Re: [Qemu-devel] [PATCH RFC v2 47/47] qapi-introspect: Hide type names

[Eric Blake]

On 07/01/2015 02:22 PM, Markus Armbruster wrote:
> To eliminate the temptation for clients to look up types by name
> (which are not ABI), replace all type names by meaningless strings.
> 
> Reduces output of query-schema by 9 out of 80KiB.

I'm not sure whether I like this or not.  It does make sense from the
perspective of forcing clients to stick to ABI queries, but makes it a
bit harder to navigate things except by automated scripts.

> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  scripts/qapi-introspect.py | 27 +++++++++++++++++++++++++--
>  1 file changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/qapi-introspect.py b/scripts/qapi-introspect.py
> index 961fe88..efb34ff 100644
> --- a/scripts/qapi-introspect.py
> +++ b/scripts/qapi-introspect.py
> @@ -9,13 +9,18 @@
>  # This work is licensed under the terms of the GNU GPL, version 2.
>  # See the COPYING file in the top-level directory.
>  
> +import string
>  from qapi import *
>  
> +def _b32digit(num):
> +    return (string.lowercase + string.digits[2:])[num]

This feels a bit too magic for me to decipher late at night.

> +
>  class QAPISchemaGenIntrospectVisitor(QAPISchemaVisitor):
>      def __init__(self):
>          self.schema = None
>          self.jsons = None
>          self.used_types = None
> +        self.name_map = None
>          self.defn = None
>          self.decl = None
>  
> @@ -23,13 +28,17 @@ class QAPISchemaGenIntrospectVisitor(QAPISchemaVisitor):
>          self.schema = schema
>          self.jsons = []
>          self.used_types = []
> +        self.name_map = {}
>          return QAPISchemaType   # don't visit types for now
>  
>      def visit_end(self):
>          # visit the types that are actually used
> +        jsons = self.jsons
> +        self.jsons = []
>          for typ in self.used_types:
>              typ.visit(self)
>          self.jsons.sort()
> +        jsons.extend(self.jsons)

I'm not sure I follow the use of .extends() here.

>          name = prefix + 'qmp_schema_json'
>          self.decl = mcgen('''
>  extern char %(c_name)s[];
> @@ -40,10 +49,19 @@ char %(c_name)s[] = "["
>      "%(c_jsons)s]";
>  ''',
>                            c_name=c_name(name),
> -                          c_jsons=', "\n    "'.join(self.jsons))
> +                          c_jsons=', "\n    "'.join(jsons))
>          self.schema = None
>          self.jsons = None
>          self.used_types = None
> +        self.name_map = None
> +
> +    def _name(self, name):
> +        if name not in self.name_map:
> +            n = len(self.name_map)
> +            self.name_map[name] = ':' + _b32digit(n / 32 / 32) \
> +                                  + _b32digit(n / 32 % 32) \
> +                                  + _b32digit(n % 32)

Caps our qapi to 32k types (including implicit ones); will that be an issue?

> +        return self.name_map[name]
>  
>      def _use_type(self, typ):
>          # Map the various integer types to plain int
> @@ -55,9 +73,14 @@ char %(c_name)s[] = "["
>          # Add type to work queue if new
>          if typ not in self.used_types:
>              self.used_types.append(typ)
> -        return typ.name
> +        # Clients should examine commands and events, not types.  Hide
> +        # type names to reduce the temptation.  Also saves a few
> +        # characters.
> +        return self._name(typ.name)
>  
>      def _gen_json(self, name, mtype, extra):
> +        if mtype != 'command' and mtype != 'event':
> +            name = self._name(name)
>          self.jsons.append("{ 'name': '%s', 'meta-type': '%s', %s }"
>                            % (name, mtype, extra))
>  
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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