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b7d7739a99
Signed-off-by: B. Watson <urchlay@slackware.uk> Signed-off-by: Willy Sudiarto Raharjo <willysr@slackbuilds.org>
93 lines
2.1 KiB
C
93 lines
2.1 KiB
C
/* interleave.c - B. Watson, April 2023, WTFPL licensed.
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Given two files of the same size, creates a 3rd file whose contents are:
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file 1, byte 1
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file 2, byte 1
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file 1, byte 2
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file 2, byte 2
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file 1, byte 3
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file 2, byte 3
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...etc.
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If file1 contains "foo" and file2 contains "bar", the output will
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be "fboaor". The output is always twice the size of one of the
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input files (or, the same size as both input files combined).
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Output file is silently overwritten if it already exists.
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Exit status is 0 for success, non-zero for failure, with a hopefully
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useful error message.
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Compile me with:
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gcc -Wall -O2 -o interleave interleave.c
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This could be done more efficiently and without an artificial file
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size limit, but the current implementation reads everything into a
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statically sized buffer for simpliticy.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#define MAX_SIZE (1024 * 1024)
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unsigned char blob1[MAX_SIZE + 1], blob2[MAX_SIZE + 1], output[MAX_SIZE * 2 + 1];
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void die(const char *msg) {
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if(msg)
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fprintf(stderr, "interleave: %s\n", msg);
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else
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perror("interleave");
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exit(1);
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}
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int read_file(const char *fname, unsigned char *dest) {
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int bytes;
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FILE *f = fopen(fname, "rb");
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if(!f) die(NULL);
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if( (bytes = fread(dest, 1, MAX_SIZE + 1, f)) < 1 ) die(NULL);
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fclose(f);
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/* fprintf(stderr, "read %d bytes from %s\n", bytes, fname); */
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return bytes;
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}
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void write_output(const char *fname, int bytes) {
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int i;
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unsigned char *p = output;
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FILE *f = fopen(fname, "wb");
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if(!f) die(NULL);
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for(i = 0; i < bytes; i++) {
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*p++ = blob1[i];
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*p++ = blob2[i];
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}
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if( (fwrite(output, 1, bytes * 2, f)) < (bytes * 2) ) die(NULL);
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fclose(f);
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}
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int main(int argc, char **argv) {
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int size1, size2;
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if(argc != 4)
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die("usage:\n\tinterleave <input1> <input2> <output>");
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size1 = read_file(argv[1], blob1);
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size2 = read_file(argv[2], blob2);
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if(size1 > MAX_SIZE)
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die("input file too big (max 1MB each)");
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if(size1 != size2)
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die("input files are not the same size");
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write_output(argv[3], size1);
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return 0;
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}
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