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/*
FUNCTION
<<strstr>>---find string segment
INDEX
strstr
SYNOPSIS
#include <string.h>
char *strstr(const char *<[s1]>, const char *<[s2]>);
DESCRIPTION
Locates the first occurrence in the string pointed to by <[s1]> of
the sequence of characters in the string pointed to by <[s2]>
(excluding the terminating null character).
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
<<strstr>> is ANSI C.
<<strstr>> requires no supporting OS subroutines.
QUICKREF
strstr ansi pure
*/
#include <string.h>
#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
# define RETURN_TYPE char *
# define AVAILABLE(h, h_l, j, n_l) \
(!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
&& ((h_l) = (j) + (n_l)))
# include "str-two-way.h"
#endif
char *
strstr (const char *searchee,
const char *lookfor)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
/* Less code size, but quadratic performance in the worst case. */
if (*searchee == 0)
{
if (*lookfor)
return (char *) NULL;
return (char *) searchee;
}
while (*searchee)
{
size_t i;
i = 0;
while (1)
{
if (lookfor[i] == 0)
{
return (char *) searchee;
}
if (lookfor[i] != searchee[i])
{
break;
}
i++;
}
searchee++;
}
return (char *) NULL;
#else /* compilation for speed */
/* Larger code size, but guaranteed linear performance. */
const char *haystack = searchee;
const char *needle = lookfor;
size_t needle_len; /* Length of NEEDLE. */
size_t haystack_len; /* Known minimum length of HAYSTACK. */
int ok = 1; /* True if NEEDLE is prefix of HAYSTACK. */
/* Determine length of NEEDLE, and in the process, make sure
HAYSTACK is at least as long (no point processing all of a long
NEEDLE if HAYSTACK is too short). */
while (*haystack && *needle)
ok &= *haystack++ == *needle++;
if (*needle)
return NULL;
if (ok)
return (char *) searchee;
/* Reduce the size of haystack using strchr, since it has a smaller
linear coefficient than the Two-Way algorithm. */
needle_len = needle - lookfor;
haystack = strchr (searchee + 1, *lookfor);
if (!haystack || needle_len == 1)
return (char *) haystack;
haystack_len = (haystack > searchee + needle_len ? 1
: needle_len + searchee - haystack);
/* Perform the search. */
if (needle_len < LONG_NEEDLE_THRESHOLD)
return two_way_short_needle ((const unsigned char *) haystack,
haystack_len,
(const unsigned char *) lookfor, needle_len);
return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
(const unsigned char *) lookfor, needle_len);
#endif /* compilation for speed */
}
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