view tests/svn/svndump-branches.sh @ 37711:65a23cc8e75b

cborutil: implement support for streaming encoding, bytestring decoding

The vendored cbor2 package is... a bit disappointing.

On the encoding side, it insists that you pass it something with
a write() to send data to. That means if you want to emit data to
a generator, you have to construct an e.g. io.BytesIO(), write()
to it, then get the data back out. There can be non-trivial overhead
involved.

The encoder also doesn't support indefinite types - bytestrings, arrays,
and maps that don't have a known length. Again, this is really
unfortunate because it requires you to buffer the entire source and
destination in memory to encode large things.

On the decoding side, it supports reading indefinite length types.
But it buffers them completely before returning. More sadness.

This commit implements "streaming" encoders for various CBOR types.
Encoding emits a generator of hunks. So you can efficiently stream
encoded data elsewhere.

It also implements support for emitting indefinite length bytestrings,
arrays, and maps.

On the decoding side, we only implement support for decoding an
indefinite length bytestring from a file object. It will emit a
generator of raw chunks from the source.

I didn't want to reinvent so many wheels. But profiling the wire
protocol revealed that the overhead of constructing io.BytesIO()
instances to temporarily hold results has a non-trivial overhead.
We're talking >15% of execution time for operations like
"transfer the fulltexts of all files in a revision." So I can
justify this effort.

Fortunately, CBOR is a relatively straightforward format. And we have
a reference implementation in the repo we can test against.

Differential Revision: https://phab.mercurial-scm.org/D3303

#!/bin/sh
#
# Use this script to generate branches.svndump
#

mkdir temp
cd temp

mkdir project-orig
cd project-orig
mkdir trunk
mkdir branches
cd ..

svnadmin create svn-repo
svnurl=file://`pwd`/svn-repo
svn import project-orig $svnurl -m "init projA"

svn co $svnurl project
cd project
echo a > trunk/a
echo b > trunk/b
echo c > trunk/c
mkdir trunk/dir
echo e > trunk/dir/e
# Add a file within branches, used to confuse branch detection
echo d > branches/notinbranch
svn add trunk/a trunk/b trunk/c trunk/dir branches/notinbranch
svn ci -m hello
svn up

# Branch to old
svn copy trunk branches/old
svn rm branches/old/c
svn rm branches/old/dir
svn ci -m "branch trunk, remove c and dir"
svn up

# Update trunk
echo a >> trunk/a
svn ci -m "change a"

# Update old branch
echo b >> branches/old/b
svn ci -m "change b"

# Create a cross-branch revision
svn move trunk/b branches/old/c
echo c >> branches/old/c
svn ci -m "move and update c"

# Update old branch again
echo b >> branches/old/b
svn ci -m "change b again"

# Move back and forth between branch of similar names
# This used to generate fake copy records
svn up
svn move branches/old branches/old2
svn ci -m "move to old2"
svn move branches/old2 branches/old
svn ci -m "move back to old"

# Update trunk again
echo a > trunk/a
svn ci -m "last change to a"

# Branch again from a converted revision
svn copy -r 1 $svnurl/trunk branches/old3
svn ci -m "branch trunk@1 into old3"
cd ..

svnadmin dump svn-repo > ../branches.svndump