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96cd660ad0
C23 does not allow K&R style function definitions. Use protyped definitions. However, don't bother with (void) in function definitions since C23 prefers (); so prefer () to (void) as this will work with older compilers anyway.
61 lines
1.5 KiB
C
61 lines
1.5 KiB
C
/* add.c not copyrighted (n) 1993 by Mark Adler */
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/* version 1.1 11 Jun 1993 */
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/* This filter reverses the effect of the sub filter. It requires no
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arguments, since sub puts the information necessary for extraction
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in the stream. See sub.c for what the filtering is and what it's
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good for. */
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#include <config.h>
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#include <stdio.h>
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#include <stdlib.h>
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#define MAGIC1 'S' /* sub data */
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#define MAGIC2 26 /* ^Z */
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#define MAX_DIST 16384
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char a[MAX_DIST]; /* last byte buffer for up to MAX_DIST differences */
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int
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main ()
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{
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int n; /* number of differences */
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int i; /* difference counter */
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int c; /* byte from input */
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/* check magic word */
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if (getchar() != MAGIC1 || getchar() != MAGIC2)
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{
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fputs("add: input stream not made by sub\n", stderr);
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exit(EXIT_FAILURE);
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}
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/* get number of differences from data */
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if ((n = getchar()) == EOF || (i = getchar()) == EOF) {
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fputs("add: unexpected end of file\n", stderr);
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exit(EXIT_FAILURE);
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}
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n += (i<<8);
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if (n <= 0 || n > MAX_DIST) {
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fprintf(stderr, "add: incorrect distance %d\n", n);
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exit(EXIT_FAILURE);
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}
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/* initialize last byte */
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i = n;
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do {
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a[--i] = 0;
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} while (i);
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/* read differenced data and restore original */
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while ((c = getchar()) != EOF)
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{
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c = (a[i++] += c) & 0xff; /* restore data, save last byte */
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putchar(c); /* write original */
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if (i == n) /* cycle on n differences */
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i = 0;
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}
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exit(EXIT_SUCCESS);
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return 0; /* avoid warning */
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}
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