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2008-09-02 11:20:52
This little utility implements the Base64 Content-Transfer-Encoding standard described in RFC1113 (). This is the coding scheme used by MIME to allow binary data to be transferred by SMTP mail.
I was attempting to look at a mime attachment in a badly formed e-mail one day. I was not able to find source that was simple to compile correctly and would actually work. I have been working on a project where code similar to this is in use. I decided that I would create a file similar to what I was looking for and make it available to others.
Hosting on SourceForge gives me a chance to work with their system and with luck will allow the source to take on a life of its own. I will also host the source on one of my sites just in case.
Specifically:
This code is a stand-alone utility to perform base64 encoding/decoding. It should be
genuinely useful when the need arises and it meets a need that is likely to occur for some
users. Code acts as sample code to show the author's design and coding style.
Generally:
This program is designed to survive: Everything you need is in a single source file. It
compiles cleanly using a vanilla ANSI C compiler. It does its job correctly with a minimum
of fuss. The code is not overly clever, not overly simplistic and not overly verbose.
Access is 'cut and paste' from a web page. Terms of use are reasonable.
I am hoping that this little source file will have all its bugs isolated and corrected in a single round of testing so that this beta code version 0.00.00B can actually be released as version 0.00.00R and stay there. Experience tells me this is a real long shot, but having reviewed and unit-tested the code, I think it's a possibility. It is, after all, a relatively simple utility.
How you can help:
I would be greatly obliged if you would compile the source and run unit test. Don't bother if it has already been done for your platforms/compilers. Take a look at the project and the news page to see what platforms have been covered. If you have access to a platform that has not been covered you can compile, run unit test and let us know the results.
Here is the source code in question:
/*********************************************************************\
MODULE NAME: b64.c
AUTHOR: Bob Trower 08/04/01
PROJECT: Crypt Data Packaging
COPYRIGHT: Copyright (c) Trantor Standard Systems Inc., 2001
NOTE: This source code may be used as you wish, subject to
the MIT license. See the LICENCE section below.
DESCRIPTION:
This little utility implements the Base64
Content-Transfer-Encoding standard described in
RFC1113 ().
This is the coding scheme used by MIME to allow
binary data to be transferred by SMTP mail.
Groups of 3 bytes from a binary stream are coded as
groups of 4 bytes in a text stream.
The input stream is 'padded' with zeros to create
an input that is an even multiple of 3.
A special character ('=') is used to denote padding so
that the stream can be decoded back to its exact size.
Encoded output is formatted in lines which should
be a maximum of 72 characters to conform to the
specification. This program defaults to 72 characters,
but will allow more or less through the use of a
switch. The program enforces a minimum line size
of 4 characters.
Example encoding:
The stream 'ABCD' is 32 bits long. It is mapped as
follows:
ABCD
A (65) B (66) C (67) D (68) (None) (None)
01000001 01000010 01000011 01000100
16 (Q) 20 (U) 9 (J) 3 (D) 17 (R) 0 (A) NA (=) NA (=)
010000 010100 001001 000011 010001 000000 000000 000000
QUJDRA==
Decoding is the process in reverse. A 'decode' lookup
table has been created to avoid string scans.
DESIGN GOALS: Specifically:
Code is a stand-alone utility to perform base64
encoding/decoding. It should be genuinely useful
when the need arises and it meets a need that is
likely to occur for some users.
Code acts as sample code to show the author's
design and coding style.
Generally:
This program is designed to survive:
Everything you need is in a single source file.
It compiles cleanly using a vanilla ANSI C compiler.
It does its job correctly with a minimum of fuss.
The code is not overly clever, not overly simplistic
and not overly verbose.
Access is 'cut and paste' from a web page.
Terms of use are reasonable.
VALIDATION: Non-trivial code is never without errors. This
file likely has some problems, since it has only
been tested by the author. It is expected with most
source code that there is a period of 'burn-in' when
problems are identified and corrected. That being
said, it is possible to have 'reasonably correct'
code by following a regime of unit test that covers
the most likely cases and regression testing prior
to release. This has been done with this code and
it has a good probability of performing as expected.
Unit Test Cases:
case 0:empty file:
CASE0.DAT -> ->
(Zero length target file created
on both encode and decode.)
case 1:One input character:
CASE1.DAT A -> QQ== -> A
case 2:Two input characters:
CASE2.DAT AB -> QUJD -> AB
case 3:Three input characters:
CASE3.DAT ABC -> QUJD -> ABC
case 4:Four input characters:
case4.dat ABCD -> QUJDRA== -> ABCD
case 5:All chars from 0 to ff, linesize set to 50:
AAECAwQFBgcICQoLDA0ODxAREhMUFRYXGBkaGxwdHh8gISIj
JCUmJygpKissLS4vMDEyMzQ1Njc4OTo7PD0+P0BBQkNERUZH
SElKS0xNTk9QUVJTVFVWV1hZWltcXV5fYGFiY2RlZmdoaWpr
bG1ub3BxcnN0dXZ3eHl6e3x9fn+AgYKDhIWGh4iJiouMjY6P
kJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmqq6ytrq+wsbKz
tLW2t7i5uru8vb6/wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX
2Nna29zd3t/g4eLj5OXm5+jp6uvs7e7v8PHy8/T19vf4+fr7
/P3+/w==
case 6:Mime Block from e-mail:
(Data same as test case 5)
case 7: Large files:
Tested 28 MB file in/out.
case 8: Random Binary Integrity:
This binary program (b64.exe) was encoded to base64,
back to binary and then executed.
case 9 Stress:
All files in a working directory encoded/decoded
and compared with file comparison utility to
ensure that multiple runs do not cause problems
such as exhausting file handles, tmp storage, etc.
