libkern/libkern/c++/OSBoolean.h

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /* OSBoolean.cpp created by rsulack on Tue Oct 12 1999 */
  29
  30 #ifndef _OS_OSBOOLEAN_H
  31 #define _OS_OSBOOLEAN_H
  32
  33 #include <libkern/c++/OSObject.h>
  34
  35 class OSString;
  36
  37 /*!
  38  * @header
  39  *
  40  * @abstract
  41  * This header declares the OSBoolean container class.
  42  */
  43
  44
  45 /*!
  46  * @class OSBoolean
  47  *
  48  * @abstract
  49  * OSBoolean wraps a boolean value in a C++ object
  50  * for use in Libkern collections.
  51  *
  52  * @discussion
  53  * OSBoolean represents a boolean <code>true</code>/<code>false</code> value
  54  * as a Libkern C++ object.
  55  * There are only two instances of OSBoolean,
  56  * <code>@link kOSBooleanTrue kOSBooleanTrue@/link</code>
  57  * and <code>@link kOSBooleanFalse kOSBooleanFalse@/link</code>.
  58  * These are shared globally and returned by the instance-creation function
  59  * <code>@link withBoolean withBoolean@/link</code>.
  60  * Thus, you can use pointer comparison
  61  * to test whether two OSBoolean objects are equal.
  62  */
  63 class OSBoolean : public OSObject
  64 {
  65     OSDeclareDefaultStructors(OSBoolean)
  66
  67 protected:
  68     bool value;
  69
  70    /*!
  71     * @function taggedRelease
  72     *
  73     * @abstract
  74     * Overrides the reference counting mechanism
  75     * for the shared global instances.
  76     *
  77     * @param tag  Unused.
  78     * @param when Unused.
  79     */
  80     virtual void taggedRelease(
  81         const void * tag,
  82         const int    when) const;
  83
  84 public:
  85     static void initialize();
  86
  87    /*!
  88     * @function withBoolean
  89     *
  90     * @abstract
  91     * Returns one of the global instances of OSBoolean.
  92     *
  93     * @param value   A boolean value.
  94     *
  95     * @result
  96     * The global instance of OSBoolean with the boolean <code>value</code>.
  97     *
  98     * @discussion
  99     * This function actually returns either
 100     * <code>@link kOSBooleanTrue kOSBooleanTrue@/link</code> or
 101     * <code>@link kOSBooleanFalse kOSBooleanFalse@/link</code>,
 102     * so that you can always use pointer comparison with OSBoolean objects.
 103     */
 104     static OSBoolean * withBoolean(bool value);
 105
 106    /*!
 107     * @function free
 108     *
 109     * @abstract
 110     * Overridden to prevent deallocation of the shared global instances.
 111     *
 112     * @discussion
 113     * This function should never be called.
 114     */
 115     virtual void free();
 116
 117
 118    /*!
 119     * @function taggedRetain
 120     *
 121     * @abstract
 122     * Overrides the reference counting mechanism for the shared global instances.
 123     *
 124     * @param tag  Unused.
 125     */
 126     virtual void taggedRetain(const void * tag) const;
 127
 128
 129    /*!
 130     * @function isTrue
 131     *
 132     * @abstract
 133     * Checks whether the OSBoolean object
 134     * represents a <code>true</code> <code>bool</code> value.
 135     *
 136     * @result
 137     * <code>true</code> if the OSBoolean object is <code>true</code>,
 138     * <code>false</code> otherwise.
 139     *
 140     * @discussion
 141     * You can also use <code>==</code> against
 142     * <code>@link kOSBooleanTrue kOSBooleanTrue@/link</code>.
 143     */
 144     virtual bool isTrue() const;
 145
 146
 147    /*!
 148     * @function isFalse
 149     *
 150     * @abstract
 151     * Checks whether the OSBoolean object
 152     * represents a <code>false</code> <code>bool</code> value.
 153     *
 154     * @result
 155     * <code>true</code> if the OSBoolean object is <code>false</code>,
 156     * <code>true</code> otherwise.
