Hallo Feng,

> Am 11.12.2014 um 05:51 schrieb Feng Xiao <xiaof...@google.com>:
> 
> Hi all,
> 
> I just published protobuf v3.0.0-alpha-1 on our github site:
> https://github.com/google/protobuf/releases/tag/v3.0.0-alpha-1

a question on structuring  web applications further downstream:


you mention node.js and JSON (de)serialisation

reading between the lines this would suggest to me a typical protobuf 
application talking to a web client would talk JSON-serialized protobuf (maybe 
over a websocket stream)

I've used this scheme and while JSON is easy for browser js engines, there are 
downsides; for instance, (de)serializing doubles from/to JSON usually creates 
conversion/rounding fuzz - that precludes signing a protobuf object in binary 
representation because the signature generally wont be valid after JSON 
conversion. Looser type checking is another drawback.

That is why I found an end-to-end binary protobuf transfer and client-side js 
bindings along the lines of https://github.com/dcodeIO/ProtoBuf.js more robust

what's the grand vision here - how are web apps going to talk to protobuf API's 
server-side?

thanks in advance,

Michael



> 
> This is the first alpha release of protobuf v3.0.0. In protobuf v3.0.0, we 
> will add a new protobuf language version (aka proto3) and support a wider 
> range of programming languages (to name a few: ruby, php, node.js, 
> objective-c). This alpha version contains C++ and Java implementation with 
> partial proto3 support (see below for details). In future releases we will 
> add support for more programming languages and implement the full proto3 
> feature set. Besides proto3, this alpha version also includes two other new 
> features: map fields and arena allocation. They are implemented for both 
> proto3 and the old protobuf language version (aka proto2).
> 
> We are currently working on the documentation of these new features and when 
> it's ready it will be updated to our protobuf developer guide. For the time 
> being if you have any questions regarding proto3 or other new features, 
> please post your question in the discussion group.
> 
> CHANGS
> =======
> Version 3.0.0-alpha-1 (C++/Java):
> 
>   General
>   * Introduced Protocol Buffers language version 3 (aka proto3).
> 
>     When protobuf was initially opensourced it implemented Protocol Buffers
>     language version 2 (aka proto2), which is why the version number
>     started from v2.0.0. From v3.0.0, a new language version (proto3) is
>     introduced while the old version (proto2) will continue to be supported.
> 
>     The main intent of introducing proto3 is to clean up protobuf before
>     pushing the language as the foundation of Google's new API platform.
>     In proto3, the language is simplified, both for ease of use and  to
>     make it available in a wider range of programming languages. At the
>     same time a few features are added to better support common idioms
>     found in APIs.
> 
>     The following are the main new features in language version 3:
> 
>       1. Removal of field presence logic for primitive value fields, removal
>          of required fields, and removal of default values. This makes proto3
>          significantly easier to implement with open struct representations,
>          as in languages like Android Java, Objective C, or Go.
>       2. Removal of unknown fields.
>       3. Removal of extensions, which are instead replaced by a new standard
>          type called Any.
>       4. Fix semantics for unknown enum values.
>       5. Addition of maps.
>       6. Addition of a small set of standard types for representation of time,
>          dynamic data, etc.
>       7. A well-defined encoding in JSON as an alternative to binary proto
>          encoding.
> 
>     This release (v3.0.0-alpha-1) includes partial proto3 support for C++ and
>     Java. Items 6 (well-known types) and 7 (JSON format) in the above feature
>     list are not implemented.
> 
>     A new notion "syntax" is introduced to specify whether a .proto file
>     uses proto2 or proto3:
> 
>       // foo.proto
>       syntax = "proto3";
>       message Bar {...}
> 
>     If omitted, the protocol compiler will generate a warning and "proto2" 
> will
>     be used as the default. This warning will be turned into an error in a
>     future release.
> 
>     We recommend that new Protocol Buffers users use proto3. However, we do 
> not
>     generally recommend that existing users migrate from proto2 from proto3 
> due
>     to API incompatibility, and we will continue to support proto2 for a long
>     time.
> 
>   * Added support for map fields (implemented in C++/Java for both proto2 and
>     proto3).
> 
>     Map fields can be declared using the following syntax:
> 
>       message Foo {
>         map<string, string> values = 1;
>       }
> 
>     Data of a map field will be stored in memory as an unordered map and it
>     can be accessed through generated accessors.
> 
>   C++
>   * Added arena allocation support (for both proto2 and proto3).
> 
>     Profiling shows memory allocation and deallocation constitutes a 
> significant
>     fraction of CPU-time spent in protobuf code and arena allocation is a
>     technique introduced to reduce this cost. With arena allocation, new
>     objects will be allocated from a large piece of preallocated memory and
>     deallocation of these objects is almost free. Early adoption shows 20% to
>     50% improvement in some Google binaries.
> 
>     To enable arena support, add the following option to your .proto file:
> 
>       option cc_enable_arenas = true;
> 
>     Protocol compiler will generate additional code to make the generated
>     message classes work with arenas. This does not change the existing API
>     of protobuf messages and does not affect wire format. Your existing code
>     should continue to work after adding this option. In the future we will
>     make this option enabled by default.
> 
>     To actually take advantage of arena allocation, you need to use the arena
>     APIs when creating messages. A quick example of using the arena API:
> 
>       {
>         google::protobuf::Arena arena;
>         // Allocate a protobuf message in the arena.
>         MyMessage* message = Arena::CreateMessage<MyMessage>(&arena);
>         // All submessages will be allocated in the same arena.
>         if (!message->ParseFromString(data)) {
>           // Deal with malformed input data.
>         }
>         // Must not delete the message here. It will be deleted automatically
>         // when the arena is destroyed.
>       }
> 
>     Currently arena does not work with map fields. Enabling arena in a .proto
>     file containing map fields will result in compile errors in the generated
>     code. This will be addressed in a future release.
> =======
> 
> Thanks,
> Feng
> 
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