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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(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);

/*

 * 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);

#endif