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
#require mtn
Monotone directory is called .monotone on *nix and monotone
on Windows.
#if windows
$ mtndir=monotone
#else
$ mtndir=.monotone
#endif
$ echo "[extensions]" >> $HGRCPATH
$ echo "convert=" >> $HGRCPATH
Windows version of monotone home
$ APPDATA=$HOME; export APPDATA
tedious monotone keys configuration
The /dev/null redirection is necessary under Windows, or
it complains about home directory permissions
$ mtn --quiet genkey test@selenic.com 1>/dev/null 2>&1 <<EOF
> passphrase
> passphrase
> EOF
$ cat >> $HOME/$mtndir/monotonerc <<EOF
> function get_passphrase(keypair_id)
> return "passphrase"
> end
> EOF
create monotone repository
$ mtn db init --db=repo.mtn
$ mtn --db=repo.mtn --branch=com.selenic.test setup workingdir
$ cd workingdir
$ echo a > a
$ mkdir dir
$ echo b > dir/b
$ echo d > dir/d
$ $PYTHON -c 'open("bin", "wb").write(b"a\\x00b")'
$ echo c > c
$ mtn add a dir/b dir/d c bin
mtn: adding 'a' to workspace manifest
mtn: adding 'bin' to workspace manifest
mtn: adding 'c' to workspace manifest
mtn: adding 'dir' to workspace manifest
mtn: adding 'dir/b' to workspace manifest
mtn: adding 'dir/d' to workspace manifest
$ mtn ci -m initialize
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 0f6e5e4f2e7d2a8ef312408f57618abf026afd90
update monotone working directory
$ mtn mv a dir/a
mtn: skipping 'dir', already accounted for in workspace
mtn: renaming 'a' to 'dir/a' in workspace manifest
$ echo a >> dir/a
$ echo b >> dir/b
$ mtn drop c
mtn: dropping 'c' from workspace manifest
$ $PYTHON -c 'open("bin", "wb").write(b"b\\x00c")'
$ mtn ci -m update1
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 51d0a982464573a2a2cf5ee2c9219c652aaebeff
$ cd ..
convert once
$ hg convert -s mtn repo.mtn
assuming destination repo.mtn-hg
initializing destination repo.mtn-hg repository
scanning source...
sorting...
converting...
1 initialize
0 update1
$ cd workingdir
$ echo e > e
$ mtn add e
mtn: adding 'e' to workspace manifest
$ mtn drop dir/b
mtn: dropping 'dir/b' from workspace manifest
$ mtn mv bin bin2
mtn: renaming 'bin' to 'bin2' in workspace manifest
$ mtn ci -m 'update2 "with" quotes'
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision ebe58335d85d8cb176b6d0a12be04f5314b998da
test directory move
$ mkdir -p dir1/subdir1
$ mkdir -p dir1/subdir2_other
$ echo file1 > dir1/subdir1/file1
$ echo file2 > dir1/subdir2_other/file1
$ mtn add dir1/subdir1/file1 dir1/subdir2_other/file1
mtn: adding 'dir1' to workspace manifest
mtn: adding 'dir1/subdir1' to workspace manifest
mtn: adding 'dir1/subdir1/file1' to workspace manifest
mtn: adding 'dir1/subdir2_other' to workspace manifest
mtn: adding 'dir1/subdir2_other/file1' to workspace manifest
$ mtn ci -m createdir1
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision a8d62bc04fee4d2936d28e98bbcc81686dd74306
$ mtn rename dir1/subdir1 dir1/subdir2
mtn: skipping 'dir1', already accounted for in workspace
mtn: renaming 'dir1/subdir1' to 'dir1/subdir2' in workspace manifest
$ mtn ci -m movedir1
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 2c3d241bbbfe538b1b51d910f5676407e3f4d3a6
test subdirectory move
$ mtn mv dir dir2
mtn: renaming 'dir' to 'dir2' in workspace manifest
$ echo newfile > dir2/newfile
$ mtn drop dir2/d
mtn: dropping 'dir2/d' from workspace manifest
$ mtn add dir2/newfile
mtn: adding 'dir2/newfile' to workspace manifest
$ mtn ci -m movedir
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision fdb5a02dae8bfce3a79b3393680af471016e1b4c
Test directory removal with empty directory
$ mkdir dir2/dir
