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/*
* Helpers for using (partial) iovecs.
*
* 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.
*/
#ifndef IOV_H
#define IOV_H
#include "qemu-common.h"
/**
* count and return data size, in bytes, of an iovec
* starting at `iov' of `iov_cnt' number of elements.
*/
size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
/**
* Copy from single continuous buffer to scatter-gather vector of buffers
* (iovec) and back like memcpy() between two continuous memory regions.
* Data in single continuous buffer starting at address `buf' and
* `bytes' bytes long will be copied to/from an iovec `iov' with
* `iov_cnt' number of elements, starting at byte position `offset'
* within the iovec. If the iovec does not contain enough space,
* only part of data will be copied, up to the end of the iovec.
* Number of bytes actually copied will be returned, which is
* min(bytes, iov_size(iov)-offset)
* `Offset' must point to the inside of iovec.
* It is okay to use very large value for `bytes' since we're
* limited by the size of the iovec anyway, provided that the
* buffer pointed to by buf has enough space. One possible
* such "large" value is -1 (sinice size_t is unsigned),
* so specifying `-1' as `bytes' means 'up to the end of iovec'.
*/
size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
size_t offset, const void *buf, size_t bytes);
size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, void *buf, size_t bytes);
static inline size_t
iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
size_t offset, const void *buf, size_t bytes)
{
if (__builtin_constant_p(bytes) && iov_cnt &&
offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
memcpy(iov[0].iov_base + offset, buf, bytes);
return bytes;
} else {
return iov_from_buf_full(iov, iov_cnt, offset, buf, bytes);
}
}
static inline size_t
iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, void *buf, size_t bytes)
{
if (__builtin_constant_p(bytes) && iov_cnt &&
offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
memcpy(buf, iov[0].iov_base + offset, bytes);
return bytes;
} else {
return iov_to_buf_full(iov, iov_cnt, offset, buf, bytes);
}
}
/**
* Set data bytes pointed out by iovec `iov' of size `iov_cnt' elements,
* starting at byte offset `start', to value `fillc', repeating it
* `bytes' number of times. `Offset' must point to the inside of iovec.
* If `bytes' is large enough, only last bytes portion of iovec,
* up to the end of it, will be filled with the specified value.
* Function return actual number of bytes processed, which is
* min(size, iov_size(iov) - offset).
* Again, it is okay to use large value for `bytes' to mean "up to the end".
*/
size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, int fillc, size_t bytes);
/*
* Send/recv data from/to iovec buffers directly
*
* `offset' bytes in the beginning of iovec buffer are skipped and
* next `bytes' bytes are used, which must be within data of iovec.
*
* r = iov_send_recv(sockfd, iov, iovcnt, offset, bytes, true);
*
* is logically equivalent to
*
* char *buf = malloc(bytes);
* iov_to_buf(iov, iovcnt, offset, buf, bytes);
* r = send(sockfd, buf, bytes, 0);
* free(buf);
*
* For iov_send_recv() _whole_ area being sent or received
* should be within the iovec, not only beginning of it.
*/
ssize_t iov_send_recv(int sockfd, const struct iovec *iov, unsigned iov_cnt,
size_t offset, size_t bytes, bool do_send);
#define iov_recv(sockfd, iov, iov_cnt, offset, bytes) \
iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, false)
#define iov_send(sockfd, iov, iov_cnt, offset, bytes) \
iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, true)
/**
* Produce a text hexdump of iovec `iov' with `iov_cnt' number of elements
* in file `fp', prefixing each line with `prefix' and processing not more
* than `limit' data bytes.
*/
void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
FILE *fp, const char *prefix, size_t limit);
/*
* Partial copy of vector from iov to dst_iov (data is not copied).
* dst_iov overlaps iov at a specified offset.
* size of dst_iov is at most bytes. dst vector count is returned.
*/
unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
const struct iovec *iov, unsigned int iov_cnt,
size_t offset, size_t bytes);
/*
* Remove a given number of bytes from the front or back of a vector.
* This may update iov and/or iov_cnt to exclude iovec elements that are
* no longer required.
*
* The number of bytes actually discarded is returned. This number may be
* smaller than requested if the vector is too small.
*/
size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
size_t bytes);
size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
size_t bytes);
#endif
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