Add a helper to copy data from a source iovec array to a destination
iovec array, each starting at an arbitrary byte offset, iterating
through both arrays simultaneously and copying in chunks matching the
smaller of the two current segments.
Signed-off-by: Laurent Vivier
Reviewed-by: David Gibson
---
iov.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
iov.h | 3 +++
2 files changed, 55 insertions(+)
diff --git a/iov.c b/iov.c
index 0188acdf5eba..dabc4f1ceea3 100644
--- a/iov.c
+++ b/iov.c
@@ -197,6 +197,58 @@ void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c,
}
}
+/**
+ * iov_memcpy() - Copy data between two iovec arrays
+ * @dst_iov: Destination iovec array
+ * @dst_iov_cnt: Number of elements in destination iovec array
+ * @dst_offset: Destination offset
+ * @src_iov: Source iovec array
+ * @src_iov_cnt: Number of elements in source iovec array
+ * @offs: Source offset
+ * @length: Number of bytes to copy
+ *
+ * Return: total number of bytes copied
+ */
+/* cppcheck-suppress unusedFunction */
+size_t iov_memcpy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_offset,
+ const struct iovec *src_iov, size_t src_iov_cnt,
+ size_t src_offset, size_t length)
+{
+ unsigned int i, j;
+ size_t total = 0;
+
+ i = iov_skip_bytes(src_iov, src_iov_cnt, src_offset, &src_offset);
+ j = iov_skip_bytes(dst_iov, dst_iov_cnt, dst_offset, &dst_offset);
+
+ /* copying data */
+ while (length && i < src_iov_cnt && j < dst_iov_cnt) {
+ size_t n = MIN(dst_iov[j].iov_len - dst_offset,
+ src_iov[i].iov_len - src_offset);
+
+ if (n > length)
+ n = length;
+
+ memcpy((char *)dst_iov[j].iov_base + dst_offset,
+ (const char *)src_iov[i].iov_base + src_offset, n);
+
+ dst_offset += n;
+ src_offset += n;
+ total += n;
+ length -= n;
+
+ if (dst_offset == dst_iov[j].iov_len) {
+ dst_offset = 0;
+ j++;
+ }
+ if (src_offset == src_iov[i].iov_len) {
+ src_offset = 0;
+ i++;
+ }
+ }
+
+ return total;
+}
+
/**
* 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 d295d05b3bab..3c63308e554f 100644
--- a/iov.h
+++ b/iov.h
@@ -32,6 +32,9 @@ 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);
+size_t iov_memcpy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_offset,
+ const struct iovec *src_iov, size_t src_iov_cnt,
+ size_t src_offset, size_t length);
/*
* DOC: Theory of Operation, struct iov_tail
--
2.53.0