-------------
Syntax, operation and failure:
All options/switches tested. Performs as
expected.
case 10:
No Args -- Shows Usage Screen
Return Code 1 (Invalid Syntax)
case 11:
One Arg (invalid) -- Shows Usage Screen
Return Code 1 (Invalid Syntax)
case 12:
One Arg Help (-?) -- Shows detailed Usage Screen.
Return Code 0 (Success -- help request is valid).
case 13:
One Arg Help (-h) -- Shows detailed Usage Screen.
Return Code 0 (Success -- help request is valid).
case 14:
One Arg (valid) -- Uses stdin/stdout (filter)
Return Code 0 (Sucess)
case 15:
Two Args (invalid file) -- shows system error.
Return Code 2 (File Error)
case 16:
Encode non-existent file -- shows system error.
Return Code 2 (File Error)
case 17:
Out of disk space -- shows system error.
Return Code 3 (File I/O Error)
-------------
Compile/Regression test:
gcc compiled binary under Cygwin
Microsoft Visual Studio under Windows 2000
Microsoft Version 6.0 C under Windows 2000
DEPENDENCIES: None
LICENCE: Copyright (c) 2001 Bob Trower, Trantor Standard Systems Inc.
Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated
documentation files (the "Software"), to deal in the
Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute,
sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so,
subject to the following conditions:
The above copyright notice and this permission notice shall
be included in all copies or substantial portions of the
Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
VERSION HISTORY:
Bob Trower 08/04/01 -- Create Version 0.00.00B
\******************************************************************* */
#include
#include
/*
** Translation Table as described in RFC1113
*/
static const char cb64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
/*
** Translation Table to decode (created by author)
*/
static const char cd64[]="|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\\]^_`abcdefghijklmnopq";
/*
** encodeblock
**
** encode 3 8-bit binary bytes as 4 '6-bit' characters
*/
void encodeblock( unsigned char in[3], unsigned char out[4], int len )
{
out[0] = cb64[ in[0] >> 2 ];
out[1] = cb64[ ((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4) ];
out[2] = (unsigned char) (len > 1 ? cb64[ ((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6) ] : '=');
out[3] = (unsigned char) (len > 2 ? cb64[ in[2] & 0x3f ] : '=');
}
/*
** encode
**
** base64 encode a stream adding padding and line breaks as per spec.
*/
void encode( FILE *infile, FILE *outfile, int linesize )
{
unsigned char in[3], out[4];
int i, len, blocksout = 0;
while( !feof( infile ) ) {
len = 0;
for( i = 0; i < 3; i++ ) {
in[i] = (unsigned char) getc( infile );
if( !feof( infile ) ) {
len++;
}
else {
in[i] = 0;
}
}
if( len ) {
encodeblock( in, out, len );
for( i = 0; i < 4; i++ ) {
putc( out[i], outfile );
}
blocksout++;
}
if( blocksout >= (linesize/4) || feof( infile ) ) {
if( blocksout ) {
fprintf( outfile, "\r\n" );
}
blocksout = 0;
}
}
}
/*
** decodeblock
**
** decode 4 '6-bit' characters into 3 8-bit binary bytes
*/
void decodeblock( unsigned char in[4], unsigned char out[3] )
{
out[ 0 ] = (unsigned char ) (in[0] << 2 | in[1] >> 4);
out[ 1 ] = (unsigned char ) (in[1] << 4 | in[2] >> 2);
out[ 2 ] = (unsigned char ) (((in[2] << 6) & 0xc0) | in[3]);
}
/*
** decode
**
** decode a base64 encoded stream discarding padding, line breaks and noise
*/
void decode( FILE *infile, FILE *outfile )
{
unsigned char in[4], out[3], v;
int i, len;
while( !feof( infile ) ) {
for( len = 0, i = 0; i < 4 && !feof( infile ); i++ ) {
v = 0;
while( !feof( infile ) && v == 0 ) {
v = (unsigned char) getc( infile );
v = (unsigned char) ((v < 43 || v > 122) ? 0 : cd64[ v - 43 ]);
if( v ) {
v = (unsigned char) ((v == '$') ? 0 : v - 61);
}
}
if( !feof( infile ) ) {
len++;
if( v ) {
in[ i ] = (unsigned char) (v - 1);
}
}
else {
in[i] = 0;
}
}
if( len ) {
decodeblock( in, out );
for( i = 0; i < len - 1; i++ ) {
putc( out[i], outfile );
}
}
}
}
/*
** returnable errors
**
** Error codes returned to the operating system.
**
*/
#define B64_SYNTAX_ERROR 1
#define B64_FILE_ERROR 2
#define B64_FILE_IO_ERROR 3
#define B64_ERROR_OUT_CLOSE 4
#define B64_LINE_SIZE_TO_MIN 5
/*
** b64_message
**
** Gather text messages in one place.
**
*/
char *b64_message( int errcode )
{
#define B64_MAX_MESSAGES 6
char *msgs[ B64_MAX_MESSAGES ] = {
"b64:000:Invalid Message Code.",
"b64:001:Syntax Error -- check help for usage.",
"b64:002:File Error Opening/Creating Files.",
"b64:003:File I/O Error -- Note: output file not removed.",
"b64:004:Error on output file close.",
"b64:004:linesize set to minimum."
