1/* 2 * Helpers for using (partial) iovecs. 3 * 4 * Copyright (C) 2010 Red Hat, Inc. 5 * 6 * Author(s): 7 * Amit Shah <amit.shah@redhat.com> 8 * Michael Tokarev <mjt@tls.msk.ru> 9 * 10 * This work is licensed under the terms of the GNU GPL, version 2. See 11 * the COPYING file in the top-level directory. 12 */ 13 14#ifndef IOV_H 15#define IOV_H 16 17#include "qemu-common.h" 18 19/** 20 * count and return data size, in bytes, of an iovec 21 * starting at `iov' of `iov_cnt' number of elements. 22 */ 23size_t iov_size(const struct iovec *iov, const unsigned int iov_cnt); 24 25/** 26 * Copy from single continuous buffer to scatter-gather vector of buffers 27 * (iovec) and back like memcpy() between two continuous memory regions. 28 * Data in single continuous buffer starting at address `buf' and 29 * `bytes' bytes long will be copied to/from an iovec `iov' with 30 * `iov_cnt' number of elements, starting at byte position `offset' 31 * within the iovec. If the iovec does not contain enough space, 32 * only part of data will be copied, up to the end of the iovec. 33 * Number of bytes actually copied will be returned, which is 34 * min(bytes, iov_size(iov)-offset) 35 * `Offset' must point to the inside of iovec. 36 * It is okay to use very large value for `bytes' since we're 37 * limited by the size of the iovec anyway, provided that the 38 * buffer pointed to by buf has enough space. One possible 39 * such "large" value is -1 (sinice size_t is unsigned), 40 * so specifying `-1' as `bytes' means 'up to the end of iovec'. 41 */ 42size_t iov_from_buf(const struct iovec *iov, unsigned int iov_cnt, 43 size_t offset, const void *buf, size_t bytes); 44size_t iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt, 45 size_t offset, void *buf, size_t bytes); 46 47/** 48 * Set data bytes pointed out by iovec `iov' of size `iov_cnt' elements, 49 * starting at byte offset `start', to value `fillc', repeating it 50 * `bytes' number of times. `Offset' must point to the inside of iovec. 51 * If `bytes' is large enough, only last bytes portion of iovec, 52 * up to the end of it, will be filled with the specified value. 53 * Function return actual number of bytes processed, which is 54 * min(size, iov_size(iov) - offset). 55 * Again, it is okay to use large value for `bytes' to mean "up to the end". 56 */ 57size_t iov_memset(const struct iovec *iov, const unsigned int iov_cnt, 58 size_t offset, int fillc, size_t bytes); 59 60/* 61 * Send/recv data from/to iovec buffers directly 62 * 63 * `offset' bytes in the beginning of iovec buffer are skipped and 64 * next `bytes' bytes are used, which must be within data of iovec. 65 * 66 * r = iov_send_recv(sockfd, iov, iovcnt, offset, bytes, true); 67 * 68 * is logically equivalent to 69 * 70 * char *buf = malloc(bytes); 71 * iov_to_buf(iov, iovcnt, offset, buf, bytes); 72 * r = send(sockfd, buf, bytes, 0); 73 * free(buf); 74 * 75 * For iov_send_recv() _whole_ area being sent or received 76 * should be within the iovec, not only beginning of it. 77 */ 78ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, 79 size_t offset, size_t bytes, bool do_send); 80#define iov_recv(sockfd, iov, iov_cnt, offset, bytes) \ 81 iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, false) 82#define iov_send(sockfd, iov, iov_cnt, offset, bytes) \ 83 iov_send_recv(sockfd, iov, iov_cnt, offset, bytes, true) 84 85/** 86 * Produce a text hexdump of iovec `iov' with `iov_cnt' number of elements 87 * in file `fp', prefixing each line with `prefix' and processing not more 88 * than `limit' data bytes. 89 */ 90void iov_hexdump(const struct iovec *iov, const unsigned int iov_cnt, 91 FILE *fp, const char *prefix, size_t limit); 92 93/* 94 * Partial copy of vector from iov to dst_iov (data is not copied). 95 * dst_iov overlaps iov at a specified offset. 96 * size of dst_iov is at most bytes. dst vector count is returned. 97 */ 98unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, 99 const struct iovec *iov, unsigned int iov_cnt, 100 size_t offset, size_t bytes); 101 102/* 103 * Remove a given number of bytes from the front or back of a vector. 104 * This may update iov and/or iov_cnt to exclude iovec elements that are 105 * no longer required. 106 * 107 * The number of bytes actually discarded is returned. This number may be 108 * smaller than requested if the vector is too small. 109 */ 110size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt, 111 size_t bytes); 112size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt, 113 size_t bytes); 114 115#endif 116