2278a69e70
This changes implementations of all iov_* functions, completing the previous step. All iov_* functions now ensure that this offset argument is within the iovec (using assertion), but lets to specify `bytes' value larger than actual length of the iovec - in this case they stops at the actual end of iovec. It is also suggested to use convinient `-1' value as `bytes' to mean just this -- "up to the end". There's one very minor semantic change here: new requiriment is that `offset' points to inside of iovec. This is checked just at the end of functions (assert()), it does not actually need to be enforced, but using any of these functions with offset pointing past the end of iovec is wrong anyway. Note: the new code in iov.c uses arithmetic with void pointers. I thought this is not supported everywhere and is a GCC extension (indeed, the C standard does not define void arithmetic). However, the original code already use void arith in iov_from_buf() function: (memcpy(..., buf + buf_off,...) which apparently works well so far (it is this way in qemu 1.0). So I left it this way and used it in other places. While at it, add a unit-test file test-iov.c, to check various corner cases with iov_from_buf(), iov_to_buf() and iov_memset(). Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
64 lines
2.6 KiB
C
64 lines
2.6 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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* 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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