Microsoft bond c++ runtime deserialization using runtime schema - c++

I could not find anything useful in their docs or examples :(
They have docs of how to deserialize schema, and then how to traverse it - that works great.
They have also two examples:
how to use bond::bonded<void> with runtime schema to convert binary to json
how to use bond::bonded<void> with runtime schema and MapTo to parse data into some custom ViewStruct
What I need is: to traverse the bond:bonded<void> to extract fields from it.
In protobuf you have field descriptors (created using FinFieldByName) and then you use them in runtime methods msg->getString, msg->getInt32 to get the typed value.

There's nothing built in that allows you to traverse a bonded<void> and inspect its fields. If you need to do that generically, you'll need to implement a custom transform and then use bond::Apply() to apply the transform to a bonded<void> constructed from a reader and a runtime schema. See in particular the transform and access_control examples for how to start writing a transform.
Bond needs this level of indirection compared to Protocol Buffers because Bond supports pluggable encoding protocols. If you know that you will only have to process a specific protocol, you could use that protocol's reader type with the runtime schema to walk the fields in the payload. See Microsoft Bond deserialization without knowing underlying schema for a C# example of the core of this algorithm.

Related

Are there tools for generating the clients model from an odata metadata?

Back in the good old days of flex (anyone?) flash builder provided a tool for generating the clients model based on the server model. Is there something similar for generating, say an ember's app model, based on the odata metadata?
datajs documentation does mention the subject. Though the reference for OData.read used in the sample doesn't say explicitly that it interprets the metadata somehow, it seems implied. You'll have to verify that.
It does take an optional metadata object however, suggesting there exists a formal representation for metadata to the library -- I would imagine generated via OData.read. Documentation seems non-existent. I don't know what that looks like.
From there, you should be able to further transform the model to something suitable for Ember.
(datajs is a low-level javascript library that implements client-side OData operations.)
I also know that JayStack provides a JaySvcUtil, a CLI process assembly (.NET program) that extracts metadata. The destination format is JavaScript code, though the model it uses is specific to JayData. Still, you may be able to work from there.
As mentioned by Maya, Microsoft provides the OData Client Code Generator, which generates .NET proxies. Might be more difficult to transform that.
If none of these work for you (which is actually likely), you can always parse the $metadata resource yourself -- I believe it always uses an XML representation in all current versions of OData.
If you need to do it dynamically in the browser, use DOMParser or XMLHttpRequest. More information.
If you can do it statically, then by all means do so -- it's simply best for performance. In this case, you can use whatever language and runtime tools you want to fetch, parse, transform and re-serialize the model.
The format (CSDL) is specified for OData here (v4) and here (v3).
Finally, check out this list, something new may appear that better fits your needs.
There are two suggestion which may help you.
1, OData provide client code generator to generate client-side proxy class. Just need to pass metadata url, .net client code will be generate for you. You can follow the following blog:
http://blogs.msdn.com/b/odatateam/archive/2014/03/11/how-to-use-odata-client-code-generator-to-generate-client-side-proxy-class.aspx
2, If the model means "EdmModel", you can just de-serialize $metadata. OData reader can de-serialize the $metadata to IEdmModel, which can be used in client side. The following is sample code:
HttpWebRequestMessage message = new HttpWebRequestMessage(new Uri(ServiceBaseUri.AbsoluteUri + "$metadata", UriKind.Absolute));
message.SetHeader("Accept", MimeTypes.ApplicationXml);
using (var messageReader = new ODataMessageReader(message.GetResponse()))
{
Model = messageReader.ReadMetadataDocument();
}

How to create a dynamic message with Protocol Buffers?

Say we want to create our message not using any preexisting .proto files and compiled out from them cpp/cxx/h files. We want to use protobuf strictly as a library. For example we got (in some only known to us format) message description: a message called MyMessage has to have MyIntFiels and optional MyStringFiels. How to create such message? for example fill it with simple data save to .bin and read from that binary its contents back?
I looked all over dynamic_message.h help description and DescriptorPool and so on but do not see how to add/remove fields to the message as well as no way to add described on fly message to DescriptorPool.
Can any one please explain?
Short answer: it can't be used that way.
The overview page of Protobuf says:
XML is also – to some extent – self-describing. A protocol buffer is only meaningful if you have the message definition (the .proto file).
Meaning the whole point of Protobuf is to throw-out self-descriptability in favor of parsing speed ==> it's just not it's purpose to create self describing messages.
Consider using XML or JSON or any other serialization format. If the protection is needed, you can use symmetric encryption and/or lzip compression.

