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#include <stdio.h>
#include <stdbool.h>
int main(int argc, char **argv)
{
FILE *in, *out;
int length_bytes = 0, length = 0, tracking = EOF, next;
if (argc != 3) {
fprintf(stderr, "usage: deflate in out\n");
return 1;
}
in = fopen(argv[1], "rb");
if (in == NULL) {
fprintf(stderr, "cannot read: %s\n", argv[1]);
return 1;
}
out = fopen(argv[2], "wb");
if (out == NULL) {
fprintf(stderr, "cannot write %s\n", argv[2]);
return 1;
}
while (next = getc(in), next != EOF) {
int diff;
if (tracking == EOF) {
tracking = next;
length = 1;
length_bytes = 0;
continue;
}
diff = tracking - next;
diff = diff < 1 ? -diff : diff;
if (diff < 2)
next = tracking;
if (tracking == next) {
length++;
if (length == 255) {
length_bytes++;
length = 0;
}
continue;
}
// write output
for (int i = 0; i < length_bytes; i++)
putc(255, out);
putc(length, out);
putc(tracking, out);
tracking = next;
length = 1;
length_bytes = 0;
}
if (length) {
for (int i = 0; i < length_bytes; i++)
putc(255, out);
putc(length, out);
putc(tracking, out);
}
return 0;
}
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