uuen/decode with checksums.
Alan J Rosenthal
flaps at utcsri.UUCP
Tue Jan 13 15:56:06 AEST 1987
I have made a simple patch which puts a checksum character at the end of each
line. Files uuencoded with this new uuencode can be uudecoded with the old
uudecode without complaint. If you use this uudecode on a file uuencoded
with the old uuencode, every line gives a checksum error, so I have made it
report only the first five checksum errors. Therefore, if you get errors
saying that there is a checksum error on lines 1, 2, 3, 4, and 5, you can
presume that the file you are uudecoding was uuencoded without checksums.
To the best of my knowledge uuen/decode are public domain. If they are not
and I am flamed I will immediately cancel this article and instead post
context diffs or something. The reason I am posting the programs intact is
that when I context-diffed them the resulting output was considerably
longer than the files themselves.
Also: flames to /dev/null if you don't like my sccsids. I don't know how
they work and don't care; you are free to edit it as required. "Dash one"
to me means "minor edit #1".
-------------------------------- uuencode.c ---------------------------------
#ifndef lint
static char sccsid[] = "@(#)uuencode.c 5.3-1 (Berkeley) 1/22/85";
#endif
/* modified by ajr to include checksums */
/*
* uuencode [input] output
*
* Encode a file so it can be mailed to a remote system.
*/
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#define SUMSIZE 64
/* ENC is the basic 1 character encoding function to make a char printing */
#define ENC(c) ((c) ? ((c) & 077) + ' ': '`')
main(argc, argv)
char **argv;
{
FILE *in;
struct stat sbuf;
int mode;
/* optional 1st argument */
if (argc > 2) {
if ((in = fopen(argv[1], "r")) == NULL) {
perror(argv[1]);
exit(1);
}
argv++; argc--;
} else
in = stdin;
if (argc != 2) {
printf("Usage: uuencode [infile] remotefile\n");
exit(2);
}
/* figure out the input file mode */
fstat(fileno(in), &sbuf);
mode = sbuf.st_mode & 0777;
printf("begin %o %s\n", mode, argv[1]);
encode(in, stdout);
printf("end\n");
exit(0);
}
/*
* copy from in to out, encoding as you go along.
*/
encode(in, out)
FILE *in;
FILE *out;
{
char buf[80];
int i, n, checksum;
for (;;) {
/* 1 (up to) 45 character line */
n = fr(in, buf, 45);
putc(ENC(n), out);
checksum = 0;
for (i=0; i<n; i += 3)
checksum = (checksum+outdec(&buf[i], out)) % SUMSIZE;
putc(ENC(checksum), out);
putc('\n', out);
if (n <= 0)
break;
}
}
/*
* output one group of 3 bytes, pointed at by p, on file f.
* return the checksum increment.
*/
int outdec(p, f)
char *p;
FILE *f;
{
int c1, c2, c3, c4;
c1 = *p >> 2;
c2 = (*p << 4) & 060 | (p[1] >> 4) & 017;
c3 = (p[1] << 2) & 074 | (p[2] >> 6) & 03;
c4 = p[2] & 077;
putc(ENC(c1), f);
putc(ENC(c2), f);
putc(ENC(c3), f);
putc(ENC(c4), f);
return((p[0]+p[1]+p[2]) % SUMSIZE);
}
/* fr: like read but stdio */
int
fr(fd, buf, cnt)
FILE *fd;
char *buf;
int cnt;
{
int c, i;
for (i=0; i<cnt; i++) {
c = getc(fd);
if (c == EOF)
return(i);
buf[i] = c;
}
return (cnt);
}
-------------------------------- uudecode.c ---------------------------------
#ifndef lint
static char sccsid[] = "@(#)uudecode.c 5.3-1 (Berkeley) 4/10/85";
#endif
/* modified by ajr to use checksums */
/*
* uudecode [input]
*
* create the specified file, decoding as you go.
* used with uuencode.
