base16.c

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/*
 * Copyright (C) 2010 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * 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 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., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

#include <stdint.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <ipxe/string.h>
#include <ipxe/vsprintf.h>
#include <ipxe/base16.h>

/** @file
 *
 * Base16 encoding
 *
 */

/**
 * Encode hexadecimal string (with optional byte separator character)
 *
 * @v separator         Byte separator character, or 0 for no separator
 * @v raw               Raw data
 * @v raw_len           Length of raw data
 * @v data              Buffer
 * @v len               Length of buffer
 * @ret len             Encoded length
 */
size_t hex_encode ( char separator, const void *raw, size_t raw_len,
                    char *data, size_t len ) {
        const uint8_t *bytes = raw;
        const char delimiter[2] = { separator, '\0' };
        size_t used = 0;
        unsigned int i;

        if ( len )
                data[0] = 0; /* Ensure that a terminating NUL exists */
        for ( i = 0 ; i < raw_len ; i++ ) {
                used += ssnprintf ( ( data + used ), ( len - used ),
                                    "%s%02x", ( used ? delimiter : "" ),
                                    bytes[i] );
        }
        return used;
}

/**
 * Decode hexadecimal string (with optional byte separator character)
 *
 * @v separator         Byte separator character, or 0 for no separator
 * @v encoded           Encoded string
 * @v data              Buffer
 * @v len               Length of buffer
 * @ret len             Length of data, or negative error
 */
int hex_decode ( char separator, const char *encoded, void *data, size_t len ) {
        uint8_t *out = data;
        unsigned int count = 0;
        unsigned int sixteens;
        unsigned int units;
        int optional;

        /* Strip out optionality flag from separator character */
        optional = ( separator & HEX_DECODE_OPTIONAL );
        separator &= ~HEX_DECODE_OPTIONAL;

        /* Decode string */
        while ( *encoded ) {

                /* Check separator, if applicable */
                if ( count && separator ) {
                        if ( *encoded == separator ) {
                                encoded++;
                        } else if ( ! optional ) {
                                return -EINVAL;
                        }
                }

                /* Extract digits.  Note that either digit may be NUL,
                 * which would be interpreted as an invalid value by
                 * digit_value(); there is therefore no need for an
                 * explicit end-of-string check.
                 */
                sixteens = digit_value ( *(encoded++) );
                if ( sixteens >= 16 )
                        return -EINVAL;
                units = digit_value ( *(encoded++) );
                if ( units >= 16 )
                        return -EINVAL;

                /* Store result */
                if ( count < len )
                        out[count] = ( ( sixteens << 4 ) | units );
                count++;

        }
        return count;
}