CachedFileStream Class

SystemObject
  SystemMarshalByRefObject
    System.IOStream
      GSF.IOCachedFileStream

public class CachedFileStream : Stream

Public Class CachedFileStream
	Inherits Stream

public ref class CachedFileStream : public Stream

type CachedFileStream = 
    class
        inherit Stream
    end

GSF.IO.CachedFileStream = function();

Type.createClass(
	'GSF.IO.CachedFileStream',
	Stream);

View Source

	Name	Description
	CachedFileStream(String, FileMode)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileAccess)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileAccess, FileShare)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileAccess, FileShare, Int32)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileAccess, FileShare, Int32, Boolean)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileAccess, FileShare, Int32, FileOptions)	Initializes a new instance of the FileStream class with the specified path, creation mode, read/write and sharing permission, the access other FileStreams can have to the same file, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions)	Initializes a new instance of the FileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, and additional file options.
	CachedFileStream(String, FileMode, FileSystemRights, FileShare, Int32, FileOptions, FileSecurity)	Initializes a new instance of the FileStream class with the specified path, creation mode, access rights and sharing permission, the buffer size, additional file options, access control and audit security.

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	Name	Description
	BlockSize	Gets the size of the cached blocks.
	CacheSize	Gets or sets the maximum size of the cache.
	CanRead	When overridden in a derived class, gets a value indicating whether the current stream supports reading. (Overrides StreamCanRead)
	CanSeek	When overridden in a derived class, gets a value indicating whether the current stream supports seeking. (Overrides StreamCanSeek)
	CanTimeout	Gets a value that determines whether the current stream can time out. (Inherited from Stream)
	CanWrite	When overridden in a derived class, gets a value indicating whether the current stream supports writing. (Overrides StreamCanWrite)
	Length	When overridden in a derived class, gets the length in bytes of the stream. (Overrides StreamLength)
	Position	When overridden in a derived class, gets or sets the position within the current stream. (Overrides StreamPosition)
	ReadTimeout	Gets or sets a value, in miliseconds, that determines how long the stream will attempt to read before timing out. (Inherited from Stream)
	WriteTimeout	Gets or sets a value, in miliseconds, that determines how long the stream will attempt to write before timing out. (Inherited from Stream)

