1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/sample/nsSample.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,149 @@
1.4 +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +
1.10 +/**
1.11 + *
1.12 + * A sample of XPConnect. This file contains an implementation nsSample
1.13 + * of the interface nsISample.
1.14 + *
1.15 + */
1.16 +#include <stdio.h>
1.17 +
1.18 +#include "nsSample.h"
1.19 +#include "nsMemory.h"
1.20 +
1.21 +#include "nsEmbedString.h"
1.22 +#include "nsIClassInfoImpl.h"
1.23 +////////////////////////////////////////////////////////////////////////
1.24 +
1.25 +nsSampleImpl::nsSampleImpl() : mValue(nullptr)
1.26 +{
1.27 + mValue = (char*)nsMemory::Clone("initial value", 14);
1.28 +}
1.29 +
1.30 +nsSampleImpl::~nsSampleImpl()
1.31 +{
1.32 + if (mValue)
1.33 + nsMemory::Free(mValue);
1.34 +}
1.35 +
1.36 +/**
1.37 + * NS_IMPL_ISUPPORTS expands to a simple implementation of the nsISupports
1.38 + * interface. This includes a proper implementation of AddRef, Release,
1.39 + * and QueryInterface. If this class supported more interfaces than just
1.40 + * nsISupports,
1.41 + * you could use NS_IMPL_ADDREF() and NS_IMPL_RELEASE() to take care of the
1.42 + * simple stuff, but you would have to create QueryInterface on your own.
1.43 + * nsSampleFactory.cpp is an example of this approach.
1.44 + * Notice that the second parameter to the macro is name of the interface, and
1.45 + * NOT the #defined IID.
1.46 + *
1.47 + * The _CI variant adds support for nsIClassInfo, which permits introspection
1.48 + * and interface flattening.
1.49 + */
1.50 +NS_IMPL_CLASSINFO(nsSampleImpl, nullptr, 0, NS_SAMPLE_CID)
1.51 +NS_IMPL_ISUPPORTS_CI(nsSampleImpl, nsISample)
1.52 +/**
1.53 + * Notice that in the protoype for this function, the NS_IMETHOD macro was
1.54 + * used to declare the return type. For the implementation, the return
1.55 + * type is declared by NS_IMETHODIMP
1.56 + */
1.57 +NS_IMETHODIMP
1.58 +nsSampleImpl::GetValue(char** aValue)
1.59 +{
1.60 + NS_PRECONDITION(aValue != nullptr, "null ptr");
1.61 + if (! aValue)
1.62 + return NS_ERROR_NULL_POINTER;
1.63 +
1.64 + if (mValue) {
1.65 + /**
1.66 + * GetValue's job is to return data known by an instance of
1.67 + * nsSampleImpl to the outside world. If we were to simply return
1.68 + * a pointer to data owned by this instance, and the client were to
1.69 + * free it, bad things would surely follow.
1.70 + * On the other hand, if we create a new copy of the data for our
1.71 + * client, and it turns out that client is implemented in JavaScript,
1.72 + * there would be no way to free the buffer. The solution to the
1.73 + * buffer ownership problem is the nsMemory singleton. Any buffer
1.74 + * returned by an XPCOM method should be allocated by the nsMemory.
1.75 + * This convention lets things like JavaScript reflection do their
1.76 + * job, and simplifies the way C++ clients deal with returned buffers.
1.77 + */
1.78 + *aValue = (char*) nsMemory::Clone(mValue, strlen(mValue) + 1);
1.79 + if (! *aValue)
1.80 + return NS_ERROR_NULL_POINTER;
1.81 + }
1.82 + else {
1.83 + *aValue = nullptr;
1.84 + }
1.85 + return NS_OK;
1.86 +}
1.87 +
1.88 +NS_IMETHODIMP
1.89 +nsSampleImpl::SetValue(const char* aValue)
1.90 +{
1.91 + NS_PRECONDITION(aValue != nullptr, "null ptr");
1.92 + if (! aValue)
1.93 + return NS_ERROR_NULL_POINTER;
1.94 +
1.95 + if (mValue) {
1.96 + nsMemory::Free(mValue);
1.97 + }
1.98 +
1.99 + /**
1.100 + * Another buffer passing convention is that buffers passed INTO your
1.101 + * object ARE NOT YOURS. Keep your hands off them, unless they are
1.102 + * declared "inout". If you want to keep the value for posterity,
1.103 + * you will have to make a copy of it.
1.104 + */
1.105 + mValue = (char*) nsMemory::Clone(aValue, strlen(aValue) + 1);
1.106 + return NS_OK;
1.107 +}
1.108 +
1.109 +NS_IMETHODIMP
1.110 +nsSampleImpl::Poke(const char* aValue)
1.111 +{
1.112 + return SetValue((char*) aValue);
1.113 +}
1.114 +
1.115 +
1.116 +static void GetStringValue(nsACString& aValue)
1.117 +{
1.118 + NS_CStringSetData(aValue, "GetValue");
1.119 +}
1.120 +
1.121 +NS_IMETHODIMP
1.122 +nsSampleImpl::WriteValue(const char* aPrefix)
1.123 +{
1.124 + NS_PRECONDITION(aPrefix != nullptr, "null ptr");
1.125 + if (! aPrefix)
1.126 + return NS_ERROR_NULL_POINTER;
1.127 +
1.128 + printf("%s %s\n", aPrefix, mValue);
1.129 +
1.130 + // This next part illustrates the nsEmbedString:
1.131 + nsEmbedString foopy;
1.132 + foopy.Append(char16_t('f'));
1.133 + foopy.Append(char16_t('o'));
1.134 + foopy.Append(char16_t('o'));
1.135 + foopy.Append(char16_t('p'));
1.136 + foopy.Append(char16_t('y'));
1.137 +
1.138 + const char16_t* f = foopy.get();
1.139 + uint32_t l = foopy.Length();
1.140 + printf("%c%c%c%c%c %d\n", char(f[0]), char(f[1]), char(f[2]), char(f[3]), char(f[4]), l);
1.141 +
1.142 + nsEmbedCString foopy2;
1.143 + GetStringValue(foopy2);
1.144 +
1.145 + //foopy2.AppendLiteral("foopy");
1.146 + const char* f2 = foopy2.get();
1.147 + uint32_t l2 = foopy2.Length();
1.148 +
1.149 + printf("%s %d\n", f2, l2);
1.150 +
1.151 + return NS_OK;
1.152 +}
