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Diffstat (limited to 'SrcShared/EcmObject.h')
| -rw-r--r-- | SrcShared/EcmObject.h | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/SrcShared/EcmObject.h b/SrcShared/EcmObject.h new file mode 100644 index 0000000..a1984b5 --- /dev/null +++ b/SrcShared/EcmObject.h @@ -0,0 +1,191 @@ +/* -*- mode: C++; tab-width: 4 -*- */ +/* ===================================================================== *\ + Copyright (c) 2001 PocketPyro, Inc. + All rights reserved. + + This file is part of the Palm OS Emulator. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 2 of the License, or + (at your option) any later version. +\* ===================================================================== */ + +#ifndef EcmObject_h +#define EcmObject_h + +#include "EcmIf.h" + +/* + This file define a concrete implementation of the IEcmComponent + interface, as defined in EcmIf.h. IEcmComponent describes an object + with RequestInterface, Refer, and Release functions. EcmObject + provides implementations of those functions that find the requested + interface, increment a refcount, and decrement a refcount (deleting + the object if necessary), respectively. + + RequestInterface works by making use of the FindInterface helper + function. FindInterface is implemented by all EcmObject subclasses + to cast itself to the right type and return the casted pointer if + the subclass supports the requested interface. + + In order to make the implementation of FindInterface in all subclasses + simple and consistant, three macros are provided: ECM_CLASS_IF_LIST_BEGIN, + ECM_CLASS_IF, and ECM_CLASS_IF_LIST_END. The first macro introduces + a list of interfaces a particular class supports, the second macro is + used once for each interface supported, and the final macro cleans up + the list. In all, the three macros as used as follows in the class + declaration of the class implementing an interface: + + class EmImplementation : public EcmObject, + ecm_implements IEmBaseInterface1, + ecm_implements IEmBaseInterface2 + { + public: + + ECM_CLASS_IF_LIST_BEGIN(EmImplementation, EcmObject) + ECM_CLASS_IF(kBaseIfn1, IEmBaseInterface1) + ECM_CLASS_IF(kBaseIfn2, IEmBaseInterface2) + ECM_CLASS_IF_LIST_END(EmImplementation, EcmObject) + + ... + }; +*/ + + +// =========================================================================== +// +// Extended Component Model (ECM) -- Base Class +// +// We're adding support for component interfaces because +// exporting c++ classes is a real pain from loadable libraries +// (at least Windows DLLs), Anyway, component design using interfaces +// works really well for "plugin" type designs. +// +// In our implementation, an interface is a c++ abstract base class. +// =========================================================================== + + +#ifdef _MSC_VER +#pragma warning( disable : 4250 ) + + // 'class1' : inherits 'class2::member' via dominance + // + // There were two or more members with the same name. The one in class2 + // was inherited since it was a base class for the other classes that + // contained this member. +#endif + + +class EcmObject : + ecm_implements IEcmComponent +{ + public: + EcmObject() : fRefCount(0) + { + } + + + + //This forms the root of the interface request implementation: + // Derived classes will implement the same function, then a request for an interface will move up + // through the ranks, until a match has been found. + // + virtual EcmErr FindInterface(const EcmIfName &name, void **iPP) + { + if (iPP == NULL) + return kEcmErrInvalidParameter; + + if (name == kEcmComponentIfn) + { + *iPP = (void *) static_cast<IEcmComponent *>(this); + return kEcmErrNone; + } + + //Interface never found: + return kEcmErrInvalidIfName; + } + + + + + /*********************************************************************** + * + * FUNCTION: RequestInterface + * + * DESCRIPTION: Requests an interface of type EcmIfName from the component + * + * PARAMETERS: name [IN ] Name of the interface being requested. + * iPP [OUT ] Interface to the event being sent. + * + * RETURNED: kEcmErrNone + * kEcmErrInvalidName + * + * + ***********************************************************************/ + virtual EcmErr RequestInterface(const EcmIfName &name, void **iPP) + { + EcmErr err = FindInterface(name, iPP); + + if (err == kEcmErrNone) + { + Refer(); + } + + return err; + } + + + /*********************************************************************** + * + * FUNCTION: Refer + * + * DESCRIPTION: Called before handing an interface pointer off to another + * "piece of code", adding an addition owner. This is used to + * maintain the reference count so the component can be destroyed + * at the appropriate time. + * + * PARAMETERS: none + * + * RETURNED: kEcmErrNone + * + * + ***********************************************************************/ + + virtual EcmErr Refer() + { + fRefCount++; + return kEcmErrNone; + } + + + /*********************************************************************** + * + * FUNCTION: Release + * + * DESCRIPTION: Releases the interface from a reference, when the reference count is 0, + * the component can be destroyed. + * + * PARAMETERS: none + * + * RETURNED: kEcmErrNone + * + * + ***********************************************************************/ + + virtual EcmErr Release() + { + fRefCount--; + + if (fRefCount == 0) + delete this; + + return kEcmErrNone; + } + + protected: + unsigned long fRefCount; +}; + + +#endif // EcmObject_h |