 157     *
 158     * @discussion
 159     * You can also use <code>==</code> against
 160     * <code>@link kOSBooleanFalse kOSBooleanFalse@/link</code>.
 161     */
 162     virtual bool isFalse() const;
 163
 164
 165    /*!
 166     * @function getValue
 167     *
 168     * @abstract
 169     * Returns the C++ <code>bool</code> value for the OSBoolean object.
 170     *
 171     * @result
 172     * Returns the C++ <code>bool</code> value of the OSBoolean object.
 173     */
 174     virtual bool getValue() const;
 175
 176
 177    /*!
 178     * @function isEqualTo
 179     *
 180     * @abstract
 181     * Tests the equality of two OSBoolean objects.
 182     *
 183     * @param aBoolean    The OSBoolean to be compared against the receiver.
 184     *
 185     * @result
 186     * <code>true</code> if the OSBoolean objects are equal,
 187     * <code>false</code> if not.
 188     *
 189     * @discussion
 190     * Two OSBoolean objects are considered equal
 191     * if they are the same exact object (pointer equality).
 192     */
 193     virtual bool isEqualTo(const OSBoolean * aBoolean) const;
 194
 195
 196    /*!
 197     * @function isEqualTo
 198     *
 199     * @abstract
 200     * Tests the equality an OSBoolean to an arbitrary object.
 201     *
 202     * @param anObject  An object to be compared against the receiver.
 203     *
 204     * @result
 205     * <code>true</code> if the objects are equal, <code>false</code> if not.
 206     *
 207     * @discussion
 208     * An OSBoolean is considered equal to another object
 209     * if that object is derived from OSBoolean
 210     * and represents the same C++ <code>bool</code> value.
 211     */
 212     virtual bool isEqualTo(const OSMetaClassBase * anObject) const;
 213
 214
 215    /*!
 216     * @function serialize
 217     *
 218     * @abstract
 219     * Archives the receiver into the provided
 220     * @link //apple_ref/doc/class/OSSerialize OSSerialize@/link object.
 221     *
 222     * @param serializer  The OSSerialize object.
 223     *
 224     * @result
 225     * <code>true</code> if serialization succeeds, <code>false</code> if not.
 226     */
 227     virtual bool serialize(OSSerialize * serializer) const;
 228
 229     OSMetaClassDeclareReservedUnused(OSBoolean, 0);
 230     OSMetaClassDeclareReservedUnused(OSBoolean, 1);
 231     OSMetaClassDeclareReservedUnused(OSBoolean, 2);
 232     OSMetaClassDeclareReservedUnused(OSBoolean, 3);
 233     OSMetaClassDeclareReservedUnused(OSBoolean, 4);
 234     OSMetaClassDeclareReservedUnused(OSBoolean, 5);
 235     OSMetaClassDeclareReservedUnused(OSBoolean, 6);
 236     OSMetaClassDeclareReservedUnused(OSBoolean, 7);
 237 };
 238
 239 /*!
 240  * @const kOSBoolean<code>true</code>
 241  *
 242  * @abstract
 243  * The OSBoolean constant for <code>true</code>.
 244  *
 245  * @discussion
 246  * The OSBoolean constant for <code>true</code>.
 247  * This object does not need to be retained or released (but it can be).
 248  * Comparisons of the form
 249  * booleanObject == kOSBooleanTrue</code> are acceptable
 250  * and are equivalent to
 251  * <code>booleanObject->getValue() == true</code>.
 252  */
 253 extern OSBoolean * const & kOSBooleanTrue;
 254
 255 /*!
 256  * @const kOSBoolean<code>false</code>
 257  *
 258  * @abstract
 259  * The OSBoolean constant for <code>false</code>.
 260  *
 261  * @discussion
 262  * The OSBoolean constant for <code>false</code>.
 263  * This object does not need to be retained or released (but it can be).
 264  * Comparisons of the form
 265  * <code>booleanObject == kOSBooleanFalse</code>
 266  * are acceptable and are equivalent to
 267  * <code>booleanObject->getValue() == <code>false</code>.
 268  */
 269 extern OSBoolean * const & kOSBooleanFalse;
 270
 271 #endif /* !_OS_OSBOOLEAN_H */