boot/common/interp_backslash.c

/*-
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * Jordan K. Hubbard
 * 29 August 1998
 *
 * Routine for doing backslash elimination.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <stand.h>
#include <string.h>
#include "bootstrap.h"

#define DIGIT(x) (isdigit(x) ? (x) - '0' : islower(x) ? (x) + 10 - 'a' : (x) + 10 - 'A')

/*
 * backslash: Return malloc'd copy of str with all standard "backslash
 * processing" done on it.  Original can be free'd if desired.
 */
char *
backslash(char *str)
{
    /*
     * Remove backslashes from the strings. Turn \040 etc. into a single
     * character (we allow eight bit values). Currently NUL is not
     * allowed.
     *
     * Turn "\n" and "\t" into '\n' and '\t' characters. Etc.
     *
     */
    char *new_str;
    int seenbs = 0;
    int i = 0;

    if ((new_str = strdup(str)) == NULL)
    return NULL;

    while (*str) {
    if (seenbs) {
        seenbs = 0;
        switch (*str) {
        case '\\':
        new_str[i++] = '\\';
        str++;
        break;

        /* preserve backslashed quotes, dollar signs */
        case '\'':
        case '"':
        case '$':
        new_str[i++] = '\\';
        new_str[i++] = *str++;
        break;

        case 'b':
        new_str[i++] = '\b';
        str++;
        break;

        case 'f':
        new_str[i++] = '\f';
        str++;
        break;

        case 'r':
        new_str[i++] = '\r';
        str++;
        break;

        case 'n':
        new_str[i++] = '\n';
        str++;
        break;

        case 's':
        new_str[i++] = ' ';
        str++;
        break;

        case 't':
        new_str[i++] = '\t';
        str++;
        break;

        case 'v':
        new_str[i++] = '\13';
        str++;
        break;

        case 'z':
        str++;
        break;

        case '0': case '1': case '2': case '3': case '4':
        case '5': case '6': case '7': case '8': case '9': {
        char val;

        /* Three digit octal constant? */
        if (*str >= '0' && *str <= '3' &&
            *(str + 1) >= '0' && *(str + 1) <= '7' &&
            *(str + 2) >= '0' && *(str + 2) <= '7') {

            val = (DIGIT(*str) << 6) + (DIGIT(*(str + 1)) << 3) +
            DIGIT(*(str + 2));

            /* Allow null value if user really wants to shoot
                       at feet, but beware! */
            new_str[i++] = val;
            str += 3;
            break;
        }

        /* One or two digit hex constant?
         * If two are there they will both be taken.
         * Use \z to split them up if this is not wanted.
         */
        if (*str == '0' &&
            (*(str + 1) == 'x' || *(str + 1) == 'X') &&
            isxdigit(*(str + 2))) {
            val = DIGIT(*(str + 2));
            if (isxdigit(*(str + 3))) {
            val = (val << 4) + DIGIT(*(str + 3));
            str += 4;
            }
            else
            str += 3;
            /* Yep, allow null value here too */
            new_str[i++] = val;
            break;
        }
        }
        break;

        default:
        new_str[i++] = *str++;
        break;
        }
    }
        else {
            if (*str == '\\') {
                seenbs = 1;
                str++;
            }
        else
        new_str[i++] = *str++;
        }
    }

    if (seenbs) {
        /*
         * The final character was a '\'. Put it in as a single backslash.
         */
    new_str[i++] = '\\';
    }
    new_str[i] = '\0';
    return new_str;
}