Re: [PATCH 02/10] iov: Add iov_memcopy() to copy data between iovec arrays

Nits, all about names: On Wed, 1 Apr 2026 21:18:18 +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 --- iov.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++ iov.h | 3 +++ 2 files changed, 55 insertions(+)

diff --git a/iov.c b/iov.c index 0188acdf5eba..83b683f3976a 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_memcopy() - Copy data between two iovec arrays

Wouldn't it be less surprising to call this iov_memcpy(), like memcpy()?

+ * @dst_iov: Destination iovec array + * @dst_iov_cnt: Number of elements in destination iovec array + * @dst_offs: Destination offset + * @iov: Source iovec array + * @iov_cnt: Number of elements in source iovec array

I think @src_iov and @src_iov_cnt would make the whole function easier to follow and look more symmetric.

+ * @offs: Source offset

What about @dst_offset and @src_offset? "offs" as a short-form for "offset" isn't really obvious (to me at least).

+ * @length: Number of bytes to copy + * + * Return: total number of bytes copied + */ +/* cppcheck-suppress unusedFunction */ +size_t iov_memcopy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_offs, + const struct iovec *iov, size_t iov_cnt, size_t offs, + size_t length) +{ + unsigned int i, j; + size_t total = 0; + + i = iov_skip_bytes(iov, iov_cnt, offs, &offs); + j = iov_skip_bytes(dst_iov, dst_iov_cnt, dst_offs, &dst_offs); + + /* copying data */ + while (length && i < iov_cnt && j < dst_iov_cnt) { + size_t n = MIN(dst_iov[j].iov_len - dst_offs, + iov[i].iov_len - offs); + + if (n > length) + n = length; + + memcpy((char *)dst_iov[j].iov_base + dst_offs, + (const char *)iov[i].iov_base + offs, n); + + dst_offs += n; + offs += n; + total += n; + length -= n; + + if (dst_offs == dst_iov[j].iov_len) { + dst_offs = 0; + j++; + } + if (offs == iov[i].iov_len) { + offs = 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..074266e127ef 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_memcopy(struct iovec *dst_iov, size_t dst_iov_cnt, size_t dst_offs, + const struct iovec *iov, size_t iov_cnt, size_t offs, + size_t length);

/* * DOC: Theory of Operation, struct iov_tail

-- Stefano