Mercurial > hg
view mercurial/cext/util.h @ 39559:07b58266bce3
wireprotov2: implement commands as a generator of objects
Previously, wire protocol version 2 inherited version 1's model of
having separate types to represent the results of different wire
protocol commands.
As I implemented more powerful commands in future commits, I found
I was using a common pattern of returning a special type to hold a
generator. This meant the command function required a closure to
do most of the work. That made logic flow more difficult to follow.
I also noticed that many commands were effectively a sequence of
objects to be CBOR encoded.
I think it makes sense to define version 2 commands as generators.
This way, commands can simply emit the data structures they wish to
send to the client. This eliminates the need for a closure in
command functions and removes encoding from the bodies of commands.
As part of this commit, the handling of response objects has been
moved into the serverreactor class. This puts the reactor in the
driver's seat with regards to CBOR encoding and error handling.
Having error handling in the function that emits frames is
particularly important because exceptions in that function can lead
to things getting in a bad state: I'm fairly certain that uncaught
exceptions in the frame generator were causing deadlocks.
I also introduced a dedicated error type for explicit error reporting
in command handlers. This will be used in subsequent commits.
There's still a bit of work to be done here, especially around
formalizing the error handling "protocol." I've added yet another
TODO to track this so we don't forget.
Test output changed because we're using generators and no longer know
we are at the end of the data until we hit the end of the generator.
This means we can't emit the end-of-stream flag until we've exhausted
the generator. Hence the introduction of 0-sized end-of-stream frames.
Differential Revision: https://phab.mercurial-scm.org/D4472
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Wed, 05 Sep 2018 09:06:40 -0700 |
parents | 9a639a33ad1f |
children | fa33196088c4 |
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/* util.h - utility functions for interfacing with the various python APIs. This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. */ #ifndef _HG_UTIL_H_ #define _HG_UTIL_H_ #include "compat.h" #if PY_MAJOR_VERSION >= 3 #define IS_PY3K #endif /* helper to switch things like string literal depending on Python version */ #ifdef IS_PY3K #define PY23(py2, py3) py3 #else #define PY23(py2, py3) py2 #endif /* clang-format off */ typedef struct { PyObject_HEAD char state; int mode; int size; int mtime; } dirstateTupleObject; /* clang-format on */ extern PyTypeObject dirstateTupleType; #define dirstate_tuple_check(op) (Py_TYPE(op) == &dirstateTupleType) #ifndef MIN #define MIN(a, b) (((a) < (b)) ? (a) : (b)) #endif /* VC9 doesn't include bool and lacks stdbool.h based on my searching */ #if defined(_MSC_VER) || __STDC_VERSION__ < 199901L #define true 1 #define false 0 typedef unsigned char bool; #else #include <stdbool.h> #endif static inline PyObject *_dict_new_presized(Py_ssize_t expected_size) { /* _PyDict_NewPresized expects a minused parameter, but it actually creates a dictionary that's the nearest power of two bigger than the parameter. For example, with the initial minused = 1000, the dictionary created has size 1024. Of course in a lot of cases that can be greater than the maximum load factor Python's dict object expects (= 2/3), so as soon as we cross the threshold we'll resize anyway. So create a dictionary that's at least 3/2 the size. */ return _PyDict_NewPresized(((1 + expected_size) / 2) * 3); } #endif /* _HG_UTIL_H_ */