src/core/base64.c

   1 /*
   2  * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <stdint.h>
  20 #include <string.h>
  21 #include <assert.h>
  22 #include <gpxe/base64.h>
  23
  24 /** @file
  25  *
  26  * Base64 encoding
  27  *
  28  */
  29
  30 static const char base64[64] =
  31         "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  32
  33 /**
  34  * Base64-encode a string
  35  *
  36  * @v raw               Raw string
  37  * @v encoded           Buffer for encoded string
  38  *
  39  * The buffer must be the correct length for the encoded string.  Use
  40  * something like
  41  *
  42  *     char buf[ base64_encoded_len ( strlen ( raw ) ) + 1 ];
  43  *
  44  * (the +1 is for the terminating NUL) to provide a buffer of the
  45  * correct size.
  46  */
  47 void base64_encode ( const char *raw, char *encoded ) {
  48         const uint8_t *raw_bytes = ( ( const uint8_t * ) raw );
  49         uint8_t *encoded_bytes = ( ( uint8_t * ) encoded );
  50         size_t raw_bit_len = ( 8 * strlen ( raw ) );
  51         unsigned int bit;
  52         unsigned int tmp;
  53
  54         for ( bit = 0 ; bit < raw_bit_len ; bit += 6 ) {
  55                 tmp = ( ( raw_bytes[ bit / 8 ] << ( bit % 8 ) ) |
  56                         ( raw_bytes[ bit / 8 + 1 ] >> ( 8 - ( bit % 8 ) ) ) );
  57                 tmp = ( ( tmp >> 2 ) & 0x3f );
  58                 *(encoded_bytes++) = base64[tmp];
  59         }
  60         for ( ; ( bit % 8 ) != 0 ; bit += 6 )
  61                 *(encoded_bytes++) = '=';
  62         *(encoded_bytes++) = '\0';
  63
  64         DBG ( "Base64-encoded \"%s\" as \"%s\"\n", raw, encoded );
  65         assert ( strlen ( encoded ) == base64_encoded_len ( strlen ( raw ) ) );
  66 }