On Fri, Apr 03, 2026 at 06:38:03PM +0200, Laurent Vivier wrote:
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
-- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson