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Diffstat (limited to 'iov.c')
| -rw-r--r-- | iov.c | 174 |
1 files changed, 174 insertions, 0 deletions
@@ -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; +} |