在 C 中使用 strncpy 更有效地复制 n 个字符

Question

我想知道考虑到 strncpy 字符的数量，是否有一种更清洁、更有效的方法来执行以下 max。我觉得我做得太过分了。

int main(void)
{

        char *string = "hello world foo!";
        int max = 5;

        char *str = malloc (max + 1);
        if (str == NULL)
                return 1;
        if (string) {
                int len = strlen (string);
                if (len > max) {
                        strncpy (str, string, max);
                        str[max] = '\0';
                } else {
                        strncpy (str, string, len);
                        str[len] = '\0';
                }
                printf("%s\n", str);
        }
        return 0;
}

Answer 1

我根本不会为此使用 strncpy。至少如果我理解你想要做什么，我可能会做这样的事情:

char *duplicate(char *input, size_t max_len) {
    // compute the size of the result -- the lesser of the specified maximum
    // and the length of the input string. 
    size_t len = min(max_len, strlen(input));

    // allocate space for the result (including NUL terminator).
    char *buffer = malloc(len+1);

    if (buffer) {
        // if the allocation succeeded, copy the specified number of 
        // characters to the destination.
        memcpy(buffer, input, len);
        // and NUL terminate the result.
        buffer[len] = '\0';
    }
    // if we copied the string, return it; otherwise, return the null pointer 
    // to indicate failure.
    return buffer;
}