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comparison: xpcom/sample/nsSample.cpp
xpcom/sample/nsSample.cpp
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| 1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ | |
| 2 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 3 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 5 | |
| 6 | |
| 7 /** | |
| 8 * | |
| 9 * A sample of XPConnect. This file contains an implementation nsSample | |
| 10 * of the interface nsISample. | |
| 11 * | |
| 12 */ | |
| 13 #include <stdio.h> | |
| 14 | |
| 15 #include "nsSample.h" | |
| 16 #include "nsMemory.h" | |
| 17 | |
| 18 #include "nsEmbedString.h" | |
| 19 #include "nsIClassInfoImpl.h" | |
| 20 //////////////////////////////////////////////////////////////////////// | |
| 21 | |
| 22 nsSampleImpl::nsSampleImpl() : mValue(nullptr) | |
| 23 { | |
| 24 mValue = (char*)nsMemory::Clone("initial value", 14); | |
| 25 } | |
| 26 | |
| 27 nsSampleImpl::~nsSampleImpl() | |
| 28 { | |
| 29 if (mValue) | |
| 30 nsMemory::Free(mValue); | |
| 31 } | |
| 32 | |
| 33 /** | |
| 34 * NS_IMPL_ISUPPORTS expands to a simple implementation of the nsISupports | |
| 35 * interface. This includes a proper implementation of AddRef, Release, | |
| 36 * and QueryInterface. If this class supported more interfaces than just | |
| 37 * nsISupports, | |
| 38 * you could use NS_IMPL_ADDREF() and NS_IMPL_RELEASE() to take care of the | |
| 39 * simple stuff, but you would have to create QueryInterface on your own. | |
| 40 * nsSampleFactory.cpp is an example of this approach. | |
| 41 * Notice that the second parameter to the macro is name of the interface, and | |
| 42 * NOT the #defined IID. | |
| 43 * | |
| 44 * The _CI variant adds support for nsIClassInfo, which permits introspection | |
| 45 * and interface flattening. | |
| 46 */ | |
| 47 NS_IMPL_CLASSINFO(nsSampleImpl, nullptr, 0, NS_SAMPLE_CID) | |
| 48 NS_IMPL_ISUPPORTS_CI(nsSampleImpl, nsISample) | |
| 49 /** | |
| 50 * Notice that in the protoype for this function, the NS_IMETHOD macro was | |
| 51 * used to declare the return type. For the implementation, the return | |
| 52 * type is declared by NS_IMETHODIMP | |
| 53 */ | |
| 54 NS_IMETHODIMP | |
| 55 nsSampleImpl::GetValue(char** aValue) | |
| 56 { | |
| 57 NS_PRECONDITION(aValue != nullptr, "null ptr"); | |
| 58 if (! aValue) | |
| 59 return NS_ERROR_NULL_POINTER; | |
| 60 | |
| 61 if (mValue) { | |
| 62 /** | |
| 63 * GetValue's job is to return data known by an instance of | |
| 64 * nsSampleImpl to the outside world. If we were to simply return | |
| 65 * a pointer to data owned by this instance, and the client were to | |
| 66 * free it, bad things would surely follow. | |
| 67 * On the other hand, if we create a new copy of the data for our | |
| 68 * client, and it turns out that client is implemented in JavaScript, | |
| 69 * there would be no way to free the buffer. The solution to the | |
| 70 * buffer ownership problem is the nsMemory singleton. Any buffer | |
| 71 * returned by an XPCOM method should be allocated by the nsMemory. | |
| 72 * This convention lets things like JavaScript reflection do their | |
| 73 * job, and simplifies the way C++ clients deal with returned buffers. | |
| 74 */ | |
| 75 *aValue = (char*) nsMemory::Clone(mValue, strlen(mValue) + 1); | |
| 76 if (! *aValue) | |
| 77 return NS_ERROR_NULL_POINTER; | |
| 78 } | |
| 79 else { | |
| 80 *aValue = nullptr; | |
| 81 } | |
| 82 return NS_OK; | |
| 83 } | |
| 84 | |
| 85 NS_IMETHODIMP | |
| 86 nsSampleImpl::SetValue(const char* aValue) | |
| 87 { | |
| 88 NS_PRECONDITION(aValue != nullptr, "null ptr"); | |
| 89 if (! aValue) | |
| 90 return NS_ERROR_NULL_POINTER; | |
| 91 | |
| 92 if (mValue) { | |
| 93 nsMemory::Free(mValue); | |
| 94 } | |
| 95 | |
| 96 /** | |
| 97 * Another buffer passing convention is that buffers passed INTO your | |
| 98 * object ARE NOT YOURS. Keep your hands off them, unless they are | |
| 99 * declared "inout". If you want to keep the value for posterity, | |
| 100 * you will have to make a copy of it. | |
| 101 */ | |
| 102 mValue = (char*) nsMemory::Clone(aValue, strlen(aValue) + 1); | |
| 103 return NS_OK; | |
| 104 } | |
| 105 | |
| 106 NS_IMETHODIMP | |
| 107 nsSampleImpl::Poke(const char* aValue) | |
| 108 { | |
| 109 return SetValue((char*) aValue); | |
| 110 } | |
| 111 | |
| 112 | |
| 113 static void GetStringValue(nsACString& aValue) | |
| 114 { | |
| 115 NS_CStringSetData(aValue, "GetValue"); | |
| 116 } | |
| 117 | |
| 118 NS_IMETHODIMP | |
| 119 nsSampleImpl::WriteValue(const char* aPrefix) | |
| 120 { | |
| 121 NS_PRECONDITION(aPrefix != nullptr, "null ptr"); | |
| 122 if (! aPrefix) | |
| 123 return NS_ERROR_NULL_POINTER; | |
| 124 | |
| 125 printf("%s %s\n", aPrefix, mValue); | |
| 126 | |
| 127 // This next part illustrates the nsEmbedString: | |
| 128 nsEmbedString foopy; | |
| 129 foopy.Append(char16_t('f')); | |
| 130 foopy.Append(char16_t('o')); | |
| 131 foopy.Append(char16_t('o')); | |
| 132 foopy.Append(char16_t('p')); | |
| 133 foopy.Append(char16_t('y')); | |
| 134 | |
| 135 const char16_t* f = foopy.get(); | |
| 136 uint32_t l = foopy.Length(); | |
| 137 printf("%c%c%c%c%c %d\n", char(f[0]), char(f[1]), char(f[2]), char(f[3]), char(f[4]), l); | |
| 138 | |
| 139 nsEmbedCString foopy2; | |
| 140 GetStringValue(foopy2); | |
| 141 | |
| 142 //foopy2.AppendLiteral("foopy"); | |
| 143 const char* f2 = foopy2.get(); | |
| 144 uint32_t l2 = foopy2.Length(); | |
| 145 | |
| 146 printf("%s %d\n", f2, l2); | |
| 147 | |
| 148 return NS_OK; | |
| 149 } |
