#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/stat.h>
#define _GNU_SOURCE
#include <fcntl.h>

#ifndef F_GETPIPE_SZ
# define F_GETPIPE_SZ	1032 /* The Linux number for the option */
#endif

const char *this_name = "agent-fifo";

static void usage(void)
{
	printf("usage: %s dev bigfile\n"
	       "\n",this_name);
	exit(-1);
}

static void __vdie(const char *fmt, va_list ap, int err)
{
	int ret = errno;
	const char *p = this_name;

	if (err && errno)
		perror(p);
	else
		ret = -1;

	fprintf(stderr, "  ");
	vfprintf(stderr, fmt, ap);

	fprintf(stderr, "\n");
	exit(ret);
}

void die(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	__vdie(fmt, ap, 0);
	va_end(ap);
}

void pdie(const char *fmt, ...)
{
	va_list ap;

	va_start(ap, fmt);
	__vdie(fmt, ap, 1);
	va_end(ap);
}

static unsigned long long time()
{
	struct timeval tv;

	gettimeofday(&tv, NULL);
	return tv.tv_sec * 1000000 + tv.tv_usec;
}

static void print_time(unsigned long long time)
{
	unsigned long long seconds;
	unsigned long long usecs;

	seconds = time / 1000000;
	usecs = time - (seconds * 1000000);

	printf("time: %llu.%06llu\n", seconds, usecs);
}

int main(int argc, char *argv[])
{
	unsigned long long start;
	unsigned long long end;
	struct stat st;
	off_t size;
	char *file;
	char *port;
	int page_size;
	int pipe_size;
	int brass[2];
	int ret;
	int cfd;
	int fd;

	if (argc < 3)
		usage();

	port = argv[1];
	file = argv[2];

	fd = open(file, O_RDONLY);
	if (fd < 0)
		pdie("Opening %s", file);

	if (pipe(brass) < 0)
		pdie("pipe");

	if (fstat(fd, &st) < 0)
		pdie("stat %s", file);

	size = st.st_size;
	if (size < 1)
		die("%s must have size found by stat");

	page_size = getpagesize();
	if (page_size <= 0)
		pdie("getting page size");

	ret = fcntl(brass[0], F_GETPIPE_SZ, &pipe_size);
	if (ret < 0 || !pipe_size)
		pipe_size = page_size;
	
	start = time();
	cfd = open(port, O_WRONLY);
	if (cfd < 0)
		pdie("Writing to %s", argv[2]);
	
	start = time();

	do {
		if (size < page_size) {
			char buf[page_size];
			ret = read(fd, buf, size);
			if (ret < 0)
				pdie("reading %s", file);
			size -= ret;
			write(cfd, buf, ret);
			continue;
		}

		if (size < pipe_size)
			pipe_size = size & ~(page_size - 1);

		ret = splice(fd, NULL, brass[1], NULL, pipe_size, 1 /* SPLICE_F_MOVE */);
		if (ret < 0)
			pdie("splice read of %s", file);

		size -= ret;

		ret = splice(brass[0], NULL, cfd, NULL, pipe_size, 3 /* and NON_BLOCK */);
		if (ret < 0)
			pdie("splice write");

	} while (size);

	end = time();

	print_time(end - start);

	exit(0);
}