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
Setup
$ cat <<EOF >> $HGRCPATH
> [ui]
> color = yes
> formatted = always
> paginate = never
> [color]
> mode = ansi
> EOF
$ hg init repo
$ cd repo
$ cat > a <<EOF
> c
> c
> a
> a
> b
> a
> a
> c
> c
> EOF
$ hg ci -Am adda
\x1b[0;32madding a\x1b[0m (esc)
$ cat > a <<EOF
> c
> c
> a
> a
> dd
> a
> a
> c
> c
> EOF
default context
$ hg diff --nodates
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
trailing whitespace
$ cp a a.orig
>>> with open('a', 'rb') as f:
... data = f.read()
>>> with open('a', 'wb') as f:
... f.write(data.replace('dd', 'dd \r'))
$ hg diff --nodates
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m\x1b[0;1;41m \x1b[0m\r (esc)
a
a
c
$ mv a.orig a
(check that 'ui.color=yes' match '--color=auto')
$ hg diff --nodates --config ui.formatted=no
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -2,7 +2,7 @@
c
a
a
-b
+dd
a
a
c
(check that 'ui.color=no' disable color)
$ hg diff --nodates --config ui.formatted=yes --config ui.color=no
diff -r cf9f4ba66af2 a
--- a/a
+++ b/a
@@ -2,7 +2,7 @@
c
a
a
-b
+dd
a
a
c
(check that 'ui.color=always' force color)
$ hg diff --nodates --config ui.formatted=no --config ui.color=always
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -2,7 +2,7 @@\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
--unified=2
$ hg diff --nodates -U 2
\x1b[0;1mdiff -r cf9f4ba66af2 a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -3,5 +3,5 @@\x1b[0m (esc)
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
diffstat
$ hg diff --stat
a | 2 \x1b[0;32m+\x1b[0m\x1b[0;31m-\x1b[0m (esc)
1 files changed, 1 insertions(+), 1 deletions(-)
$ cat <<EOF >> $HGRCPATH
> [extensions]
> record =
> [ui]
> interactive = true
> [diff]
> git = True
> EOF
#if execbit
record
$ chmod +x a
$ hg record -m moda a <<EOF
> y
> y
> EOF
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;36;1mold mode 100644\x1b[0m (esc)
\x1b[0;36;1mnew mode 100755\x1b[0m (esc)
1 hunks, 1 lines changed
\x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
\x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
\x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg rollback
repository tip rolled back to revision 0 (undo commit)
working directory now based on revision 0
qrecord
$ hg qrecord -m moda patch <<EOF
> y
> y
> EOF
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;36;1mold mode 100644\x1b[0m (esc)
\x1b[0;36;1mnew mode 100755\x1b[0m (esc)
1 hunks, 1 lines changed
\x1b[0;33mexamine changes to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
\x1b[0;35m@@ -2,7 +2,7 @@ c\x1b[0m (esc)
c
a
a
\x1b[0;31m-b\x1b[0m (esc)
\x1b[0;32m+dd\x1b[0m (esc)
a
a
c
\x1b[0;33mrecord this change to 'a'? [Ynesfdaq?]\x1b[0m y (esc)
$ hg qpop -a
popping patch
patch queue now empty
#endif
issue3712: test colorization of subrepo diff
$ hg init sub
$ echo b > sub/b
$ hg -R sub commit -Am 'create sub'
\x1b[0;32madding b\x1b[0m (esc)
$ echo 'sub = sub' > .hgsub
$ hg add .hgsub
$ hg commit -m 'add subrepo sub'
$ echo aa >> a
$ echo bb >> sub/b
$ hg diff -S
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,4 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;1mdiff --git a/sub/b b/sub/b\x1b[0m (esc)
\x1b[0;31;1m--- a/sub/b\x1b[0m (esc)
\x1b[0;32;1m+++ b/sub/b\x1b[0m (esc)
\x1b[0;35m@@ -1,1 +1,2 @@\x1b[0m (esc)
