about summary refs log tree commit diff
path: root/absl/strings/string_view.cc
blob: dc034a83eea87304336128e547173d2fd1fda199 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "absl/strings/string_view.h"

#ifndef ABSL_HAVE_STD_STRING_VIEW

#include <algorithm>
#include <climits>
#include <cstring>
#include <ostream>

#include "absl/strings/internal/memutil.h"

namespace absl {

namespace {
void WritePadding(std::ostream& o, size_t pad) {
  char fill_buf[32];
  memset(fill_buf, o.fill(), sizeof(fill_buf));
  while (pad) {
    size_t n = std::min(pad, sizeof(fill_buf));
    o.write(fill_buf, n);
    pad -= n;
  }
}

class LookupTable {
 public:
  // For each character in wanted, sets the index corresponding
  // to the ASCII code of that character. This is used by
  // the find_.*_of methods below to tell whether or not a character is in
  // the lookup table in constant time.
  explicit LookupTable(string_view wanted) {
    for (char c : wanted) {
      table_[Index(c)] = true;
    }
  }
  bool operator[](char c) const { return table_[Index(c)]; }

 private:
  static unsigned char Index(char c) { return static_cast<unsigned char>(c); }
  bool table_[UCHAR_MAX + 1] = {};
};

}  // namespace

std::ostream& operator<<(std::ostream& o, string_view piece) {
  std::ostream::sentry sentry(o);
  if (sentry) {
    size_t lpad = 0;
    size_t rpad = 0;
    if (static_cast<size_t>(o.width()) > piece.size()) {
      size_t pad = o.width() - piece.size();
      if ((o.flags() & o.adjustfield) == o.left) {
        rpad = pad;
      } else {
        lpad = pad;
      }
    }
    if (lpad) WritePadding(o, lpad);
    o.write(piece.data(), piece.size());
    if (rpad) WritePadding(o, rpad);
    o.width(0);
  }
  return o;
}

string_view::size_type string_view::find(string_view s, size_type pos) const
    noexcept {
  if (empty() || pos > length_) {
    if (empty() && pos == 0 && s.empty()) return 0;
    return npos;
  }
  const char* result =
      strings_internal::memmatch(ptr_ + pos, length_ - pos, s.ptr_, s.length_);
  return result ? result - ptr_ : npos;
}

string_view::size_type string_view::find(char c, size_type pos) const noexcept {
  if (empty() || pos >= length_) {
    return npos;
  }
  const char* result =
      static_cast<const char*>(memchr(ptr_ + pos, c, length_ - pos));
  return result != nullptr ? result - ptr_ : npos;
}

string_view::size_type string_view::rfind(string_view s, size_type pos) const
    noexcept {
  if (length_ < s.length_) return npos;
  if (s.empty()) return std::min(length_, pos);
  const char* last = ptr_ + std::min(length_ - s.length_, pos) + s.length_;
  const char* result = std::find_end(ptr_, last, s.ptr_, s.ptr_ + s.length_);
  return result != last ? result - ptr_ : npos;
}

// Search range is [0..pos] inclusive.  If pos == npos, search everything.
string_view::size_type string_view::rfind(char c, size_type pos) const
    noexcept {
  // Note: memrchr() is not available on Windows.
  if (empty()) return npos;
  for (size_type i = std::min(pos, length_ - 1);; --i) {
    if (ptr_[i] == c) {
      return i;
    }
    if (i == 0) break;
  }
  return npos;
}

string_view::size_type string_view::find_first_of(string_view s,
                                                  size_type pos) const
    noexcept {
  if (empty() || s.empty()) {
    return npos;
  }
  // Avoid the cost of LookupTable() for a single-character search.
  if (s.length_ == 1) return find_first_of(s.ptr_[0], pos);
  LookupTable tbl(s);
  for (size_type i = pos; i < length_; ++i) {
    if (tbl[ptr_[i]]) {
      return i;
    }
  }
  return npos;
}

string_view::size_type string_view::find_first_not_of(string_view s,
                                                      size_type pos) const
    noexcept {
  if (empty()) return npos;
  // Avoid the cost of LookupTable() for a single-character search.
  if (s.length_ == 1) return find_first_not_of(s.ptr_[0], pos);
  LookupTable tbl(s);
  for (size_type i = pos; i < length_; ++i) {
    if (!tbl[ptr_[i]]) {
      return i;
    }
  }
  return npos;
}

string_view::size_type string_view::find_first_not_of(char c,
                                                      size_type pos) const
    noexcept {
  if (empty()) return npos;
  for (; pos < length_; ++pos) {
    if (ptr_[pos] != c) {
      return pos;
    }
  }
  return npos;
}

string_view::size_type string_view::find_last_of(string_view s,
                                                 size_type pos) const noexcept {
  if (empty() || s.empty()) return npos;
  // Avoid the cost of LookupTable() for a single-character search.
  if (s.length_ == 1) return find_last_of(s.ptr_[0], pos);
  LookupTable tbl(s);
  for (size_type i = std::min(pos, length_ - 1);; --i) {
    if (tbl[ptr_[i]]) {
      return i;
    }
    if (i == 0) break;
  }
  return npos;
}

string_view::size_type string_view::find_last_not_of(string_view s,
                                                     size_type pos) const
    noexcept {
  if (empty()) return npos;
  size_type i = std::min(pos, length_ - 1);
  if (s.empty()) return i;
  // Avoid the cost of LookupTable() for a single-character search.
  if (s.length_ == 1) return find_last_not_of(s.ptr_[0], pos);
  LookupTable tbl(s);
  for (;; --i) {
    if (!tbl[ptr_[i]]) {
      return i;
    }
    if (i == 0) break;
  }
  return npos;
}

string_view::size_type string_view::find_last_not_of(char c,
                                                     size_type pos) const
    noexcept {
  if (empty()) return npos;
  size_type i = std::min(pos, length_ - 1);
  for (;; --i) {
    if (ptr_[i] != c) {
      return i;
    }
    if (i == 0) break;
  }
  return npos;
}

// MSVC has non-standard behavior that implicitly creates definitions for static
// const members. These implicit definitions conflict with explicit out-of-class
// member definitions that are required by the C++ standard, resulting in
// LNK1169 "multiply defined" errors at link time. __declspec(selectany) asks
// MSVC to choose only one definition for the symbol it decorates. See details
// at https://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx
#ifdef _MSC_VER
#define ABSL_STRING_VIEW_SELECTANY __declspec(selectany)
#else
#define ABSL_STRING_VIEW_SELECTANY
#endif

ABSL_STRING_VIEW_SELECTANY
constexpr string_view::size_type string_view::npos;
ABSL_STRING_VIEW_SELECTANY
constexpr string_view::size_type string_view::kMaxSize;

}  // namespace absl

#endif  // ABSL_HAVE_STD_STRING_VIEW