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authorLaurent Vivier <lvivier@redhat.com>2024-02-28 12:52:00 +1100
committerStefano Brivio <sbrivio@redhat.com>2024-02-29 06:23:49 +0100
commit2a6f8bcca77ae7391a8943a3791be2fbb98a918b (patch)
tree9bcead16830db4d915f1cdb16556e3e7801211bd /iov.c
parent90f1d3b3546eba0e454d227c24b391e184ac092c (diff)
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iov: add some functions to manage iovec
Introduce functions to copy to/from a buffer from/to an iovec array, to compute data length in in bytes of an iovec and to copy memory from an iovec to another. iov_from_buf(), iov_to_buf(), iov_size(), iov_copy(). Signed-off-by: Laurent Vivier <lvivier@redhat.com> Message-ID: <20240217150725.661467-2-lvivier@redhat.com> [dwg: Small changes to suppress cppcheck warnings] Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Diffstat (limited to 'iov.c')
-rw-r--r--iov.c174
1 files changed, 174 insertions, 0 deletions
diff --git a/iov.c b/iov.c
new file mode 100644
index 0000000..8a48acb
--- /dev/null
+++ b/iov.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * iov.h - helpers for using (partial) iovecs.
+ *
+ * Copyright Red Hat
+ * Author: Laurent Vivier <lvivier@redhat.com>
+ *
+ * This file also contains code originally from QEMU include/qemu/iov.h
+ * and licensed under the following terms:
+ *
+ * Copyright (C) 2010 Red Hat, Inc.
+ *
+ * Author(s):
+ * Amit Shah <amit.shah@redhat.com>
+ * Michael Tokarev <mjt@tls.msk.ru>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+#include <sys/socket.h>
+
+#include "util.h"
+#include "iov.h"
+
+/**
+ * iov_from_buf - Copy data from a buffer to an I/O vector (struct iovec)
+ * efficiently.
+ *
+ * @iov: Pointer to the array of struct iovec describing the
+ * scatter/gather I/O vector.
+ * @iov_cnt: Number of elements in the iov array.
+ * @offset: Byte offset in the iov array where copying should start.
+ * @buf: Pointer to the source buffer containing the data to copy.
+ * @bytes: Total number of bytes to copy from buf to iov.
+ *
+ * Returns: The number of bytes successfully copied.
+ */
+/* cppcheck-suppress unusedFunction */
+size_t iov_from_buf(const struct iovec *iov, size_t iov_cnt,
+ size_t offset, const void *buf, size_t bytes)
+{
+ unsigned int i;
+ size_t copied;
+
+ if (__builtin_constant_p(bytes) && iov_cnt &&
+ offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
+ memcpy((char *)iov[0].iov_base + offset, buf, bytes);
+ return bytes;
+ }
+
+ /* skipping offset bytes in the iovec */
+ for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
+ offset -= iov[i].iov_len;
+
+ /* copying data */
+ for (copied = 0; copied < bytes && i < iov_cnt; i++) {
+ size_t len = MIN(iov[i].iov_len - offset, bytes - copied);
+
+ memcpy((char *)iov[i].iov_base + offset, (char *)buf + copied,
+ len);
+ copied += len;
+ offset = 0;
+ }
+
+ return copied;
+}
+
+/**
+ * iov_to_buf - Copy data from a scatter/gather I/O vector (struct iovec) to
+ * a buffer efficiently.
+ *
+ * @iov: Pointer to the array of struct iovec describing the scatter/gather
+ * I/O vector.
+ * @iov_cnt: Number of elements in the iov array.
+ * @offset: Offset within the first element of iov from where copying should start.
+ * @buf: Pointer to the destination buffer where data will be copied.
+ * @bytes: Total number of bytes to copy from iov to buf.
+ *
+ * Returns: The number of bytes successfully copied.
+ */
+/* cppcheck-suppress unusedFunction */
+size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,
+ size_t offset, void *buf, size_t bytes)
+{
+ unsigned int i;
+ size_t copied;
+
+ if (__builtin_constant_p(bytes) && iov_cnt &&
+ offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
+ memcpy(buf, (char *)iov[0].iov_base + offset, bytes);
+ return bytes;
+ }
+
+ /* skipping offset bytes in the iovec */
+ for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
+ offset -= iov[i].iov_len;
+
+ /* copying data */
+ for (copied = 0; copied < bytes && i < iov_cnt; i++) {
+ size_t len = MIN(iov[i].iov_len - offset, bytes - copied);
+ memcpy((char *)buf + copied, (char *)iov[i].iov_base + offset,
+ len);
+ copied += len;
+ offset = 0;
+ }
+
+ return copied;
+}
+
+/**
+ * iov_size - Calculate the total size of a scatter/gather I/O vector
+ * (struct iovec).
+ *
+ * @iov: Pointer to the array of struct iovec describing the
+ * scatter/gather I/O vector.
+ * @iov_cnt: Number of elements in the iov array.
+ *
+ * Returns: The total size in bytes.
+ */
+/* cppcheck-suppress unusedFunction */
+size_t iov_size(const struct iovec *iov, size_t iov_cnt)
+{
+ unsigned int i;
+ size_t len;
+
+ for (i = 0, len = 0; i < iov_cnt; i++)
+ len += iov[i].iov_len;
+
+ return len;
+}
+
+/**
+ * iov_copy - Copy data from one scatter/gather I/O vector (struct iovec) to
+ * another.
+ *
+ * @dst_iov: Pointer to the destination array of struct iovec describing
+ * the scatter/gather I/O vector to copy to.
+ * @dst_iov_cnt: 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: Number of elements in the source iov array.
+ * @offset: Offset within the source iov from where copying should start.
+ * @bytes: Total number of bytes to copy from iov to dst_iov.
+ *
+ * Returns: The number of elements successfully copied to the destination
+ * iov array.
+ */
+/* cppcheck-suppress unusedFunction */
+unsigned iov_copy(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;
+
+ /* skipping offset bytes in the iovec */
+ for (i = 0; i < iov_cnt && offset >= iov[i].iov_len; i++)
+ offset -= iov[i].iov_len;
+
+ /* copying data */
+ for (j = 0; i < iov_cnt && j < dst_iov_cnt && bytes; i++) {
+ size_t len = MIN(bytes, iov[i].iov_len - offset);
+
+ dst_iov[j].iov_base = (char *)iov[i].iov_base + offset;
+ dst_iov[j].iov_len = len;
+ j++;
+ bytes -= len;
+ offset = 0;
+ }
+
+ return j;
+}