cborutil: implement sans I/O decoder
The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:
* Uses blocking I/O. If sufficient data is not available, the decoder
will hang until it is.
* No support for partial reads. If the read(n) returns less data than
requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
decoder.
In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:
* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
property is useful when implementing a "hardened" decoder that is
less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
institute checks around behavior. These are useful for implementing
a "hardened" decoder.
This all adds up to a reasonable set of justifications for writing our
own decoder.
So, this commit implements our own CBOR decoder.
At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.
The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.
I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.
I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.
Differential Revision: https://phab.mercurial-scm.org/D4414
$ cat > loop.py <<EOF
> from __future__ import absolute_import
> import time
> from mercurial import commands, registrar
>
> cmdtable = {}
> command = registrar.command(cmdtable)
>
> class incrementingtime(object):
> def __init__(self):
> self._time = 0.0
> def __call__(self):
> self._time += 0.25
> return self._time
> time.time = incrementingtime()
>
> @command(b'loop',
> [(b'', b'total', b'', b'override for total'),
> (b'', b'nested', False, b'show nested results'),
> (b'', b'parallel', False, b'show parallel sets of results')],
> b'hg loop LOOPS',
> norepo=True)
> def loop(ui, loops, **opts):
> loops = int(loops)
> total = None
> if loops >= 0:
> total = loops
> if opts.get('total', None):
> total = int(opts.get('total'))
> nested = False
> if opts.get('nested', None):
> nested = True
> loops = abs(loops)
>
> progress = ui.makeprogress(topiclabel, unit='loopnum', total=total)
> other = ui.makeprogress('other', unit='othernum', total=total)
> for i in range(loops):
> progress.update(i, item=getloopitem(i))
> if opts.get('parallel'):
> other.update(i, item='other.%d' % i)
> if nested:
> nested_steps = 2
> if i and i % 4 == 0:
> nested_steps = 5
> nested = ui.makeprogress('nested', unit='nestnum',
> total=nested_steps)
> for j in range(nested_steps):
> nested.update(j, item='nested.%d' % j)
> nested.complete()
> progress.complete()
>
> topiclabel = 'loop'
> def getloopitem(i):
> return 'loop.%d' % i
>
> EOF
$ cp $HGRCPATH $HGRCPATH.orig
$ echo "[extensions]" >> $HGRCPATH
$ echo "progress=" >> $HGRCPATH
$ echo "loop=`pwd`/loop.py" >> $HGRCPATH
$ echo "[progress]" >> $HGRCPATH
$ echo "format = topic bar number" >> $HGRCPATH
$ echo "assume-tty=1" >> $HGRCPATH
$ echo "width=60" >> $HGRCPATH
test default params, display nothing because of delay
$ hg -y loop 3
$ echo "delay=0" >> $HGRCPATH
$ echo "refresh=0" >> $HGRCPATH
test with delay=0, refresh=0
$ hg -y loop 3
\r (no-eol) (esc)
loop [ ] 0/3\r (no-eol) (esc)
loop [===============> ] 1/3\r (no-eol) (esc)
loop [===============================> ] 2/3\r (no-eol) (esc)
\r (no-eol) (esc)
no progress with --quiet
$ hg -y loop 3 --quiet
test plain mode exception
$ HGPLAINEXCEPT=progress hg -y loop 1
\r (no-eol) (esc)
loop [ ] 0/1\r (no-eol) (esc)
\r (no-eol) (esc)
test nested short-lived topics (which shouldn't display with nestdelay):
$ hg -y loop 3 --nested
\r (no-eol) (esc)
loop [ ] 0/3\r (no-eol) (esc)
loop [===============> ] 1/3\r (no-eol) (esc)
loop [===============================> ] 2/3\r (no-eol) (esc)
\r (no-eol) (esc)
Test nested long-lived topic which has the same name as a short-lived
peer. We shouldn't get stuck showing the short-lived inner steps, and
should go back to skipping the inner steps when the slow nested step
finishes.