b
\x1b[0;32m+bb\x1b[0m (esc)
test tabs
$ cat >> a <<EOF
> one tab
> two tabs
> end tab
> mid tab
> all tabs
> EOF
$ hg diff --nodates
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mone tab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mtwo tabs\x1b[0m (esc)
\x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
\x1b[0;32m+mid\x1b[0m \x1b[0;32mtab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m \x1b[0;32mall\x1b[0m \x1b[0;32mtabs\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
$ echo "[color]" >> $HGRCPATH
$ echo "diff.tab = bold magenta" >> $HGRCPATH
$ hg diff --nodates
\x1b[0;1mdiff --git a/a b/a\x1b[0m (esc)
\x1b[0;31;1m--- a/a\x1b[0m (esc)
\x1b[0;32;1m+++ b/a\x1b[0m (esc)
\x1b[0;35m@@ -7,3 +7,9 @@\x1b[0m (esc)
a
c
c
\x1b[0;32m+aa\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mone tab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtwo tabs\x1b[0m (esc)
\x1b[0;32m+end tab\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
\x1b[0;32m+mid\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtab\x1b[0m (esc)
\x1b[0;32m+\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mall\x1b[0m\x1b[0;1;35m \x1b[0m\x1b[0;32mtabs\x1b[0m\x1b[0;1;41m \x1b[0m (esc)
$ cd ..
test inline color diff
$ hg init inline
$ cd inline
$ cat > file1 << EOF
> this is the first line
> this is the second line
> third line starts with space
> + starts with a plus sign
> this one with one tab
> now with full two tabs
> now tabs everywhere, much fun
>
> this line won't change
>
> two lines are going to
> be changed into three!
>
> three of those lines will
> collapse onto one
> (to see if it works)
> EOF
$ hg add file1
$ hg ci -m 'commit'
$ cat > file1 << EOF
> that is the first paragraph
> this is the second line
> third line starts with space
> - starts with a minus sign
> this one with two tab
> now with full three tabs
> now there are tabs everywhere, much fun
>
> this line won't change
>
> two lines are going to
> (entirely magically,
> assuming this works)
> be changed into four!
>
> three of those lines have
> collapsed onto one
> EOF
$ hg diff --config diff.word-diff=False --color=debug
[diff.diffline|diff --git a/file1 b/file1]
[diff.file_a|--- a/file1]
[diff.file_b|+++ b/file1]
[diff.hunk|@@ -1,16 +1,17 @@]
[diff.deleted|-this is the first line]
[diff.deleted|-this is the second line]
[diff.deleted|- third line starts with space]
[diff.deleted|-+ starts with a plus sign]
[diff.deleted|-][diff.tab| ][diff.deleted|this one with one tab]
[diff.deleted|-][diff.tab| ][diff.deleted|now with full two tabs]
[diff.deleted|-][diff.tab| ][diff.deleted|now tabs][diff.tab| ][diff.deleted|everywhere, much fun]
[diff.inserted|+that is the first paragraph]
[diff.inserted|+ this is the second line]
[diff.inserted|+third line starts with space]
[diff.inserted|+- starts with a minus sign]
[diff.inserted|+][diff.tab| ][diff.inserted|this one with two tab]
[diff.inserted|+][diff.tab| ][diff.inserted|now with full three tabs]
[diff.inserted|+][diff.tab| ][diff.inserted|now there are tabs][diff.tab| ][diff.inserted|everywhere, much fun]
this line won't change
two lines are going to
[diff.deleted|-be changed into three!]
[diff.inserted|+(entirely magically,]
[diff.inserted|+ assuming this works)]
[diff.inserted|+be changed into four!]
