Expand 2 bit raw to byte

2bitexpand.c

#include <stdio.h>

void expand(const char c, char b[4]) {
	b[0] = c & 3;
	b[1] = (c >> 2) & 3;
	b[2] = (c >> 4) & 3;
	b[3] = (c >> 6) & 3;
}

int main(int argc,char* argv[]) {
	FILE* fp = fopen("password.raw","rb");
	if(!fp) {
		printf("Error al abrir el fichero\n");
		exit(-1);
	}
	FILE* of = fopen("password_byte.raw","wb");
	if(!of) {
		printf("Error al abrir el fichero de salida\n");
		exit(-2);
	}

	char c = 0;
	char buff[4];

	while((c=fgetc(fp))!=FEOF) {
		expand(c,buff)
		fputc(of,buff[0]);
		fputc(of,buff[1]);
		fputc(of,buff[2]);
		fputc(of,buff[3]);
	}

	fclose(fp);
	fclose(of);

	exit(0);

	return 0;
}