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 >> $HGRCPATH <<EOF
> [extensions]
> rebase=
> histedit=
>
> [alias]
> tglog = log -G --template "{rev}: {node|short} '{desc}' {branches}\n"
> EOF
$ hg init a
$ cd a
$ echo C1 > C1
$ hg ci -Am C1
adding C1
$ echo C2 > C2
$ hg ci -Am C2
adding C2
$ cd ..
$ hg clone a b
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg clone a c
updating to branch default
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ cd b
$ echo L1 > L1
$ hg ci -Am L1
adding L1
$ cd ../a
$ echo R1 > R1
$ hg ci -Am R1
adding R1
$ cd ../b
Now b has one revision to be pulled from a:
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 77ae9631bcca
rebasing 2:ff8d69a621f9 "L1"
saved backup bundle to $TESTTMP/b/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
$ hg tglog
@ 3: d80cc2da061e 'L1'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
Re-run:
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
no changes found
Abort pull early if working dir is not clean:
$ echo L1-mod > L1
$ hg pull --rebase
abort: uncommitted changes
(cannot pull with rebase: please commit or shelve your changes first)
[255]
$ hg update --clean --quiet
Abort pull early if another operation (histedit) is in progress:
$ hg histedit . -q --commands - << EOF
> edit d80cc2da061e histedit: generate unfinished state
> EOF
Editing (d80cc2da061e), you may commit or record as needed now.
(hg histedit --continue to resume)
[1]
$ hg pull --rebase
abort: histedit in progress
(use 'hg histedit --continue' or 'hg histedit --abort')
[255]
$ hg histedit --abort --quiet
Abort pull early with pending uncommitted merge:
$ cd ..
$ hg clone --noupdate c d
$ cd d
$ hg tglog
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ hg update --quiet 0
$ echo M1 > M1
$ hg commit --quiet -Am M1
$ hg update --quiet 1
$ hg merge 2
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg pull --rebase
abort: outstanding uncommitted merge
(cannot pull with rebase: please commit or shelve your changes first)
[255]
$ hg update --clean --quiet
Abort pull early with unclean subrepo:
$ echo s = s > .hgsub
$ hg add .hgsub
$ hg init s
$ hg commit -m "generated a subrepo"
$ echo a > s/a
$ hg -R s add s/a
$ hg pull --rebase
abort: uncommitted changes in subrepository "s"
(cannot pull with rebase: please commit or shelve your changes first)
[255]
Invoke pull --rebase and nothing to rebase:
$ cd ../c
$ hg book norebase
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 77ae9631bcca
nothing to rebase - updating instead
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updating bookmark norebase
$ hg tglog -l 1
@ 2: 77ae9631bcca 'R1'
|
~
pull --rebase --update should ignore --update:
$ hg pull --rebase --update
pulling from $TESTTMP/a
searching for changes
no changes found
pull --rebase doesn't update if nothing has been pulled:
$ hg up -q 1
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
no changes found
$ hg tglog -l 1
o 2: 77ae9631bcca 'R1'
|
~
$ cd ..
pull --rebase works when a specific revision is pulled (issue3619)
$ cd a
$ hg tglog
@ 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ echo R2 > R2
$ hg ci -Am R2
adding R2
$ echo R3 > R3
$ hg ci -Am R3
adding R3
$ cd ../c
$ hg tglog
o 2: 77ae9631bcca 'R1'
|
@ 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ echo L1 > L1
$ hg ci -Am L1
adding L1
created new head
$ hg pull --rev tip --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 2 changesets with 2 changes to 2 files
new changesets 31cd3a05214e:770a61882ace
rebasing 3:ff8d69a621f9 "L1"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/ff8d69a621f9-160fa373-rebase.hg
$ hg tglog
@ 5: 518d153c0ba3 'L1'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase works with bundle2 turned on
$ cd ../a
$ echo R4 > R4
$ hg ci -Am R4
adding R4
$ hg tglog
@ 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ cd ../c
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 00e3b7781125
rebasing 5:518d153c0ba3 "L1"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/518d153c0ba3-73407f14-rebase.hg
$ hg tglog
@ 6: 0d0727eb7ce0 'L1'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase only update if there is nothing to rebase
$ cd ../a
$ echo R5 > R5
$ hg ci -Am R5
adding R5
$ hg tglog
@ 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
$ cd ../c
$ echo L2 > L2
$ hg ci -Am L2
adding L2
$ hg up 'desc(L1)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 88dd24261747
rebasing 6:0d0727eb7ce0 "L1"
rebasing 7:c1f58876e3bf "L2"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/0d0727eb7ce0-ef61ccb2-rebase.hg
$ hg tglog
o 8: 6dc0ea5dcf55 'L2'
|
@ 7: 864e0a2d2614 'L1'
|
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
pull --rebase update (no rebase) use proper update:
- warn about other head.
$ cd ../a
$ echo R6 > R6
$ hg ci -Am R6
adding R6
$ cd ../c
$ hg up 'desc(R5)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets 65bc164c1d9b
nothing to rebase - updating instead
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
updated to "65bc164c1d9b: R6"
1 other heads for branch "default"
$ hg tglog
@ 9: 65bc164c1d9b 'R6'
|
| o 8: 6dc0ea5dcf55 'L2'
| |
| o 7: 864e0a2d2614 'L1'
|/
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'
Multiple pre-existing heads on the branch
-----------------------------------------
Pull bring content, but nothing on the current branch, we should not consider
pre-existing heads.
$ cd ../a
$ hg branch unrelatedbranch
marked working directory as branch unrelatedbranch
(branches are permanent and global, did you want a bookmark?)
$ echo B1 > B1
$ hg commit -Am B1
adding B1
$ cd ../c
$ hg up 'desc(L2)'
2 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
new changesets 39c381359968
nothing to rebase
There is two local heads and we pull a third one.
The second local head should not confuse the `hg pull rebase`.
$ hg up 'desc(R6)'
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ echo M1 > M1
$ hg commit -Am M1
adding M1
$ cd ../a
$ hg up 'desc(R6)'
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo R7 > R7
$ hg commit -Am R7
adding R7
$ cd ../c
$ hg up 'desc(L2)'
2 files updated, 0 files merged, 2 files removed, 0 files unresolved
$ hg pull --rebase
pulling from $TESTTMP/a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files (+1 heads)
new changesets f7d3e42052f9
rebasing 7:864e0a2d2614 "L1"
rebasing 8:6dc0ea5dcf55 "L2"
saved backup bundle to $TESTTMP/c/.hg/strip-backup/864e0a2d2614-2f72c89c-rebase.hg
$ hg tglog
@ 12: 3603a865eea0 'L2'
|
o 11: bcc8a9cd04bf 'L1'
|
o 10: f7d3e42052f9 'R7'
|
| o 9: 41fab4eef82f 'M1'
|/
| o 8: 39c381359968 'B1' unrelatedbranch
|/
o 7: 65bc164c1d9b 'R6'
|
o 6: 88dd24261747 'R5'
|
o 5: 00e3b7781125 'R4'
|
o 4: 770a61882ace 'R3'
|
o 3: 31cd3a05214e 'R2'
|
o 2: 77ae9631bcca 'R1'
|
o 1: 783333faa078 'C2'
|
o 0: 05d58a0c15dd 'C1'