这是一篇简短的记录。
C++ 标准模板库的 std::string 很好很强大，但是并没有提供判断一个字符串是否以另一个字符串开始/结束的接口。这里为 std::basic_string<charT> 提供这两个接口。
string_predicate.hpp1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
| #include <string>
namespace std {
template <typename charT>
inline bool starts_with(const basic_string<charT>& big, const basic_string<charT>& small) {
if (&big == &small) return true;
const typename basic_string<charT>::size_type big_size = big.size();
const typename basic_string<charT>::size_type small_size = small.size();
const bool valid_ = (big_size >= small_size);
const bool starts_with_ = (big.compare(0, small_size, small) == 0);
return valid_ and starts_with_;
}
template <typename charT>
inline bool ends_with(const basic_string<charT>& big, const basic_string<charT>& small) {
if (&big == &small) return true;
const typename basic_string<charT>::size_type big_size = big.size();
const typename basic_string<charT>::size_type small_size = small.size();
const bool valid_ = (big_size >= small_size);
const bool ends_with_ = (big.compare(big_size - small_size, small_size, small) == 0);
return valid_ and ends_with_;
}
}
|
用法：
test.cc1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
| #include <iostream>
#include <string>
#include "string_predicate.hpp"
int main() {
std::string compared = "Hello world!";
std::string start = "Hello";
std::string end = "world!";
std::cout << std::starts_with(compared, start) << std::endl;
std::cout << std::ends_with(compared, end) << std::endl;
std::wstring wcompared = L"你好世界";
std::wstring wstart = L"你好";
std::wstring wend = L"世界";
std::cout << std::starts_with(wcompared, wstart) << std::endl;
std::cout << std::ends_with(wcompared, wend) << std::endl;
return 0;
}
|
结果：
1
2
3
4
5
6
| $ g++ test.cc
$ ./a.out
1
1
1
1
|
