EPICS pvData C++
Overview
2010.08.02

Introduction

This project has the begining of the C++ implementation of pvData. The following is done:

introspection interfaces

The introspection interfaces for clients are described.

introspection implementation

The following have been implemented: Type, ScalarType, Field, Scalar

test

A test of Scalar.

As mentioned below there are major problems with the current implementation.

Since the last version the following are the main changes:

• The name space no longer has the trailing " namespace pvData {"
• A typedef has been added to define a StringConst and all string arguments are now a StringConst. See gargage collection below for details.
• typedefs have been added for FieldPtr, ScalarPtr, etc. These make the boost stuff somewhat transparent.
• The array arguments have been changed from using * to using [].
• Other arguments were change to be more understandable.
• All the toString methods were changed from something like:

      static const std::string toString(...

  to

  static void toString(std::string &buf,

  This should be more efficent.

Building

The project is structured as an epics base client application. Edit configure/RELEASE so that it references your EPICS base and then just type:

   make

At the top. Then execute the test in the bin directory.

pvDataApp has the following sub directories:

pv

pvData.h has the interface descriptions for client code.

factory

FieldCreateFactory.cpp has the current implementation

test

Has a test for the current implementation.

Questions about Classes

The pure virtual classes defined in pvData.h now work. But there are still some things that are not so nice. Amoung these are:

• User code sees pointers instead of references. Can this be changed while keeping the boost::shared_ptr support?
• The toString methods have an argument of "std::string &buf" instead of "std::string *". But in the test code I could not create a "std::string &" to work. I do not know why.
• Can arguments and return descriptions be defined better?
• Is const present everywhere it should be? Remember that introspection classes are immutable and are shared whereever possible.
• The code is NOT thread safe. When we decide for sure what thread/lock support to choose I will fix this.

HELP WILL BE GREATLY APPRECIATED. because I am still coming up to speed with c++

Garbage Collection

boost::shared_ptr is currenly used for implementations of Field, Scalar, etc. It is also used for all string arguments passed to methods. Since string values are freely shared by pvData, pvAccess, etc, this is really important. questions:

1. Is the implementation using shared_ptr correctly?
2. Should other things currently defined use stared_ptr?