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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static void usage(const char *name)
{
printf("Usage: %s <filter> <file>\n", name);
}
static size_t file_size(FILE *file)
{
fseek(file, 0, SEEK_END);
size_t size = ftell(file);
rewind(file);
return size;
}
static char *read_file(FILE *file, size_t bytes)
{
char *buf = malloc(bytes);
fread(buf, bytes, 1, file);
rewind(file);
return buf;
}
static int try_filter(FILE *filter, FILE *file)
{
size_t filtsize = file_size(filter);
char *filtbuf = read_file(filter, filtsize);
size_t filsize = file_size(file);
char *filbuf = read_file(file, filsize);
// inform the user?
if (filsize < filtsize) {
free(filtbuf);
free(filbuf);
return 0;
}
size_t off = filsize - filtsize;
if (strncmp(filbuf + off, filtbuf, filtsize) != 0) {
// filter didn't match
free(filtbuf);
free(filbuf);
return 0;
}
// write everything except filtered part back to file
freopen(NULL, "w+", file);
fwrite(filbuf, off, 1, file);
free(filtbuf);
free(filbuf);
return 0;
}
int main(int argc, char *argv[])
{
if (argc != 3) {
usage(argv[0]);
return -1;
}
FILE *filter = fopen(argv[1], "r");
if (!filter) {
fprintf(stderr, "failed opening filter file %s\n", argv[1]);
return -1;
}
FILE *file = fopen(argv[2], "r");
if (!file) {
fprintf(stderr, "failed opening file %s\n", argv[2]);
fclose(filter);
return -1;
}
int ret = try_filter(filter, file);
fclose(filter);
fclose(file);
return ret;
}
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