$ mkdir dir2/dir/subdir
$ echo f > dir2/dir/subdir/f
$ mkdir dir2/dir/emptydir
$ mtn add --quiet -R dir2/dir
$ mtn ci -m emptydir
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 8bbf76d717001d24964e4604739fdcd0f539fc88
$ mtn drop -R dir2/dir
mtn: dropping 'dir2/dir/subdir/f' from workspace manifest
mtn: dropping 'dir2/dir/subdir' from workspace manifest
mtn: dropping 'dir2/dir/emptydir' from workspace manifest
mtn: dropping 'dir2/dir' from workspace manifest
$ mtn ci -m dropdirectory
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 2323d4bc324e6c82628dc04d47a9fd32ad24e322
test directory and file move
$ mkdir -p dir3/d1
$ echo a > dir3/a
$ mtn add dir3/a dir3/d1
mtn: adding 'dir3' to workspace manifest
mtn: adding 'dir3/a' to workspace manifest
mtn: adding 'dir3/d1' to workspace manifest
$ mtn ci -m dirfilemove
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 47b192f720faa622f48c68d1eb075b26d405aa8b
$ mtn mv dir3/a dir3/d1/a
mtn: skipping 'dir3/d1', already accounted for in workspace
mtn: renaming 'dir3/a' to 'dir3/d1/a' in workspace manifest
$ mtn mv dir3/d1 dir3/d2
mtn: skipping 'dir3', already accounted for in workspace
mtn: renaming 'dir3/d1' to 'dir3/d2' in workspace manifest
$ mtn ci -m dirfilemove2
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 8b543a400d3ee7f6d4bb1835b9b9e3747c8cb632
test directory move into another directory move
$ mkdir dir4
$ mkdir dir5
$ echo a > dir4/a
$ mtn add dir4/a dir5
mtn: adding 'dir4' to workspace manifest
mtn: adding 'dir4/a' to workspace manifest
mtn: adding 'dir5' to workspace manifest
$ mtn ci -m dirdirmove
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 466e0b2afc7a55aa2b4ab2f57cb240bb6cd66fc7
$ mtn mv dir5 dir6
mtn: renaming 'dir5' to 'dir6' in workspace manifest
$ mtn mv dir4 dir6/dir4
mtn: skipping 'dir6', already accounted for in workspace
mtn: renaming 'dir4' to 'dir6/dir4' in workspace manifest
$ mtn ci -m dirdirmove2
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 3d1f77ebad0c23a5d14911be3b670f990991b749
test diverging directory moves
$ mkdir -p dir7/dir9/dir8
$ echo a > dir7/dir9/dir8/a
$ echo b > dir7/dir9/b
$ echo c > dir7/c
$ mtn add -R dir7
mtn: adding 'dir7' to workspace manifest
mtn: adding 'dir7/c' to workspace manifest
mtn: adding 'dir7/dir9' to workspace manifest
mtn: adding 'dir7/dir9/b' to workspace manifest
mtn: adding 'dir7/dir9/dir8' to workspace manifest
mtn: adding 'dir7/dir9/dir8/a' to workspace manifest
$ mtn ci -m divergentdirmove
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 08a08511f18b428d840199b062de90d0396bc2ed
$ mtn mv dir7 dir7-2
mtn: renaming 'dir7' to 'dir7-2' in workspace manifest
$ mtn mv dir7-2/dir9 dir9-2
mtn: renaming 'dir7-2/dir9' to 'dir9-2' in workspace manifest
$ mtn mv dir9-2/dir8 dir8-2
mtn: renaming 'dir9-2/dir8' to 'dir8-2' in workspace manifest
$ mtn ci -m divergentdirmove2
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision 4a736634505795f17786fffdf2c9cbf5b11df6f6
test large file support (> 32kB)
>>> fp = open('large-file', 'wb')
>>> for x in range(10000): fp.write(b'%d\n' % x)
>>> fp.close()
$ md5sum.py large-file
5d6de8a95c3b6bf9e0ffb808ba5299c1 large-file
$ mtn add large-file
mtn: adding 'large-file' to workspace manifest
$ mtn ci -m largefile
mtn: beginning commit on branch 'com.selenic.test'
mtn: committed revision f0a20fecd10dc4392d18fe69a03f1f4919d3387b
test suspending (closing a branch)
$ mtn suspend f0a20fecd10dc4392d18fe69a03f1f4919d3387b 2> /dev/null
$ cd ..
convert incrementally
$ hg convert -s mtn repo.mtn
assuming destination repo.mtn-hg
scanning source...
sorting...
converting...
