aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/restricted/abseil-cpp/absl/strings/str_join.h
blob: 33534536cfdd23a19beecdb7ffdae84bb9f07797 (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
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
//
// 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.
//
// -----------------------------------------------------------------------------
// File: str_join.h
// -----------------------------------------------------------------------------
//
// This header file contains functions for joining a range of elements and
// returning the result as a std::string. StrJoin operations are specified by
// passing a range, a separator string to use between the elements joined, and
// an optional Formatter responsible for converting each argument in the range
// to a string. If omitted, a default `AlphaNumFormatter()` is called on the
// elements to be joined, using the same formatting that `absl::StrCat()` uses.
// This package defines a number of default formatters, and you can define your
// own implementations.
//
// Ranges are specified by passing a container with `std::begin()` and
// `std::end()` iterators, container-specific `begin()` and `end()` iterators, a
// brace-initialized `std::initializer_list`, or a `std::tuple` of heterogeneous
// objects. The separator string is specified as an `absl::string_view`.
//
// Because the default formatter uses the `absl::AlphaNum` class,
// `absl::StrJoin()`, like `absl::StrCat()`, will work out-of-the-box on
// collections of strings, ints, floats, doubles, etc.
//
// Example:
//
//   std::vector<std::string> v = {"foo", "bar", "baz"};
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("foo-bar-baz", s);
//
// See comments on the `absl::StrJoin()` function for more examples.

#ifndef ABSL_STRINGS_STR_JOIN_H_
#define ABSL_STRINGS_STR_JOIN_H_

#include <cstdio>
#include <cstring>
#include <initializer_list>
#include <iterator>
#include <string>
#include <tuple>
#include <type_traits>
#include <utility>

#include "absl/base/macros.h"
#include "absl/strings/internal/str_join_internal.h"
#include "absl/strings/string_view.h"

namespace absl {
ABSL_NAMESPACE_BEGIN

// -----------------------------------------------------------------------------
// Concept: Formatter
// -----------------------------------------------------------------------------
//
// A Formatter is a function object that is responsible for formatting its
// argument as a string and appending it to a given output std::string.
// Formatters may be implemented as function objects, lambdas, or normal
// functions. You may provide your own Formatter to enable `absl::StrJoin()` to
// work with arbitrary types.
//
// The following is an example of a custom Formatter that simply uses
// `std::to_string()` to format an integer as a std::string.
//
//   struct MyFormatter {
//     void operator()(std::string* out, int i) const {
//       out->append(std::to_string(i));
//     }
//   };
//
// You would use the above formatter by passing an instance of it as the final
// argument to `absl::StrJoin()`:
//
//   std::vector<int> v = {1, 2, 3, 4};
//   std::string s = absl::StrJoin(v, "-", MyFormatter());
//   EXPECT_EQ("1-2-3-4", s);
//
// The following standard formatters are provided within this file:
//
// - `AlphaNumFormatter()` (the default)
// - `StreamFormatter()`
// - `PairFormatter()`
// - `DereferenceFormatter()`

// AlphaNumFormatter()
//
// Default formatter used if none is specified. Uses `absl::AlphaNum` to convert
// numeric arguments to strings.
inline strings_internal::AlphaNumFormatterImpl AlphaNumFormatter() {
  return strings_internal::AlphaNumFormatterImpl();
}

// StreamFormatter()
//
// Formats its argument using the << operator.
inline strings_internal::StreamFormatterImpl StreamFormatter() {
  return strings_internal::StreamFormatterImpl();
}

// Function Template: PairFormatter(Formatter, absl::string_view, Formatter)
//
// Formats a `std::pair` by putting a given separator between the pair's
// `.first` and `.second` members. This formatter allows you to specify
// custom Formatters for both the first and second member of each pair.
template <typename FirstFormatter, typename SecondFormatter>
inline strings_internal::PairFormatterImpl<FirstFormatter, SecondFormatter>
PairFormatter(FirstFormatter f1, absl::string_view sep, SecondFormatter f2) {
  return strings_internal::PairFormatterImpl<FirstFormatter, SecondFormatter>(
      std::move(f1), sep, std::move(f2));
}

// Function overload of PairFormatter() for using a default
// `AlphaNumFormatter()` for each Formatter in the pair.
inline strings_internal::PairFormatterImpl<
    strings_internal::AlphaNumFormatterImpl,
    strings_internal::AlphaNumFormatterImpl>
PairFormatter(absl::string_view sep) {
  return PairFormatter(AlphaNumFormatter(), sep, AlphaNumFormatter());
}

// Function Template: DereferenceFormatter(Formatter)
//
// Formats its argument by dereferencing it and then applying the given
// formatter. This formatter is useful for formatting a container of
// pointer-to-T. This pattern often shows up when joining repeated fields in
// protocol buffers.
template <typename Formatter>
strings_internal::DereferenceFormatterImpl<Formatter> DereferenceFormatter(
    Formatter&& f) {
  return strings_internal::DereferenceFormatterImpl<Formatter>(
      std::forward<Formatter>(f));
}

// Function overload of `DereferenceFormatter()` for using a default
// `AlphaNumFormatter()`.
inline strings_internal::DereferenceFormatterImpl<
    strings_internal::AlphaNumFormatterImpl>
DereferenceFormatter() {
  return strings_internal::DereferenceFormatterImpl<
      strings_internal::AlphaNumFormatterImpl>(AlphaNumFormatter());
}

