std::wstring 长度
std::wstring.length() 函数的结果是什么，wchar_t(s) 中的长度还是符号中的长度？为什么？
TCHAR r2[3];
r2[0] = 0xD834; // D834, DD1E - musical G clef
r2[1] = 0xDD1E; //
r2[2] = 0x0000; // '/0'
std::wstring r = r2;
std::cout << "capacity: " << r.capacity() << std::endl;
std::cout << "length: " << r.length() << std::endl;
std::cout << "size: " << r.size() << std::endl;
std::cout << "max_size: " << r.max_size() << std::endl;
Output>
capacity: 351
length: 2
size: 2
max_size: 2147483646
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std::wstring::size()返回字符串中宽字符元素的数量。这与字符数不同（正如您正确注意到的那样）。不幸的是，
std::basic_string模板（及其实例，例如std::string和std::wstring）正在编码 -不可知论者。从这个意义上说，它实际上只是一个字节串的模板，而不是字符串的模板。std::wstring::size()returns the number of wide-char elements in the string. This is not the same as the number of characters (as you correctly noticed).Unfortunately, the
std::basic_stringtemplate (and thus its instantiations, such asstd::stringandstd::wstring) is encoding-agnostic. In this sense, it is actually just a template for a string of bytes and not a string of characters.首先 std::wstring 是 std::basic_string、std::allocator 的实例化。 >。
虽然大部分实际工作是由 char_traits 完成的，并且可以编写自己的工作，但这主要是为了能够使用具有不同字符大小的 C 运行时库。
解析 Element* 指针的方法是，直到到达 char_traits 指示的作为终止符的字符。
但是，您可以使用指针和长度进行构造，在这种情况下，它将读取它告诉您的字符数，其中包括任何空字节。您可能在 basic_string 中嵌入了空字节，如果您调用 length() 或 size() （它们是同一事物的别名），它会告诉您它包含多少个字符。
char_traits 中没有将多元素字符解码为一个的魔法，您也不应该尝试以这种方式实现它。
Firstly std::wstring is an instantiation of
std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >.Although most of the real work is done by char_traits, and one can write their own, this is done primarily to enable use of the C runtime library with different character sizes.
The way to parse in a pointer of Element* is until the character indicated by the char_traits as the terminator is reached.
However you can construct with a pointer and a length, in which case it will read the number of characters it tells you to, which will include any null-bytes. You may have embedded null-bytes in a basic_string, and if you call length() or size() which are aliases for the same thing, it will tell you how many characters it contains.
There is no magic in char_traits to decode multi-element characters as one, nor should you try to implement it that way.
size 方法返回字符串中当前元素的数量。它与 wstring::length 相同
人们通常谈论单词、句子或段落的长度，而不是它的大小
size method returns the current number of elements in the string. It is the same as wstring::length
People usually talk about a word, sentence or paragraph's length, not its size
length()和size()通常返回字符串中“字符”的数量（不考虑宽度）不包括 null ，这里是长度& size 为 2。capacity()返回在字符串重新分配之前通常可用的内存量（读取：有多少个字符，因为这是多字节）。length()andsize()typically return the number of "characters" (irrespective of width) in the string excluding thenull, here the length & size is 2.capacity()returns how much memory (read: how many characters, as this is multi-byte) is typically available before the string will re-allocate.