Add a helper to set a range of bytes across an IO vector to a given
value, similar to memset() but operating over scatter-gather buffers.
It skips to the given offset and fills across iovec entries up to the
requested length.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
---
iov.c | 27 +++++++++++++++++++++++++++
iov.h | 2 ++
2 files changed, 29 insertions(+)
diff --git a/iov.c b/iov.c
index ae0743931d18..0188acdf5eba 100644
--- a/iov.c
+++ b/iov.c
@@ -170,6 +170,33 @@ size_t iov_truncate(struct iovec *iov, size_t iov_cnt, size_t size)
return i;
}
+/**
+ * iov_memset() - Set bytes of an IO vector to a given value
+ * @iov: IO vector
+ * @iov_cnt: Number of elements in @iov
+ * @offset: Byte offset in the iovec at which to start
+ * @c: Byte value to fill with
+ * @length: Number of bytes to set
+ * Will write less than @length bytes if it runs out of space in
+ * the iov
+ */
+/* cppcheck-suppress unusedFunction */
+void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c,
+ size_t length)
+{
+ size_t i;
+
+ i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
+
+ for ( ; i < iov_cnt && length; i++) {
+ size_t n = MIN(iov[i].iov_len - offset, length);
+
+ memset((char *)iov[i].iov_base + offset, c, n);
+ offset = 0;
+ length -= n;
+ }
+}
+
/**
* iov_tail_prune() - Remove any unneeded buffers from an IOV tail
* @tail: IO vector tail (modified)
diff --git a/iov.h b/iov.h
index b4e50b0fca5a..d295d05b3bab 100644
--- a/iov.h
+++ b/iov.h
@@ -30,6 +30,8 @@ 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);
size_t iov_truncate(struct iovec *iov, size_t iov_cnt, size_t size);
+void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c,
+ size_t length);
/*
* DOC: Theory of Operation, struct iov_tail
--
2.53.0