获取 UTF-8 编码的 std::string 的实际长度?

2021-12-06 00:00:00 algorithm c++

我的 std::string 显然是 utf-8 编码的，str.length() 返回了错误的结果.

my std::string is utf-8 encoded so obviously, str.length() returns the wrong result.

我找到了此信息，但我不确定如何使用它来执行此操作:

I found this information but I'm not sure how I can use it to do this:

以下字节序列是用来表示一个字符.这顺序是使用取决于字符的 UCS 代码编号:

The following byte sequences are used to represent a character. The sequence to be used depends on the UCS code number of the character:

   0x00000000 - 0x0000007F:
       0xxxxxxx

   0x00000080 - 0x000007FF:
       110xxxxx 10xxxxxx

   0x00000800 - 0x0000FFFF:
       1110xxxx 10xxxxxx 10xxxxxx

   0x00010000 - 0x001FFFFF:
       11110xxx 10xxxxxx 10xxxxxx 10xxxxxx

如何找到 UTF-8 编码的 std::string 的实际长度?谢谢

How can I find the actual length of a UTF-8 encoded std::string? Thanks

推荐答案

计算所有首字节(与 10xxxxxx 不匹配的字节).

Count all first-bytes (the ones that don't match 10xxxxxx).

int len = 0;
while (*s) len += (*s++ & 0xc0) != 0x80;

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