/*      $NetBSD: interp_backslash.c,v 1.3 2009/07/20 04:59:03 kiyohara Exp $    */

/*-
 * 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: src/sys/boot/common/interp_backslash.c,v 1.6 2003/08/25 23:30:41 obrien Exp $"); */

#include <lib/libsa/stand.h>
#include <lib/libsa/loadfile.h>
#include <lib/libkern/libkern.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;
}