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/*

FUNCTION

        <<strstr>>---find string segment

INDEX

        strstr

ANSI_SYNOPSIS

        #include <string.h>

        char *strstr(const char *<[s1]>, const char *<[s2]>);

TRAD_SYNOPSIS

        #include <string.h>

        char *strstr(<[s1]>, <[s2]>)

        char *<[s1]>;

        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 *

_DEFUN (strstr, (searchee, lookfor),

        _CONST char *searchee _AND

        _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 */

}