зеркало из https://github.com/mozilla/gecko-dev.git
150 строки
4.5 KiB
C++
150 строки
4.5 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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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 <stdio.h>
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#include "nsSample.h"
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#include "nsMemory.h"
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#include "nsEmbedString.h"
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#include "nsIClassInfoImpl.h"
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////////////////////////////////////////////////////////////////////////
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nsSampleImpl::nsSampleImpl() : mValue(nullptr)
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{
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mValue = (char*)nsMemory::Clone("initial value", 14);
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}
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nsSampleImpl::~nsSampleImpl()
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{
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if (mValue)
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nsMemory::Free(mValue);
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}
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/**
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* NS_IMPL_ISUPPORTS 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 name of the interface, and
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* NOT the #defined IID.
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*
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* The _CI variant adds support for nsIClassInfo, which permits introspection
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* and interface flattening.
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*/
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NS_IMPL_CLASSINFO(nsSampleImpl, nullptr, 0, NS_SAMPLE_CID)
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NS_IMPL_ISUPPORTS_CI(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 != nullptr, "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::Clone(mValue, strlen(mValue) + 1);
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if (! *aValue)
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return NS_ERROR_NULL_POINTER;
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}
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else {
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*aValue = nullptr;
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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 != nullptr, "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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nsMemory::Free(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 = (char*) nsMemory::Clone(aValue, strlen(aValue) + 1);
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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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static void GetStringValue(nsACString& aValue)
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{
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NS_CStringSetData(aValue, "GetValue");
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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 != nullptr, "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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// This next part illustrates the nsEmbedString:
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nsEmbedString foopy;
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foopy.Append(char16_t('f'));
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foopy.Append(char16_t('o'));
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foopy.Append(char16_t('o'));
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foopy.Append(char16_t('p'));
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foopy.Append(char16_t('y'));
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const char16_t* f = foopy.get();
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uint32_t l = foopy.Length();
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printf("%c%c%c%c%c %d\n", char(f[0]), char(f[1]), char(f[2]), char(f[3]), char(f[4]), l);
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nsEmbedCString foopy2;
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GetStringValue(foopy2);
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//foopy2.AppendLiteral("foopy");
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const char* f2 = foopy2.get();
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uint32_t l2 = foopy2.Length();
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printf("%s %d\n", f2, l2);
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return NS_OK;
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}
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