How to Accurately Determine the Length of a UTF-8 Encoded String in C ?

Determining UTF-8 Encoded String Length

In C , std::string encoding may vary, and using the length() function on a UTF-8 encoded string can yield an inaccurate representation of its actual length. To ascertain the correct length, consider the following byte sequence patterns:

0x00000000 - 0x0000007F:
       0xxxxxxx

0x00000080 - 0x000007FF:
       110xxxxx 10xxxxxx

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

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

To calculate the actual length of a UTF-8 encoded string:

1. Initialize a variable len to 0.
2. Iterate through the string character by character.
3. For each character, check if it follows the byte sequence pattern for a single-byte character (0xxxxxxx).
4. If it does, increment len by 1.
5. Otherwise, skip the current and next byte(s).

The following code snippet illustrates the implementation:

<code class="cpp">int len = 0;
const char *s = str.c_str(); // convert to C-style string
while (*s) len += (*s++ & 0xc0) != 0x80;</code>

The above is the detailed content of How to Accurately Determine the Length of a UTF-8 Encoded String in C ?. For more information, please follow other related articles on the PHP Chinese website!