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	u64.c - 9base - revived minimalist port of Plan 9 userland to Unix
	git clone git://git.suckless.org/9base
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	---
	u64.c (3267B)
	---
	1 #include <lib9.h>
	2
	3 enum {
	4 INVAL= 255
	5 };
	6
	7 static uchar t64d[256] = {
	8 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	9 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	10 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL, …
	11 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,INVAL,INV…
	12 INVAL, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, …
	13 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,INV…
	14 INVAL, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, …
	15 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,INV…
	16 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	17 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	18 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	19 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	20 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	21 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	22 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	23 INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INVAL,INV…
	24 };
	25 static char t64e[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwx…
	26
	27 int
	28 dec64(uchar out, int lim, char in, int n)
	29 {
	30 ulong b24;
	31 uchar *start = out;
	32 uchar *e = out + lim;
	33 int i, c;
	34
	35 b24 = 0;
	36 i = 0;
	37 while(n-- > 0){
	38
	39 c = t64d[(uchar)in++];
	40 if(c == INVAL)
	41 continue;
	42 switch(i){
	43 case 0:
	44 b24 = c<<18;
	45 break;
	46 case 1:
	47 b24 \|= c<<12;
	48 break;
	49 case 2:
	50 b24 \|= c<<6;
	51 break;
	52 case 3:
	53 if(out + 3 > e)
	54 goto exhausted;
	55
	56 b24 \|= c;
	57 *out++ = b24>>16;
	58 *out++ = b24>>8;
	59 *out++ = b24;
	60 i = -1;
	61 break;
	62 }
	63 i++;
	64 }
	65 switch(i){
	66 case 2:
	67 if(out + 1 > e)
	68 goto exhausted;
	69 *out++ = b24>>16;
	70 break;
	71 case 3:
	72 if(out + 2 > e)
	73 goto exhausted;
	74 *out++ = b24>>16;
	75 *out++ = b24>>8;
	76 break;
	77 }
	78 exhausted:
	79 return out - start;
	80 }
	81
	82 int
	83 enc64(char out, int lim, uchar in, int n)
	84 {
	85 int i;
	86 ulong b24;
	87 char *start = out;
	88 char *e = out + lim;
	89
	90 for(i = n/3; i > 0; i--){
	91 b24 = (*in++)<<16;
	92 b24 \|= (*in++)<<8;
	93 b24 \|= *in++;
	94 if(out + 4 >= e)
	95 goto exhausted;
	96 *out++ = t64e[(b24>>18)];
	97 *out++ = t64e[(b24>>12)&0x3f];
	98 *out++ = t64e[(b24>>6)&0x3f];
	99 *out++ = t64e[(b24)&0x3f];
	100 }
	101
	102 switch(n%3){
	103 case 2:
	104 b24 = (*in++)<<16;
	105 b24 \|= (*in)<<8;
	106 if(out + 4 >= e)
	107 goto exhausted;
	108 *out++ = t64e[(b24>>18)];
	109 *out++ = t64e[(b24>>12)&0x3f];
	110 *out++ = t64e[(b24>>6)&0x3f];
	111 *out++ = '=';
	112 break;
	113 case 1:
	114 b24 = (*in)<<16;
	115 if(out + 4 >= e)
	116 goto exhausted;
	117 *out++ = t64e[(b24>>18)];
	118 *out++ = t64e[(b24>>12)&0x3f];
	119 *out++ = '=';
	120 *out++ = '=';
	121 break;
	122 }
	123 exhausted:
	124 *out = 0;
	125 return out - start;
	126 }