// SPDX-License-Identifier: GPL-2.0
/*
 * Simple test program that demonstrates a file copy through io_uring. This
 * uses the API exposed by liburing.
 *
 * Copyright (C) 2018-2019 Jens Axboe
 */
#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);
                }
        }

        /* wait out pending writes */
        while (writes) {
                struct io_data *data;

                ret = io_uring_wait_cqe(ring, &cqe);
                if (ret) {
                        fprintf(stderr, "wait_cqe=%d\n", ret);
                        return 1;
                }
                if (cqe->res < 0) {
                        fprintf(stderr, "write res=%d\n", cqe->res);
                        return 1;
                }
                data = io_uring_cqe_get_data(cqe);
                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;
}