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#include <u.h>
#include <libc.h>
#define between(x,min,max) (((min-1-x) & (x-max-1))>>8)
int
enc64chr(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;
}
int
dec64chr(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;
}
int
dec64(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;
}
int
enc64(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;
}
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