cborutil: change buffering strategy
Profiling revealed that we were spending a lot of time on the
line that was concatenating the old buffer with the incoming data
when attempting to decode long byte strings, such as manifest
revisions.
Essentially, we were feeding N chunks of size len(X) << len(Y) into
decode() and continuously allocating a new, larger buffer to hold
the undecoded input. This created substantial memory churn and
slowed down execution.
Changing the code to aggregate pending chunks in a list until we
have enough data to fully decode the next atom makes things much
more efficient.
I don't have exact data, but I recall the old code spending >1s
on manifest fulltexts from the mozilla-unified repo. The new code
doesn't significantly appear in profile output.
Differential Revision: https://phab.mercurial-scm.org/D4854
Test illegal name
-----------------
on commit:
$ hg init hgname
$ cd hgname
$ mkdir sub
$ hg init sub/.hg
$ echo 'sub/.hg = sub/.hg' >> .hgsub
$ hg ci -qAm 'add subrepo "sub/.hg"'
abort: path 'sub/.hg' is inside nested repo 'sub'
[255]
prepare tampered repo (including the commit above):
$ hg import --bypass -qm 'add subrepo "sub/.hg"' - <<'EOF'
> diff --git a/.hgsub b/.hgsub
> new file mode 100644
> --- /dev/null
> +++ b/.hgsub
> @@ -0,0 +1,1 @@
> +sub/.hg = sub/.hg
> diff --git a/.hgsubstate b/.hgsubstate
> new file mode 100644
> --- /dev/null
> +++ b/.hgsubstate
> @@ -0,0 +1,1 @@
> +0000000000000000000000000000000000000000 sub/.hg
> EOF
$ cd ..
on clone (and update):
$ hg clone -q hgname hgname2
abort: path 'sub/.hg' is inside nested repo 'sub'
[255]
Test direct symlink traversal
-----------------------------
#if symlink
on commit:
$ mkdir hgsymdir
$ hg init hgsymdir/root
$ cd hgsymdir/root
$ ln -s ../out
$ hg ci -qAm 'add symlink "out"'
$ hg init ../out
$ echo 'out = out' >> .hgsub
$ hg ci -qAm 'add subrepo "out"'
abort: subrepo 'out' traverses symbolic link
[255]
prepare tampered repo (including the commit above):
$ hg import --bypass -qm 'add subrepo "out"' - <<'EOF'
> diff --git a/.hgsub b/.hgsub
> new file mode 100644
> --- /dev/null
> +++ b/.hgsub
> @@ -0,0 +1,1 @@
> +out = out
> diff --git a/.hgsubstate b/.hgsubstate
> new file mode 100644
> --- /dev/null
> +++ b/.hgsubstate
> @@ -0,0 +1,1 @@
> +0000000000000000000000000000000000000000 out
> EOF
$ cd ../..
on clone (and update):
$ mkdir hgsymdir2
$ hg clone -q hgsymdir/root hgsymdir2/root
abort: subrepo 'out' traverses symbolic link
[255]
$ ls hgsymdir2
root
#endif
Test indirect symlink traversal
-------------------------------
#if symlink
on commit:
$ mkdir hgsymin
$ hg init hgsymin/root
$ cd hgsymin/root
$ ln -s ../out
$ hg ci -qAm 'add symlink "out"'
$ mkdir ../out
$ hg init ../out/sub
$ echo 'out/sub = out/sub' >> .hgsub
$ hg ci -qAm 'add subrepo "out/sub"'
abort: path 'out/sub' traverses symbolic link 'out'
[255]
prepare tampered repo (including the commit above):
$ hg import --bypass -qm 'add subrepo "out/sub"' - <<'EOF'
> diff --git a/.hgsub b/.hgsub
> new file mode 100644
> --- /dev/null
> +++ b/.hgsub
> @@ -0,0 +1,1 @@
> +out/sub = out/sub
> diff --git a/.hgsubstate b/.hgsubstate
> new file mode 100644
> --- /dev/null
> +++ b/.hgsubstate
> @@ -0,0 +1,1 @@
> +0000000000000000000000000000000000000000 out/sub
> EOF
$ cd ../..
on clone (and update):
$ mkdir hgsymin2
$ hg clone -q hgsymin/root hgsymin2/root
abort: path 'out/sub' traverses symbolic link 'out'
[255]
$ ls hgsymin2
root
#endif