t> string16_char_traits;
42868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
43868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)}  // namespace base
44868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
45868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#elif defined(WCHAR_T_IS_UTF32)
46868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
47868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)namespace base {
48868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
49868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)typedef uint16 char16;
50868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
51868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// char16 versions of the functions required by string16_char_traits; these
52868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// are based on the wide character functions of similar names ("w" or "wcs"
53868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// instead of "c16").
54868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT int c16memcmp(const char16* s1, const char16* s2, size_t n);
55868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT size_t c16len(const char16* s);
56868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT const char16* c16memchr(const char16* s, char16 c, size_t n);
57868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT char16* c16memmove(char16* s1, const char16* s2, size_t n);
58868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT char16* c16memcpy(char16* s1, const char16* s2, size_t n);
59868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT char16* c16memset(char16* s, char16 c, size_t n);
60868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
61868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)struct string16_char_traits {
62868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  typedef char16 char_type;
63868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  typedef int int_type;
64868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
65868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  // int_type needs to be able to hold each possible value of char_type, and in
66868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  // addition, the distinct value of eof().
67868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  COMPILE_ASSERT(sizeof(int_type) > sizeof(char_type), unexpected_type_width);
68868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
69868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  typedef std::streamoff off_type;
70868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  typedef mbstate_t state_type;
71868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  typedef std::fpos<state_type> pos_type;
72868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
73868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static void assign(char_type& c1, const char_type& c2) {
74868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    c1 = c2;
75868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
76868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
77868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static bool eq(const char_type& c1, const char_type& c2) {
78868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c1 == c2;
79868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
80868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static bool lt(const char_type& c1, const char_type& c2) {
81868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c1 < c2;
82868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
83868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
84868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static int compare(const char_type* s1, const char_type* s2, size_t n) {
85868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16memcmp(s1, s2, n);
86868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
87868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
88868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static size_t length(const char_type* s) {
89868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16len(s);
90868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
91868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
92868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static const char_type* find(const char_type* s, size_t n,
93868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)                               const char_type& a) {
94868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16memchr(s, a, n);
95868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
96868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
97868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static char_type* move(char_type* s1, const char_type* s2, int_type n) {
98868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16memmove(s1, s2, n);
99868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
100868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
101868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static char_type* copy(char_type* s1, const char_type* s2, size_t n) {
102868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16memcpy(s1, s2, n);
103868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
104868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
105868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static char_type* assign(char_type* s, size_t n, char_type a) {
106868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c16memset(s, a, n);
107868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
108868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
109868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static int_type not_eof(const int_type& c) {
110868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return eq_int_type(c, eof()) ? 0 : c;
111868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
112868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
113868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static char_type to_char_type(const int_type& c) {
114868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return char_type(c);
115868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
116868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
117868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static int_type to_int_type(const char_type& c) {
118868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return int_type(c);
119868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
120868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
121868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static bool eq_int_type(const int_type& c1, const int_type& c2) {
122868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return c1 == c2;
123868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
124868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
125868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  static int_type eof() {
126868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)    return static_cast<int_type>(EOF);
127868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)  }
128868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)};
129868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
130868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)typedef std::basic_string<char16, base::string16_char_traits> string16;
131868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
132868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT extern std::ostream& operator<<(std::ostream& out,
133868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)                                            const string16& str);
134868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
135868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// This is required by googletest to print a readable output on test failures.
136868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)BASE_EXPORT extern void PrintTo(const string16& str, std::ostream* out);
137868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
138868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)}  // namespace base
139868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
140868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// The string class will be explicitly instantiated only once, in string16.cc.
141868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
142868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// std::basic_string<> in GNU libstdc++ contains a static data member,
143868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// _S_empty_rep_storage, to represent empty strings.  When an operation such
144868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// as assignment or destruction is performed on a string, causing its existing
145868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// data member to be invalidated, it must not be freed if this static data
146868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// member is being used.  Otherwise, it counts as an attempt to free static
147868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// (and not allocated) data, which is a memory error.
148868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
149868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// Generally, due to C++ template magic, _S_empty_rep_storage will be marked
150868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// as a coalesced symbol, meaning that the linker will combine multiple
151868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// instances into a single one when generating output.
152868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
153868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// If a string class is used by multiple shared libraries, a problem occurs.
154868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// Each library will get its own copy of _S_empty_rep_storage.  When strings
155868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// are passed across a library boundary for alteration or destruction, memory
156868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// errors will result.  GNU libstdc++ contains a configuration option,
157868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// --enable-fully-dynamic-string (_GLIBCXX_FULLY_DYNAMIC_STRING), which
158868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// disables the static data member optimization, but it's a good optimization
159868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// and non-STL code is generally at the mercy of the system's STL
160868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// configuration.  Fully-dynamic strings are not the default for GNU libstdc++
161868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// libstdc++ itself or for the libstdc++ installations on the systems we care
162868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// about, such as Mac OS X and relevant flavors of Linux.
163868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
164868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// See also http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24196 .
165868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
166868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// To avoid problems, string classes need to be explicitly instantiated only
167868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// once, in exactly one library.  All other string users see it via an "extern"
168868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// declaration.  This is precisely how GNU libstdc++ handles
169868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// std::basic_string<char> (string) and std::basic_string<wchar_t> (wstring).
170868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
171868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// This also works around a Mac OS X linker bug in ld64-85.2.1 (Xcode 3.1.2),
172868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// in which the linker does not fully coalesce symbols when dead code
173868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// stripping is enabled.  This bug causes the memory errors described above
174868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// to occur even when a std::basic_string<> does not cross shared library
175868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// boundaries, such as in statically-linked executables.
176868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)//
177868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)// TODO(mark): File this bug with Apple and update this note with a bug number.
178868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
179868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)extern template
180868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)class BASE_EXPORT std::basic_string<base::char16, base::string16_char_traits>;
181868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
182868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#endif  // WCHAR_T_IS_UTF32
183868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)
184868fa2fe829687343ffae624259930155e16dbd8Torne (Richard Coles)#endif  // BASE_STRINGS_STRING16_H_
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