port protobuf-lite to wince

protobuf is a wonderful project that helps us implement communication protocol. There are a lot of benefits to use it in practical project, including:

1. It has an efficient binary serialization algorithm
2. It runs cross platforms
3. It support mainstream programming languages, c++, python and java. there are also lots of porting out there for other popular languages.
4. It's designed to make protocols both backward and forward compatible.
5. It enables developers to focus on protocol design.

 Currently, there is no official windows CE version for protobuf. It's not an easy task to port protobuf full version to windows CE. But the lite version, which supports less feature than full version (check the explanation for optimize_for option in this page for what's the difference), is easier to port. Here is how I port it:

1. Create a Win32 Smart Device Project library project, name it protobuf-lite-ce
2. Copy all source files from protobuf-lite project to protobuf-lite-ce project in Solution Explorer
3. Create a ce_port folder in the project's directory, and copy the errno.h header file from (Visual_Studio_Root)/VC/include into the folder. This is because Windows CE doesn't have this file, so we need to provide one. Actually, this errno.h can be a pure empty file.
4. Add "../src;.;./ce_port" to the project's Additional Include Directories.
5. The windef.h header file already defines OPTIONAL macro, it conflicts with Cardinality::OPTIONAL enum. So the extension_set.cc fails to compile, to solve this, add following code before enum Cardinality definition to undefine OPTIONAL:

#if defined(OPTIONAL)
#if defined(_MSC_VER)
#pragma message ("Unexpected OPTIONAL macro definition, #undefine OPTIONAL")
#else
#warning  "Unexpected OPTIONAL macro definition, #undefine OPTIONAL"
#endif
#undef OPTIONAL
#endif
namespace {

enum Cardinality {
  REPEATED,
  OPTIONAL
};

}  // namespace

Now the protobuf-lite-ce project should compiles fine.
Here is the project file for downloading. Just get everything there and place them in protobuf/vsprojects/ directory.