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 #include <stand.h>
  19 #include <string.h>
  20 #include "bootstrap.h"
  21
  22 #define DIGIT(x) (isdigit(x) ? (x) - '0' : islower(x) ? (x) + 10 - 'a' : (x) + 10 - 'A')
  23
  24 /*
  25  * backslash: Return malloc'd copy of str with all standard "backslash
  26  * processing" done on it.  Original can be free'd if desired.
  27  */
  28 char *
  29 backslash(const char *str)
  30 {
  31         /*
  32          * Remove backslashes from the strings. Turn \040 etc. into a single
  33          * character (we allow eight bit values). Currently NUL is not
  34          * allowed.
  35          *
  36          * Turn "\n" and "\t" into '\n' and '\t' characters. Etc.
  37          *
  38          */
  39         char *new_str;
  40         int seenbs = 0;
  41         int i = 0;
  42
  43         if ((new_str = strdup(str)) == NULL)
  44                 return NULL;
  45
  46         while (*str) {
  47                 if (seenbs) {
  48                         seenbs = 0;
  49                         switch (*str) {
  50                         case '\\':
  51                                 new_str[i++] = '\\';
  52                                 str++;
  53                                 break;
  54
  55                                 /* preserve backslashed quotes, dollar signs */
  56                         case '\'':
  57                         case '"':
  58                         case '$':
  59                                 new_str[i++] = '\\';
  60                                 new_str[i++] = *str++;
  61                                 break;
  62
  63                         case 'b':
  64                                 new_str[i++] = '\b';
  65                                 str++;
  66                                 break;
  67
  68                         case 'f':
  69                                 new_str[i++] = '\f';
  70                                 str++;
  71                                 break;
  72
  73                         case 'r':
  74                                 new_str[i++] = '\r';
  75                                 str++;
  76                                 break;
  77
  78                         case 'n':
  79                                 new_str[i++] = '\n';
  80                                 str++;
  81                                 break;
  82
  83                         case 's':
  84                                 new_str[i++] = ' ';
  85                                 str++;
  86                                 break;
  87
  88                         case 't':
  89                                 new_str[i++] = '\t';
  90                                 str++;
  91                                 break;
  92
  93                         case 'v':
  94                                 new_str[i++] = '\13';
  95                                 str++;
  96                                 break;
  97
  98                         case 'z':
  99                                 str++;
 100                                 break;
 101
 102                         case '0': case '1': case '2': case '3': case '4':
 103                         case '5': case '6': case '7': case '8': case '9': {
 104                                 char val;
 105
 106                                 /* Three digit octal constant? */
 107                                 if (*str >= '0' && *str <= '3' &&
 108                                     *(str + 1) >= '0' && *(str + 1) <= '7' &&
 109                                     *(str + 2) >= '0' && *(str + 2) <= '7') {
 110
 111                                         val = (DIGIT(*str) << 6) + (DIGIT(*(str + 1)) << 3) +
 112                                             DIGIT(*(str + 2));
 113
 114                                         /* Allow null value if user really wants to shoot
 115                                            at feet, but beware! */
 116                                         new_str[i++] = val;
 117                                         str += 3;
 118                                         break;
 119                                 }
 120
 121                                 /* One or two digit hex constant?
 122                                  * If two are there they will both be taken.
 123                                  * Use \z to split them up if this is not wanted.
 124                                  */
 125                                 if (*str == '0' &&
 126                                     (*(str + 1) == 'x' || *(str + 1) == 'X') &&
 127                                     isxdigit(*(str + 2))) {
 128                                         val = DIGIT(*(str + 2));
 129                                         if (isxdigit(*(str + 3))) {
 130                                                 val = (val << 4) + DIGIT(*(str + 3));
 131                                                 str += 4;
 132                                         }
 133                                         else
 134                                                 str += 3;
 135                                         /* Yep, allow null value here too */
 136                                         new_str[i++] = val;
 137                                         break;
 138                                 }
 139                         }
 140                                 break;
 141
 142                         default:
 143                                 new_str[i++] = *str++;
 144                                 break;
 145                         }
 146                 }
 147                 else {
 148                         if (*str == '\\') {
 149                                 seenbs = 1;
 150                                 str++;
 151                         }
 152                         else
 153                                 new_str[i++] = *str++;
 154                 }
 155         }
 156
 157         if (seenbs) {
 158                 /*
 159                  * The final character was a '\'. Put it in as a single backslash.
 160                  */
 161                 new_str[i++] = '\\';
 162         }
 163         new_str[i] = '\0';
 164         return new_str;
 165 }