Byteorder.net

Order from Chaos, eight bits at a time. ^* _

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Coming soon: A Whole New Set of Tubes.

^*Give or take two bits.

Comments welcome.

#include <stdio.h>

void usage(int argc,char *argv[]) {
	printf("%s: <infile> <outfile>\n",argv[0]);
	printf("Copy infile to outfile, producing sparse output if possible.\n");
}

int main(int argc, char* argv[]) {

	FILE *in;
	FILE *out;
	char buf;
	int res;

	if(argc < 3) {usage(argc,argv);return(1);}

	if(!(in = fopen(argv[1],"rb"))) {
		printf("Can't open %s for reading!\n",argv[1]);return(1);}
	if(!(out = fopen(argv[2],"wb"))) {
		printf("Can't open %s for writing!\n",argv[2]);return(1);}

	/* One byte at a time is probably a little slow,
	but will produce a perfectly compact output file */
	while (res = fread(&buf,1,1,in) ) {
		if (res < 1) {fflush(out);fclose(out);fclose(in);return(0);}
		/* The only difference between a dense and sparse file
		is that we seek instead of writing zeros.  That is, in
		a sparse file, the zeros are implied. */
		if (buf == 0) {
			res=fseek(out,1,SEEK_CUR);
			if (res) {
				printf("Seek error in destination\n");
				return(1);
			}
		} else {
			res=fwrite(&buf,1,1,out);
			if (res<1) {
				printf("Write error in destination\n");
				return(1);
			}
		}
	}

	/*Can't need this, but just in case*/
	fclose(in);
	fflush(out);
	fclose(out);

	return(0);

}