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139 lines
4.2 KiB
C++
139 lines
4.2 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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*
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* The contents of this file are subject to the Netscape Public
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/NPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations under the License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is Netscape
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* Communications Corporation. Portions created by Netscape are
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* Copyright (C) 1998 Netscape Communications Corporation. All
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* Rights Reserved.
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*
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* Contributor(s):
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* Pierre Phaneuf <pp@ludusdesign.com>
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*/
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/**
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*
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* A sample of XPConnect. This file contains an implementation nsSample
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* of the interface nsISample.
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*
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*/
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#include "plstr.h"
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#include "stdio.h"
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#include "nsSample.h"
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#include "nsMemory.h"
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////////////////////////////////////////////////////////////////////////
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nsSampleImpl::nsSampleImpl() : mValue(nsnull)
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{
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NS_INIT_REFCNT();
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mValue = PL_strdup("initial value");
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}
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nsSampleImpl::~nsSampleImpl()
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{
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if (mValue)
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PL_strfree(mValue);
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}
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/**
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* NS_IMPL_ISUPPORTS1 expands to a simple implementation of the nsISupports
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* interface. This includes a proper implementation of AddRef, Release,
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* and QueryInterface. If this class supported more interfaces than just
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* nsISupports,
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* you could use NS_IMPL_ADDREF() and NS_IMPL_RELEASE() to take care of the
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* simple stuff, but you would have to create QueryInterface on your own.
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* nsSampleFactory.cpp is an example of this approach.
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* Notice that the second parameter to the macro is the static IID accessor
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* method, and NOT the #defined IID.
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*/
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NS_IMPL_ISUPPORTS1(nsSampleImpl, nsISample);
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/**
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* Notice that in the protoype for this function, the NS_IMETHOD macro was
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* used to declare the return type. For the implementation, the return
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* type is declared by NS_IMETHODIMP
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*/
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NS_IMETHODIMP
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nsSampleImpl::GetValue(char** aValue)
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{
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NS_PRECONDITION(aValue != nsnull, "null ptr");
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if (! aValue)
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return NS_ERROR_NULL_POINTER;
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if (mValue) {
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/**
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* GetValue's job is to return data known by an instance of
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* nsSampleImpl to the outside world. If we were to simply return
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* a pointer to data owned by this instance, and the client were to
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* free it, bad things would surely follow.
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* On the other hand, if we create a new copy of the data for our
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* client, and it turns out that client is implemented in JavaScript,
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* there would be no way to free the buffer. The solution to the
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* buffer ownership problem is the nsMemory singleton. Any buffer
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* returned by an XPCOM method should be allocated by the nsMemory.
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* This convention lets things like JavaScript reflection do their
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* job, and simplifies the way C++ clients deal with returned buffers.
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*/
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*aValue = (char*) nsMemory::Alloc(PL_strlen(mValue) + 1);
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if (! *aValue)
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return NS_ERROR_NULL_POINTER;
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PL_strcpy(*aValue, mValue);
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}
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else {
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*aValue = nsnull;
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}
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return NS_OK;
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}
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NS_IMETHODIMP
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nsSampleImpl::SetValue(const char* aValue)
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{
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NS_PRECONDITION(aValue != nsnull, "null ptr");
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if (! aValue)
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return NS_ERROR_NULL_POINTER;
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if (mValue) {
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PL_strfree(mValue);
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}
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/**
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* Another buffer passing convention is that buffers passed INTO your
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* object ARE NOT YOURS. Keep your hands off them, unless they are
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* declared "inout". If you want to keep the value for posterity,
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* you will have to make a copy of it.
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*/
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mValue = PL_strdup(aValue);
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return NS_OK;
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}
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NS_IMETHODIMP
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nsSampleImpl::Poke(const char* aValue)
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{
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return SetValue((char*) aValue);
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}
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NS_IMETHODIMP
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nsSampleImpl::WriteValue(const char* aPrefix)
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{
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NS_PRECONDITION(aPrefix != nsnull, "null ptr");
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if (! aPrefix)
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return NS_ERROR_NULL_POINTER;
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printf("%s %s\n", aPrefix, mValue);
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return NS_OK;
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}
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