stand/common/interp_backslash.c

   1 /*-
   2  * Redistribution and use in source and binary forms, with or without
   3  * modification, are permitted provided that the following conditions
   4  * are met:
   5  * 1. Redistributions of source code must retain the above copyright
   6  *    notice, this list of conditions and the following disclaimer.
   7  * 2. Redistributions in binary form must reproduce the above copyright
   8  *    notice, this list of conditions and the following disclaimer in the
   9  *    documentation and/or other materials provided with the distribution.
  10  *
  11  * Jordan K. Hubbard
  12  * 29 August 1998
  13  *
  14  * Routine for doing backslash elimination.
  15  */
  16
  17 #include <sys/cdefs.h>
  18 __FBSDID("$FreeBSD$");
  19
  20 #include <stand.h>
  21 #include <string.h>
  22 #include "bootstrap.h"
  23
  24 #define DIGIT(x) (isdigit(x) ? (x) - '0' : islower(x) ? (x) + 10 - 'a' : (x) + 10 - 'A')
  25
  26 /*
  27  * backslash: Return malloc'd copy of str with all standard "backslash
  28  * processing" done on it.  Original can be free'd if desired.
  29  */
  30 char *
  31 backslash(const char *str)
  32 {
  33         /*
  34          * Remove backslashes from the strings. Turn \040 etc. into a single
  35          * character (we allow eight bit values). Currently NUL is not
  36          * allowed.
  37          *
  38          * Turn "\n" and "\t" into '\n' and '\t' characters. Etc.
  39          *
  40          */
  41         char *new_str;
  42         int seenbs = 0;
  43         int i = 0;
  44
  45         if ((new_str = strdup(str)) == NULL)
  46                 return NULL;
  47
  48         while (*str) {
  49                 if (seenbs) {
  50                         seenbs = 0;
  51                         switch (*str) {
  52                         case '\\':
  53                                 new_str[i++] = '\\';
  54                                 str++;
  55                                 break;
  56
  57                                 /* preserve backslashed quotes, dollar signs */
  58                         case '\'':
  59                         case '"':
  60                         case '$':
  61                                 new_str[i++] = '\\';
  62                                 new_str[i++] = *str++;
  63                                 break;
  64
  65                         case 'b':
  66                                 new_str[i++] = '\b';
  67                                 str++;
  68                                 break;
  69
  70                         case 'f':
  71                                 new_str[i++] = '\f';
  72                                 str++;
  73                                 break;
  74
  75                         case 'r':
  76                                 new_str[i++] = '\r';
  77                                 str++;
  78                                 break;
  79
  80                         case 'n':
  81                                 new_str[i++] = '\n';
  82                                 str++;
  83                                 break;
  84
  85                         case 's':
  86                                 new_str[i++] = ' ';
  87                                 str++;
  88                                 break;
  89
  90                         case 't':
  91                                 new_str[i++] = '\t';
  92                                 str++;
  93                                 break;
  94
  95                         case 'v':
  96                                 new_str[i++] = '\13';
  97                                 str++;
  98                                 break;
  99
 100                         case 'z':
 101                                 str++;
 102                                 break;
 103
 104                         case '0': case '1': case '2': case '3': case '4':
 105                         case '5': case '6': case '7': case '8': case '9': {
 106                                 char val;
 107
 108                                 /* Three digit octal constant? */
 109                                 if (*str >= '0' && *str <= '3' &&
 110                                     *(str + 1) >= '0' && *(str + 1) <= '7' &&
 111                                     *(str + 2) >= '0' && *(str + 2) <= '7') {
 112
 113                                         val = (DIGIT(*str) << 6) + (DIGIT(*(str + 1)) << 3) +
 114                                             DIGIT(*(str + 2));
 115
 116                                         /* Allow null value if user really wants to shoot
 117                                            at feet, but beware! */
 118                                         new_str[i++] = val;
 119                                         str += 3;
 120                                         break;
 121                                 }
 122
 123                                 /* One or two digit hex constant?
 124                                  * If two are there they will both be taken.
 125                                  * Use \z to split them up if this is not wanted.
 126                                  */
 127                                 if (*str == '0' &&
 128                                     (*(str + 1) == 'x' || *(str + 1) == 'X') &&
 129                                     isxdigit(*(str + 2))) {
 130                                         val = DIGIT(*(str + 2));
 131                                         if (isxdigit(*(str + 3))) {
 132                                                 val = (val << 4) + DIGIT(*(str + 3));
 133                                                 str += 4;
 134                                         }
 135                                         else
 136                                                 str += 3;
 137                                         /* Yep, allow null value here too */
 138                                         new_str[i++] = val;
 139                                         break;
 140                                 }
 141                         }
 142                                 break;
 143
 144                         default:
 145                                 new_str[i++] = *str++;
 146                                 break;
 147                         }
 148                 }
 149                 else {
 150                         if (*str == '\\') {
 151                                 seenbs = 1;
 152                                 str++;
 153                         }
 154                         else
 155                                 new_str[i++] = *str++;
 156                 }
 157         }
 158
 159         if (seenbs) {
 160                 /*
 161                  * The final character was a '\'. Put it in as a single backslash.
 162                  */
 163                 new_str[i++] = '\\';
 164         }
 165         new_str[i] = '\0';
 166         return new_str;
 167 }