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/* Copyright (c) 2017 Sichen Zhao <1473996754@qq.com> */
/*
FUNCTION
<<strnstr>>---find string segment
INDEX
strnstr
SYNOPSIS
#include <string.h>
size_t strnstr(const char *<[s1]>, const char *<[s2]>, size_t <[n]>);
DESCRIPTION
Locates the first occurrence in the string pointed to by <[s1]> of
the sequence of limited to the <[n]> characters in the string
pointed to by <[s2]>
RETURNS
Returns a pointer to the located string segment, or a null
pointer if the string <[s2]> is not found. If <[s2]> points to
a string with zero length, <[s1]> is returned.
PORTABILITY
<<strnstr>> is a BSD extension.
<<strnstr>> requires no supporting OS subroutines.
QUICKREF
strnstr pure
*/
#define _GNU_SOURCE
#include <string.h>
/*
* Find the first occurrence of find in s, where the search is limited to the
* first slen characters of s.
*/
char *
strnstr(const char *haystack, const char *needle, size_t haystack_len)
{
size_t needle_len = strnlen(needle, haystack_len);
if (needle_len < haystack_len || !needle[needle_len]) {
char *x = memmem(haystack, haystack_len, needle, needle_len);
if (x && !memchr(haystack, 0, x - haystack))
return x;
}
return NULL;
}