soltanis
February 26th, 2009, 03:41 AM
C got long.
/* C code */
#include <stdio.h>
#include <assert.h>
char delim[8] = { 0x52, 0x49, 0x46, 0x46, 0xE8, 0xCC, 0x6C, 0x01 };
char file[] = "/path/to/file";
int file_number = 0;
/* you should probably modify this to accept command-line arguments */
/* copy the contents of src to dest */
void copy(FILE *src, FILE *dest, long from_offset, long to_offset) {
char buf;
long offset = from_offset;
fseek(src, SEEK_SET, from_offset);
while(fread(&buf, 1, sizeof(char), src) > 0 && offset <= to_offset) {
assert(fwrite(buf, 512, sizeof(char), dest) > 0);
offset++;
}
}
/* split the file into two parts. then, modify
the file pointer to point to the next file */
int split(long cutoff, FILE **fp) {
long offset = cutoff, flen;
FILE *before, *after;
char before_name[100], after_name[100]; /* eh, filenames < 100 chars */
/* measure the file length */
fseek(*fp, SEEK_END, 0);
flen = ftell(*fp);
rewind(*fp);
/* open some files */
sprintf(before_name, "%s%n", file, file_number++); /* post-incremented */
sprintf(after_name, "%s%n", file, file_number); /* not incremented */
assert((before = fopen(before_name, "wb")));
assert((after = fopen(after_name, "wb")));
/* now copy the current file up to cutoff into before */
copy(*fp, before, 0, cutoff);
/* copy from cutoff to the end into after */
copy(*fp, after, cutoff, flen);
/* close files */
fclose(before);
fclose(after);
/* reset the pointer of fp to the new file */
fclose(*fp);
assert((*fp = fopen(after_name, "rb")));
return 1;
}
/* walk through the file trying to match the delimiter
and split the file when the entire delimiter is matched */
void walkfile(FILE *fp) {
long offset = 0;
char nextbyte;
int index = 0, max = 8; /* max is the delimiter's length */
while(fread(&nextbyte, 1, sizeof(char), fp) > 0) {
offset++;
if(nextbyte == delim[index]) {
if(index == max) { /* matched the entire delimiter */
assert(split(offset, &fp));
index = 0;
} else {
index++; /* increment matching index */
}
} else { /* didn't match, reset index to 0 */
index = 0;
}
}
}
/* adding command-line argument support should probably be done */
int main() {
FILE *fp;
assert((fp = fopen(file, "rb")));
walkfile(fp);
return 0;
}