Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / Sys / System / IO / compression / InputBuffer.cs / 1 / InputBuffer.cs
namespace System.IO.Compression { using System; using System.Diagnostics; // This class can be used to read bits from an byte array quickly. // Normally we get bits from 'bitBuffer' field and bitsInBuffer stores // the number of bits available in 'BitBuffer'. // When we used up the bits in bitBuffer, we will try to get byte from // the byte array and copy the byte to appropiate position in bitBuffer. // // The byte array is not reused. We will go from 'start' to 'end'. // When we reach the end, most read operations will return -1, // which means we are running out of input. internal class InputBuffer { private byte[] buffer; // byte array to store input private int start; // start poisition of the buffer private int end; // end position of the buffer private uint bitBuffer = 0; // store the bits here, we can quickly shift in this buffer private int bitsInBuffer = 0; // number of bits available in bitBuffer // Total bits available in the input buffer public int AvailableBits { get{ return bitsInBuffer; } } // Total bytes available in the input buffer public int AvailableBytes { get{ return(end - start) + (bitsInBuffer / 8); } } // Ensure that count bits are in the bit buffer. // Returns false if input is not sufficient to make this true. // Count can be up to 16. public bool EnsureBitsAvailable(int count) { Debug.Assert( 0 < count && count <= 16, "count is invalid."); // manual inlining to improve perf if (bitsInBuffer < count) { if (NeedsInput()) { return false; } // insert a byte to bitbuffer bitBuffer |= (uint)buffer[start++] << bitsInBuffer; bitsInBuffer += 8; if (bitsInBuffer < count) { if (NeedsInput()) { return false; } // insert a byte to bitbuffer bitBuffer |= (uint)buffer[start++] << bitsInBuffer; bitsInBuffer += 8; } } return true; } // This function will try to load 16 or more bits into bitBuffer. // It returns whatever is contained in bitBuffer after loading. // The main difference between this and GetBits is that this will // never return -1. So the caller needs to check AvailableBits to // see how many bits are available. public uint TryLoad16Bits() { if(bitsInBuffer < 8) { if( start < end) { bitBuffer |= (uint)buffer[start++] << bitsInBuffer; bitsInBuffer += 8; } if( start < end) { bitBuffer |= (uint)buffer[start++] << bitsInBuffer; bitsInBuffer += 8; } } else if(bitsInBuffer < 16) { if( start < end) { bitBuffer |= (uint)buffer[start++] << bitsInBuffer; bitsInBuffer += 8; } } return bitBuffer; } private uint GetBitMask(int count) { return ((uint)1 << count) - 1; } // Gets count bits from the input buffer. Returns -1 if not enough bits available. public int GetBits(int count) { Debug.Assert( 0 < count && count <= 16, "count is invalid."); if ( !EnsureBitsAvailable(count) ) { return -1; } int result = (int)(bitBuffer & GetBitMask(count)); bitBuffer >>= count; bitsInBuffer -= count; return result; } /// Copies length bytes from input buffer to output buffer starting /// at output[offset]. You have to make sure, that the buffer is /// byte aligned. If not enough bytes are available, copies fewer /// bytes. /// Returns the number of bytes copied, 0 if no byte is available. public int CopyTo(byte[] output, int offset, int length) { Debug.Assert( output != null, ""); Debug.Assert( offset >=0 , ""); Debug.Assert( length >=0 , ""); Debug.Assert( offset <= output.Length - length, ""); Debug.Assert( (bitsInBuffer % 8) ==0, ""); // Copy the bytes in bitBuffer first. int bytesFromBitBuffer = 0; while (bitsInBuffer > 0 && length > 0) { output[offset++] = (byte) bitBuffer; bitBuffer >>= 8; bitsInBuffer -= 8; length--; bytesFromBitBuffer++; } if (length == 0) { return bytesFromBitBuffer; } int avail = end - start; if (length > avail) { length = avail; } Array.Copy(buffer, start, output, offset, length); start += length; return bytesFromBitBuffer + length; } // Return true is all input bytes are used. // This means the caller can call SetInput to add more input. public bool NeedsInput() { return start == end; } // Set the byte array to be processed. // All the bits remained in bitBuffer will be processed before the new bytes. // We don't clone the byte array here since it is expensive. // The caller should make sure after a buffer is passed in. // It will not be changed before calling this function again. public void SetInput(byte[] buffer, int offset, int length) { Debug.Assert( buffer != null, ""); Debug.Assert( offset >=0 , ""); Debug.Assert( length >=0 , ""); Debug.Assert( offset <= buffer.Length - length, ""); Debug.Assert( start == end, ""); this.buffer = buffer; start = offset; end = offset + length; } // Skip n bits in the buffer public void SkipBits(int n) { Debug.Assert(bitsInBuffer >= n, "No enough bits in the buffer, Did you call EnsureBitsAvailable?"); bitBuffer >>= n; bitsInBuffer -= n; } // Skips to the next byte boundary. public void SkipToByteBoundary() { bitBuffer >>= (bitsInBuffer % 8); bitsInBuffer = bitsInBuffer - (bitsInBuffer % 8); } } }
Link Menu
This book is available now!
