perf: introduce safeattrsetter to replace direct attribute assignment
Referring not-existing attribute immediately causes failure, but
assigning a value to such attribute doesn't.
For example, perf.py has code paths below, which assign a value to
not-existing attribute. This causes incorrect performance measurement,
but these code paths are executed successfully.
- "repo._tags = None" in perftags()
recent Mercurial has tags cache information in repo._tagscache
- "branchmap.write = lambda repo: None" in perfbranchmap()
branchmap cache is written out by branchcache.write() in branchmap.py
"util.safehasattr() before assignment" can avoid this issue, but might
increase mistake at "copy & paste" attribute name or so.
To centralize (1) examining existence of, (2) assigning a value to,
and (3) restoring an old value to the attribute, this patch introduces
safeattrsetter(). This is used to replace direct attribute assignment
in subsequent patches.
Encapsulation of restoring is needed to completely remove direct
attribute assignment from perf.py, even though restoring isn't needed
so often.
from __future__ import absolute_import
import cffi
import os
ffi = cffi.FFI()
mpatch_c = os.path.join(os.path.join(os.path.dirname(__file__), 'mercurial',
'mpatch.c'))
ffi.set_source("_mpatch_cffi", 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()