libbb/process_escape_sequence.c

/* vi: set sw=4 ts=4: */
/*
 * Utility routines.
 *
 * Copyright (C) tons of folks.  Tracking down who wrote what
 * isn't something I'm going to worry about...  If you wrote something
 * here, please feel free to acknowledge your work.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 * Based in part on code from sash, Copyright (c) 1999 by David I. Bell 
 * Permission has been granted to redistribute this code under the GPL.
 *
 */

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



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

       const char *p;
	   char *q;
       int num_digits;
       unsigned int n;

       n = 0;
	   q = *ptr;

       for ( num_digits = 0 ; num_digits < 3 ; ++num_digits) {
	       if ((*q < '0') || (*q > '7')) { /* not a digit? */
		       break;
	       }
	       n = n * 8 + (*q++ - '0');
       }

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

	   /* doesn't hurt to fall through to here from mnemonic case */
	   if (n > UCHAR_MAX) {	/* is octal code too big for a char? */
		   n /= 8;			/* adjust value and */
		   --q;				/* back up one char */
	   }

	   *ptr = q;
	   return (char) n;
}


/* END CODE */
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