1 /*
2 * Copyright (C) 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #ifndef LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
18 #define LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
19
20 #include <stddef.h>
21 #include <string>
22
23 #include "utils/base/logging.h"
24
25 namespace libtextclassifier3 {
26
27 // Read-only "view" of a piece of data. Does not own the underlying data.
28 class StringPiece {
29 public:
StringPiece()30 StringPiece() : StringPiece(nullptr, 0) {}
31
StringPiece(const char * str)32 StringPiece(const char *str) // NOLINT(runtime/explicit)
33 : start_(str), size_(str == nullptr ? 0 : strlen(str)) {}
34
StringPiece(const char * start,size_t size)35 StringPiece(const char *start, size_t size) : start_(start), size_(size) {}
36
37 // Intentionally no "explicit" keyword: in function calls, we want strings to
38 // be converted to StringPiece implicitly.
StringPiece(const std::string & s)39 StringPiece(const std::string &s) // NOLINT(runtime/explicit)
40 : StringPiece(s.data(), s.size()) {}
41
StringPiece(const std::string & s,int offset,int len)42 StringPiece(const std::string &s, int offset, int len)
43 : StringPiece(s.data() + offset, len) {}
44
45 char operator[](size_t i) const { return start_[i]; }
46
47 // Returns start address of underlying data.
data()48 const char *data() const { return start_; }
49
50 // Returns number of bytes of underlying data.
size()51 size_t size() const { return size_; }
length()52 size_t length() const { return size_; }
53
empty()54 bool empty() const { return size_ == 0; }
55
56 // Returns a std::string containing a copy of the underlying data.
ToString()57 std::string ToString() const { return std::string(data(), size()); }
58
59 // Returns whether string ends with a given suffix.
EndsWith(StringPiece suffix)60 bool EndsWith(StringPiece suffix) const {
61 return suffix.empty() || (size_ >= suffix.size() &&
62 memcmp(start_ + (size_ - suffix.size()),
63 suffix.data(), suffix.size()) == 0);
64 }
65
66 // Returns whether the string begins with a given prefix.
StartsWith(StringPiece prefix)67 bool StartsWith(StringPiece prefix) const {
68 return prefix.empty() ||
69 (size_ >= prefix.size() &&
70 memcmp(start_, prefix.data(), prefix.size()) == 0);
71 }
72
Equals(StringPiece other)73 bool Equals(StringPiece other) const {
74 return size() == other.size() && memcmp(start_, other.data(), size_) == 0;
75 }
76
77 // Removes the first `n` characters from the string piece. Note that the
78 // underlying string is not changed, only the view.
RemovePrefix(int n)79 void RemovePrefix(int n) {
80 TC3_CHECK_LE(n, size_);
81 start_ += n;
82 size_ -= n;
83 }
84
85 private:
86 const char *start_; // Not owned.
87 size_t size_;
88 };
89
EndsWith(StringPiece text,StringPiece suffix)90 inline bool EndsWith(StringPiece text, StringPiece suffix) {
91 return text.EndsWith(suffix);
92 }
93
StartsWith(StringPiece text,StringPiece prefix)94 inline bool StartsWith(StringPiece text, StringPiece prefix) {
95 return text.StartsWith(prefix);
96 }
97
ConsumePrefix(StringPiece * text,StringPiece prefix)98 inline bool ConsumePrefix(StringPiece *text, StringPiece prefix) {
99 if (!text->StartsWith(prefix)) {
100 return false;
101 }
102 text->RemovePrefix(prefix.size());
103 return true;
104 }
105
106 } // namespace libtextclassifier3
107
108 #endif // LIBTEXTCLASSIFIER_UTILS_STRINGS_STRINGPIECE_H_
109