$ hg -y loop 7 --nested
\r (no-eol) (esc)
loop [ ] 0/7\r (no-eol) (esc)
loop [=====> ] 1/7\r (no-eol) (esc)
loop [============> ] 2/7\r (no-eol) (esc)
loop [===================> ] 3/7\r (no-eol) (esc)
loop [==========================> ] 4/7\r (no-eol) (esc)
nested [==========================> ] 3/5\r (no-eol) (esc)
nested [===================================> ] 4/5\r (no-eol) (esc)
loop [=================================> ] 5/7\r (no-eol) (esc)
loop [========================================> ] 6/7\r (no-eol) (esc)
\r (no-eol) (esc)
$ hg --config progress.changedelay=0 -y loop 3 --nested
\r (no-eol) (esc)
loop [ ] 0/3\r (no-eol) (esc)
nested [ ] 0/2\r (no-eol) (esc)
nested [======================> ] 1/2\r (no-eol) (esc)
loop [===============> ] 1/3\r (no-eol) (esc)
nested [ ] 0/2\r (no-eol) (esc)
nested [======================> ] 1/2\r (no-eol) (esc)
loop [===============================> ] 2/3\r (no-eol) (esc)
nested [ ] 0/2\r (no-eol) (esc)
nested [======================> ] 1/2\r (no-eol) (esc)
\r (no-eol) (esc)
test two topics being printed in parallel (as when we're doing a local
--pull clone, where you get the unbundle and bundle progress at the
same time):
$ hg loop 3 --parallel
\r (no-eol) (esc)
loop [ ] 0/3\r (no-eol) (esc)
loop [===============> ] 1/3\r (no-eol) (esc)
loop [===============================> ] 2/3\r (no-eol) (esc)
\r (no-eol) (esc)
test refresh is taken in account
$ hg -y --config progress.refresh=100 loop 3
test format options 1
$ hg -y --config 'progress.format=number topic item+2' loop 2
\r (no-eol) (esc)
0/2 loop lo\r (no-eol) (esc)
1/2 loop lo\r (no-eol) (esc)
\r (no-eol) (esc)
test format options 2
$ hg -y --config 'progress.format=number item-3 bar' loop 2
\r (no-eol) (esc)
0/2 p.0 [ ]\r (no-eol) (esc)
1/2 p.1 [=======================> ]\r (no-eol) (esc)
\r (no-eol) (esc)
test format options and indeterminate progress
$ hg -y --config 'progress.format=number item bar' loop -- -2
\r (no-eol) (esc)
0 loop.0 [ <=> ]\r (no-eol) (esc)
1 loop.1 [ <=> ]\r (no-eol) (esc)
\r (no-eol) (esc)
make sure things don't fall over if count > total
$ hg -y loop --total 4 6
\r (no-eol) (esc)
loop [ ] 0/4\r (no-eol) (esc)
loop [===========> ] 1/4\r (no-eol) (esc)
loop [=======================> ] 2/4\r (no-eol) (esc)
loop [===================================> ] 3/4\r (no-eol) (esc)
loop [===============================================>] 4/4\r (no-eol) (esc)
loop [ <=> ] 5/4\r (no-eol) (esc)
\r (no-eol) (esc)
test immediate progress completion
$ hg -y loop 0
test delay time estimates
#if no-chg
$ cp $HGRCPATH.orig $HGRCPATH
$ echo "[extensions]" >> $HGRCPATH
$ echo "mocktime=$TESTDIR/mocktime.py" >> $HGRCPATH
$ echo "progress=" >> $HGRCPATH
$ echo "loop=`pwd`/loop.py" >> $HGRCPATH
$ echo "[progress]" >> $HGRCPATH
$ echo "assume-tty=1" >> $HGRCPATH
$ echo "delay=25" >> $HGRCPATH
$ echo "width=60" >> $HGRCPATH
$ MOCKTIME=11 hg -y loop 8
\r (no-eol) (esc)
loop [=========> ] 2/8 1m07s\r (no-eol) (esc)
loop [===============> ] 3/8 56s\r (no-eol) (esc)
loop [=====================> ] 4/8 45s\r (no-eol) (esc)
loop [==========================> ] 5/8 34s\r (no-eol) (esc)
loop [================================> ] 6/8 23s\r (no-eol) (esc)
loop [=====================================> ] 7/8 12s\r (no-eol) (esc)
\r (no-eol) (esc)
$ MOCKTIME=10000 hg -y loop 4
\r (no-eol) (esc)
loop [ ] 0/4\r (no-eol) (esc)
loop [=========> ] 1/4 8h21m\r (no-eol) (esc)
loop [====================> ] 2/4 5h34m\r (no-eol) (esc)
loop [==============================> ] 3/4 2h47m\r (no-eol) (esc)
\r (no-eol) (esc)
$ MOCKTIME=1000000 hg -y loop 4
\r (no-eol) (esc)
loop [ ] 0/4\r (no-eol) (esc)
loop [=========> ] 1/4 5w00d\r (no-eol) (esc)
loop [====================> ] 2/4 3w03d\r (no-eol) (esc)
loop [=============================> ] 3/4 11d14h\r (no-eol) (esc)
\r (no-eol) (esc)
$ MOCKTIME=14000000 hg -y loop 4
\r (no-eol) (esc)
loop [ ] 0/4\r (no-eol) (esc)
loop [=========> ] 1/4 1y18w\r (no-eol) (esc)
loop [===================> ] 2/4 46w03d\r (no-eol) (esc)
loop [=============================> ] 3/4 23w02d\r (no-eol) (esc)
