iov_tail_drop() discards a header from the iov_tail,
iov_slice() makes a new iov referencing a subset of the data
in the original iov.
iov_tail_slice() is a wrapper for iov_slice() using iov_tail
Signed-off-by: Laurent Vivier <lvivier(a)redhat.com>
---
iov.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
iov.h | 6 ++++
2 files changed, 98 insertions(+)
diff --git a/iov.c b/iov.c
index 8c63b7ea6e31..047fcbce7fcd 100644
--- a/iov.c
+++ b/iov.c
@@ -156,6 +156,59 @@ size_t iov_size(const struct iovec *iov, size_t iov_cnt)
return len;
}
+/**
+ * iov_slice - Make a new iov referencing a subset of the data in the original iov
+ *
+ * @dst_iov: Pointer to the destination array of struct iovec describing
+ * the scatter/gather I/O vector to copy to.
+ * @dst_iov_cnt: Maximum number of elements in the destination iov array.
+ * @iov: Pointer to the source array of struct iovec describing
+ * the scatter/gather I/O vector to copy from.
+ * @iov_cnt: Maximum number of elements in the source iov array.
+ * @offset: Offset within the source iov from where copying should start.
+ * @bytes: On input, total number of bytes to copy from @iov to @dst_iov,
+ * if @bytes is NULL, copy all the content of @iov,
+ * on output actual number of bytes copied.
+ *
+ * Returns: The number of elements successfully copied to the destination
+ * iov array, a negative value if there is not enough room in the
+ * destination iov array
+ */
+/* cppcheck-suppress staticFunction */
+ssize_t iov_slice(struct iovec *dst_iov, size_t dst_iov_cnt,
+ const struct iovec *iov, size_t iov_cnt,
+ size_t offset, size_t *bytes)
+{
+ unsigned int i, j;
+ size_t remaining = bytes ? *bytes : SIZE_MAX;
+
+ i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
+
+ /* create a new iov array referencing a subset of the source one */
+ for (j = 0; i < iov_cnt && j < dst_iov_cnt && remaining; i++) {
+ size_t len = MIN(remaining, iov[i].iov_len - offset);
+
+ dst_iov[j].iov_base = (char *)iov[i].iov_base + offset;
+ dst_iov[j].iov_len = len;
+ j++;
+ remaining -= len;
+ offset = 0;
+ }
+ if (j == dst_iov_cnt) {
+ if (bytes) {
+ if (remaining)
+ return -1;
+ } else if (i != iov_cnt) {
+ return -1;
+ }
+ }
+
+ if (bytes)
+ *bytes -= remaining;
+
+ return j;
+}
+
/**
* iov_tail_prune() - Remove any unneeded buffers from an IOV tail
* @tail: IO vector tail (modified)
@@ -191,6 +244,21 @@ size_t iov_tail_size(struct iov_tail *tail)
return iov_size(tail->iov, tail->cnt) - tail->off;
}
+/**
+ * iov_tail_drop() - Discard a header from an IOV tail
+ * @tail: IO vector tail
+ * @len: length to move the head of the tail
+ *
+ * Returns: true if the tail still contains any bytes, otherwise false
+ */
+/* cppcheck-suppress unusedFunction */
+bool iov_tail_drop(struct iov_tail *tail, size_t len)
+{
+ tail->off = tail->off + len;
+
+ return iov_tail_prune(tail);
+}
+
/**
* iov_peek_header_() - Get pointer to a header from an IOV tail
* @tail: IOV tail to get header from
@@ -247,3 +315,27 @@ void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t
align)
tail->off = tail->off + len;
return p;
}
+
+/**
+ * iov_tail_slice - Make a new iov referencing a subset of the data
+ * in an iov_tail
+ *
+ * @dst_iov: Pointer to the destination array of struct iovec describing
+ * the scatter/gather I/O vector to copy to.
+ * @dst_iov_cnt: Maximum number of elements in the destination iov array.
+ * @tail: Pointer to the source iov_tail
+ * @bytes: On input, total number of bytes to copy from @iov to @dst_iov,
+ * if @bytes is NULL, copy all the content of @iov,
+ * on output actual number of bytes copied.
+ *
+ * Returns: The number of elements successfully copied to the destination
+ * iov array, a negative value if there is not enough room in the
+ * destination iov array
+ */
+/* cppcheck-suppress unusedFunction */
+int iov_tail_slice(struct iovec *dst_iov, size_t dst_iov_cnt,
+ struct iov_tail *tail, size_t *bytes)
+{
+ return iov_slice(dst_iov, dst_iov_cnt, &tail->iov[0], tail->cnt,
+ tail->off, bytes);
+}
diff --git a/iov.h b/iov.h
index 9855bf0c0c32..809f84a2c0a0 100644
--- a/iov.h
+++ b/iov.h
@@ -28,6 +28,9 @@ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,
size_t offset, void *buf, size_t bytes);
size_t iov_size(const struct iovec *iov, size_t iov_cnt);
+ssize_t iov_slice(struct iovec *dst_iov, size_t dst_iov_cnt,
+ const struct iovec *iov, size_t iov_cnt,
+ size_t offset, size_t *bytes);
/*
* DOC: Theory of Operation, struct iov_tail
@@ -72,8 +75,11 @@ struct iov_tail {
bool iov_tail_prune(struct iov_tail *tail);
size_t iov_tail_size(struct iov_tail *tail);
+bool iov_tail_drop(struct iov_tail *tail, size_t len);
void *iov_peek_header_(struct iov_tail *tail, size_t len, size_t align);
void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t align);
+int iov_tail_slice(struct iovec *dst_iov, size_t dst_iov_cnt,
+ struct iov_tail *tail, size_t *bytes);
/**
* IOV_PEEK_HEADER() - Get typed pointer to a header from an IOV tail
--
2.49.0