/* SPDX-License-Identifier: MIT */

/*

 * gcc -Wall -O2 -D_GNU_SOURCE -o io_uring-cp io_uring-cp.c -luring

 */

#include <stdio.h>

#include <fcntl.h>

#include <string.h>

#include <stdlib.h>

#include <unistd.h>

#include <assert.h>

#include <errno.h>

#include <inttypes.h>

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/ioctl.h>

#include "liburing.h"

#define QD	64

#define BS	(32*1024)

static int infd, outfd;

struct io_data {

	int read;

	off_t first_offset, offset;

	size_t first_len;

	struct iovec iov;

};

static int setup_context(unsigned entries, struct io_uring *ring)

{

	int ret;

	ret = io_uring_queue_init(entries, ring, 0);

	if (ret < 0) {

		fprintf(stderr, "queue_init: %s\n", strerror(-ret));

		return -1;

	}

	return 0;

}

static int get_file_size(int fd, off_t *size)

{

	struct stat st;

	if (fstat(fd, &st) < 0)

		return -1;

	if (S_ISREG(st.st_mode)) {

		*size = st.st_size;

		return 0;

	} else if (S_ISBLK(st.st_mode)) {

		unsigned long long bytes;

		if (ioctl(fd, BLKGETSIZE64, &bytes) != 0)

			return -1;

		*size = bytes;

		return 0;

	}

	return -1;

}

static void queue_prepped(struct io_uring *ring, struct io_data *data)

{

	struct io_uring_sqe *sqe;

	sqe = io_uring_get_sqe(ring);

	assert(sqe);

	if (data->read)

		io_uring_prep_readv(sqe, infd, &data->iov, 1, data->offset);

	else

		io_uring_prep_writev(sqe, outfd, &data->iov, 1, data->offset);

	io_uring_sqe_set_data(sqe, data);

}

static int queue_read(struct io_uring *ring, off_t size, off_t offset)

{

	struct io_uring_sqe *sqe;

	struct io_data *data;

	data = malloc(size + sizeof(*data));

	if (!data)

		return 1;

	sqe = io_uring_get_sqe(ring);

	if (!sqe) {

		free(data);

		return 1;

	}

	data->read = 1;

	data->offset = data->first_offset = offset;

	data->iov.iov_base = data + 1;

	data->iov.iov_len = size;

	data->first_len = size;

	io_uring_prep_readv(sqe, infd, &data->iov, 1, offset);

	io_uring_sqe_set_data(sqe, data);

	return 0;

}

static void queue_write(struct io_uring *ring, struct io_data *data)

{

	data->read = 0;

	data->offset = data->first_offset;

	data->iov.iov_base = data + 1;

	data->iov.iov_len = data->first_len;

	queue_prepped(ring, data);

	io_uring_submit(ring);

}

static int copy_file(struct io_uring *ring, off_t insize)

{

	unsigned long reads, writes;

	struct io_uring_cqe *cqe;

	off_t write_left, offset;

	int ret;

	write_left = insize;

	writes = reads = offset = 0;

	while (insize || write_left) {

		int had_reads, got_comp;

		/*

		 * Queue up as many reads as we can

		 */

		had_reads = reads;

		while (insize) {

			off_t this_size = insize;

			if (reads + writes >= QD)

				break;

			if (this_size > BS)

				this_size = BS;

			else if (!this_size)

				break;

			if (queue_read(ring, this_size, offset))

				break;

			insize -= this_size;

			offset += this_size;

			reads++;

		}

		if (had_reads != reads) {

			ret = io_uring_submit(ring);

			if (ret < 0) {

				fprintf(stderr, "io_uring_submit: %s\n", strerror(-ret));

				break;

			}

		}

		/*

		 * Queue is full at this point. Find at least one completion.

		 */

		got_comp = 0;

		while (write_left) {

			struct io_data *data;

			if (!got_comp) {

				ret = io_uring_wait_cqe(ring, &cqe);

				got_comp = 1;

			} else {

				ret = io_uring_peek_cqe(ring, &cqe);

				if (ret == -EAGAIN) {

					cqe = NULL;

					ret = 0;

				}

			}

			if (ret < 0) {

				fprintf(stderr, "io_uring_peek_cqe: %s\n",

							strerror(-ret));

				return 1;

			}

			if (!cqe)

				break;

			data = io_uring_cqe_get_data(cqe);

			if (cqe->res < 0) {

				if (cqe->res == -EAGAIN) {

					queue_prepped(ring, data);

					io_uring_cqe_seen(ring, cqe);

					continue;

				}

				fprintf(stderr, "cqe failed: %s\n",

						strerror(-cqe->res));

				return 1;

			} else if (cqe->res != data->iov.iov_len) {

				/* Short read/write, adjust and requeue */

				data->iov.iov_base += cqe->res;

				data->iov.iov_len -= cqe->res;

				data->offset += cqe->res;

				queue_prepped(ring, data);

				io_uring_cqe_seen(ring, cqe);

				continue;

			}

			/*

			 * All done. if write, nothing else to do. if read,

			 * queue up corresponding write.

			 */

			if (data->read) {

				queue_write(ring, data);

				write_left -= data->first_len;

				reads--;

				writes++;

			} else {

				free(data);

				writes--;

			}

			io_uring_cqe_seen(ring, cqe);

		}

	}

	return 0;

}

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

{

	struct io_uring ring;

	off_t insize;

	int ret;

	if (argc < 3) {

		printf("%s: infile outfile\n", argv[0]);

		return 1;

	}

	infd = open(argv[1], O_RDONLY);

	if (infd < 0) {

		perror("open infile");

		return 1;

	}

	outfd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0644);

	if (outfd < 0) {

		perror("open outfile");

		return 1;

	}

	if (setup_context(QD, &ring))

		return 1;

	if (get_file_size(infd, &insize))

		return 1;

	ret = copy_file(&ring, insize);

	close(infd);

	close(outfd);

	io_uring_queue_exit(&ring);

	return ret;

}