// -----------------------------------------------------------------------------
// StrJoin()
// -----------------------------------------------------------------------------
//
// Joins a range of elements and returns the result as a std::string.
// `absl::StrJoin()` takes a range, a separator string to use between the
// elements joined, and an optional Formatter responsible for converting each
// argument in the range to a string.
//
// If omitted, the default `AlphaNumFormatter()` is called on the elements to be
// joined.
//
// Example 1:
//   // Joins a collection of strings. This pattern also works with a collection
//   // of `absl::string_view` or even `const char*`.
//   std::vector<std::string> v = {"foo", "bar", "baz"};
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("foo-bar-baz", s);
//
// Example 2:
//   // Joins the values in the given `std::initializer_list<>` specified using
//   // brace initialization. This pattern also works with an initializer_list
//   // of ints or `absl::string_view` -- any `AlphaNum`-compatible type.
//   std::string s = absl::StrJoin({"foo", "bar", "baz"}, "-");
//   EXPECT_EQ("foo-bar-baz", s);
//
// Example 3:
//   // Joins a collection of ints. This pattern also works with floats,
//   // doubles, int64s -- any `StrCat()`-compatible type.
//   std::vector<int> v = {1, 2, 3, -4};
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("1-2-3--4", s);
//
// Example 4:
//   // Joins a collection of pointer-to-int. By default, pointers are
//   // dereferenced and the pointee is formatted using the default format for
//   // that type; such dereferencing occurs for all levels of indirection, so
//   // this pattern works just as well for `std::vector<int**>` as for
//   // `std::vector<int*>`.
//   int x = 1, y = 2, z = 3;
//   std::vector<int*> v = {&x, &y, &z};
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("1-2-3", s);
//
// Example 5:
//   // Dereferencing of `std::unique_ptr<>` is also supported:
//   std::vector<std::unique_ptr<int>> v
//   v.emplace_back(new int(1));
//   v.emplace_back(new int(2));
//   v.emplace_back(new int(3));
//   std::string s = absl::StrJoin(v, "-");
//   EXPECT_EQ("1-2-3", s);
//
// Example 6:
//   // Joins a `std::map`, with each key-value pair separated by an equals
//   // sign. This pattern would also work with, say, a
//   // `std::vector<std::pair<>>`.
//   std::map<std::string, int> m = {
//       std::make_pair("a", 1),
//       std::make_pair("b", 2),
//       std::make_pair("c", 3)};
//   std::string s = absl::StrJoin(m, ",", absl::PairFormatter("="));
//   EXPECT_EQ("a=1,b=2,c=3", s);
//
// Example 7:
//   // These examples show how `absl::StrJoin()` handles a few common edge
//   // cases:
//   std::vector<std::string> v_empty;
//   EXPECT_EQ("", absl::StrJoin(v_empty, "-"));
//
//   std::vector<std::string> v_one_item = {"foo"};
//   EXPECT_EQ("foo", absl::StrJoin(v_one_item, "-"));
//
//   std::vector<std::string> v_empty_string = {""};
//   EXPECT_EQ("", absl::StrJoin(v_empty_string, "-"));
//
//   std::vector<std::string> v_one_item_empty_string = {"a", ""};
//   EXPECT_EQ("a-", absl::StrJoin(v_one_item_empty_string, "-"));
//
//   std::vector<std::string> v_two_empty_string = {"", ""};
//   EXPECT_EQ("-", absl::StrJoin(v_two_empty_string, "-"));
//
// Example 8:
//   // Joins a `std::tuple<T...>` of heterogeneous types, converting each to
//   // a std::string using the `absl::AlphaNum` class.
//   std::string s = absl::StrJoin(std::make_tuple(123, "abc", 0.456), "-");
//   EXPECT_EQ("123-abc-0.456", s);

template <typename Iterator, typename Formatter>
std::string StrJoin(Iterator start, Iterator end, absl::string_view sep,
                    Formatter&& fmt) {
  return strings_internal::JoinAlgorithm(start, end, sep, fmt);
}

template <typename Range, typename Formatter>
std::string StrJoin(const Range& range, absl::string_view separator,
                    Formatter&& fmt) {
  return strings_internal::JoinRange(range, separator, fmt);
}

template <typename T, typename Formatter>
std::string StrJoin(std::initializer_list<T> il, absl::string_view separator,
                    Formatter&& fmt) {
  return strings_internal::JoinRange(il, separator, fmt);
}

template <typename... T, typename Formatter>
std::string StrJoin(const std::tuple<T...>& value, absl::string_view separator,
                    Formatter&& fmt) {
  return strings_internal::JoinAlgorithm(value, separator, fmt);
}

template <typename Iterator>
std::string StrJoin(Iterator start, Iterator end, absl::string_view separator) {
  return strings_internal::JoinRange(start, end, separator);
}

template <typename Range>
std::string StrJoin(const Range& range, absl::string_view separator) {
  return strings_internal::JoinRange(range, separator);
}

template <typename T>
std::string StrJoin(std::initializer_list<T> il,
                    absl::string_view separator) {
  return strings_internal::JoinRange(il, separator);
}

template <typename... T>
std::string StrJoin(const std::tuple<T...>& value,
                    absl::string_view separator) {
  return strings_internal::JoinAlgorithm(value, separator, AlphaNumFormatter());
}

ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_STRINGS_STR_JOIN_H_