/* $Revision: 1.3 $ ** Produce a seven-bit printable encoding of stdin on stdout. ** From @(#)encode.c 1.3 5/15/85, distributed with B2.11 News. ** ** ** The encoding uses characters from 0x20 (' ') through 0x7A ('z'). ** (That fits nicely into the UUCP 'f' protocol by Piet Beertema.) First, ** expand three eight-bit charcters into four six-bit ones. Collect ** until we have 13, and spread the last one over the first 12, so that ** we have 12 6.5-bit characters. Since there are very few half-bit ** machines, collect them into pairs, making six 13-bit characters. We ** can do this as A * 91 + B where A and B are less then 91 after we add ** 0x20 to make it printable. ** ** And if you thought that was unclear, then we won't even get into the ** terminating conditions! */ #include "configdata.h" #include <stdio.h> #include <sys/types.h> #include "clibrary.h" /* ** These characters can't appear in normal output, so we use them to ** mark that the data that follows is the terminator. The character ** immediately following this pair is the length of the terminator (which ** otherwise might be indeterminable) */ #define ENDMARK1 ((90 * 91 + 90) / 91 + ' ') #define ENDMARK2 ((90 * 91 + 90) % 91 + ' ') static char Buffer[13]; static int Count; static void dumpcode(p, n) register char *p; register int n; { register int last; register int c; if (n == 13) { n--; last = p[12]; } else if (n & 1) last = 1 << (6 - 1); else last = 0; for (; n > 0; n -= 2) { c = *p++ << 6; c |= *p++; if (last & (1 << (6 - 1))) c |= (1 << 12); last <<= 1; (void)putchar((c / 91) + ' '); (void)putchar((c % 91) + ' '); } } static void flushout() { (void)putchar(ENDMARK1); (void)putchar(ENDMARK2); (void)putchar(Count + ' '); dumpcode(Buffer, Count); } static void encode(dest, n) register char *dest; int n; { register char *p; register int i; register int j; char b4[4]; b4[0] = (dest[0] >> 2) & 0x3F; b4[1] = ((dest[0] & 0x03) << 4) | ((dest[1] >> 4) & 0x0F); b4[2] = ((dest[1] & 0x0F) << 2) | ((dest[2] >> 6) & 0x03); b4[3] = (char)(n == 3 ? dest[2] & 0x3F : n); for (p = b4, i = Count, dest = &Buffer[i], j = 4; --j >= 0; i++) { if (i == 13) { dumpcode(Buffer, 13); dest = Buffer; i = 0; } *dest++ = *p++; } Count = i; } /* ARGSUSED0 */ int main(ac, av) int ac; char *av[]; { register char *p; register int c; char b3[3]; for (p = b3; (c = getchar()) != EOF; ) { *p++ = (char)c; if (p == &b3[3]) { encode(b3, 3); p = b3; } } encode(b3, p - b3); flushout(); exit(0); /* NOTREACHED */ }