25e5e4c7e9
Make it much more understandable, add a missing iov_cnt argument (number of iovs in the iov), and add comments to it. The new implementation has been extensively tested by splitting a large buffer into many small randomly-sized chunks, sending it over socket to another, slow process and verifying the receiving data is the same. Also add a unit test for iov_send_recv(), sending/ receiving data between two processes over a socketpair using random vectors and random sizes. Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
89 lines
3.5 KiB
C
89 lines
3.5 KiB
C
/*
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* Helpers for using (partial) iovecs.
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*
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* Copyright (C) 2010 Red Hat, Inc.
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*
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* Author(s):
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* Amit Shah <amit.shah@redhat.com>
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* Michael Tokarev <mjt@tls.msk.ru>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*/
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#include "qemu-common.h"
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/**
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* count and return data size, in bytes, of an iovec
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* starting at `iov' of `iov_cnt' number of elements.
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*/
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size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt);
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/**
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* Copy from single continuous buffer to scatter-gather vector of buffers
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* (iovec) and back like memcpy() between two continuous memory regions.
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* Data in single continuous buffer starting at address `buf' and
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* `bytes' bytes long will be copied to/from an iovec `iov' with
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* `iov_cnt' number of elements, starting at byte position `offset'
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* within the iovec. If the iovec does not contain enough space,
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* only part of data will be copied, up to the end of the iovec.
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* Number of bytes actually copied will be returned, which is
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* min(bytes, iov_size(iov)-offset)
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* `Offset' must point to the inside of iovec.
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* It is okay to use very large value for `bytes' since we're
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* limited by the size of the iovec anyway, provided that the
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* buffer pointed to by buf has enough space. One possible
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* such "large" value is -1 (sinice size_t is unsigned),
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* so specifying `-1' as `bytes' means 'up to the end of iovec'.
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*/
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size_t iov_from_buf(struct iovec *iov, unsigned int iov_cnt,
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size_t offset, const void *buf, size_t bytes);
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size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
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size_t offset, void *buf, size_t bytes);
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/**
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* Set data bytes pointed out by iovec `iov' of size `iov_cnt' elements,
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* starting at byte offset `start', to value `fillc', repeating it
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* `bytes' number of times. `Offset' must point to the inside of iovec.
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* If `bytes' is large enough, only last bytes portion of iovec,
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* up to the end of it, will be filled with the specified value.
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* Function return actual number of bytes processed, which is
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* min(size, iov_size(iov) - offset).
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* Again, it is okay to use large value for `bytes' to mean "up to the end".
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*/
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size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt,
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size_t offset, int fillc, size_t bytes);
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/*
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* Send/recv data from/to iovec buffers directly
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*
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* `offset' bytes in the beginning of iovec buffer are skipped and
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* next `bytes' bytes are used, which must be within data of iovec.
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*
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* r = iov_send_recv(sockfd, iov, iovcnt, offset, bytes, true);
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*
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* is logically equivalent to
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*
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* char *buf = malloc(bytes);
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* iov_to_buf(iov, iovcnt, offset, buf, bytes);
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* r = send(sockfd, buf, bytes, 0);
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* free(buf);
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*
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* For iov_send_recv() _whole_ area being sent or received
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* should be within the iovec, not only beginning of it.
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*/
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ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt,
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size_t offset, size_t bytes, bool do_send);
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#define iov_recv(sockfd, iov, iov_cnt, offset, bytes) \
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iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, false)
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#define iov_send(sockfd, iov, iov_cnt, offset, bytes) \
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iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, true)
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/**
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* Produce a text hexdump of iovec `iov' with `iov_cnt' number of elements
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* in file `fp', prefixing each line with `prefix' and processing not more
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* than `limit' data bytes.
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*/
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void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt,
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FILE *fp, const char *prefix, size_t limit);
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