AngelScript: ANSI C library interface

# ANSI C library interface

Path: /sdk/add_on/clib/

This add-on defines a pure C interface, that can be used in those applications that do not understand C++ code but do understand C, e.g. Delphi, Java, and D.

To compile the AngelScript C library, you need to compile the library source files in sdk/angelscript/source together with the source files in sdk/add-on/clib, and link them as a shared dynamic library. In the application that will use the AngelScript C library, you'll include the `angelscript_c.h` header file, instead of the ordinary `angelscript.h` header file. After that you can use the library much the same way that it's used in C++.

To find the name of the C functions to call, you normally take the corresponding interface method and give a prefix according to the following table:

interface | prefix
asIScriptEngine | asEngine_
asIScriptModule | asModule_
asIScriptContext | asContext_
asIScriptGeneric | asGeneric_
asIScriptArray | asArray_
asIScriptObject | asObject_
asIObjectType | asObjectType_
asIScriptFunction | asScriptFunction_

All interface methods take the interface pointer as the first parameter when in the C function format, the rest of the parameters are the same as in the C++ interface. There are a few exceptions though, e.g. all parameters that take an `asSFuncPtr` take a normal function pointer in the C function format.

Example:

    #include <stdio.h>
    #include <assert.h>
    #include "angelscript_c.h"

    void MessageCallback(asSMessageInfo *msg, void *);
    void PrintSomething();

    int main(int argc, char **argv)
    {
      int r = 0;

      // Create and initialize the script engine
      asIScriptEngine *engine = asCreateScriptEngine(ANGELSCRIPT_VERSION);
      r = asEngine_SetMessageCallback(engine, (asFUNCTION_t)MessageCallback, 0, asCALL_CDECL); assert( r >= 0 );
      r = asEngine_RegisterGlobalFunction(engine, "void print()", (asFUNCTION_t)PrintSomething, asCALL_CDECL); assert( r >= 0 );

      // Execute a simple script
      r = asEngine_ExecuteString(engine, 0, "print()", 0, 0);
      if( r != asEXECUTION_FINISHED )
      {
          printf("Something wen't wrong with the execution\n");
      }
      else
      {
          printf("The script was executed successfully\n");
      }

      // Release the script engine
      asEngine_Release(engine);

      return r;
    }

    void MessageCallback(asSMessageInfo *msg, void *)
    {
      const char *msgType = 0;
      if( msg->type == 0 ) msgType = "Error  ";
      if( msg->type == 1 ) msgType = "Warning";
      if( msg->type == 2 ) msgType = "Info   ";

      printf("%s (%d, %d) : %s : %s\n", msg->section, msg->row, msg->col, msgType, msg->message);
    }

    void PrintSomething()
    {
      printf("Called from the script\n");
    }