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     friend class OSSerialize;
  67
  68 protected:
  69     bool value;
  70
  71    /*!
  72     * @function taggedRelease
  73     *
  74     * @abstract
  75     * Overrides the reference counting mechanism
  76     * for the shared global instances.
  77     *
  78     * @param tag  Unused.
  79     * @param when Unused.
  80     */
  81     virtual void taggedRelease(
  82         const void * tag,
  83         const int    when) const;
  84
  85 public:
  86     static void initialize();
  87
  88    /*!
  89     * @function withBoolean
  90     *
  91     * @abstract
  92     * Returns one of the global instances of OSBoolean.
  93     *
  94     * @param value   A boolean value.
  95     *
  96     * @result
  97     * The global instance of OSBoolean with the boolean <code>value</code>.
  98     *
  99     * @discussion
 100     * This function actually returns either
 101     * <code>@link kOSBooleanTrue kOSBooleanTrue@/link</code> or
 102     * <code>@link kOSBooleanFalse kOSBooleanFalse@/link</code>,
 103     * so that you can always use pointer comparison with OSBoolean objects.
 104     */
 105     static OSBoolean * withBoolean(bool value);
 106
 107    /*!
 108     * @function free
 109     *
 110     * @abstract
 111     * Overridden to prevent deallocation of the shared global instances.
 112     *
 113     * @discussion
 114     * This function should never be called.
 115     */
 116     virtual void free();
 117
 118
 119    /*!
 120     * @function taggedRetain
 121     *
 122     * @abstract
 123     * Overrides the reference counting mechanism for the shared global instances.
 124     *
 125     * @param tag  Unused.
 126     */
 127     virtual void taggedRetain(const void * tag) const;
 128
 129
 130    /*!
 131     * @function isTrue
 132     *
 133     * @abstract
 134     * Checks whether the OSBoolean object
 135     * represents a <code>true</code> <code>bool</code> value.
 136     *
 137     * @result
 138     * <code>true</code> if the OSBoolean object is <code>true</code>,
 139     * <code>false</code> otherwise.
 140     *
 141     * @discussion
 142     * You can also use <code>==</code> against
 143     * <code>@link kOSBooleanTrue kOSBooleanTrue@/link</code>.
 144     */
 145     virtual bool isTrue() const;
 146
 147
 148    /*!
 149     * @function isFalse
 150     *
 151     * @abstract
 152     * Checks whether the OSBoolean object
 153     * represents a <code>false</code> <code>bool</code> value.
 154     *
 155     * @result
 156     * <code>true</code> if the OSBoolean object is <code>false</code>,
 157     * <code>true</code> otherwise.
 158     *
 159     * @discussion
 160     * You can also use <code>==</code> against
 161     * <code>@link kOSBooleanFalse kOSBooleanFalse@/link</code>.
 162     */
 163     virtual bool isFalse() const;
 164
 165
 166    /*!
 167     * @function getValue
 168     *
 169     * @abstract
 170     * Returns the C++ <code>bool</code> value for the OSBoolean object.
 171     *
 172     * @result
 173     * Returns the C++ <code>bool</code> value of the OSBoolean object.
 174     */
 175     virtual bool getValue() const;
 176
 177
 178    /*!
 179     * @function isEqualTo
 180     *
 181     * @abstract
 182     * Tests the equality of two OSBoolean objects.
 183     *
 184     * @param aBoolean    The OSBoolean to be compared against the receiver.
 185     *
 186     * @result
 187     * <code>true</code> if the OSBoolean objects are equal,
 188     * <code>false</code> if not.
 189     *
 190     * @discussion
 191     * Two OSBoolean objects are considered equal
 192     * if they are the same exact object (pointer equality).
 193     */
 194     virtual bool isEqualTo(const OSBoolean * aBoolean) const;
 195
 196
 197    /*!
 198     * @function isEqualTo
 199     *
 200     * @abstract
 201     * Tests the equality an OSBoolean to an arbitrary object.
 202     *
 203     * @param anObject  An object to be compared against the receiver.
 204     *
 205     * @result
 206     * <code>true</code> if the objects are equal, <code>false</code> if not.
 207     *
 208     * @discussion
 209     * An OSBoolean is considered equal to another object
 210     * if that object is derived from OSBoolean
 211     * and represents the same C++ <code>bool</code> value.
 212     */
 213     virtual bool isEqualTo(const OSMetaClassBase * anObject) const;
 214
 215
 216    /*!
 217     * @function serialize
 218     *
 219     * @abstract
 220     * Archives the receiver into the provided
 221     * @link //apple_ref/doc/class/OSSerialize OSSerialize@/link object.
 222     *
 223     * @param serializer  The OSSerialize object.
 224     *
 225     * @result
 226     * <code>true</code> if serialization succeeds, <code>false</code> if not.
 227     */
 228     virtual bool serialize(OSSerialize * serializer) const;
 229
 230     OSMetaClassDeclareReservedUnused(OSBoolean, 0);
 231     OSMetaClassDeclareReservedUnused(OSBoolean, 1);
 232     OSMetaClassDeclareReservedUnused(OSBoolean, 2);
 233     OSMetaClassDeclareReservedUnused(OSBoolean, 3);
 234     OSMetaClassDeclareReservedUnused(OSBoolean, 4);
 235     OSMetaClassDeclareReservedUnused(OSBoolean, 5);
 236     OSMetaClassDeclareReservedUnused(OSBoolean, 6);
 237     OSMetaClassDeclareReservedUnused(OSBoolean, 7);
 238 };
 239
 240 /*!
 241  * @const kOSBooleanTrue
 242  *
 243  * @abstract
 244  * The OSBoolean constant for <code>true</code>.
 245  *
 246  * @discussion
 247  * kOSBooleanTrue is the OSBoolean constant for <code>true</code>.
 248  * This object does not need to be retained or released (but it can be).
 249  * Comparisons of the form
 250  * <code>booleanObject == kOSBooleanTrue</code>
 251  * are acceptable and are equivalent to
 252  * <code>booleanObject->getValue() == true</code>.
 253  */
 254 extern OSBoolean * const & kOSBooleanTrue;
 255
 256 /*!
 257  * @const kOSBooleanFalse
 258  *
 259  * @abstract
 260  * The OSBoolean constant for <code>false</code>.
 261  *
 262  * @discussion
 263  * kOSBooleanFalse is the OSBoolean constant for <code>false</code>.
 264  * This object does not need to be retained or released (but it can be).
 265  * Comparisons of the form
 266  * <code>booleanObject == kOSBooleanFalse</code>
 267  * are acceptable and are equivalent to
 268  * <code>booleanObject->getValue() == false</code>.
 269  */
 270 extern OSBoolean * const & kOSBooleanFalse;
 271
 272 #endif /* !_OS_OSBOOLEAN_H */