[Qemu-devel] [PATCHv2 0/7] cleanup/consolidate some iovec functions

[Michael Tokarev]

This is a little cleanup/consolidation for some iovec-related
low-level routines in qemu.

The plan is to make library functions more understandable,
consistent and useful.

The patch changes prototypes of several iov and qiov functions
to match each other, changes types of arguments for some
functions, _swaps_ some function arguments with each other,
and makes use of common code in r/w path.

The result of all these changes.

1. Most qiov-related (qemu_iovec_*) functions now accepts
 'offset' parameter to specify from which (byte) position to
 start operation.  This is added for _memset (removing
 _memset_skip), _from_buffer (allowing to copy a bounce-
 buffer to a middle of qiov).  Typical:

  void qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, int c, size_t 
bytes);

2. All functions that accepts this `offset' argument does
 it in a similar manner, following the
   iov,fromwhere,bytes
 pattern.  This is consistent with (updated) qemu_sendv()
 and qemu_recvv() and friends, where `offset' and `bytes'
 arguments were _renamed_, with the following prototypes:

   int qemu_sendv(sockfd, iov, size_t offset, size_t bytes)

 instead of

   int qemu_sendv(sockfd, iov, int len, int iov_offset)

 See how offset & bytes are used in the same way as for qemu_iovec_*
 A few callers of these are verified and converted.

3. Used size_t instead of various variations for byte counts.
 Including qemu_iovec_copy which used uint64_t(!) type.

4. Function arguments are renamed to better match with their
 actual meaning.  Compare new and original prototype of
 qemu_sendv() above: old prototype with `len' does not
 tell if `len' refers to number of iov elements (as
 regular writev() call) or to number of data bytes.
 Ditto for several usages of `count' for some qemu_iovec_*,
 which is also replaced to `bytes'.

The resulting function usage is much more consistent, the
functions themselves are nice and understandable, which
means they're easier to use and less error-prone.

This patchset also consolidates a few low-level send&recv
functions into one, since both versions were exactly
the same (and were finally calling common function anyway).
This is done by exporting a common send_recv function with
one extra bool argument, and making current send&recv to
be just #defines.

And while at it all, also made some implementations shorter,
cleaner and much easier to read/understand, and add some
code comments.

The read&write consolidation has great potential for the
block layer, as has been demonstrated before.
Unification and generalization of qemu_iovec_* functions
will let to optimize/simplify some more code in block/*,
especially qemu_iovec_memset() and _from_buffer() (this
optimization/simplification isn't done in this series)

Michael Tokarev (7):
  Consolidate qemu_iovec_memset{,_skip}() into single, simplified function
  allow qemu_iovec_from_buffer() to specify offset from which to start copying
  consolidate qemu_iovec_copy() and qemu_iovec_concat() and make them consistent
  change prototypes of qemu_sendv() and qemu_recvv()
  Export qemu_sendv_recvv() and use it in qemu_sendv() and qemu_recvv()
  cleanup qemu_co_sendv(), qemu_co_recvv() and friends
  rewrite and comment qemu_sendv_recvv()

 block.c             |    8 +-
 block/curl.c        |    4 +-
 block/nbd.c         |    4 +-
 block/qcow.c        |    2 +-
 block/qcow2.c       |   14 ++--
 block/qed.c         |   10 +-
 block/sheepdog.c    |    6 +-
 block/vdi.c         |    2 +-
 cutils.c            |  275 +++++++++++++++++++++------------------------------
 hw/9pfs/virtio-9p.c |    8 +-
 linux-aio.c         |    4 +-
 posix-aio-compat.c  |    2 +-
 qemu-common.h       |   64 +++++++-----
 qemu-coroutine-io.c |   83 ++++-----------
 14 files changed, 205 insertions(+), 281 deletions(-)

-- 
1.7.9.1