Is there a strchr with boundary?

Question

There is a char *strchr( const char *str, int ch ) function defined in <string.h>.

It has no boundary, after which it stops the search.

Is there a similar function somewhere, which you can pass a boundary to?

Edit:

I have a char* pos and a length of a substring and I want to find a specific ASCII character in it, but I don't want it to search up to the very null-terminator, because I don't care for the second part of the character sequence.

Answer 1

You can try:

void* memchr( const void* ptr, int ch, size_t count )

Answer 2

As the other answer points out, you can use memchr, but you'll need to call it twice if you want to avoid going out of bounds:

char *strnchr(const char *s, int c, size_t n)
{
    char *nul = memchr(s, 0, n);
    if(!c) return nul;
    if(nul) n = nul - s;
    return memchr(s, c, n); 
}

With the right hardware optimization, this may be more efficient than just checking the first n characters:

char *strnchr(const char *s, int c, size_t n)
{
     for(char *p = s; (p - s) < n; p++) {
         if(*p == c) return p;
         if(!*p) break;
     }
     return NULL;
}