Transmit raw vertex information to XTK?

We're using XTK to display data processed and created on a server. In our particular case, it's a parallel isocontouring application. As it currently stands we're converting to the (textual) VTK format and passing the entire (imaginary) VTK file over the wire to the client, where XTK renders it. This provides some substantial overhead, as the text format outweighs in the in-memory format by a considerably amount.
Is there a recommended mechanism available for transmitting binary data directly, either through an alternate format that is well-described or by constructing XTK primitives inside the JavaScript code itself?
It should be supported to parse an X.object from JSON. So you could generate the JSON on the serverside and use the X.object(jsonobject) copy constructor to safe down cast it. This should also give the advantage that the objects can be 'webgl-ready' and do not require any clientside parsing which should result in instant loading.
I was planning to play with that myself soon but if you get anything to work, please let us know.
Just have in mind that you need to match the X.object structure even in JSON. The best way to see what is expected by xtk is to JSON.stringify a webgl-ready X.object.
XMLHTTPRequest, in its second specification (the last one), allows trans-domain http requests (but you must have the control of the php header on the server side).
In addition it allows to sent ArrayBuffer, or Blobs or Documents (look here). And then on the client side you can write your own parser for that blob or (I think it fits more in you case) that BinaryBuffer using binary buffer views (see doc here). However XMLHTTPRequest is from client to server, but look HTML5 WebSocket, it seems it can transfert binaryArrays too (they say it here : ).
In every case you will need a parser to transform binary to string or to X.object at the client side.
I wish it helped you.

Is there a lightweight approach in producing XML with Xerces-C++?

This application runs on an embedded platform with low processing power and memory. I want to produce huge XML from the application. Currently I am constructing DOM and serializing into XML using Xerces-C++ 3.1.1. But the DOM construction takes long time and consumes lot of memory.
I know SAX is lightweight approach of parsing XML compared to DOM. Like that is there a lightweight approach for producing XML? Ofcourse I can produce the XML by concatenating strings but I didn't choose that approach because I want to make sure I produce a well-formed XML and sanitize the texts I include in it.
What you are looking for is normally called streaming serialization where parts of the document are written out as they become available instead of accumulation them all and writing them out at the end (which is what the DOM approach entails).
Xerces-C++ does not currently have streaming serialization support. But it is not very difficult to emulate it using DOM. The idea is to construct a DOM document fragment when a chunk of your data is ready to be serialized, write it out using the DOMWriter API, and free it once done. When you have another chunk ready, repeat the above steps. The result is an application that uses only a fraction of the memory that would be required to create the complete document.
We use this approach in CodeSynthesis XSD, an XML data binding toolkit for C++, to be able to handle XML documents that are too big to fit into memory. In fact, we have written some helper classes that simplify all this and wich you can find as part of the 'streaming' example in the examples/cxx/tree/ directory (the example code is public domain so feel free to borrow it ;-)).

c++ linux library for creating an xml and reading from an xml (serialize/ deserialize)

I am working in Ubuntu. I have a .h file with a class and a lot of nested classes. I would like to create an XML file from an object. Can someone please give me a library that creates XML files, serializes, and deserializes objects? I am compiling with g++.
Try libxml2.
But it seems like you want to serialize and desirialize an object from and to XML. Boost::serialization might come in handy. it also supports serialization from and to XML.
Here you can find an example for Boost::serialization with XML.
If you want to handle XML in C++ you may have a look at these projects
http://xmlsoft.org/
http://www.grinninglizard.com/tinyxml/
http://xerces.apache.org/xerces-c/
It doesn't serialize with XML (which I consider a feature, personally), but Google protocol buffers does a good job of serializing (in a binary format) objects that are defined in the .proto language.
You may want to explore the XML Data Binding. The main idea is that given an xml schema the data binding software generates a class hierarchy corresponding to the schema, and the code to serialize / unserialize (called marshal / unmarshal). There are several tools that can do this, gsoap is a free one, xmlSpy is one of the commercial ones.
What you describe is an XML data binding for C++. There are several tools for what you want to do, see e.g. XML Data Binding Tools. I've used gSOAP for several C++ projects, including starting from C++ files with classes which is really nice (other tools force you to start from XML schemas or WSDLs). With gSOAP I have been able to generate XML schemas and XML, see e.g. map C/C++ types to XML schema.
A super-lightweight, simple xml library is pugixml.
Though keep in mind that C++ does not have the reflection capabilities that .NET has. No library will generate the serialization/deserialization code for you (which I guess you hoped for).