Need Help with base64

[pycraze]

Hi ,

I am currently trying to implement base64 encoding and decoding
scheme in C . Python has a module , base64 , that will do the
encoding and decoding with ease . I am aware of OpenSSL having support
for base64 encoding and decoding , but i will have to now implement
both in C without using the openssl libraries .

I was able to download a code w.r.t. base 64 encoding and
decoding . I am attaching the code below .


void encodeblock( unsigned char cin[3], unsigned char cout[4], int
nlen )
{

cout[0] = cb64[ cin[0] >> 2 ];
cout[1] = cb64[ ((cin[0] & 0x03) << 4) | ((cin[1] & 0xf0) >> 4) ];
cout[2] = (unsigned char) (nlen > 1 ? cb64[ ((cin[1] & 0x0f) << 2)
| ((cin[2] & 0xc0) >> 6) ] : '=');
cout[3] = (unsigned char) (nlen > 2 ? cb64[ cin[2] & 0x3f ] :
'=');
}


void decodeblock( unsigned char cin[4], unsigned char cout[3] )
{
cout[ 0 ] = (unsigned char ) (cin[0] << 2 | cin[1] >> 4);
cout[ 1 ] = (unsigned char ) (cin[1] << 4 | cin[2] >> 2);
cout[ 2 ] = (unsigned char ) (((cin[2] << 6) & 0xc0) | cin[3]);
}


int base641_decodestring(char* pcstr,int size,char** ppcdest)
{
unsigned char cin[4] = {""};
unsigned char cout[3] = {""};
unsigned char cv = 0;
int ni = 0;
int nlen = 0;
char* cptr = pcstr;
*ppcdest = malloc(sizeof(char)*160);
if (!*ppcdest)
{
return 1;
}
memset(*ppcdest,0,sizeof(char)*160);

char* pcstring = malloc( sizeof(char) * SIZE);
if (!pcstring)
{
aps_log("APS_log.txt","\nbae64.c:base64encode:malloc failed
\n");
return 1;
}
memset(pcstring,'\0',SIZE);

for( nlen = 0, ni = 0; ni < 4; ni++ )
{
cv = 0;
while( cv == 0 )
{
cv = (unsigned char) *cptr;
cv = (unsigned char) ((cv < 43 || cv > 122) ? 0 :
cd64[ cv - 43 ]);
if( cv )
{
cv = (unsigned char) ((cv == '$') ? 0 : cv - 61);
}
}
if( cptr++ )
{
nlen++;
if( cv )
{
cin[ ni ] = (unsigned char) (cv - 1);
}
}
else
{
cin[ni] = 0;
}
}
if( nlen )
{
decodeblock( cin, cout );

}
memcpy(*ppcdest,cout,160);
return 0;
}/*end of base64_decode */

char* base64_encode(char* pcstr)
{
unsigned char cin[3] = {""};
unsigned char cout[4] = {""};
int ni = 0;
int nlen = 0;
int flag = 1;
char* cptr = pcstr;
char* pcstring = malloc( sizeof(char) * SIZE);
if (!pcstring)
{
aps_log("APS_log.txt","\nbae64.c:base64encode:malloc failed
\n");
return (void*)0;
}
memset(pcstring,'\0',SIZE);
while( flag )
{
for( ni = 0; ni < 3; ni++ )
{
cin[ni] = (unsigned char)*cptr;
if( *++cptr != '\0' )
nlen++;
else
{
cin[ni] = 0;
flag = 0;
break;
}
}
encodeblock(cin, cout,nlen);
strcat(pcstring,cout);
}

return pcstring;

}/* end of base64_encode */


But this code gives different hex values as compared to the
python base64.encodestring and base64.decodestring respectively .

I need some help on this matter . I need some pointers on
where is the mistake for the above file .

 

[Diez B. Roggisch]

Hi ,

I am currently trying to implement base64 encoding and decoding
scheme in C . Python has a module , base64 , that will do the
encoding and decoding with ease . I am aware of OpenSSL having support
for base64 encoding and decoding , but i will have to now implement
both in C without using the openssl libraries .

I was able to download a code w.r.t. base 64 encoding and
decoding . I am attaching the code below .


void encodeblock( unsigned char cin[3], unsigned char cout[4], int
nlen )
{

cout[0] = cb64[ cin[0] >> 2 ];
cout[1] = cb64[ ((cin[0] & 0x03) << 4) | ((cin[1] & 0xf0) >> 4) ];
cout[2] = (unsigned char) (nlen > 1 ? cb64[ ((cin[1] & 0x0f) << 2)
| ((cin[2] & 0xc0) >> 6) ] : '=');
cout[3] = (unsigned char) (nlen > 2 ? cb64[ cin[2] & 0x3f ] :
'=');
}


void decodeblock( unsigned char cin[4], unsigned char cout[3] )
{
cout[ 0 ] = (unsigned char ) (cin[0] << 2 | cin[1] >> 4);
cout[ 1 ] = (unsigned char ) (cin[1] << 4 | cin[2] >> 2);
cout[ 2 ] = (unsigned char ) (((cin[2] << 6) & 0xc0) | cin[3]);
}


