/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2016 Jakub Klama <jceel@FreeBSD.org>.
 * Copyright (c) 2018 Alexander Motin <mav@FreeBSD.org>
 * Copyright (c) 2026 Hans Rosenfeld
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 */
/* This file is dual-licensed; see usr/src/contrib/bhyve/LICENSE */

/*
 * Copyright 2025 Oxide Computer Company
 */

#include <sys/param.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/debug.h>
#include <sys/sysmacros.h>

#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <limits.h>
#include <errno.h>
#include "iov.h"

/*
 * Given an iovec and an offset, split the iovec into two at the offset and
 * return a pointer to the beginning of the second iovec.
 *
 * The caller is responsible for providing an extra iovec in the array for the
 * split.  That is, there should be space for *niov1 + 1 iovecs in the array.
 */
struct iovec *
split_iov(struct iovec *iov, size_t *niov1, size_t offset, size_t *niov2)
{
        size_t count, resid;

        /* Find the iovec entry that contains the offset. */
        resid = offset;
        for (count = 0; count < *niov1; count++) {
                if (resid < iov[count].iov_len)
                        break;
                resid -= iov[count].iov_len;
        }

        if (resid == 0 || count == *niov1) {
                /* Easy case, we don't have to split an iovec entry. */
                *niov2 = *niov1 - count;
                *niov1 = count;
                if (*niov2 == 0)
                        return (NULL);
                return (&iov[count]);
        }

        /* The entry iov[count] needs to be split. */
        *niov1 = count + 1;
        *niov2 = *niov1 - count;
        memmove(&iov[count + 1], &iov[count], sizeof(struct iovec) * (*niov2));
        iov[count].iov_len = resid;
        iov[count + 1].iov_base = (char *)iov[count].iov_base + resid;
        iov[count + 1].iov_len -= resid;
        return (&iov[count + 1]);
}

size_t
count_iov(const struct iovec *iov, size_t niov)
{
        size_t total = 0;
        size_t i;

        for (i = 0; i < niov; i++) {
                assert(total <= SIZE_MAX - iov[i].iov_len);
                total += iov[i].iov_len;
        }

        return (total);
}

bool
check_iov_len(const struct iovec *iov, size_t niov, size_t len)
{
        size_t total = 0;
        size_t i;

        for (i = 0; i < niov; i++) {
                assert(total <= SIZE_MAX - iov[i].iov_len);
                total += iov[i].iov_len;
                if (total >= len)
                        return (true);
        }

        return (false);
}

size_t
iov_to_buf(const struct iovec *iov, size_t niov, void **buf)
{
        size_t ptr, total;
        size_t i;

        total = count_iov(iov, niov);
        *buf = reallocf(*buf, total);
        if (*buf == NULL)
                return (0);

        for (i = 0, ptr = 0; i < niov; i++) {
                memcpy((uint8_t *)*buf + ptr, iov[i].iov_base, iov[i].iov_len);
                ptr += iov[i].iov_len;
        }

        return (total);
}

size_t
buf_to_iov(const void *buf, size_t buflen, const struct iovec *iov, size_t niov)
{
        size_t off = 0, len;
        size_t  i;

        for (i = 0; i < niov && off < buflen; i++) {
                len = MIN(iov[i].iov_len, buflen - off);
                memcpy(iov[i].iov_base, (const uint8_t *)buf + off, len);
                off += len;
        }

        return (off);
}

size_t
iov_bunch_init(iov_bunch_t *iob, struct iovec *iov, int niov)
{
        bzero(iob, sizeof (*iob));
        iob->ib_iov = iov;
        iob->ib_remain = count_iov(iov, niov);

        return (iob->ib_remain);
}

/*
 * Copy `sz` bytes from iovecs contained in `iob` to `dst`.
 *
 * Returns `true` if copy was successful (implying adequate data was remaining
 * in the iov_bunch_t).
 */
bool
iov_bunch_copy(iov_bunch_t *iob, void *dst, size_t sz)
{
        if (sz > iob->ib_remain)
                return (false);
        if (sz == 0)
                return (true);

        caddr_t dest = dst;
        do {
                struct iovec *iov = iob->ib_iov;

                ASSERT3U(iov->iov_len, !=, 0);

