source: src/router/busybox/libbb/process_escape_sequence.c @ 8864

/* 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 "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[] ALIGN1 = {
                '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 char)(*q) - '0';
#ifdef WANT_HEX_ESCAPES
                if (d >= 10) {
                        d = (unsigned char)(_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;
}