12 update2 "with" quotes
11 createdir1
10 movedir1
9 movedir
8 emptydir
7 dropdirectory
6 dirfilemove
5 dirfilemove2
4 dirdirmove
3 dirdirmove2
2 divergentdirmove
1 divergentdirmove2
0 largefile
$ glog()
> {
> hg log -G --template '{rev} "{desc|firstline}" files: {files}\n' "$@"
> }
$ cd repo.mtn-hg
$ hg up -C
12 files updated, 0 files merged, 0 files removed, 0 files unresolved
no open descendant heads on branch "com.selenic.test", updating to a closed head
(committing will reopen branch "com.selenic.test")
$ glog
@ 14 "largefile" files: large-file
|
o 13 "divergentdirmove2" files: dir7-2/c dir7/c dir7/dir9/b dir7/dir9/dir8/a dir8-2/a dir9-2/b
|
o 12 "divergentdirmove" files: dir7/c dir7/dir9/b dir7/dir9/dir8/a
|
o 11 "dirdirmove2" files: dir4/a dir6/dir4/a
|
o 10 "dirdirmove" files: dir4/a
|
o 9 "dirfilemove2" files: dir3/a dir3/d2/a
|
o 8 "dirfilemove" files: dir3/a
|
o 7 "dropdirectory" files: dir2/dir/subdir/f
|
o 6 "emptydir" files: dir2/dir/subdir/f
|
o 5 "movedir" files: dir/a dir/d dir2/a dir2/newfile
|
o 4 "movedir1" files: dir1/subdir1/file1 dir1/subdir2/file1
|
o 3 "createdir1" files: dir1/subdir1/file1 dir1/subdir2_other/file1
|
o 2 "update2 "with" quotes" files: bin bin2 dir/b e
|
o 1 "update1" files: a bin c dir/a dir/b
|
o 0 "initialize" files: a bin c dir/b dir/d
manifest
$ hg manifest
bin2
dir1/subdir2/file1
dir1/subdir2_other/file1
dir2/a
dir2/newfile
dir3/d2/a
dir6/dir4/a
dir7-2/c
dir8-2/a
dir9-2/b
e
large-file
contents
$ cat dir2/a
a
a
$ test -d dir2/dir && echo 'removed dir2/dir is still there!'
[1]
file move
$ hg log -v -C -r 1 | grep copies
copies: dir/a (a)
check directory move
$ hg manifest -r 4
bin2
dir/a
dir/d
dir1/subdir2/file1
dir1/subdir2_other/file1
e
$ test -d dir1/subdir2 || echo 'new dir1/subdir2 does not exist!'
$ test -d dir1/subdir1 && echo 'renamed dir1/subdir1 is still there!'
[1]
$ hg log -v -C -r 4 | grep copies
copies: dir1/subdir2/file1 (dir1/subdir1/file1)
check file remove with directory move
$ hg manifest -r 5
bin2
dir1/subdir2/file1
dir1/subdir2_other/file1
dir2/a
dir2/newfile
e
check file move with directory move
$ hg manifest -r 9
bin2
dir1/subdir2/file1
dir1/subdir2_other/file1
dir2/a
dir2/newfile
dir3/d2/a
e
check file directory directory move
$ hg manifest -r 11
bin2
dir1/subdir2/file1
dir1/subdir2_other/file1
dir2/a
dir2/newfile
dir3/d2/a
dir6/dir4/a
e
check divergent directory moves
$ hg manifest -r 13
bin2
dir1/subdir2/file1
dir1/subdir2_other/file1
dir2/a
dir2/newfile
dir3/d2/a
dir6/dir4/a
dir7-2/c
dir8-2/a
dir9-2/b
e
test large file support (> 32kB)
$ md5sum.py large-file
5d6de8a95c3b6bf9e0ffb808ba5299c1 large-file
check branch closing
$ hg branches -a
$ hg branches -c
com.selenic.test 14:* (closed) (glob)