JSON export/import in generate-bindings.pl

Source/bindings/scripts/IDLSerializer.pm

+# Copyright (C) 2013 Google Inc. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+# Convert the intermediate representation of IDLs between Perl and JSON, for:

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

Convert => Converts

since this is just a library; "Convert" sounds very imperative.

[Nils Barth (inactive), 2013/06/13 04:33:38]

Done.

+# 1. Modularity between frontend parser and backend code generator; and

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

frontend parser => parser
backend code generator => code generator

I don't think there will be any confusion, and this matches the names of the
modules that implement those parts more closely (IDLParser/CodeGeneratorV8).

[Nils Barth (inactive), 2013/06/13 04:33:38]

Done.

(I've been using "Frontend" b/c in Python, we have a separate lexer, parser, and
IDL Attribute Checker + partial interface merger, but these aren't distinguished
in Perl, so no need for extra words.)

+# 2. Porting to Python, so can connect Perl scripts and Python scripts.

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

"so can connect" is ungrammatical; maybe

Piecemeal porting to Python, by letting us connect Perl and Python scripts.

[Nils Barth (inactive), 2013/06/13 04:33:38]

Done.

+
+use strict;
+use warnings;
+
+use Class::Struct;
+use JSON -convert_blessed_universally;  # IR contains objects (blessed references)
+
+
+sub serializeJSON
+{
+    my $document = shift;
+    my $json = JSON->new->utf8;
+    # JSON.pm defaults to dying on objects (blessed references) and returning

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

Nice comment.

+    # keys in indeterminate order. We set options to change this:
+    # allow_blessed: don't die when encounter a blessed reference
+    #                (but default to return null)
+    # convert_blessed: convert blessed reference as if unblessed
+    #                  (rather than returning null)
+    # canonical: sort keys when writing JSON, so JSON always in same order,
+    #            so can compare output between runs or between Perl and Python
+    $json = $json->allow_blessed->convert_blessed->canonical();
+    return $json->encode($document);
+}
+
+sub deserializeJSON
+{
+    my $jsonText = shift;
+    my $json = JSON->new->utf8;
+    my $jsonHash = $json->decode($jsonText);
+    return jsonToPerl($jsonHash);
+}
+
+sub jsonToPerl
+{
+    # JSON.pm serializes Perl objects as a type of hash, so need to rebuild

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

type of hash => hash

is simpler and no less precise, right?

[Nils Barth (inactive), 2013/06/13 04:33:38]

I've reworded;
point is that it's a hash of a certain form (keys CLASS::KEY),
so we recognize these and rebuild objects from them.

+    # objects when deserializing
+    my $jsonData = shift;
+
+    if (ref $jsonData eq "ARRAY") {
+        my $perlData = [];

[dominicc (has gone to gerrit), 2013/06/12 13:39:53]

Ich nicht bin ein Perliner, but could this just be

return map(jsonToPerl, @$jsonData);

?

[Nils Barth (inactive), 2013/06/13 04:33:38]

Good point, done!

Perl being Perl, syntax is actually:
return [map(jsonToPerl($_), @$jsonData)];
(return reference, specify argument)
...and there's no built-in equivalent for hashes, but makes this block shorter
at least.

+        foreach my $element (@$jsonData) {
+            push(@$perlData, jsonToPerl($element));
+        }
+        return $perlData;
+    }
+
+    if (ref $jsonData eq "HASH") {
+        my @keys = keys %$jsonData;
+        return {} unless @keys;
+
+        my $class = determineClassFromKeys(@keys);
+        return jsonHashToPerlObject($jsonData, $class) if $class;
+
+        # just a hash
+        my $hashRef = {};
+        foreach my $key (@keys) {
+            $hashRef->{$key} = jsonToPerl($jsonData->{$key});
+        }
+        return $hashRef;
+    }
+
+    die "Unexpected reference type: " . ref $jsonData . "\n" if ref $jsonData;
+
+    return $jsonData;
+}
+
+sub determineClassFromKeys
+{
+    my @keys = shift;
+
+    # Detect objects as hashes where all keys are of the form CLASS::KEY.
+    # One exception: overloadedIndex is not part of domFunction struct,
+    # (just a hash key, not an object member), so need to special case.
+    my $firstKey = $keys[0];
+    $firstKey = $keys[1] if $firstKey eq "overloadedIndex";
+    my $isObject = $firstKey =~ /::/;
+
+    return unless $isObject;
+
+    my $class = (split('::', $firstKey))[0];
+    return $class;
+}
+
+sub jsonHashToPerlObject
+{
+    # JSON.pm serializes hash objects of class CLASS as a hash with keys
+    # CLASS::KEY1, CLASS::KEY2, etc.
+    # When deserializing, need to rebuild objects by stripping prefix
+    # and calling the constructor.
+    my $jsonHash = shift;
+    my $class = shift;
+
+    my %keysValues = ();
+    foreach my $classAndKey (keys %{$jsonHash}) {
+        next if $classAndKey eq "overloadedIndex";
+        my $key = (split('::', $classAndKey))[1];
+        $keysValues{$key} = jsonToPerl($jsonHash->{$classAndKey});
+    }
+    my $object = $class->new(%keysValues);  # Build object
+    # overloadedIndex not part of constructor; add separately
+    $object->{overloadedIndex} = $jsonHash->{overloadedIndex} if exists $jsonHash->{overloadedIndex};
+    return $object;
+}
+
+1;