Buy at Amazon US or
Buy at Amazon UK
- ListView.cs
- BookmarkUndoUnit.cs
- DbInsertCommandTree.cs
- TextOnlyOutput.cs
- ActivityExecutorDelegateInfo.cs
- TreeNodeMouseHoverEvent.cs
- ExpressionList.cs
- SoapElementAttribute.cs
- Pair.cs
- Color.cs
- TableLayoutCellPaintEventArgs.cs
- WebPartConnectionsCloseVerb.cs
- ThemeInfoAttribute.cs
- DebuggerAttributes.cs
- ConvertBinder.cs
- MediaSystem.cs
- TextEndOfLine.cs
- SpellerInterop.cs
- serverconfig.cs
- ClientSideQueueItem.cs
- SqlError.cs
- ExpressionConverter.cs
- XPathDocumentNavigator.cs
- MinimizableAttributeTypeConverter.cs
- Calendar.cs
- ReflectionPermission.cs
- PageClientProxyGenerator.cs
- TargetPerspective.cs
- RowCache.cs
- CombinedHttpChannel.cs
- NotifyCollectionChangedEventArgs.cs
- SqlDataAdapter.cs
- NotFiniteNumberException.cs
- NetworkStream.cs
- PropertyRef.cs
- DataServiceClientException.cs
- XmlSchemaProviderAttribute.cs
- BitmapDecoder.cs
- UserControlFileEditor.cs
- ResourceSetExpression.cs
- ObjectTokenCategory.cs
- TableRow.cs
- CommandBindingCollection.cs
- EditorZone.cs
- PingOptions.cs
- MediaTimeline.cs
- XmlValueConverter.cs
- BooleanFunctions.cs
- TogglePatternIdentifiers.cs
- RijndaelCryptoServiceProvider.cs
- ValuePattern.cs
- BufferedGraphicsContext.cs
- CookielessHelper.cs
- WinFormsComponentEditor.cs
- RemotingService.cs
- ConstraintStruct.cs
- ComponentEditorPage.cs
- DataGridViewCheckBoxCell.cs
- DefaultMemberAttribute.cs
- DesignerObjectListAdapter.cs
- SQLDateTimeStorage.cs
- DataKey.cs
- CodeAttributeArgumentCollection.cs
- TransactionFlowBindingElement.cs
- EntityCommandExecutionException.cs
- X509Certificate2.cs
- ListViewCommandEventArgs.cs
- SqlBooleanizer.cs
- PropertyDescriptors.cs
- WebPartActionVerb.cs
- EntityTemplateFactory.cs
- ActiveXHost.cs
- RepeatEnumerable.cs
- RolePrincipal.cs
- CodeSnippetCompileUnit.cs
- oledbmetadatacolumnnames.cs
- BitArray.cs
- SchemaObjectWriter.cs
- ListBox.cs
- DataTableMapping.cs
- DataExpression.cs
- EditorAttributeInfo.cs
- LongValidatorAttribute.cs
- Rotation3D.cs
- RelationshipEndMember.cs
- BamlRecordWriter.cs
- RichTextBoxAutomationPeer.cs
- OleDbRowUpdatedEvent.cs
- GridViewCellAutomationPeer.cs
- SolidColorBrush.cs
- ParserHooks.cs
- CacheOutputQuery.cs
- RegexGroupCollection.cs
- MDIWindowDialog.cs
- TypeUtil.cs
- KeyManager.cs
- ToolStripContentPanelRenderEventArgs.cs
- HyperLinkField.cs
- LocatorPartList.cs
- URLMembershipCondition.cs