source: MondoRescue/branches/2.2.3/mindi-busybox/libbb/process_escape_sequence.c@ 1333

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) Manuel Novoa III <mjn3@codepoet.org>
 * and Vladimir Oleynik <dzo@simtreas.ru>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include <stdio.h>
#include <limits.h>
#include <ctype.h>
#include "libbb.h"

#define WANT_HEX_ESCAPES 1

/* Usual "this only works for ascii compatible encodings" disclaimer. */
#undef _tolower
#define _tolower(X) ((X)|((char) 0x20))

char bb_process_escape_sequence(const char **ptr)
{
    static const char charmap[] = {
        'a',  'b',  'f',  'n',  'r',  't',  'v',  '\\', 0,
        '\a', '\b', '\f', '\n', '\r', '\t', '\v', '\\', '\\' };

    const char *p;
    const char *q;
    unsigned int num_digits;
    unsigned int r;
    unsigned int n;
    unsigned int d;
    unsigned int base;

    num_digits = n = 0;
    base = 8;
    q = *ptr;

#ifdef WANT_HEX_ESCAPES
    if (*q == 'x') {
        ++q;
        base = 16;
        ++num_digits;
    }
#endif

    do {
        d = (unsigned int)(*q - '0');
#ifdef WANT_HEX_ESCAPES
        if (d >= 10) {
            d = ((unsigned int)(_tolower(*q) - 'a')) + 10;
        }
#endif

        if (d >= base) {
#ifdef WANT_HEX_ESCAPES
            if ((base == 16) && (!--num_digits)) {
/*              return '\\'; */
                --q;
            }
#endif
            break;
        }

        r = n * base + d;
        if (r > UCHAR_MAX) {
            break;
        }

        n = r;
        ++q;
    } while (++num_digits < 3);

    if (num_digits == 0) {  /* mnemonic escape sequence? */
        p = charmap;
        do {
            if (*p == *q) {
                q++;
                break;
            }
        } while (*++p);
        n = *(p+(sizeof(charmap)/2));
    }

    *ptr = q;

    return (char) n;
}