[diff.deleted|-three of those lines will]
[diff.deleted|-collapse onto one]
[diff.deleted|-(to see if it works)]
[diff.inserted|+three of those lines have]
[diff.inserted|+collapsed onto one]
$ hg diff --config diff.word-diff=True --color=debug
[diff.diffline|diff --git a/file1 b/file1]
[diff.file_a|--- a/file1]
[diff.file_b|+++ b/file1]
[diff.hunk|@@ -1,16 +1,17 @@]
[diff.deleted|-][diff.deleted.changed|this][diff.deleted.unchanged| is the first ][diff.deleted.changed|line]
[diff.deleted|-][diff.deleted.unchanged|this is the second line]
[diff.deleted|-][diff.deleted.changed| ][diff.deleted.unchanged|third line starts with space]
[diff.deleted|-][diff.deleted.changed|+][diff.deleted.unchanged| starts with a ][diff.deleted.changed|plus][diff.deleted.unchanged| sign]
[diff.deleted|-][diff.tab| ][diff.deleted.unchanged|this one with ][diff.deleted.changed|one][diff.deleted.unchanged| tab]
[diff.deleted|-][diff.tab| ][diff.deleted.unchanged|now with full ][diff.deleted.changed|two][diff.deleted.unchanged| tabs]
[diff.deleted|-][diff.tab| ][diff.deleted.unchanged|now ][diff.deleted.unchanged|tabs][diff.tab| ][diff.deleted.unchanged|everywhere, much fun]
[diff.inserted|+][diff.inserted.changed|that][diff.inserted.unchanged| is the first ][diff.inserted.changed|paragraph]
[diff.inserted|+][diff.inserted.changed| ][diff.inserted.unchanged|this is the second line]
[diff.inserted|+][diff.inserted.unchanged|third line starts with space]
[diff.inserted|+][diff.inserted.changed|-][diff.inserted.unchanged| starts with a ][diff.inserted.changed|minus][diff.inserted.unchanged| sign]
[diff.inserted|+][diff.tab| ][diff.inserted.unchanged|this one with ][diff.inserted.changed|two][diff.inserted.unchanged| tab]
[diff.inserted|+][diff.tab| ][diff.inserted.unchanged|now with full ][diff.inserted.changed|three][diff.inserted.unchanged| tabs]
[diff.inserted|+][diff.tab| ][diff.inserted.unchanged|now ][diff.inserted.changed|there are ][diff.inserted.unchanged|tabs][diff.tab| ][diff.inserted.unchanged|everywhere, much fun]
this line won't change
two lines are going to
[diff.deleted|-][diff.deleted.unchanged|be changed into ][diff.deleted.changed|three][diff.deleted.unchanged|!]
[diff.inserted|+][diff.inserted.changed|(entirely magically,]
[diff.inserted|+][diff.inserted.changed| assuming this works)]
[diff.inserted|+][diff.inserted.unchanged|be changed into ][diff.inserted.changed|four][diff.inserted.unchanged|!]
[diff.deleted|-][diff.deleted.unchanged|three of those lines ][diff.deleted.changed|will]
[diff.deleted|-][diff.deleted.changed|collapse][diff.deleted.unchanged| onto one]
[diff.deleted|-][diff.deleted.changed|(to see if it works)]
[diff.inserted|+][diff.inserted.unchanged|three of those lines ][diff.inserted.changed|have]
[diff.inserted|+][diff.inserted.changed|collapsed][diff.inserted.unchanged| onto one]
multibyte character shouldn't be broken up in word diff:
$ $PYTHON <<'EOF'
> with open("utf8", "wb") as f:
> f.write(b"blah \xe3\x82\xa2 blah\n")
> EOF
$ hg ci -Am 'add utf8 char' utf8
$ $PYTHON <<'EOF'
> with open("utf8", "wb") as f:
> f.write(b"blah \xe3\x82\xa4 blah\n")
> EOF
$ hg ci -m 'slightly change utf8 char' utf8
$ hg diff --config diff.word-diff=True --color=debug -c.
[diff.diffline|diff --git a/utf8 b/utf8]
[diff.file_a|--- a/utf8]
[diff.file_b|+++ b/utf8]
[diff.hunk|@@ -1,1 +1,1 @@]
[diff.deleted|-][diff.deleted.unchanged|blah ][diff.deleted.changed|\xe3\x82\xa2][diff.deleted.unchanged| blah] (esc)
[diff.inserted|+][diff.inserted.unchanged|blah ][diff.inserted.changed|\xe3\x82\xa4][diff.inserted.unchanged| blah] (esc)