From 9104da3261db96779e80f4713a50f5d19921ade8 Mon Sep 17 00:00:00 2001 From: Feng Xiao Date: Tue, 9 Dec 2014 11:57:52 -0800 Subject: Down-integrate from internal code base. --- CHANGES.txt | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) (limited to 'CHANGES.txt') diff --git a/CHANGES.txt b/CHANGES.txt index 0d0ac814..0d4ce0ec 100644 --- a/CHANGES.txt +++ b/CHANGES.txt @@ -1,3 +1,107 @@ +2014-12-01 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 impelmented. + + 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 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(&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. + 2014-10-20 version 2.6.1: C++ -- cgit v1.2.3