Class.h

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/*
 * Copyright 2015 Brendan Bruner
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * bbruner@ualberta.ca
 * Nov. 2015
 */
#ifndef CLASS_H_
#define CLASS_H_        

#include <stddef.h>
#include <stdlib.h>

/************************************************************************/
/* Bool type                                */
/************************************************************************/
#define CBool unsigned char
#define CTRUE 1
#define CFALSE !CTRUE

/************************************************************************/
/* Configuration options                        */
/************************************************************************/
/*
 * Define this to reduce the memory footprint used in .bss
 * for error messages when an assert fails. Error messages will be much smaller,
 * but less descriptive.
 *  2:
 *      Error message prints line, file, and description of error,
 *      then calls assert hook.
 *  1:
 *      Error message prints line and file of error, then calls assert
 *      failure hook.
 *  0:
 *      No error message, only calls assert failure hook.
 *
 * Note, the symbol DEBUG must be defined for run time checks to be enabled.
 * If DEBUG is not defined then asserts resolve to empty statements and the
 * assert failure hook is never called on failed asserts.
 */
#define C_DEBUG_DIAG_LEVEL  2

/* Default memory clean up method used. */
/* Calling CDynamic( ) on an object will invoke this free method */
/* being called after destruction. */
/* Note, this must resolve to a method with an address in memory. */
/* ie, the default free method cannot be a macro function. */
#define CDefaultFree            free
#define CFree               CDefaultFree    

/* Default memory allocation method to use. */
#define CMalloc             malloc

/* Method declaration of memory free method. */
typedef void (*CFreeType)( void* );

/* All classes and interfaces contain a pointer to their class */
/* this is the name of that pointer. */
#define C_CLASS             _cc

/* All classes and interfaces contain a pointer to their highest */
/* super class, the base object, this is the name of that pointer. */
#define C_ROOT              _rt

/* All classes and interfaces contain a pointer to their virtual table, */
/* this is the name of that pointer. */
#define C_VTABLE            _vt

#define C_VTABLE_OFFSET         _vo

/* These define how to print formatted strings and what to */
/* do when an assertion fails. */
#include <stdio.h>
#define C_PRINT( ... )          printf( __VA_ARGS__ )
#define C_FAILED_ASSERT_HANDLE( )   for( ;; )


/************************************************************************/
/* Assert Messages                          */
/************************************************************************/
/* Different reasons for asserting. */
#if C_DEBUG_DIAG_LEVEL == 2

#define C_ASSERT_VIRTUAL_MESSAGE \
    "Virtual method not linked. Possible causes:\n"\
    "\t* [A0] Class constructor did not link virtual table with CVTable\n"\
    "\t* [A1] Constructor was never called on object\n"\
    "\t* [A2] Constructor was called, but super's constructor was not called\n"\
    "\t* [A3] Virtual table function assignment is incomplete\n"

#define C_ASSERT_OBJECT_MESSAGE \
    "NULL pointer used as input\n"

#define C_ASSERT_CAST_MESSAGE \
    "Failure to cast object. Possible causes:\n"\
    "\t* [C0] Did not call interface constructor, CInterface( )\n"\
    "\t* [C1] Did not call super's constructor.\n"

extern const char* CAssertVirtualMessage_;
extern const char* CAssertObjectMessage_;
extern const char* CAssertCastMessage_;

#else

#define CAssertVirtualMessage_      NULL
#define CAssertObjectMessage_       NULL
#define CAssertCastMessage_         NULL

#endif


/************************************************************************/
/* Assert macros                            */
/************************************************************************/
#if defined( DEBUG )
extern void CAssert( char exp, char const* msg, char const* file, int line );
#else
#define CAssert( exp, msg, file, line ) \
    do {                \
        (void) (exp);       \
        (void) (file);      \
        (void) (line);      \
    } while( 0 )
#endif

#define C_ASSERT_VIRTUAL( method )\
    CAssert( ((method)==NULL), CAssertVirtualMessage_, __FILE__, __LINE__ )
#define C_ASSERT_OBJECT( object )\
    CAssert( ((object)==NULL), CAssertObjectMessage_, __FILE__, __LINE__ )
#define C_ASSERT_CAST( object, file, line )\
    CAssert( (object) == NULL, CAssertCastMessage_, file, line )


/************************************************************************/
/* Base object structures                       */
/************************************************************************/
struct CClass
{
    /* C_ROOT must be first variable in this struct. */
    /* Do not change. */
    void* C_ROOT;
    size_t C_VTABLE_OFFSET;
};

struct CObject
{
    /* C_CLASS must be first variable in this struct. */
    /* Do not change. */
    struct CClass C_CLASS; 
    const void* C_VTABLE;
    CFreeType CObject_Free;
};

struct CObject_VTable
{
    void (*CDestructor)( void* );
};

const struct CObject_VTable* CObject_GetVTable( );

struct CObject* CObject_Constructor( struct CObject* self );

void CObject_Destroy( struct CObject* self );

void CObject_SetFree( struct CObject* self, CFreeType free_method );

/* Help macro for object construction. 
 */
#define CObject( self ) \
    CObject_Constructor(self)

/* Helper macro for object destruction. 
 */
#define CDestroy( mem ) \
    CObject_Destroy((void*) (mem))

/* Helper macro for declaring object dynamic. 
 */
#define CDynamic( obj ) \
    CObject_SetFree(((struct CClass*) (obj))->C_ROOT, CDefaultFree)

/* Helper macro for declaring free method for object. 
 */
#define CFreeWith( obj, freep ) \
    CObject_SetFree(((struct CClass*) (obj))->C_ROOT, (freep))


/************************************************************************/
/* Base interface structures                        */
/************************************************************************/
struct CInterface
{
    /* C_CLASS must be the first member of this struct. */
    /* Do not change. */
    struct CClass C_CLASS;
};

void CInterface( void* self, void* iface, const void* vtable );


/************************************************************************/
/* Helper macros for asserting and defining class methods       */
/************************************************************************/
/* Asserts virtual method before calling it. */
#define CAssertVirtual( func )\
    C_ASSERT_VIRTUAL(func)

/* Helper macro for asserting pointers. */
#define CAssertObject( object )\
    C_ASSERT_OBJECT((object))

/* Cast object pointer to desired class. */
#if C_DEBUG_DIAG_LEVEL == 0
#define CCast( self_ )\
    CObjectCast_(self_, NULL, 0)
#else
#define CCast( self_ )\
    CObjectCast_( self_, __FILE__, __LINE__ )
#endif


/************************************************************************/
/* Casting and virtual table handling.                  */
/************************************************************************/
void* CObjectCast_( void* super_reference, const char* file_name, int line_num );


void CVTable( void* self, const void* vtable);

const void* CGetVTable( void* self_ );


#endif /* CLASS_H_ */