From 9361b6bab7b7e661b1a4a6b4847800e82dad0224 Mon Sep 17 00:00:00 2001 From: Laurent Vivier Date: Wed, 20 May 2026 11:55:25 +0200 Subject: iov: Introduce IOV_PUSH_HEADER() macro Add iov_push_header_() and its typed wrapper IOV_PUSH_HEADER() to write a header into an iov_tail at the current offset and advance past it. This is the write counterpart to IOV_PEEK_HEADER() / IOV_REMOVE_HEADER(), using iov_from_buf() to copy the header data across iovec boundaries. Signed-off-by: Laurent Vivier Reviewed-by: David Gibson Signed-off-by: Stefano Brivio --- iov.c | 31 +++++++++++++++++++++++++++++++ iov.h | 11 +++++++++++ 2 files changed, 42 insertions(+) diff --git a/iov.c b/iov.c index 7c18941..6a5d7d3 100644 --- a/iov.c +++ b/iov.c @@ -359,6 +359,37 @@ void *iov_peek_header_(struct iov_tail *tail, void *v, size_t len, size_t align) return v; } +/** + * iov_push_header_() - Write a new header to an IOV tail + * @tail: IOV tail to write header to + * @v: Pointer to header data to write + * @len: Length of header to write, in bytes + * + * Return: number of bytes written + */ +/* cppcheck-suppress unusedFunction */ +size_t iov_push_header_(struct iov_tail *tail, const void *v, size_t len) +{ + size_t l; + + if (!iov_tail_prune(tail)) + return 0; /* No space */ + + if ((char *)tail->iov[0].iov_base + tail->off == v) /* already in place */ + l = len; + else + l = iov_from_buf(tail->iov, tail->cnt, tail->off, v, len); + + if (l != len) { + warn("iov_push_header_(): Not enough space to store header" + " (%zu != %zu)", l, len); + } + + tail->off = tail->off + l; + + return l; +} + /** * iov_remove_header_() - Remove a header from an IOV tail * @tail: IOV tail to remove header from (modified) diff --git a/iov.h b/iov.h index 3c63308..4fdf14a 100644 --- a/iov.h +++ b/iov.h @@ -93,6 +93,7 @@ bool iov_tail_prune(struct iov_tail *tail); size_t iov_tail_size(struct iov_tail *tail); bool iov_drop_header(struct iov_tail *tail, size_t len); void *iov_peek_header_(struct iov_tail *tail, void *v, size_t len, size_t align); +size_t iov_push_header_(struct iov_tail *tail, const void *v, size_t len); void *iov_remove_header_(struct iov_tail *tail, void *v, size_t len, size_t align); ssize_t iov_tail_clone(struct iovec *dst_iov, size_t dst_iov_cnt, struct iov_tail *tail); @@ -115,6 +116,16 @@ ssize_t iov_tail_clone(struct iovec *dst_iov, size_t dst_iov_cnt, sizeof(var_), \ __alignof__(var_)))) +/** + * IOV_PUSH_HEADER() - Write a new header to an IOV tail + * @tail_: IOV tail to write header to + * @var_: A variable containing the header data to write + * + * Return: number of bytes written + */ +#define IOV_PUSH_HEADER(tail_, var_) \ + (iov_push_header_((tail_), &(var_), sizeof(var_))) + /** * IOV_REMOVE_HEADER() - Remove and return typed header from an IOV tail * @tail_: IOV tail to remove header from (modified) -- cgit v1.2.3