libio/dbz/case.c

   1 /*
   2  * case-mapping stuff
   3  *
   4  * We exploit the fact that we are dealing only with headers here, and
   5  * headers are limited to the ASCII characters by RFC822.  It is barely
   6  * possible that we might be dealing with a translation into another
   7  * character set, but in particular it's very unlikely for a header
   8  * character to be outside -128..255.
   9  *
  10  * Life would be a whole lot simpler if tolower() could safely and portably
  11  * be applied to any char.
  12  */
  13 #include <stdio.h>
  14 #include "string.h"
  15 #include "case.h"
  16
  17 /* note that case.h knows the value of OFFSET */
  18 #define OFFSET  128             /* avoid trouble with negative chars */
  19 #define MAPSIZE (256+OFFSET)
  20 char casemap[MAPSIZE];          /* relies on init to '\0' */
  21 static int primed = 0;          /* has casemap been set up? */
  22
  23 /*
  24  - prime - set up case-mapping stuff
  25  */
  26 static void
  27 prime()
  28 {
  29         register char *lp;
  30         register char *up;
  31         register int c;
  32         register int i;
  33         static char lower[] = "abcdefghijklmnopqrstuvwxyz";
  34         static char upper[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  35
  36         for (lp = lower, up = upper; *lp != '\0'; lp++, up++) {
  37                 c = *lp;
  38                 casemap[c+OFFSET] = c;
  39                 casemap[*up+OFFSET] = c;
  40         }
  41         for (i = 0; i < MAPSIZE; i++)
  42                 if (casemap[i] == '\0')
  43                         casemap[i] = (char)(i-OFFSET);
  44         primed = 1;
  45 }
  46
  47 /*
  48  - cistrncmp - case-independent strncmp
  49  */
  50 int                             /* < == > 0 */
  51 cistrncmp(s1, s2, len)
  52 char *s1;
  53 char *s2;
  54 int len;
  55 {
  56         register char *p1;
  57         register char *p2;
  58         register int n;
  59
  60         if (!primed)
  61                 prime();
  62
  63         p1 = s1;
  64         p2 = s2;
  65         n = len;
  66         while (--n >= 0 && *p1 != '\0' && TOLOW(*p1) == TOLOW(*p2)) {
  67                 p1++;
  68                 p2++;
  69         }
  70         if (n < 0)
  71                 return(0);
  72
  73         /*
  74          * The following case analysis is necessary so that characters
  75          * which look negative collate low against normal characters but
  76          * high against the end-of-string NUL.
  77          */
  78         if (*p1 == '\0' && *p2 == '\0')
  79                 return(0);
  80         else if (*p1 == '\0')
  81                 return(-1);
  82         else if (*p2 == '\0')
  83                 return(1);
  84         else
  85                 return(TOLOW(*p1) - TOLOW(*p2));
  86 }
  87
  88 /*
  89  - rfc822ize - do the bizarre case conversion needed for rfc822 message-ids
  90  *
  91  * Actually, this is not quite complete.  Absolute, total, full RFC822
  92  * compliance requires a horrible parsing job, because of the arcane
  93  * quoting conventions -- abc"def"ghi is not equivalent to abc"DEF"ghi,
  94  * for example.  There are three or four things that might occur in the
  95  * domain part of a message-id that are case-sensitive.  They don't seem
  96  * to ever occur in real news, thank Cthulhu.  (What?  You were expecting
  97  * a merciful and forgiving deity to be invoked in connection with RFC822?
  98  * Forget it; none of them would come near it.)
  99  */
 100 char *                          /* returns the argument */
 101 rfc822ize(s)
 102 char *s;
 103 {
 104         register char *p;
 105         static char post[] = "postmaster";
 106         static int postlen = sizeof(post)-1;
 107
 108         if (!primed)
 109                 prime();
 110
 111         p = strrchr(s, '@');
 112         if (p == NULL)                  /* no local/domain split */
 113                 p = "";                 /* assume all local */
 114         else if (p - (s+1) == postlen && CISTREQN(s+1, post, postlen)) {
 115                 /* crazy special case -- "postmaster" is case-insensitive */
 116                 p = s;
 117         }
 118 #ifdef NONSTANDARD
 119 #ifdef RFCVIOLATION
 120 #ifdef B_2_11_MISTAKE
 121         p = s;                          /* all case-insensitive */
 122 #endif
 123 #endif
 124 #endif
 125         for (; *p != '\0'; p++)
 126                 *p = TOLOW(*p);
 127
 128         return(s);
 129 }