/*
* 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
/**
* 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.
*/
size_t iov_from_buf_full(const struct iovec *iov, unsigned int iov_cnt,
size_t offset, const void *buf, size_t bytes);
size_t iov_to_buf_full(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, void *buf, size_t bytes);
static inline size_t
iov_from_buf(const struct iovec *iov, unsigned int iov_cnt,
size_t offset, const void *buf, size_t bytes)
{
if (__builtin_constant_p(bytes) && iov_cnt &&
offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
memcpy(iov[0].iov_base + offset, buf, bytes);
return bytes;
} else {
return iov_from_buf_full(iov, iov_cnt, offset, buf, bytes);
}
}
static inline size_t
iov_to_buf(const struct iovec *iov, const unsigned int iov_cnt,
size_t offset, void *buf, size_t bytes)
{
if (__builtin_constant_p(bytes) && iov_cnt &&
offset <= iov[0].iov_len && bytes <= iov[0].iov_len - offset) {
memcpy(buf, iov[0].iov_base + offset, bytes);
return bytes;
} else {
return iov_to_buf_full(iov, iov_cnt, offset, buf, 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).
*/
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, const 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);
/*
* Remove a given number of bytes from the front or back of a vector.
* This may update iov and/or iov_cnt to exclude iovec elements that are
* no longer required.
*
* The number of bytes actually discarded is returned. This number may be
* smaller than requested if the vector is too small.
*/
size_t iov_discard_front(struct iovec **iov, unsigned int *iov_cnt,
size_t bytes);
size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
size_t bytes);
/* Information needed to undo an iov_discard_*() operation */
typedef struct {
struct iovec *modified_iov;
struct iovec orig;
} IOVDiscardUndo;
/*
* Undo an iov_discard_front_undoable() or iov_discard_back_undoable()
* operation. If multiple operations are made then each one needs a separate
* IOVDiscardUndo and iov_discard_undo() must be called in the reverse order
* that the operations were made.
*/
void iov_discard_undo(IOVDiscardUndo *undo);
/*
* Undoable versions of iov_discard_front() and iov_discard_back(). Use
* iov_discard_undo() to reset to the state before the discard operations.
*/
size_t iov_discard_front_undoable(struct iovec **iov, unsigned int *iov_cnt,
size_t bytes, IOVDiscardUndo *undo);
size_t iov_discard_back_undoable(struct iovec *iov, unsigned int *iov_cnt,
size_t bytes, IOVDiscardUndo *undo);
typedef struct QEMUIOVector {
struct iovec *iov;
int niov;
/*
* For external @iov (qemu_iovec_init_external()) or allocated @iov
* (qemu_iovec_init()), @size is the cumulative size of iovecs and
* @local_iov is invalid and unused.
*
* For embedded @iov (QEMU_IOVEC_INIT_BUF() or qemu_iovec_init_buf()),
* @iov is equal to &@local_iov, and @size is valid, as it has same
* offset and type as @local_iov.iov_len, which is guaranteed by
* static assertion below.
*
* @nalloc is always valid and is -1 both for embedded and external
* cases. It is included in the union only to ensure the padding prior
* to the @size field will not result in a 0-length array.
*/
union {
struct {
int nalloc;
struct iovec local_iov;
};
struct {
char __pad[sizeof(int) + offsetof(struct iovec, iov_len)];
size_t size;
};
};
} QEMUIOVector;
QEMU_BUILD_BUG_ON(offsetof(QEMUIOVector, size) !=
offsetof(QEMUIOVector, local_iov.iov_len));
#define QEMU_IOVEC_INIT_BUF(self, buf, len) \
{ \
.iov = &(self).local_iov, \
.niov = 1, \
.nalloc = -1, \
.local_iov = { \
.iov_base = (void *)(buf), /* cast away const */ \
.iov_len = (len), \
}, \
}
/*
* qemu_iovec_init_buf
*
* Initialize embedded QEMUIOVector.
*
* Note: "const" is used over @buf pointer to make it simple to pass
* const pointers, appearing in read functions. Then this "const" is
* cast away by QEMU_IOVEC_INIT_BUF().
*/
static inline void qemu_iovec_init_buf(QEMUIOVector *qiov,
const void *buf, size_t len)
{
*qiov = (QEMUIOVector) QEMU_IOVEC_INIT_BUF(*qiov, buf, len);
}
static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
{
/* Only supports embedded iov */
assert(qiov->nalloc == -1 && qiov->iov == &qiov->local_iov);
return qiov->local_iov.iov_base;
}
void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
int qemu_iovec_init_extended(
QEMUIOVector *qiov,
void *head_buf, size_t head_len,
QEMUIOVector *mid_qiov, size_t mid_offset, size_t mid_len,
void *tail_buf, size_t tail_len);
void qemu_iovec_init_slice(QEMUIOVector *qiov, QEMUIOVector *source,
size_t offset, size_t len);
int qemu_iovec_subvec_niov(QEMUIOVector *qiov, size_t offset, size_t len);
void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);
void qemu_iovec_concat(QEMUIOVector *dst,
QEMUIOVector *src, size_t soffset, size_t sbytes);
size_t qemu_iovec_concat_iov(QEMUIOVector *dst,
struct iovec *src_iov, unsigned int src_cnt,
size_t soffset, size_t sbytes);
bool qemu_iovec_is_zero(QEMUIOVector *qiov, size_t qiov_offeset, size_t bytes);
void qemu_iovec_destroy(QEMUIOVector *qiov);
void qemu_iovec_reset(QEMUIOVector *qiov);
size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
void *buf, size_t bytes);
size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
const void *buf, size_t bytes);
size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
int fillc, size_t bytes);
ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b);
void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf);
void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes);
#endif
