Commit 530c0bbd authored by Stefan Hajnoczi's avatar Stefan Hajnoczi
Browse files

iov: add qemu_iovec_concat_iov() 



The qemu_iovec_concat() function copies a subset of a QEMUIOVector.  The
new qemu_iovec_concat_iov() function does the same for a iov/cnt pair.

It is easy to define qemu_iovec_concat() in terms of
qemu_iovec_concat_iov().  The existing code is mostly unchanged, except
for the assertion src->size >= soffset, which cannot be efficiently
checked upfront on a iov/cnt pair.  Instead we assert upon hitting the
end of src with an unsatisfied soffset.

Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 8962e44f

include/qemu-common.h

+3 −0
Original line number Diff line number Diff line
@@ -329,6 +329,9 @@ void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov); 
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);

void qemu_iovec_concat_iov(QEMUIOVector *dst,

                           struct iovec *src_iov, unsigned int src_cnt,

                           size_t soffset, size_t sbytes);

void qemu_iovec_destroy(QEMUIOVector *qiov);

void qemu_iovec_reset(QEMUIOVector *qiov);

size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,

iov.c

+27 −12
Original line number Diff line number Diff line
@@ -289,34 +289,49 @@ void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len) 
}



/*

 * Concatenates (partial) iovecs from src to the end of dst.

 * Concatenates (partial) iovecs from src_iov to the end of dst.

 * It starts copying after skipping `soffset' bytes at the

 * beginning of src and adds individual vectors from src to

 * dst copies up to `sbytes' bytes total, or up to the end

 * of src if it comes first.  This way, it is okay to specify

 * of src_iov if it comes first.  This way, it is okay to specify

 * very large value for `sbytes' to indicate "up to the end

 * of src".

 * Only vector pointers are processed, not the actual data buffers.

 */

void qemu_iovec_concat(QEMUIOVector *dst,

                       QEMUIOVector *src, size_t soffset, size_t sbytes)

void qemu_iovec_concat_iov(QEMUIOVector *dst,

                           struct iovec *src_iov, unsigned int src_cnt,

                           size_t soffset, size_t sbytes)

{

    int i;

    size_t done;

    struct iovec *siov = src->iov;

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

    assert(src->size >= soffset);

    for (i = 0, done = 0; done < sbytes && i < src->niov; i++) {

        if (soffset < siov[i].iov_len) {

            size_t len = MIN(siov[i].iov_len - soffset, sbytes - done);

            qemu_iovec_add(dst, siov[i].iov_base + soffset, len);

    for (i = 0, done = 0; done < sbytes && i < src_cnt; i++) {

        if (soffset < src_iov[i].iov_len) {

            size_t len = MIN(src_iov[i].iov_len - soffset, sbytes - done);

            qemu_iovec_add(dst, src_iov[i].iov_base + soffset, len);

            done += len;

            soffset = 0;

        } else {

            soffset -= siov[i].iov_len;

            soffset -= src_iov[i].iov_len;

        }

    }

    assert(soffset == 0); /* offset beyond end of src */

}

    /* return done; */



/*

 * Concatenates (partial) iovecs from src to the end of dst.

 * It starts copying after skipping `soffset' bytes at the

 * beginning of src and adds individual vectors from src to

 * dst copies up to `sbytes' bytes total, or up to the end

 * of src if it comes first.  This way, it is okay to specify

 * very large value for `sbytes' to indicate "up to the end

 * of src".

 * Only vector pointers are processed, not the actual data buffers.

 */

void qemu_iovec_concat(QEMUIOVector *dst,

                       QEMUIOVector *src, size_t soffset, size_t sbytes)

{

    qemu_iovec_concat_iov(dst, src->iov, src->niov, soffset, sbytes);

}



void qemu_iovec_destroy(QEMUIOVector *qiov)