*/
#include <stdio.h>
#include <pwd.h>
#include <sys/types.h>
#include <sys/stat.h>
#define SUMSIZE 64
/* single character decode */
#define DEC(c) (((c) - ' ') & 077)
main(argc, argv)
char **argv;
{
FILE *in, *out;
int mode;
char dest[128];
char buf[80];
/* optional input arg */
if (argc > 1) {
if ((in = fopen(argv[1], "r")) == NULL) {
perror(argv[1]);
exit(1);
}
argv++; argc--;
} else
in = stdin;
if (argc != 1) {
printf("Usage: uudecode [infile]\n");
exit(2);
}
/* search for header line */
for (;;) {
if (fgets(buf, sizeof buf, in) == NULL) {
fprintf(stderr, "No begin line\n");
exit(3);
}
if (strncmp(buf, "begin ", 6) == 0)
break;
}
sscanf(buf, "begin %o %s", &mode, dest);
/* handle ~user/file format */
if (dest[0] == '~') {
char *sl;
struct passwd *getpwnam();
char *index();
struct passwd *user;
char dnbuf[100];
sl = index(dest, '/');
if (sl == NULL) {
fprintf(stderr, "Illegal ~user\n");
exit(3);
}
*sl++ = 0;
user = getpwnam(dest+1);
if (user == NULL) {
fprintf(stderr, "No such user as %s\n", dest);
exit(4);
}
strcpy(dnbuf, user->pw_dir);
strcat(dnbuf, "/");
strcat(dnbuf, sl);
strcpy(dest, dnbuf);
}
/* create output file */
out = fopen(dest, "w");
if (out == NULL) {
perror(dest);
exit(4);
}
chmod(dest, mode);
decode(in, out);
if (fgets(buf, sizeof buf, in) == NULL || strcmp(buf, "end\n")) {
fprintf(stderr, "No end line\n");
exit(5);
}
exit(0);
}
/*
* copy from in to out, decoding as you go along.
*/
decode(in, out)
FILE *in;
FILE *out;
{
char buf[80];
char *bp;
int n, checksum, line;
int warnings = 5;
for (line = 1; ; line++) {
/* for each input line */
if (fgets(buf, sizeof buf, in) == NULL) {
printf("Short file\n");
exit(10);
}
checksum = 0;
n = DEC(buf[0]);
if (n <= 0)
break;
bp = &buf[1];
while (n > 0) {
checksum = (checksum+outdec(bp, out, n)) % SUMSIZE;
bp += 4;
n -= 3;
}
if (checksum != DEC(*bp))
if (warnings > 0) {
printf("Checksum error, line %d.\n",line);
warnings--;
} else if (warnings == 0) {
printf("more...\n");
warnings--;
}
}
}
/*
* output a group of 3 bytes (4 input characters).
* the input chars are pointed to by p, they are to
* be output to file f. n is used to tell us not to
* output all of them at the end of the file.
* we return a checksum increment.
*/
int outdec(p, f, n)
char *p;
FILE *f;
{
int c1, c2, c3;
c1 = DEC(*p) << 2 | DEC(p[1]) >> 4;
c2 = DEC(p[1]) << 4 | DEC(p[2]) >> 2;
c3 = DEC(p[2]) << 6 | DEC(p[3]);
if (n >= 1)
putc(c1, f);
if (n >= 2)
putc(c2, f);
if (n >= 3)
putc(c3, f);
return((c1+c2+c3) % SUMSIZE);
}
/* fr: like read but stdio */
int
fr(fd, buf, cnt)
FILE *fd;
char *buf;
int cnt;
{
int c, i;
for (i=0; i<cnt; i++) {
c = getc(fd);
if (c == EOF)
return(i);
buf[i] = c;
}
return (cnt);
}
/*
* Return the ptr in sp at which the character c appears;
* NULL if not found
*/
#define NULL 0
char *
index(sp, c)
register char *sp, c;
{
do {
if (*sp == c)
return(sp);
} while (*sp++);
return(NULL);
}
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