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authorVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>2019-06-04 19:15:03 +0300
committerStefan Hajnoczi <stefanha@redhat.com>2019-08-27 14:52:45 +0100
commitd953169d4840f312d3b9a54952f4a7ccfcb3b311 (patch)
tree79c227914cced3681a12abfd8c28f143f60419e0 /util
parentdac03af5d5482ec7ee9c23db467bb7230b33c0d9 (diff)
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: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20190604161514.262241-2-vsementsov@virtuozzo.com Message-Id: <20190604161514.262241-2-vsementsov@virtuozzo.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'util')
-rw-r--r--util/iov.c112
1 files changed, 107 insertions, 5 deletions
diff --git a/util/iov.c b/util/iov.c
index 74e6ca8ed7..366ff9cdd1 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -354,6 +354,103 @@ void qemu_iovec_concat(QEMUIOVector *dst,
}
/*
+ * 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
*/
bool qemu_iovec_is_zero(QEMUIOVector *qiov)
@@ -374,14 +471,19 @@ bool qemu_iovec_is_zero(QEMUIOVector *qiov)
return true;
}
+void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
+ size_t offset, size_t len)
+{
+ qemu_iovec_init_extended(qiov, NULL, 0, source, offset, len, NULL, 0);
+}
+
void qemu_iovec_destroy(QEMUIOVector *qiov)
{
- assert(qiov->nalloc != -1);
+ if (qiov->nalloc != -1) {
+ g_free(qiov->iov);
+ }
- qemu_iovec_reset(qiov);
- g_free(qiov->iov);
- qiov->nalloc = 0;
- qiov->iov = NULL;
+ memset(qiov, 0, sizeof(*qiov));
}
void qemu_iovec_reset(QEMUIOVector *qiov)