int base641_decodestring(char* pcstr,int size,char** ppcdest)
{
unsigned char cin[4] = {""};
unsigned char cout[3] = {""};
unsigned char cv = 0;
int ni = 0;
int nlen = 0;
char* cptr = pcstr;
*ppcdest = malloc(sizeof(char)*160);
if (!*ppcdest)
{
return 1;
}
memset(*ppcdest,0,sizeof(char)*160);

char* pcstring = malloc( sizeof(char) * SIZE);
if (!pcstring)
{
aps_log("APS_log.txt","\nbae64.c:base64encode:malloc failed
\n");
return 1;
}
memset(pcstring,'\0',SIZE);

for( nlen = 0, ni = 0; ni < 4; ni++ )
{
cv = 0;
while( cv == 0 )
{
cv = (unsigned char) *cptr;
cv = (unsigned char) ((cv < 43 || cv > 122) ? 0 :
cd64[ cv - 43 ]);
if( cv )
{
cv = (unsigned char) ((cv == '$') ? 0 : cv - 61);
}
}
if( cptr++ )
{
nlen++;
if( cv )
{
cin[ ni ] = (unsigned char) (cv - 1);
}
}
else
{
cin[ni] = 0;
}
}
if( nlen )
{
decodeblock( cin, cout );

}
memcpy(*ppcdest,cout,160);
return 0;
}/*end of base64_decode */

char* base64_encode(char* pcstr)
{
unsigned char cin[3] = {""};
unsigned char cout[4] = {""};
int ni = 0;
int nlen = 0;
int flag = 1;
char* cptr = pcstr;
char* pcstring = malloc( sizeof(char) * SIZE);
if (!pcstring)
{
aps_log("APS_log.txt","\nbae64.c:base64encode:malloc failed
\n");
return (void*)0;
}
memset(pcstring,'\0',SIZE);
while( flag )
{
for( ni = 0; ni < 3; ni++ )
{
cin[ni] = (unsigned char)*cptr;
if( *++cptr != '\0' )
nlen++;
else
{
cin[ni] = 0;
flag = 0;
break;
}
}
encodeblock(cin, cout,nlen);
strcat(pcstring,cout);
}

return pcstring;

}/* end of base64_encode */


But this code gives different hex values as compared to the
python base64.encodestring and base64.decodestring respectively .

I need some help on this matter . I need some pointers on
where is the mistake for the above file .

How about posting that in a C-newsgroup? python _has_ base64-encoding
support.

Diez

 

[Terry Reedy]

| Hi ,
|
| I am currently trying to implement base64 encoding and decoding
| scheme in C . Python has a module , base64 , that will do the
| encoding and decoding with ease . I am aware of OpenSSL having support
| for base64 encoding and decoding , but i will have to now implement
| both in C without using the openssl libraries .
|
| I was able to download a code w.r.t. base 64 encoding and
| decoding . I am attaching the code below .

[C coce snipped]

| But this code gives different hex values as compared to the
| python base64.encodestring and base64.decodestring respectively .
|
| I need some help on this matter . I need some pointers on
| where is the mistake for the above file .

Looking at the source code for those functions might tell you why you get
different outputs. The python code for base64 is in /Lib. Those two
functions are thin wrappers around corresponding C-coded binascii
functions. You can access that module via this source tree directory:
http://svn.python.org/view/python/trunk/Modules/

The current binascii code is
http://svn.python.org/view/python/trunk/Modules/binascii.c?rev=55205&view=auto

The interpreter is open source with a liberal license that should allow you
to pluck the functions for use elsewhere as long as the add a copyright
notice.

Otherwise, I agree with Diez that this is OT here.

tjr

 

[Tim Roberts]

int base641_decodestring(char* pcstr,int size,char** ppcdest)
{
unsigned char cin[4] = {""};
unsigned char cout[3] = {""};
unsigned char cv = 0;
int ni = 0;
int nlen = 0;
char* cptr = pcstr;
*ppcdest = malloc(sizeof(char)*160);
if (!*ppcdest)
{
return 1;
}
memset(*ppcdest,0,sizeof(char)*160);

char* pcstring = malloc( sizeof(char) * SIZE);
if (!pcstring)
{
aps_log("APS_log.txt","\nbae64.c:base64encode:malloc failed
\n");
return 1;
}
memset(pcstring,'\0',SIZE);

Those last 7 lines must have been leftover; pcstring is not used in this
routine.

for( nlen = 0, ni = 0; ni < 4; ni++ )
{
cv = 0;
while( cv == 0 )
{
cv = (unsigned char) *cptr;
cv = (unsigned char) ((cv < 43 || cv > 122) ? 0 :
cd64[ cv - 43 ]);
if( cv )
{
cv = (unsigned char) ((cv == '$') ? 0 : cv - 61);
}
}
if( cptr++ )
{
nlen++;
if( cv )
{
cin[ ni ] = (unsigned char) (cv - 1);
}
}
else
{
cin[ni] = 0;
}
}
if( nlen )
{
decodeblock( cin, cout );

}
memcpy(*ppcdest,cout,160);
return 0;

"cout" is an array of 3 characters. Where do you think the memcpy is going
to find 160 bytes? I suspect you intended to have this loop inside a
SECOND loop, copying 3 characters at a time into *ppcdest.