#include <u.h>#include <libc.h> #define between(x,min,max)	(((min-1-x) & (x-max-1))>>8) intenc64chr(int o){	int c; 	c  = between(o,  0, 25) & ('A'+o);	c |= between(o, 26, 51) & ('a'+(o-26));	c |= between(o, 52, 61) & ('0'+(o-52));	c |= between(o, 62, 62) & ('+');	c |= between(o, 63, 63) & ('/');	return c;} intdec64chr(int c){	int o; 	o  = between(c, 'A', 'Z') & (1+(c-'A'));	o |= between(c, 'a', 'z') & (1+26+(c-'a'));	o |= between(c, '0', '9') & (1+52+(c-'0'));	o |= between(c, '+', '+') & (1+62);	o |= between(c, '/', '/') & (1+63);	return o-1;} intdec64(uchar *out, int lim, char *in, int n){	ulong b24;	uchar *start = out;	uchar *e = out + lim;	int i, c; 	b24 = 0;	i = 0;	while(n-- > 0){		c = dec64chr(*in++);		if(c < 0)			continue;		switch(i){		case 0:			b24 = c<<18;			break;		case 1:			b24 |= c<<12;			break;		case 2:			b24 |= c<<6;			break;		case 3:			if(out + 3 > e)				goto exhausted; 			b24 |= c;			*out++ = b24>>16;			*out++ = b24>>8;			*out++ = b24;			i = 0;			continue;		}		i++;	}	switch(i){	case 2:		if(out + 1 > e)			goto exhausted;		*out++ = b24>>16;		break;	case 3:		if(out + 2 > e)			goto exhausted;		*out++ = b24>>16;		*out++ = b24>>8;		break;	}exhausted:	return out - start;} intenc64(char *out, int lim, uchar *in, int n){	int i;	ulong b24;	char *start = out;	char *e = out + lim; 	for(i = n/3; i > 0; i--){		b24 = *in++<<16;		b24 |= *in++<<8;		b24 |= *in++;		if(out + 4 >= e)			goto exhausted;		*out++ = enc64chr(b24>>18);		*out++ = enc64chr((b24>>12)&0x3f);		*out++ = enc64chr((b24>>6)&0x3f);		*out++ = enc64chr(b24&0x3f);	} 	switch(n%3){	case 2:		b24 = *in++<<16;		b24 |= *in<<8;		if(out + 4 >= e)			goto exhausted;		*out++ = enc64chr(b24>>18);		*out++ = enc64chr((b24>>12)&0x3f);		*out++ = enc64chr((b24>>6)&0x3f);		*out++ = '=';		break;	case 1:		b24 = *in<<16;		if(out + 4 >= e)			goto exhausted;		*out++ = enc64chr(b24>>18);		*out++ = enc64chr((b24>>12)&0x3f);		*out++ = '=';		*out++ = '=';		break;	}exhausted:	*out = 0;	return out - start;}