/* * 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. */ #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(const struct iovec *iov, unsigned int iov_cnt, size_t offset, const void *buf, size_t bytes); size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt, size_t offset, void *buf, size_t 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, 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);