Commit d953169d authored by Vladimir Sementsov-Ogievskiy's avatar Vladimir Sementsov-Ogievskiy Committed by Stefan Hajnoczi
Browse files

util/iov: introduce qemu_iovec_init_extended 



Introduce new initialization API, to create requests with padding. Will
be used in the following patch. New API uses qemu_iovec_init_buf if
resulting io vector has only one element, to avoid extra allocations.
So, we need to update qemu_iovec_destroy to support destroying such
QIOVs.

Signed-off-by: default avatarVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Acked-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190604161514.262241-2-vsementsov@virtuozzo.com
Message-Id: <20190604161514.262241-2-vsementsov@virtuozzo.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent dac03af5

include/qemu/iov.h

+7 −0
Original line number Diff line number Diff line
@@ -199,6 +199,13 @@ static inline void *qemu_iovec_buf(QEMUIOVector *qiov) 


void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);

void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);

void qemu_iovec_init_extended(

        QEMUIOVector *qiov,

        void *head_buf, size_t head_len,

        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,

        void *tail_buf, size_t tail_len);

void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,

                           size_t offset, size_t len);

void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);

void qemu_iovec_concat(QEMUIOVector *dst,

                       QEMUIOVector *src, size_t soffset, size_t sbytes);

util/iov.c

+107 −5
Original line number Diff line number Diff line
@@ -353,6 +353,103 @@ void qemu_iovec_concat(QEMUIOVector *dst, 
    qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);

}



/*

 * qiov_find_iov

 *

 * Return pointer to iovec structure, where byte at @offset in original vector

 * @iov exactly is.

 * Set @remaining_offset to be offset inside that iovec to the same byte.

 */

static struct iovec *iov_skip_offset(struct iovec *iov, size_t offset,

                                     size_t *remaining_offset)

{

    while (offset > 0 && offset >= iov->iov_len) {

        offset -= iov->iov_len;

        iov++;

    }

    *remaining_offset = offset;



    return iov;

}



/*

 * qiov_slice

 *

 * Find subarray of iovec's, containing requested range. @head would

 * be offset in first iov (returned by the function), @tail would be

 * count of extra bytes in last iovec (returned iov + @niov - 1).

 */

static struct iovec *qiov_slice(QEMUIOVector *qiov,

                                size_t offset, size_t len,

                                size_t *head, size_t *tail, int *niov)

{

    struct iovec *iov, *end_iov;



    assert(offset + len <= qiov->size);



    iov = iov_skip_offset(qiov->iov, offset, head);

    end_iov = iov_skip_offset(iov, *head + len, tail);



    if (*tail > 0) {

        assert(*tail < end_iov->iov_len);

        *tail = end_iov->iov_len - *tail;

        end_iov++;

    }



    *niov = end_iov - iov;



    return iov;

}



/*

 * Compile new iovec, combining @head_buf buffer, sub-qiov of @mid_qiov,

 * and @tail_buf buffer into new qiov.

 */

void qemu_iovec_init_extended(

        QEMUIOVector *qiov,

        void *head_buf, size_t head_len,

        QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,

        void *tail_buf, size_t tail_len)

{

    size_t mid_head, mid_tail;

    int total_niov, mid_niov = 0;

    struct iovec *p, *mid_iov;



    if (mid_len) {

        mid_iov = qiov_slice(mid_qiov, mid_offset, mid_len,

                             &mid_head, &mid_tail, &mid_niov);

    }



    total_niov = !!head_len + mid_niov + !!tail_len;

    if (total_niov == 1) {

        qemu_iovec_init_buf(qiov, NULL, 0);

        p = &qiov->local_iov;

    } else {

        qiov->niov = qiov->nalloc = total_niov;

        qiov->size = head_len + mid_len + tail_len;

        p = qiov->iov = g_new(struct iovec, qiov->niov);

    }



    if (head_len) {

        p->iov_base = head_buf;

        p->iov_len = head_len;

        p++;

    }



    if (mid_len) {

        memcpy(p, mid_iov, mid_niov * sizeof(*p));

        p[0].iov_base = (uint8_t *)p[0].iov_base + mid_head;

        p[0].iov_len -= mid_head;

        p[mid_niov - 1].iov_len -= mid_tail;

        p += mid_niov;

    }



    if (tail_len) {

        p->iov_base = tail_buf;

        p->iov_len = tail_len;

    }

}



/*

 * Check if the contents of the iovecs are all zero

 */
@@ -374,14 +471,19 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov) 
    return true;

}



void qemu_iovec_destroy(QEMUIOVector *qiov)

void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,

                           size_t offset, size_t len)

{

    assert(qiov->nalloc != -1);

    qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);

}



    qemu_iovec_reset(qiov);

void qemu_iovec_destroy(QEMUIOVector *qiov)

{

    if (qiov->nalloc != -1) {

        g_free(qiov->iov);

    qiov->nalloc = 0;

    qiov->iov = NULL;

    }



    memset(qiov, 0, sizeof(*qiov));

}



void qemu_iovec_reset(QEMUIOVector *qiov)