mercurial/cffi/mpatchbuild.py

cmdutil: convert _revertprefetch() to a generic stored file hook (API)

This will be used by LFS to fetch required files in a group for multiple
commands, prior to being accessed.  That avoids the one-at-a-time fetch when the
filelog wrapper goes to access it, and it is missing locally (which costs two
round trips to the server.)  The core command list that needs this is probably
at least:

  - annotate
  - archive (which is also used by extdiff)
  - cat
  - diff
  - export
  - grep
  - verify (sadly)
  - anything that has the '{data}' template

There are no core users of the revert prefetch hook, and never have been since
it was introduced in 45e02cfad4bd for remotefilelog.  Thanks to Yuya for
figuring out a way to reliably trigger the deprecated warning.  Unfortunately,
it wanted to blame the caller of revert.  Passing along an adjusted stack level
seemed the least bad choice (although it still blames a core function).

One thing to note is that the store lock isn't being held when this is called.
I'm not at all familiar with remotefilelog or its locking requirements, so this
may not be a big deal.  Currently, LFS doesn't hold a lock when downloading
files.  Even though largefiles doesn't either, I'm starting to think it should,
and maybe the .hg/store/lock isn't good enough to cover the globally shared
cache.

.. api::

   The cmdutil._revertprefetch() hook point for prefetching stored files has
   been replaced by the command agnostic cmdutil._prefetchfiles().  The new
   function takes a list of files, instead of a list of lists of files.

from __future__ import absolute_import

import cffi
import os

ffi = cffi.FFI()
mpatch_c = os.path.join(os.path.join(os.path.dirname(__file__), '..',
                                     'mpatch.c'))
ffi.set_source("mercurial.cffi._mpatch", open(mpatch_c).read(),
               include_dirs=["mercurial"])
ffi.cdef("""

struct mpatch_frag {
       int start, end, len;
       const char *data;
};

struct mpatch_flist {
       struct mpatch_frag *base, *head, *tail;
};

extern "Python" struct mpatch_flist* cffi_get_next_item(void*, ssize_t);

int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist** res);
ssize_t mpatch_calcsize(size_t len, struct mpatch_flist *l);
void mpatch_lfree(struct mpatch_flist *a);
static int mpatch_apply(char *buf, const char *orig, size_t len,
                        struct mpatch_flist *l);
struct mpatch_flist *mpatch_fold(void *bins,
                       struct mpatch_flist* (*get_next_item)(void*, ssize_t),
                       ssize_t start, ssize_t end);
""")

if __name__ == '__main__':
    ffi.compile()