strstr.c File Reference

#include <string.h>

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Functions
char *	strstr (const char *string, const char *substring)
	Finds the first occurrence of the substring in the string. More...

Function Documentation

strstr()

char* strstr	(	const char *	string,
		const char *	substring
	)

Finds the first occurrence of the substring in the string.

Finds the first occurrence of the null-terminated byte string pointed to by substring in the null-terminated byte string pointed to by string. The terminating null characters are not compared.

The behavior is undefined if either stirng or substring is not a pointer to a null-terminated byte string.

Parameters

string	pointer to the null-terminated byte string to examine
substring	pointer to the null-terminated byte string to search for

Returns

Pointer to the first character of the found substring in string, or NULL if no such substring is found. If substring points to an empty string, string is returned.

Definition at line 38 of file strstr.c.

{
    const char *a, *b;

    /* First scan quickly through the two strings looking for a
     * single-character match.  When it's found, then compare the
     * rest of the substring.
     */

    b = substring;

    if(*b == 0)
    {
        return (char*)(uintptr_t)string;
    }

    for(; *string != 0; string += 1)
    {
        if(*string != *b)
        {
            continue;
        }

        a = string;

        while(1)
        {
            if(*b == 0)
            {
                return (char*)(uintptr_t)string;
            }
            if(*a++ != *b++)
            {
                break;
            }
        }

        b = substring;
    }

    return NULL;
}

References NULL.