                /* ib_offset is the offset within the current head of ib_iov */
                const size_t iov_avail = iov->iov_len - iob->ib_offset;
                const size_t to_copy = MIN(sz, iov_avail);

                if (to_copy != 0 && dest != NULL) {
                        bcopy((caddr_t)iov->iov_base + iob->ib_offset, dest,
                            to_copy);
                        dest += to_copy;
                }

                sz -= to_copy;
                iob->ib_remain -= to_copy;
                iob->ib_offset += to_copy;

                ASSERT3U(iob->ib_offset, <=, iov->iov_len);

                if (iob->ib_offset == iov->iov_len) {
                        iob->ib_iov++;
                        iob->ib_offset = 0;
                }
        } while (sz > 0);

        return (true);
}

/*
 * Skip `sz` bytes from iovecs contained in `iob`.
 *
 * Returns `true` if the skip was successful (implying adequate data was
 * remaining in the iov_bunch_t).
 */
bool
iov_bunch_skip(iov_bunch_t *iob, size_t sz)
{
        return (iov_bunch_copy(iob, NULL, sz));
}

/*
 * Get the data pointer and length of the current head iovec, less any
 * offsetting from prior copy operations. This will advance the iov_bunch_t as
 * if the caller had performed a copy of that chunk length.
 *
 * Returns `true` if the iov_bunch_t had at least one iovec (unconsumed bytes)
 * remaining, setting `chunk` and `chunk_sz` to the chunk pointer and size,
 * respectively.
 */
bool
iov_bunch_next_chunk(iov_bunch_t *iob, caddr_t *chunk, size_t *chunk_sz)
{
        if (iob->ib_remain == 0) {
                *chunk = NULL;
                *chunk_sz = 0;
                return (false);
        }

        *chunk_sz = iob->ib_iov->iov_len - iob->ib_offset;
        *chunk = (caddr_t)iob->ib_iov->iov_base + iob->ib_offset;
        iob->ib_remain -= *chunk_sz;
        iob->ib_iov++;
        iob->ib_offset = 0;
        return (true);
}

/*
 * Extract the remaining data in an iov_bunch_t into a new iovec.
 */
void
iov_bunch_to_iov(iov_bunch_t *iob, struct iovec *iov, int *niov, uint_t size)
{
        *niov = 0;

        while (size-- > 0) {
                caddr_t chunk;
                size_t sz;

                if (!iov_bunch_next_chunk(iob, &chunk, &sz))
                        break;

                iov->iov_base = chunk;
                iov->iov_len = sz;
                iov++;
                (*niov)++;
        }
}

/*
 * Extract the remaining data in an iov_bunch_t into a buffer, reallocating it
 * to the required size. If there are no bytes remaining in the iov_bunch_t any
 * supplied buffer will be freed and this function will return 0.
 */
ssize_t
iov_bunch_to_buf(iov_bunch_t *iob, void **buf)
{
        size_t total = iob->ib_remain;

        if (total == 0) {
                free(*buf);
                *buf = NULL;
                return (0);
        }

        *buf = reallocf(*buf, total);
        if (*buf == NULL)
                return (-1);

        if (!iov_bunch_copy(iob, buf, total))
                return (-1);

        if (total > SSIZE_MAX) {
                errno = EOVERFLOW;
                return (-1);
        }

        return (total);
}

/*
 * Copy data from a buffer into an iob_bunch_t. Returns true if there was
 * sufficient space for the data, false otherwise.
 */
bool
buf_to_iov_bunch(iov_bunch_t *iob, const void *buf, size_t len)
{
        const char *src = buf;

        if (iob->ib_remain < len)
                return (false);

        do {
                struct iovec *iov = iob->ib_iov;

                /* ib_offset is the offset within the current head of ib_iov */
                const size_t iov_avail = iov->iov_len - iob->ib_offset;
                const size_t to_copy = MIN(len, iov_avail);

                if (to_copy != 0) {
                        bcopy(src, (caddr_t)iov->iov_base + iob->ib_offset,
                            to_copy);
                }

                src += to_copy;
                len -= to_copy;
                iob->ib_remain -= to_copy;
                iob->ib_offset += to_copy;

                ASSERT3U(iob->ib_offset, <=, iov->iov_len);

                if (iob->ib_offset == iov->iov_len) {
                        iob->ib_iov++;
                        iob->ib_offset = 0;
                }
        } while (len > 0);

        return (true);
}