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

#define T_TEST_TEXT "This is a test\n"
#define BUF_SIZE 32
/* 16 won't work, 17 will cause segfault */
//#define READ_SIZE 16
#define READ_SIZE 17

int test_write(char *testfile)
{
	int fd;
	int ret;
	int status;
	char buf[BUF_SIZE];

	status = 0;
	printf("Write file with O_DIRECT\n");
	memset(buf, 'a', BUF_SIZE);
	/* Buffered write or direct write both work */
	fd = open(testfile, O_CREAT | O_RDWR | O_DIRECT | O_TRUNC, 0644);
//	fd = open(testfile, O_CREAT | O_RDWR | O_TRUNC, 0644);
	if (fd == -1) {
		printf("FAIL - open: %s\n", strerror(errno));
		exit(EXIT_FAILURE);
	}

	ret = write(fd, T_TEST_TEXT, sizeof(T_TEST_TEXT));
	if (ret == -1) {
		printf("FAIL - write: %s\n", strerror(errno));
		exit(EXIT_FAILURE);
	}

	close(fd);

	printf("Read file with O_DIRECT\n");
	/* Only direct read would get segfault */
	fd = open(testfile, O_RDONLY | O_DIRECT);
//	fd = open(testfile, O_RDONLY);
	ret = read(fd, buf, READ_SIZE);
	if (ret == -1) {
		printf("FAIL - re-read: %s\n", strerror(errno));
		exit(EXIT_FAILURE);
	}

	if (!strcmp(buf, T_TEST_TEXT)) {
		printf("PASS\n");
	} else {
		printf("FAIL - expect \"%s\" - got \"%s\"\n",
			T_TEST_TEXT, buf);
		status++;
	}
	close(fd);

	return status;
}

int main(int argc, char *argv[])
{
	int ret;
	ret = test_write(argv[1]);
	exit(ret);
}