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 icasefs
$ hg debugfs | grep 'case-sensitive:'
case-sensitive: no
test file addition with bad case
$ hg init repo1
$ cd repo1
$ echo a > a
$ hg add A
$ hg st
A a
$ hg ci -m adda
$ hg manifest
a
$ cd ..
test case collision on rename (issue750)
$ hg init repo2
$ cd repo2
$ echo a > a
$ hg --debug ci -Am adda
adding a
committing files:
a
committing manifest
committing changelog
updating the branch cache
committed changeset 0:07f4944404050f47db2e5c5071e0e84e7a27bba9
Case-changing renames should work:
$ hg mv a A
$ hg mv A a
$ hg st
addremove after case-changing rename has no effect (issue4590)
$ hg mv a A
$ hg addremove
recording removal of a as rename to A (100% similar)
$ hg revert --all
forgetting A
undeleting a
test changing case of path components
$ mkdir D
$ echo b > D/b
$ hg ci -Am addb D/b
$ hg mv D/b d/b
D/b: not overwriting - file already committed
('hg rename --force' to replace the file by recording a rename)
[1]
$ hg mv D/b d/c
$ hg st
A D/c
R D/b
$ mv D temp
$ mv temp d
$ hg st
A D/c
R D/b
$ hg revert -aq
$ rm d/c
$ echo c > D/c
$ hg add D/c
$ hg st
A D/c
$ hg ci -m addc D/c
$ hg mv d/b d/e
$ hg st
A D/e
R D/b
$ hg revert -aq
$ rm d/e
$ hg mv d/b D/B
$ hg st
A D/B
R D/b
$ cd ..
test case collision between revisions (issue912)
$ hg init repo3
$ cd repo3
$ echo a > a
$ hg ci -Am adda
adding a
$ hg rm a
$ hg ci -Am removea
$ echo A > A
on linux hfs keeps the old case stored, force it
$ mv a aa
$ mv aa A
$ hg ci -Am addA
adding A
used to fail under case insensitive fs
$ hg up -C 0
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg up -C
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
no clobbering of untracked files with wrong casing
$ hg up -r null
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo gold > a
$ hg up
A: untracked file differs
abort: untracked files in working directory differ from files in requested revision
[255]
$ cat a
gold
$ rm a
test that normal file in different case on target context is not
unlinked by largefiles extension.
$ cat >> .hg/hgrc <<EOF
> [extensions]
> largefiles=
> EOF
$ hg update -q -C 1
$ hg status -A
$ echo 'A as largefiles' > A
$ hg add --large A
$ hg commit -m '#3'
created new head
$ hg manifest -r 3
.hglf/A
$ hg manifest -r 0
a
$ hg update -q -C 0
$ hg status -A
C a
$ hg update -q -C 3
$ hg update -q 0
$ hg up -C -r 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg mv A a
$ hg diff -g > rename.diff
$ hg ci -m 'A -> a'
$ hg up -q '.^'
$ hg import rename.diff -m "import rename A -> a"
applying rename.diff
$ hg st
? rename.diff
$ hg files
a
$ find * | sort
a
rename.diff
$ rm rename.diff
$ cd ..
issue 3342: file in nested directory causes unexpected abort
$ hg init issue3342
$ cd issue3342
$ mkdir -p a/B/c/D
$ echo e > a/B/c/D/e
$ hg add a/B/c/D/e
$ hg ci -m 'add e'
issue 4481: revert across case only renames
$ hg mv a/B/c/D/e a/B/c/d/E
$ hg ci -m "uppercase E"
$ echo 'foo' > a/B/c/D/E
$ hg ci -m 'e content change'
$ hg revert --all -r 0
removing a/B/c/D/E
adding a/B/c/D/e
$ find * | sort
a
a/B
a/B/c
a/B/c/D
a/B/c/D/e
a/B/c/D/e.orig
$ cd ..
issue 3340: mq does not handle case changes correctly
in addition to reported case, 'hg qrefresh' is also tested against
case changes.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init issue3340
$ cd issue3340
$ echo a > mIxEdCaSe
$ hg add mIxEdCaSe
$ hg commit -m '#0'
$ hg rename mIxEdCaSe tmp
$ hg rename tmp MiXeDcAsE
$ hg status -A
A MiXeDcAsE
mIxEdCaSe
R mIxEdCaSe
$ hg qnew changecase
$ hg status -A
C MiXeDcAsE
$ hg qpop -a
popping changecase
patch queue now empty
$ hg qnew refresh-casechange
$ hg status -A
C mIxEdCaSe
$ hg rename mIxEdCaSe tmp
$ hg rename tmp MiXeDcAsE
$ hg status -A
A MiXeDcAsE
mIxEdCaSe
R mIxEdCaSe
$ hg qrefresh
$ hg status -A
C MiXeDcAsE
$ hg qpop -a
popping refresh-casechange
patch queue now empty
$ hg qnew refresh-pattern
$ hg status
$ echo A > A
$ hg add
adding A
$ hg qrefresh a # issue 3271, qrefresh with file handled case wrong
$ hg status # empty status means the qrefresh worked
#if osx
We assume anyone running the tests on a case-insensitive volume on OS
X will be using HFS+. If that's not true, this test will fail.
$ rm A
>>> open(u'a\u200c'.encode('utf-8'), 'w').write('unicode is fun')
$ hg status
M A
#endif
$ cd ..