Code:
/ 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / CompMod / System / Collections / Generic / BitHelper.cs / 1305376 / BitHelper.cs
using System; using System.Collections; using System.Text; namespace System.Collections.Generic { ////// ABOUT: /// Helps with operations that rely on bit marking to indicate whether an item in the /// collection should be added, removed, visited already, etc. /// /// BitHelper doesn't allocate the array; you must pass in an array or ints allocated on the /// stack or heap. ToIntArrayLength() tells you the int array size you must allocate. /// /// USAGE: /// Suppose you need to represent a bit array of length (i.e. logical bit array length) /// BIT_ARRAY_LENGTH. Then this is the suggested way to instantiate BitHelper: /// **************************************************************************** /// int intArrayLength = BitHelper.ToIntArrayLength(BIT_ARRAY_LENGTH); /// BitHelper bitHelper; /// if (intArrayLength less than stack alloc threshold) /// int* m_arrayPtr = stackalloc int[intArrayLength]; /// bitHelper = new BitHelper(m_arrayPtr, intArrayLength); /// else /// int[] m_arrayPtr = new int[intArrayLength]; /// bitHelper = new BitHelper(m_arrayPtr, intArrayLength); /// *************************************************************************** /// /// IMPORTANT: /// The second ctor args, length, should be specified as the length of the int array, not /// the logical bit array. Because length is used for bounds checking into the int array, /// it's especially important to get this correct for the stackalloc version. See the code /// samples above; this is the value gotten from ToIntArrayLength(). /// /// The length ctor argument is the only exception; for other methods -- MarkBit and /// IsMarked -- pass in values as indices into the logical bit array, and it will be mapped /// to the position within the array of ints. /// /// unsafe internal class BitHelper { // should not be serialized private const byte MarkedBitFlag = 1; private const byte IntSize = 32; // m_length of underlying int array (not logical bit array) private int m_length; // ptr to stack alloc'd array of ints private int* m_arrayPtr; // array of ints private int[] m_array; // whether to operate on stack alloc'd or heap alloc'd array private bool useStackAlloc; /// /// Instantiates a BitHelper with a heap alloc'd array of ints /// /// int array to hold bits /// length of int array //// [System.Security.SecurityCritical] internal BitHelper(int* bitArrayPtr, int length) { this.m_arrayPtr = bitArrayPtr; this.m_length = length; useStackAlloc = true; } ///// // /// Instantiates a BitHelper with a heap alloc'd array of ints /// /// int array to hold bits /// length of int array internal BitHelper(int[] bitArray, int length) { this.m_array = bitArray; this.m_length = length; } ////// Mark bit at specified position /// /// //// [System.Security.SecurityCritical] internal unsafe void MarkBit(int bitPosition) { if (useStackAlloc) { int bitArrayIndex = bitPosition / IntSize; if (bitArrayIndex < m_length && bitArrayIndex >= 0) { m_arrayPtr[bitArrayIndex] |= (MarkedBitFlag << (bitPosition % IntSize)); } } else { int bitArrayIndex = bitPosition / IntSize; if (bitArrayIndex < m_length && bitArrayIndex >= 0) { m_array[bitArrayIndex] |= (MarkedBitFlag << (bitPosition % IntSize)); } } } ///// /// Is bit at specified position marked? /// /// ///// // [System.Security.SecurityCritical] internal unsafe bool IsMarked(int bitPosition) { if (useStackAlloc) { int bitArrayIndex = bitPosition / IntSize; if (bitArrayIndex < m_length && bitArrayIndex >= 0) { return ((m_arrayPtr[bitArrayIndex] & (MarkedBitFlag << (bitPosition % IntSize))) != 0); } return false; } else { int bitArrayIndex = bitPosition / IntSize; if (bitArrayIndex < m_length && bitArrayIndex >= 0) { return ((m_array[bitArrayIndex] & (MarkedBitFlag << (bitPosition % IntSize))) != 0); } return false; } } ///// /// How many ints must be allocated to represent n bits. Returns (n+31)/32, but /// avoids overflow /// /// ///internal static int ToIntArrayLength(int n) { return n > 0 ? ((n - 1) / IntSize + 1) : 0; } } } // File provided for Reference Use Only by Microsoft Corporation (c) 2007. // Copyright (c) Microsoft Corporation. All rights reserved.
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- WindowsPen.cs
- TimeSpanConverter.cs
- SqlCacheDependencyDatabase.cs
- SqlCacheDependencySection.cs
- PointHitTestParameters.cs
- RecognizedPhrase.cs
- NullableIntSumAggregationOperator.cs
- TextDocumentView.cs
- NamedPipeAppDomainProtocolHandler.cs
- TransformConverter.cs
- TerminatingOperationBehavior.cs
- ClientCultureInfo.cs
- Internal.cs
- ColumnResizeUndoUnit.cs
- DataTablePropertyDescriptor.cs
- Focus.cs
- SymbolType.cs
- log.cs
- PageCatalogPart.cs
- SqlInternalConnectionTds.cs
- NumericExpr.cs
- TdsParser.cs
- PrintPageEvent.cs
- TimeoutTimer.cs
- EventlogProvider.cs
- Msec.cs
- HtmlTable.cs
- CategoryNameCollection.cs
- VerificationException.cs
- ContentValidator.cs
- DesignerDeviceConfig.cs
- WebPartConnectVerb.cs
- ResourceReferenceExpressionConverter.cs
- XmlSchemaInferenceException.cs
- XmlSerializerFactory.cs
- JournalEntryStack.cs
- XmlSerializationReader.cs
- ProcessHostMapPath.cs
- WindowsGraphics.cs
- EmissiveMaterial.cs
- XmlSchemaComplexContentRestriction.cs
- BufferedResponseStream.cs
- FlowPanelDesigner.cs
- SQLBytes.cs
- ResourceProviderFactory.cs
- StringValueSerializer.cs
- Message.cs
- PageThemeCodeDomTreeGenerator.cs
- _UncName.cs
- NativeCppClassAttribute.cs
- GregorianCalendar.cs
- DataRowCollection.cs
- PaperSize.cs
- FormatterServices.cs
- Ppl.cs
- Pen.cs
- TextTreeInsertElementUndoUnit.cs
- MouseActionValueSerializer.cs
- WebPartConnectionsConnectVerb.cs
- NumberSubstitution.cs
- DataGridViewColumn.cs
- XPathSingletonIterator.cs
- IDispatchConstantAttribute.cs
- Lazy.cs
- AddInAttribute.cs
- TraceProvider.cs
- PingReply.cs
- BitmapVisualManager.cs
- ViewCellRelation.cs
- EllipticalNodeOperations.cs
- BehaviorEditorPart.cs
- XPathParser.cs
- AutomationAttributeInfo.cs
- OdbcErrorCollection.cs
- SessionViewState.cs
- Native.cs
- SessionStateItemCollection.cs
- RemoteWebConfigurationHostServer.cs
- EpmContentDeSerializerBase.cs
- DataFormats.cs
- SerializationFieldInfo.cs
- Error.cs
- ConditionedDesigner.cs
- DefaultValueConverter.cs
- GridViewActionList.cs
- Comparer.cs
- CodeCommentStatement.cs
- HWStack.cs
- DbConnectionStringCommon.cs
- PauseStoryboard.cs
- HtmlTable.cs
- CapiSafeHandles.cs
- X509Extension.cs
- XmlReflectionMember.cs
- IWorkflowDebuggerService.cs
- CaseInsensitiveComparer.cs
- XslException.cs
- StoreAnnotationsMap.cs
- ScriptReferenceEventArgs.cs
- WebFormDesignerActionService.cs