From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=doUVCDkc; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTPS id 426BE5A061B for ; Thu, 17 Apr 2025 18:51:49 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744908708; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=kvjhr4FoMekQGbkITRMpjPfyVLglVZlGMYb1eDZqar8=; b=doUVCDkcBnxwFQLoQszdoY4UZLrBdD0AzYUmry2PROfjF7sd+FelG4drPM3Q5kYroWRykc jtZUOex8kcl5+E0n7WuJ0rOyrKnc0pHWiFNRdq7M6oOgtU3Z0B8ndfik/pBckPhQ+9mYik yAr3mY48fubrdkDE6PrELb5iGjI+vJk= Received: from mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-694-yD0Bdy2TNMuuA_IgLImYIQ-1; Thu, 17 Apr 2025 12:51:44 -0400 X-MC-Unique: yD0Bdy2TNMuuA_IgLImYIQ-1 X-Mimecast-MFC-AGG-ID: yD0Bdy2TNMuuA_IgLImYIQ_1744908703 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6F84A1955DD0 for ; Thu, 17 Apr 2025 16:51:43 +0000 (UTC) Received: from lenovo-t14s.redhat.com (unknown [10.44.32.6]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 5C8E11800362; Thu, 17 Apr 2025 16:51:42 +0000 (UTC) From: Laurent Vivier To: passt-dev@passt.top Subject: [PATCH v5 02/29] iov: Introduce iov_slice(), iov_tail_slice() and iov_tail_drop(). Date: Thu, 17 Apr 2025 18:51:09 +0200 Message-ID: <20250417165136.2688884-3-lvivier@redhat.com> In-Reply-To: <20250417165136.2688884-1-lvivier@redhat.com> References: <20250417165136.2688884-1-lvivier@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: ciKDGQr8uMPEcX6d-yl7hDcpJdnPO6jUo4rodIN6bd0_1744908703 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true Message-ID-Hash: A6WTCFVQWSVZRP67ZVNMICKEARK6PAP3 X-Message-ID-Hash: A6WTCFVQWSVZRP67ZVNMICKEARK6PAP3 X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: Laurent Vivier X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: iov_tail_drop() discards a header from the iov_tail, iov_slice() makes a new iov referencing a subset of the data in the original iov. iov_tail_slice() is a wrapper for iov_slice() using iov_tail Signed-off-by: Laurent Vivier --- iov.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ iov.h | 6 ++++ 2 files changed, 98 insertions(+) diff --git a/iov.c b/iov.c index 8c63b7ea6e31..047fcbce7fcd 100644 --- a/iov.c +++ b/iov.c @@ -156,6 +156,59 @@ size_t iov_size(const struct iovec *iov, size_t iov_cnt) return len; } +/** + * iov_slice - Make a new iov referencing a subset of the data in the original iov + * + * @dst_iov: Pointer to the destination array of struct iovec describing + * the scatter/gather I/O vector to copy to. + * @dst_iov_cnt: Maximum number of elements in the destination iov array. + * @iov: Pointer to the source array of struct iovec describing + * the scatter/gather I/O vector to copy from. + * @iov_cnt: Maximum number of elements in the source iov array. + * @offset: Offset within the source iov from where copying should start. + * @bytes: On input, total number of bytes to copy from @iov to @dst_iov, + * if @bytes is NULL, copy all the content of @iov, + * on output actual number of bytes copied. + * + * Returns: The number of elements successfully copied to the destination + * iov array, a negative value if there is not enough room in the + * destination iov array + */ +/* cppcheck-suppress staticFunction */ +ssize_t iov_slice(struct iovec *dst_iov, size_t dst_iov_cnt, + const struct iovec *iov, size_t iov_cnt, + size_t offset, size_t *bytes) +{ + unsigned int i, j; + size_t remaining = bytes ? *bytes : SIZE_MAX; + + i = iov_skip_bytes(iov, iov_cnt, offset, &offset); + + /* create a new iov array referencing a subset of the source one */ + for (j = 0; i < iov_cnt && j < dst_iov_cnt && remaining; i++) { + size_t len = MIN(remaining, iov[i].iov_len - offset); + + dst_iov[j].iov_base = (char *)iov[i].iov_base + offset; + dst_iov[j].iov_len = len; + j++; + remaining -= len; + offset = 0; + } + if (j == dst_iov_cnt) { + if (bytes) { + if (remaining) + return -1; + } else if (i != iov_cnt) { + return -1; + } + } + + if (bytes) + *bytes -= remaining; + + return j; +} + /** * iov_tail_prune() - Remove any unneeded buffers from an IOV tail * @tail: IO vector tail (modified) @@ -191,6 +244,21 @@ size_t iov_tail_size(struct iov_tail *tail) return iov_size(tail->iov, tail->cnt) - tail->off; } +/** + * iov_tail_drop() - Discard a header from an IOV tail + * @tail: IO vector tail + * @len: length to move the head of the tail + * + * Returns: true if the tail still contains any bytes, otherwise false + */ +/* cppcheck-suppress unusedFunction */ +bool iov_tail_drop(struct iov_tail *tail, size_t len) +{ + tail->off = tail->off + len; + + return iov_tail_prune(tail); +} + /** * iov_peek_header_() - Get pointer to a header from an IOV tail * @tail: IOV tail to get header from @@ -247,3 +315,27 @@ void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t align) tail->off = tail->off + len; return p; } + +/** + * iov_tail_slice - Make a new iov referencing a subset of the data + * in an iov_tail + * + * @dst_iov: Pointer to the destination array of struct iovec describing + * the scatter/gather I/O vector to copy to. + * @dst_iov_cnt: Maximum number of elements in the destination iov array. + * @tail: Pointer to the source iov_tail + * @bytes: On input, total number of bytes to copy from @iov to @dst_iov, + * if @bytes is NULL, copy all the content of @iov, + * on output actual number of bytes copied. + * + * Returns: The number of elements successfully copied to the destination + * iov array, a negative value if there is not enough room in the + * destination iov array + */ +/* cppcheck-suppress unusedFunction */ +int iov_tail_slice(struct iovec *dst_iov, size_t dst_iov_cnt, + struct iov_tail *tail, size_t *bytes) +{ + return iov_slice(dst_iov, dst_iov_cnt, &tail->iov[0], tail->cnt, + tail->off, bytes); +} diff --git a/iov.h b/iov.h index 9855bf0c0c32..809f84a2c0a0 100644 --- a/iov.h +++ b/iov.h @@ -28,6 +28,9 @@ size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt, 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); +ssize_t iov_slice(struct iovec *dst_iov, size_t dst_iov_cnt, + const struct iovec *iov, size_t iov_cnt, + size_t offset, size_t *bytes); /* * DOC: Theory of Operation, struct iov_tail @@ -72,8 +75,11 @@ struct iov_tail { bool iov_tail_prune(struct iov_tail *tail); size_t iov_tail_size(struct iov_tail *tail); +bool iov_tail_drop(struct iov_tail *tail, size_t len); void *iov_peek_header_(struct iov_tail *tail, size_t len, size_t align); void *iov_remove_header_(struct iov_tail *tail, size_t len, size_t align); +int iov_tail_slice(struct iovec *dst_iov, size_t dst_iov_cnt, + struct iov_tail *tail, size_t *bytes); /** * IOV_PEEK_HEADER() - Get typed pointer to a header from an IOV tail -- 2.49.0