/*-
 * 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 <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(const 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;
}