(same as my format for #.obj files in the lib/world/obj/ dir) and then i made
it so that characters could rent their mail.. but for security purposes I
wanted to write an encryption routine so that noisy ftper's could d/l
someone's rent file and read their mail (the letter text is still stored
in the action desc) and ALSO for another reason:
If a player were to send a solitary '~' character on a line it would
cause the recipients obj file to get outta wack (the mud uses that to
deliminate the end of the initial object text strings) .. so what i was
left with writing was a routine which would encode a persons mail in a
nice even format which didnt include the '~' character in the output.
and here's what i came up with.. NOTE: this took me about 2 hours to
write and I personally have never written an encoder/encryption program..
so the routines below are VERY wasteful of space.. they double the size
of the original text (although in cases of repitition they do better).
I would be obliged if someone could post a better version of what
i've done or point me in the direction of some 'real' encryption sources.
(something a little more space worthy).. anyways what you send to these
routines is a buffer large enough to store double the size of the
original text which is also sent. (I also return the buffer pointer for
utility purposes). The routine itself DOES NOT ALLOCATE memory for that
buffer, it needs to be already created..
----------------------- cut here ----------------------------------
/*
* File: encode.c
* Usage: used to generate a coded version of an ASCII buffer. which
* is formatted to 70 width and doesnt have an empty line with a ~ on it
*/
#include <strings.h>
#include <stdlib.h>
#include <stdio.h>
#define CHAR_TAB 9
#define CHAR_NL 10
#define CHAR_CR 13
#define TAB_LENGTH 4
#define OFFSET 29
#define PRINT_BYTE_OFFSET 65
#define PRINTABLE_SET_LENGTH 26
#define NL_LINE_LENGTH 70
#define MAX_REPEAT 3
#define SET_CONTROL_CHAR(r,s) \
(coded_bytes[0] = (r) + ((s)<<2) + PRINT_BYTE_OFFSET)
char *msg_encode(char *buffer, char *orig) {
int i, total;
char j, k, l;
char coded_bytes[3] = "\0\0\0";
total = 0;
*buffer = '\0';
for (i = 0; (orig[i] != '\0'); i++) {
j = 0;
while ((orig[i+j+1] == orig[i]) && (j < MAX_REPEAT)) {
j++;
}
if (orig[i] == CHAR_TAB) {
l = ' ' - OFFSET;
k = l / PRINTABLE_SET_LENGTH;
l -= k*PRINTABLE_SET_LENGTH;
l += PRINT_BYTE_OFFSET;
j = 3;
}
else if (orig[i] == CHAR_NL) { l = PRINT_BYTE_OFFSET+1; k = 0; }
else if (orig[i] == CHAR_CR) { l = PRINT_BYTE_OFFSET+2; k = 0; }
else {
l = orig[i] - OFFSET;
k = l / PRINTABLE_SET_LENGTH;
l -= k*PRINTABLE_SET_LENGTH;
l += PRINT_BYTE_OFFSET;
}
SET_CONTROL_CHAR(j,k);
coded_bytes[1] = l;
strcat(buffer, coded_bytes);
total += 2;
i += j;
if ((total > 0) && ((total % NL_LINE_LENGTH) == 0)) strcat(buffer, "\n");
}
strcat(buffer, "*\n");
return buffer;
}
char *msg_decode(char *buffer, char *orig) {
int i, rep, set, k, n;
char l;
n = 0;
for (i = 0; ((orig[i] != '*') && (orig[i] != '\0')); i++) {
if ((orig[i] >= PRINT_BYTE_OFFSET) && (orig[i] < (PRINT_BYTE_OFFSET + PRINTABLE_SET_LENGTH))) {
l = orig[i] - PRINT_BYTE_OFFSET;
rep = (int)(l & 3); /* get the # of repeats */
set = (int)((l & 12)>>2); /* get the set # */
while ((orig[++i] < PRINT_BYTE_OFFSET) && (orig[i] >= (PRINT_BYTE_OFFSET + PRINTABLE_SET_LENGTH)) && (orig[i] != '*') && (orig[i] != '\0'));
if ((orig[i] == '\0') || (orig[i] == '*')) break;
l = orig[i] - PRINT_BYTE_OFFSET;
l += (set * PRINTABLE_SET_LENGTH);
if (i == 0) {
rep = TAB_LENGTH;
l = ' ';
}
else if (l == 1) l = CHAR_NL;
else if (l == 2) l = CHAR_CR;
else l += OFFSET;
for (k = 0; k <= rep; k++)
buffer[n++] = l;
}
}
buffer[n] = '\0';
return buffer;
}
---------------------------------- cut here -------------------------
Sorry for the code spam.
Michael Scott -- "Living in the Eye of the Hurricane."
FLAMES/COMMENTS to scottm@workcomm.net
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