#include <sys/sendfile.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/poll.h>
#include <sys/socket.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

int transmit(int ifd, int ofd) {
	struct stat sbuf;
	off_t offset=0;
	int res;

	
	fstat(ifd, &sbuf);
	printf("Transmitting testfile - size %d\n", sbuf.st_size);
	res=sendfile(ofd, ifd, &offset, sbuf.st_size);
	if (res>0)
		printf("Transmitted %d bytes - offset %d\n", res, offset);
	else {
		printf("sendfile() =  %d %s (@%d)\n", res, strerror(errno), offset);
		fflush(stdout);
	}
	fflush(stdout);


	close(ifd);
}

int receive(int ifd) {
	struct pollfd pfd[1];
	int rdsize;
	int rdtotal=0;
	char *rbuf=0;

	rbuf=malloc(64 * 1024); // 64k reads.

	pfd[0].fd=ifd;
	pfd[0].events=POLLIN;

	while(1) {
		poll(pfd, 1, -1);
		if (pfd->revents & POLLIN) {
			while(1) {
			rdsize=read(ifd, rbuf, 64*1024);
				if (rdsize <= 0)
					break;
				rdtotal+=rdsize;
			}
			if (0==rdsize)
				break;
		}
	}
	printf("Read %d bytes.\n", rdtotal);
	free(rbuf);
}


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

	int child_pid;
	int ret;

	int ifd;

	int sv[2];

	ret=socketpair(AF_UNIX, SOCK_STREAM, 0, sv);

	if (argc>1) {
		ifd=open(argv[1], O_RDONLY, 0);
		if (ifd<0) {
			printf("File not found: %s\n", argv[1]);
			exit(1);
		}
	} else {
		printf("usage: %s <filename>\n", argv[0]);
		exit(0);
	}

	if ((child_pid = fork()) == -1)
		perror("forking");
	else if (child_pid==0) {
		close(sv[0]);
		receive(sv[1]);
		exit(0);
	}

		

	close(sv[1]);
	transmit(ifd, sv[0]);
	close(sv[0]);
	waitpid(child_pid, 0, 0);
	
	exit(0);
}