base64sub.c

/*
 * $Log: base64sub.c,v $
 * Revision 1.6  2010-03-03 09:33:16+05:30  Cprogrammer
 * renamed base64 to base64sub
 *
 * Revision 1.5  2004-10-22 20:18:37+05:30  Cprogrammer
 * added RCS id
 *
 * Revision 1.4  2004-09-19 14:36:11+05:30  Cprogrammer
 * corrected number of bytes in stralloc variable 'out'
 *
 * Revision 1.3  2004-07-30 17:36:47+05:30  Cprogrammer
 * fixed bugs in b64decode()
 *
 * Revision 1.2  2004-07-17 21:16:27+05:30  Cprogrammer
 * added RCS log
 *
 */
#include "base64.h"
#include "stralloc.h"
#include "substdio.h"
#include "str.h"

static char    *b64alpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
#define B64PAD '='

/*
 * returns 0 ok, 1 illegal, -1 problem 
 */

int
b64decode(in, l, out)
	const unsigned char *in;
	int             l;
	stralloc       *out;		/*- not null terminated */
{
	int             p = 0;
	int             n;
	unsigned int    x;
	int             i, j;
	char           *s;
	unsigned char   b[3];

	if (l == 0)
	{
		if (!stralloc_copys(out, ""))
			return -1;
		return 0;
	}
	while (in[l - 1] == B64PAD)
	{
		p++;
		l--;
	}
	n = (l + p) / 4;
	out->len = (n * 3) - p;
	if (!stralloc_ready(out, out->len))
		return -1;
	s = out->s;
	for (i = 0; i < n - 1; i++)
	{
		x = 0;
		for (j = 0; j < 4; j++)
		{
			if (in[j] >= 'A' && in[j] <= 'Z')
				x = (x << 6) + (unsigned int) (in[j] - 'A' + 0);
			else
			if (in[j] >= 'a' && in[j] <= 'z')
				x = (x << 6) + (unsigned int) (in[j] - 'a' + 26);
			else
			if (in[j] >= '0' && in[j] <= '9')
				x = (x << 6) + (unsigned int) (in[j] - '0' + 52);
			else
			if (in[j] == '+')
				x = (x << 6) + 62;
			else
			if (in[j] == '/')
				x = (x << 6) + 63;
			else
			if (in[j] == '=')
				x = (x << 6);
		}
		s[2] = (unsigned char) (x & 255);
		x >>= 8;
		s[1] = (unsigned char) (x & 255);
		x >>= 8;
		s[0] = (unsigned char) (x & 255);
		x >>= 8;
		s += 3;
		in += 4;
	}
	x = 0;
	for (j = 0; j < 4; j++)
	{
		if (in[j] >= 'A' && in[j] <= 'Z')
			x = (x << 6) + (unsigned int) (in[j] - 'A' + 0);
		else
		if (in[j] >= 'a' && in[j] <= 'z')
			x = (x << 6) + (unsigned int) (in[j] - 'a' + 26);
		else
		if (in[j] >= '0' && in[j] <= '9')
			x = (x << 6) + (unsigned int) (in[j] - '0' + 52);
		else
		if (in[j] == '+')
			x = (x << 6) + 62;
		else
		if (in[j] == '/')
			x = (x << 6) + 63;
		else
		if (in[j] == '=')
			x = (x << 6);
	}
	b[2] = (unsigned char) (x & 255);
	x >>= 8;
	b[1] = (unsigned char) (x & 255);
	x >>= 8;
	b[0] = (unsigned char) (x & 255);
	x >>= 8;
	for (i = 0; i < 3 - p; i++)
		s[i] = b[i];
	out->len = (n * 3) - p;
	return 0;
}

int
b64encode(in, out)
	stralloc       *in;
	stralloc       *out;		/*- not null terminated */
{
	unsigned char   a, b, c;
	int             i;
	char           *s;

	if (in->len == 0)
	{
		if (!stralloc_copys(out, ""))
			return -1;
		return 0;
	}
	if (!stralloc_ready(out, in->len / 3 * 4 + 4))
		return -1;
	s = out->s;
	for (i = 0; i < in->len; i += 3)
	{
		a = in->s[i];
		b = i + 1 < in->len ? in->s[i + 1] : 0;
		c = i + 2 < in->len ? in->s[i + 2] : 0;
		*s++ = b64alpha[a >> 2];
		*s++ = b64alpha[((a & 3) << 4) | (b >> 4)];
		if (i + 1 >= in->len)
			*s++ = B64PAD;
		else
			*s++ = b64alpha[((b & 15) << 2) | (c >> 6)];

		if (i + 2 >= in->len)
			*s++ = B64PAD;
		else
			*s++ = b64alpha[c & 63];
	}
	out->len = s - out->s;
	return 0;
}

void
getversion_base64sub_c()
{
	static char    *x = "$Id: base64sub.c,v 1.6 2010-03-03 09:33:16+05:30 Cprogrammer Stab mbhangui $";

	x++;
}