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
|
//
// 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_replace.h
// -----------------------------------------------------------------------------
//
// This file defines `absl::StrReplaceAll()`, a general-purpose string
// replacement function designed for large, arbitrary text substitutions,
// especially on strings which you are receiving from some other system for
// further processing (e.g. processing regular expressions, escaping HTML
// entities, etc.). `StrReplaceAll` is designed to be efficient even when only
// one substitution is being performed, or when substitution is rare.
//
// If the string being modified is known at compile-time, and the substitutions
// vary, `absl::Substitute()` may be a better choice.
//
// Example:
//
// std::string html_escaped = absl::StrReplaceAll(user_input, {
// {"&", "&"},
// {"<", "<"},
// {">", ">"},
// {"\"", """},
// {"'", "'"}});
#ifndef ABSL_STRINGS_STR_REPLACE_H_
#define ABSL_STRINGS_STR_REPLACE_H_
#include <string>
#include <utility>
#include <vector>
#include "absl/base/attributes.h"
#include "absl/strings/string_view.h"
namespace absl {
inline namespace lts_2019_08_08 {
// StrReplaceAll()
//
// Replaces character sequences within a given string with replacements provided
// within an initializer list of key/value pairs. Candidate replacements are
// considered in order as they occur within the string, with earlier matches
// taking precedence, and longer matches taking precedence for candidates
// starting at the same position in the string. Once a substitution is made, the
// replaced text is not considered for any further substitutions.
//
// Example:
//
// std::string s = absl::StrReplaceAll(
// "$who bought $count #Noun. Thanks $who!",
// {{"$count", absl::StrCat(5)},
// {"$who", "Bob"},
// {"#Noun", "Apples"}});
// EXPECT_EQ("Bob bought 5 Apples. Thanks Bob!", s);
ABSL_MUST_USE_RESULT std::string StrReplaceAll(
absl::string_view s,
std::initializer_list<std::pair<absl::string_view, absl::string_view>>
replacements);
// Overload of `StrReplaceAll()` to accept a container of key/value replacement
// pairs (typically either an associative map or a `std::vector` of `std::pair`
// elements). A vector of pairs is generally more efficient.
//
// Examples:
//
// std::map<const absl::string_view, const absl::string_view> replacements;
// replacements["$who"] = "Bob";
// replacements["$count"] = "5";
// replacements["#Noun"] = "Apples";
// std::string s = absl::StrReplaceAll(
// "$who bought $count #Noun. Thanks $who!",
// replacements);
// EXPECT_EQ("Bob bought 5 Apples. Thanks Bob!", s);
//
// // A std::vector of std::pair elements can be more efficient.
// std::vector<std::pair<const absl::string_view, std::string>> replacements;
// replacements.push_back({"&", "&"});
// replacements.push_back({"<", "<"});
// replacements.push_back({">", ">"});
// std::string s = absl::StrReplaceAll("if (ptr < &foo)",
// replacements);
// EXPECT_EQ("if (ptr < &foo)", s);
template <typename StrToStrMapping>
std::string StrReplaceAll(absl::string_view s,
const StrToStrMapping& replacements);
// Overload of `StrReplaceAll()` to replace character sequences within a given
// output string *in place* with replacements provided within an initializer
// list of key/value pairs, returning the number of substitutions that occurred.
//
// Example:
//
// std::string s = std::string("$who bought $count #Noun. Thanks $who!");
// int count;
// count = absl::StrReplaceAll({{"$count", absl::StrCat(5)},
// {"$who", "Bob"},
// {"#Noun", "Apples"}}, &s);
// EXPECT_EQ(count, 4);
// EXPECT_EQ("Bob bought 5 Apples. Thanks Bob!", s);
int StrReplaceAll(
std::initializer_list<std::pair<absl::string_view, absl::string_view>>
replacements,
std::string* target);
// Overload of `StrReplaceAll()` to replace patterns within a given output
// string *in place* with replacements provided within a container of key/value
// pairs.
//
// Example:
//
// std::string s = std::string("if (ptr < &foo)");
// int count = absl::StrReplaceAll({{"&", "&"},
// {"<", "<"},
// {">", ">"}}, &s);
// EXPECT_EQ(count, 2);
// EXPECT_EQ("if (ptr < &foo)", s);
template <typename StrToStrMapping>
int StrReplaceAll(const StrToStrMapping& replacements, std::string* target);
// Implementation details only, past this point.
namespace strings_internal {
struct ViableSubstitution {
absl::string_view old;
absl::string_view replacement;
size_t offset;
ViableSubstitution(absl::string_view old_str,
absl::string_view replacement_str, size_t offset_val)
: old(old_str), replacement(replacement_str), offset(offset_val) {}
// One substitution occurs "before" another (takes priority) if either
// it has the lowest offset, or it has the same offset but a larger size.
bool OccursBefore(const ViableSubstitution& y) const {
if (offset != y.offset) return offset < y.offset;
return old.size() > y.old.size();
}
};
// Build a vector of ViableSubstitutions based on the given list of
// replacements. subs can be implemented as a priority_queue. However, it turns
// out that most callers have small enough a list of substitutions that the
// overhead of such a queue isn't worth it.
template <typename StrToStrMapping>
std::vector<ViableSubstitution> FindSubstitutions(
absl::string_view s, const StrToStrMapping& replacements) {
std::vector<ViableSubstitution> subs;
subs.reserve(replacements.size());
for (const auto& rep : replacements) {
using std::get;
absl::string_view old(get<0>(rep));
size_t pos = s.find(old);
if (pos == s.npos) continue;
// Ignore attempts to replace "". This condition is almost never true,
// but above condition is frequently true. That's why we test for this
// now and not before.
if (old.empty()) continue;
subs.emplace_back(old, get<1>(rep), pos);
// Insertion sort to ensure the last ViableSubstitution comes before
// all the others.
size_t index = subs.size();
while (--index && subs[index - 1].OccursBefore(subs[index])) {
std::swap(subs[index], subs[index - 1]);
}
}
return subs;
}
int ApplySubstitutions(absl::string_view s,
std::vector<ViableSubstitution>* subs_ptr,
std::string* result_ptr);
} // namespace strings_internal
template <typename StrToStrMapping>
std::string StrReplaceAll(absl::string_view s,
const StrToStrMapping& replacements) {
auto subs = strings_internal::FindSubstitutions(s, replacements);
std::string result;
result.reserve(s.size());
strings_internal::ApplySubstitutions(s, &subs, &result);
return result;
}
template <typename StrToStrMapping>
int StrReplaceAll(const StrToStrMapping& replacements, std::string* target) {
auto subs = strings_internal::FindSubstitutions(*target, replacements);
if (subs.empty()) return 0;
std::string result;
result.reserve(target->size());
int substitutions =
strings_internal::ApplySubstitutions(*target, &subs, &result);
target->swap(result);
return substitutions;
}
} // inline namespace lts_2019_08_08
} // namespace absl
#endif // ABSL_STRINGS_STR_REPLACE_H_
|
