firmware/common/strcasestr.c

   1 /* Return the offset of one string within another.
   2    Copyright (C) 1994,1996,1997,1998,1999,2000 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 /*
  21  * My personal strstr() implementation that beats most other algorithms.
  22  * Until someone tells me otherwise, I assume that this is the
  23  * fastest implementation of strstr() in C.
  24  * I deliberately chose not to comment it.  You should have at least
  25  * as much fun trying to understand it, as I had to write it :-).
  26  *
  27  * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de*/
  28
  29 /* Faster looping by precalculating bl, bu, cl, cu before looping.
  30  * 2004 Apr 08 Jose Da Silva, digital@joescat@com */
  31
  32 #include <string.h>
  33 #include <ctype.h>
  34
  35 typedef unsigned chartype;
  36
  37 char* strcasestr (const char* phaystack, const char* pneedle)
  38 {
  39     const unsigned char *haystack, *needle;
  40     chartype bl, bu, cl, cu;
  41
  42     haystack = (const unsigned char *) phaystack;
  43     needle = (const unsigned char *) pneedle;
  44
  45     bl = tolower (*needle);
  46     if (bl != '\0')
  47     {
  48         bu = toupper (bl);
  49         haystack--;/* possible ANSI violation */
  50         do
  51         {
  52             cl = *++haystack;
  53             if (cl == '\0')
  54                 goto ret0;
  55         }
  56         while ((cl != bl) && (cl != bu));
  57
  58         cl = tolower (*++needle);
  59         if (cl == '\0')
  60             goto foundneedle;
  61         cu = toupper (cl);
  62         ++needle;
  63         goto jin;
  64
  65         for (;;)
  66         {
  67             chartype a;
  68             const unsigned char *rhaystack, *rneedle;
  69
  70             do
  71             {
  72                 a = *++haystack;
  73                 if (a == '\0')
  74                     goto ret0;
  75                 if ((a == bl) || (a == bu))
  76                     break;
  77                 a = *++haystack;
  78                 if (a == '\0')
  79                     goto ret0;
  80               shloop:
  81                 ;
  82             }
  83             while ((a != bl) && (a != bu));
  84
  85           jin:  a = *++haystack;
  86             if (a == '\0')
  87                 goto ret0;
  88
  89             if ((a != cl) && (a != cu))
  90                 goto shloop;
  91
  92             rhaystack = haystack-- + 1;
  93             rneedle = needle;
  94             a = tolower (*rneedle);
  95
  96             if (tolower (*rhaystack) == (int) a)
  97                 do
  98                 {
  99                     if (a == '\0')
 100                         goto foundneedle;
 101                     ++rhaystack;
 102                     a = tolower (*++needle);
 103                     if (tolower (*rhaystack) != (int) a)
 104                         break;
 105                     if (a == '\0')
 106                         goto foundneedle;
 107                     ++rhaystack;
 108                     a = tolower (*++needle);
 109                 }
 110                 while (tolower (*rhaystack) == (int) a);
 111
 112             needle = rneedle;/* took the register-poor approach */
 113
 114             if (a == '\0')
 115                 break;
 116         }
 117     }
 118   foundneedle:
 119     return (char*) haystack;
 120   ret0:
 121     return 0;
 122 }