Initial draft for changelog.

[liujisi]

I have left some TODOs for people who are working on this to add more details. @haberman @anandolee @nmittler @jskeet @danielweis

[liujisi]

@thomasvl

[jskeet]

Here's the change list for the C# part.

In general: some changes are breaking, which require regenerating messages. Most user-written code will not be impacted except for the renaming of enum values.

• Allow custom type URL prefixes in Any packing, and ignore them when unpacking
• protoc is now in a separate NuGet package (Google.Protobuf.Tools)
• New option: internal_access to generate internal classes
• Enum values are now PascalCased, and if there's a prefix which matches the name of the enum, that is removed (so an enum COLOR with a value COLOR_BLUE would generate a value of just Blue). An option (legacy_enum_values) is temporarily available to disable this, but the option will be removed for GA.
• json_name option is now honored
• If group tags are encountered when parsing, they are validated more thoroughly (although we don't support actual groups)
• NuGet dependencies are better specified
• Breaking: Preconditions is renamed to ProtoPreconditions
• Breaking: GeneratedCodeInfo is renamed to GeneratedClrTypeInfo
• JsonFormatter now allows writing to a TextWriter
• New interface, ICustomDiagnosticMessage to allow more compact representations from ToString
• CodedInputStream and CodedOutputStream now implement IDisposable, which simply disposes of the streams they were constructed with
• Map fields no longer support null values (in line with other languages)
• Improvements in JSON formatting and parsing

[nmittler]

Here's some more details for zero-copy:

• Introduction of the ByteOutput interface. This is similar to OutputStream but provides semantics for lazy writing (i.e. no immediate copy required) of fields that are considered to be immutable.
• ByteString now supports writing to a ByteOutput, which will directly expose the internals of the ByteString (i.e. byte[] or ByteBuffer) to the ByteOutput without copying.
• CodedOutputStream now supports writing to a ByteOutput. ByteString instances that are too large to fit in the internal buffer will be (lazily) written to the ByteOutput directly.
• This allows applications using large ByteString fields to avoid duplication of these fields entirely. Such an application can supply a ByteOutput that chains together the chunks received from CodedOutputStream before forwarding them onto the IO system.

Other related changes to CodedOutputStream:

• Additional use of sun.misc.Unsafe where possible to perform fast access to byte[] and ByteBuffer values and avoiding unnecessary range checking.
• ByteBuffer-backed CodedOutputStream now writes directly to the ByteBuffer rather than to an intermediate array.

[thomasvl]

Here's ObjC:

• Proto comments now come over as HeaderDoc comments in the generated sources so Xcode can pick them up and display them.
• The library headers have been updated to use HeaderDoc comments so Xcode can pick them up and display them.
• The per message and per field overhead in both generated code and runtime object sizes was reduced.
• Generated code now include deprecated annotations when the proto file included them.

[liujisi]

Thanks for the info. I updated the doc for csharp, zero copy and objc. I will merge the PR now so other can send PRs to add more stuffs.