};
char *msg = msgs[ 0 ];
if( errcode > 0 && errcode < B64_MAX_MESSAGES ) {
msg = msgs[ errcode ];
}
return( msg );
}
/*
** b64
**
** 'engine' that opens streams and calls encode/decode
*/
int b64( int opt, char *infilename, char *outfilename, int linesize )
{
FILE *infile;
int retcode = B64_FILE_ERROR;
if( !infilename ) {
infile = stdin;
}
else {
infile = fopen( infilename, "rb" );
}
if( !infile ) {
perror( infilename );
}
else {
FILE *outfile;
if( !outfilename ) {
outfile = stdout;
}
else {
outfile = fopen( outfilename, "wb" );
}
if( !outfile ) {
perror( outfilename );
}
else {
if( opt == 'e' ) {
encode( infile, outfile, linesize );
}
else {
decode( infile, outfile );
}
if (ferror( infile ) || ferror( outfile )) {
retcode = B64_FILE_IO_ERROR;
}
else {
retcode = 0;
}
if( outfile != stdout ) {
if( fclose( outfile ) != 0 ) {
perror( b64_message( B64_ERROR_OUT_CLOSE ) );
retcode = B64_FILE_IO_ERROR;
}
}
}
if( infile != stdin ) {
fclose( infile );
}
}
return( retcode );
}
/*
** showuse
**
** display usage information, help, version info
*/
void showuse( int morehelp )
{
{
printf( "\n" );
printf( " b64 (Base64 Encode/Decode) Bob Trower 08/03/01 \n" );
printf( " (C) Copr Bob Trower 1986-01. Version 0.00B \n" );
printf( " Usage: b64 -option [ -l num ] [[ ]] \n" );
printf( " Purpose: This program is a simple utility that implements\n" );
printf( " Base64 Content-Transfer-Encoding (RFC1113). \n" );
}
if( !morehelp ) {
printf( " Use -h option for additional help. \n" );
}
else {
printf( " Options: -e encode to Base64 -h This help text. \n" );
printf( " -d decode from Base64 -? This help text. \n" );
printf( " Note: -l use to change line size (from 72 characters)\n" );
printf( " Returns: 0 = success. Non-zero is an error code. \n" );
printf( " ErrCode: 1 = Bad Syntax, 2 = File Open, 3 = File I/O \n" );
printf( " Example: b64 -e binfile b64file <- Encode to b64 \n" );
printf( " b64 -d b64file binfile <- Decode from b64 \n" );
printf( " b64 -e -l40 infile outfile <- Line Length of 40 \n" );
printf( " Note: Will act as a filter, but this should only be \n" );
printf( " used on text files due to translations made by \n" );
printf( " operating systems. \n" );
printf( " Release: 0.00.00, Tue Aug 7 2:00:00 2001, ANSI-SOURCE C\n" );
}
}
#define B64_DEF_LINE_SIZE 72
#define B64_MIN_LINE_SIZE 4
#define THIS_OPT(ac, av) (ac > 1 ? av[1][0] == '-' ? av[1][1] : 0 : 0)
/*
** main
**
** parse and validate arguments and call b64 engine or help
*/
int main( int argc, char **argv )
{
int opt = 0;
int retcode = 0;
int linesize = B64_DEF_LINE_SIZE;
char *infilename = NULL, *outfilename = NULL;
while( THIS_OPT( argc, argv ) ) {
switch( THIS_OPT(argc, argv) ) {
case 'l':
linesize = atoi( &(argv[1][2]) );
if( linesize < B64_MIN_LINE_SIZE ) {
linesize = B64_MIN_LINE_SIZE;
printf( "%s\n", b64_message( B64_LINE_SIZE_TO_MIN ) );
}
break;
case '?':
case 'h':
opt = 'h';
break;
case 'e':
case 'd':
opt = THIS_OPT(argc, argv);
break;
default:
opt = 0;
break;
}
argv++;
argc--;
}
switch( opt ) {
case 'e':
case 'd':
infilename = argc > 1 ? argv[1] : NULL;
outfilename = argc > 2 ? argv[2] : NULL;
retcode = b64( opt, infilename, outfilename, linesize );
break;
case 0:
retcode = B64_SYNTAX_ERROR;
case 'h':
showuse( opt );
break;
}
if( retcode ) {
printf( "%s\n", b64_message( retcode ) );
}
return( retcode );
}
