char_traits

博客介绍了C++中base_string的模板参数char_traits,它负责字符属性和方法,可重载以改变string字符相关内部属性,如大小写敏感、字符串比较等。通过简单重载char_traits可实现大小写不敏感的string,参考自Exceptional C++。

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c++标准库中,有一个string,这个相信大家都知道,其实它是一个basic_string的一个typedef,其实在msdn这些地方,查string查不到什么太多东西,需要了解内部接口,得查basic_string

至于char_traits,是base_string的一个模板参数,它主要负责关于字符的属性和方法,譬如 eq、lt、compare、find 这些,比较字符大小,查找字符等等,这个类有什么用呢?

可以重载来改变string的一些字符相关的内部属性,譬如大小写敏感、字符串比较这些,具体的接口,而且,里面的接口基本上都是 static ,可以类似strcpy、strlen这样的接口直接使用(这个好像意义不大:P)

大小写不敏感的string的具体实现,只需要简单的重载一下 char_traits 就OK了,主要就是几个字符比较接口

以上参考自 Exceptional C++

In file included from /usr/include/c++/13/string:42, from /root/workspace/sylar/sylar/uri.h:13, from /root/workspace/sylar/sylar/uri.rl:1: In static member function ‘static std::char_traits<char>::char_type* std::char_traits<char>::copy(char_type*, const char_type*, std::size_t)’, inlined from ‘static void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /usr/include/c++/13/bits/basic_string.h:430:21, inlined from ‘static void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy(_CharT*, const _CharT*, size_type) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /usr/include/c++/13/bits/basic_string.h:425:7, inlined from ‘static void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_S_copy_chars(_CharT*, const _CharT*, const _CharT*) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /usr/include/c++/13/bits/basic_string.h:484:16, inlined from ‘void std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::_M_construct(_InIterator, _InIterator, std::forward_iterator_tag) [with _FwdIterator = const char*; _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /usr/include/c++/13/bits/basic_string.tcc:247:21, inlined from ‘std::__cxx11::basic_string<_CharT, _Traits, _Alloc>::basic_string(const _CharT*, size_type, const _Alloc&) [with _CharT = char; _Traits = std::char_traits<char>; _Alloc = std::allocator<char>]’ at /usr/include/c++/13/bits/basic_string.h:627:14, inlined from ‘static sylar::Uri::ptr sylar::Uri::Create(const std::string&)’ at /root/workspace/sylar/sylar/uri.rl:80:27: /usr/include/c++/13/bits/char_traits.h:435:56: error: argument 2 null where non-null expected [-Werror=nonnull] 435 | return static_cast<char_type*>(__builtin_memcpy(__s1, __s2, __n)); | ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~ /usr/include/c++/13/bits/char_traits.h:435:56: note: in a call to built-in function ‘void* __builtin_memcpy(void*, const void*, long unsigned int)’
最新发布
06-24
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