\r (no-eol) (esc)
Non-linear progress:
$ MOCKTIME='20 20 20 20 20 20 20 20 20 20 500 500 500 500 500 20 20 20 20 20' hg -y loop 20
\r (no-eol) (esc)
loop [=> ] 1/20 6m21s\r (no-eol) (esc)
loop [===> ] 2/20 6m01s\r (no-eol) (esc)
loop [=====> ] 3/20 5m41s\r (no-eol) (esc)
loop [=======> ] 4/20 5m21s\r (no-eol) (esc)
loop [=========> ] 5/20 5m01s\r (no-eol) (esc)
loop [===========> ] 6/20 4m41s\r (no-eol) (esc)
loop [=============> ] 7/20 4m21s\r (no-eol) (esc)
loop [===============> ] 8/20 4m01s\r (no-eol) (esc)
loop [================> ] 9/20 25m40s\r (no-eol) (esc)
loop [===================> ] 10/20 1h06m\r (no-eol) (esc)
loop [=====================> ] 11/20 1h13m\r (no-eol) (esc)
loop [=======================> ] 12/20 1h07m\r (no-eol) (esc)
loop [========================> ] 13/20 58m19s\r (no-eol) (esc)
loop [===========================> ] 14/20 7m09s\r (no-eol) (esc)
loop [=============================> ] 15/20 3m38s\r (no-eol) (esc)
loop [===============================> ] 16/20 2m15s\r (no-eol) (esc)
loop [=================================> ] 17/20 1m27s\r (no-eol) (esc)
loop [====================================> ] 18/20 52s\r (no-eol) (esc)
loop [======================================> ] 19/20 25s\r (no-eol) (esc)
\r (no-eol) (esc)
Time estimates should not fail when there's no end point:
$ MOCKTIME=11 hg -y loop -- -4
\r (no-eol) (esc)
loop [ <=> ] 2\r (no-eol) (esc)
loop [ <=> ] 3\r (no-eol) (esc)
\r (no-eol) (esc)
#endif
test line trimming by '[progress] width', when progress topic contains
multi-byte characters, of which length of byte sequence and columns in
display are different from each other.
$ cp $HGRCPATH.orig $HGRCPATH
$ cat >> $HGRCPATH <<EOF
> [extensions]
> progress=
> loop=`pwd`/loop.py
> [progress]
> assume-tty = 1
> delay = 0
> refresh = 0
> EOF
$ rm -f loop.pyc
$ cat >> loop.py <<EOF
> # use non-ascii characters as topic label of progress
> # 2 x 4 = 8 columns, but 3 x 4 = 12 bytes
> topiclabel = u'\u3042\u3044\u3046\u3048'.encode('utf-8')
> EOF
$ cat >> $HGRCPATH <<EOF
> [progress]
> format = topic number
> width= 12
> EOF
$ hg --encoding utf-8 -y loop --total 3 3
\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 0/3\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 1/3\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 2/3\r (no-eol) (esc)
\r (no-eol) (esc)
test calculation of bar width, when progress topic contains multi-byte
characters, of which length of byte sequence and columns in display
are different from each other.
$ cat >> $HGRCPATH <<EOF
> [progress]
> format = topic bar
> width= 21
> # progwidth should be 9 (= 21 - (8+1) - 3)
> EOF
$ hg --encoding utf-8 -y loop --total 3 3
\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [ ]\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [==> ]\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88 [=====> ]\r (no-eol) (esc)
\r (no-eol) (esc)
test trimming progress items, when they contain multi-byte characters,
of which length of byte sequence and columns in display are different
from each other.
$ rm -f loop.pyc
$ rm -Rf __pycache__
$ cat >> loop.py <<EOF
> # use non-ascii characters as loop items of progress
> loopitems = [
> u'\u3042\u3044'.encode('utf-8'), # 2 x 2 = 4 columns
> u'\u3042\u3044\u3046'.encode('utf-8'), # 2 x 3 = 6 columns
> u'\u3042\u3044\u3046\u3048'.encode('utf-8'), # 2 x 4 = 8 columns
> ]
> def getloopitem(i):
> return loopitems[i % len(loopitems)]
> EOF
$ cat >> $HGRCPATH <<EOF
> [progress]
> # trim at tail side
> format = item+6
> EOF
$ hg --encoding utf-8 -y loop --total 3 3
\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84 \r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
\r (no-eol) (esc)
$ cat >> $HGRCPATH <<EOF
> [progress]
> # trim at left side
> format = item-6
> EOF
$ hg --encoding utf-8 -y loop --total 3 3
\r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84 \r (no-eol) (esc)
\xe3\x81\x82\xe3\x81\x84\xe3\x81\x86\r (no-eol) (esc)
\xe3\x81\x84\xe3\x81\x86\xe3\x81\x88\r (no-eol) (esc)
\r (no-eol) (esc)