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	Name	Description
	BeginRead	Begins an asynchronous read operation. (Consider using ReadAsync(Byte, Int32, Int32) instead.) (Inherited from Stream)
	BeginWrite	Begins an asynchronous write operation. (Consider using WriteAsync(Byte, Int32, Int32) instead.) (Inherited from Stream)
	Close	Closes the current stream and releases any resources (such as sockets and file handles) associated with the current stream. Instead of calling this method, ensure that the stream is properly disposed. (Inherited from Stream)
	CopyTo(Stream)	Reads the bytes from the current stream and writes them to another stream. (Inherited from Stream)
	CopyTo(Stream, Int32)	Reads the bytes from the current stream and writes them to another stream, using a specified buffer size. (Inherited from Stream)
	CopyToAsync(Stream)	Asynchronously reads the bytes from the current stream and writes them to another stream. (Inherited from Stream)
	CopyToAsync(Stream, Int32)	Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size. (Inherited from Stream)
	CopyToAsync(Stream, Int32, CancellationToken)	Asynchronously reads the bytes from the current stream and writes them to another stream, using a specified buffer size and cancellation token. (Inherited from Stream)
	CreateObjRef	Creates an object that contains all the relevant information required to generate a proxy used to communicate with a remote object. (Inherited from MarshalByRefObject)
	CreateWaitHandle	Obsolete. Allocates a WaitHandle object. (Inherited from Stream)
	Dispose	Releases all resources used by the Stream. (Inherited from Stream)
	Dispose(Boolean)	Releases the unmanaged resources used by the Stream and optionally releases the managed resources. (Overrides StreamDispose(Boolean))
	EndRead	Waits for the pending asynchronous read to complete. (Consider using ReadAsync(Byte, Int32, Int32) instead.) (Inherited from Stream)
	EndWrite	Ends an asynchronous write operation. (Consider using WriteAsync(Byte, Int32, Int32) instead.) (Inherited from Stream)
	Equals	Determines whether the specified object is equal to the current object. (Inherited from Object)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object)
	Flush	Clears buffers for this stream and causes any buffered data to be written to the file. (Overrides StreamFlush)
	Flush(Boolean)	Clears buffers for this stream and causes any buffered data to be written to the file, and also clears all intermediate file buffers.
	FlushAsync	Asynchronously clears all buffers for this stream and causes any buffered data to be written to the underlying device. (Inherited from Stream)
	FlushAsync(CancellationToken)	Asynchronously clears all buffers for this stream, causes any buffered data to be written to the underlying device, and monitors cancellation requests. (Inherited from Stream)
	GetHashCode	Serves as the default hash function. (Inherited from Object)
	GetLifetimeService	Retrieves the current lifetime service object that controls the lifetime policy for this instance. (Inherited from MarshalByRefObject)
	GetType	Gets the Type of the current instance. (Inherited from Object)
	InitializeLifetimeService	Obtains a lifetime service object to control the lifetime policy for this instance. (Inherited from MarshalByRefObject)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object)
	MemberwiseClone(Boolean)	Creates a shallow copy of the current MarshalByRefObject object. (Inherited from MarshalByRefObject)
	ObjectInvariant	Obsolete. Provides support for a Contract. (Inherited from Stream)
	Read	When overridden in a derived class, reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Overrides StreamRead(Byte, Int32, Int32))
	ReadAsync(Byte, Int32, Int32)	Asynchronously reads a sequence of bytes from the current stream and advances the position within the stream by the number of bytes read. (Inherited from Stream)
	ReadAsync(Byte, Int32, Int32, CancellationToken)	Asynchronously reads a sequence of bytes from the current stream, advances the position within the stream by the number of bytes read, and monitors cancellation requests. (Inherited from Stream)
	ReadByte	Reads a byte from the stream and advances the position within the stream by one byte, or returns -1 if at the end of the stream. (Inherited from Stream)
	Seek	When overridden in a derived class, sets the position within the current stream. (Overrides StreamSeek(Int64, SeekOrigin))
	SetLength	When overridden in a derived class, sets the length of the current stream. (Overrides StreamSetLength(Int64))
	ToString	Returns a string that represents the current object. (Inherited from Object)
	Write	When overridden in a derived class, writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Overrides StreamWrite(Byte, Int32, Int32))
	WriteAsync(Byte, Int32, Int32)	Asynchronously writes a sequence of bytes to the current stream and advances the current position within this stream by the number of bytes written. (Inherited from Stream)
	WriteAsync(Byte, Int32, Int32, CancellationToken)	Asynchronously writes a sequence of bytes to the current stream, advances the current position within this stream by the number of bytes written, and monitors cancellation requests. (Inherited from Stream)
	WriteByte	Writes a byte to the current position in the stream and advances the position within the stream by one byte. (Inherited from Stream)

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	Name	Description
	DefaultBlockSize	Default value for the BlockSize property.
	DefaultCacheSize	Default value for the CacheSize property.

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	Name	Description
	Compress	Compress a stream using specified compression strength. (Defined by CompressionExtensions)
	Compress	Compress a stream onto given output stream using specified compression strength. (Defined by CompressionExtensions)
	CopyStream	Copies input Stream onto output Stream. (Defined by StreamExtensions)
	CopyTo	Writes the contents of a stream to the provided stream. (Defined by StreamExtensions)
	Decompress	Decompress a stream. (Defined by CompressionExtensions)
	Decompress	Decompress a stream onto given output stream. (Defined by CompressionExtensions)
	Decrypt	Returns a stream of decrypted data for the given parameters. (Defined by Cipher)
	Decrypt	Decrypts input stream onto output stream for the given parameters. (Defined by Cipher)
	DeserializeToDataSet	Deserializes a DataSet from a Stream. (Defined by DataSetExtensions)
	Encrypt	Returns a stream of encrypted data for the given parameters. (Defined by Cipher)
	Encrypt	Encrypts input stream onto output stream for the given parameters. (Defined by Cipher)
	GetEnumValueOrDefault	Gets the enumeration constant for value, if defined in the enumeration, or a default value. (Defined by EnumExtensions)
	GetEnumValueOrDefaultT	Gets the enumeration constant for this value, if defined in the enumeration, or a default value. (Defined by EnumExtensions)
	Read7BitUInt32	Reads the 7-bit encoded value from the stream. (Defined by StreamExtensions)
	ReadAll	Reads all of the provided bytes. Will not return prematurely, but continue to execute a Read(Byte, Int32, Int32) command until the entire length has been read. (Defined by StreamExtensions)
	ReadBoolean	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadBytes	Reads a byte array from a Stream. The number of bytes should be prefixed in the stream. (Defined by StreamExtensions)
	ReadBytes	Reads a byte array from a Stream. The number of bytes should be prefixed in the stream. (Defined by StreamExtensions)
	ReadChar	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadDateTime	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadDecimal	Reads a decimal from the stream in Little Endian bytes. (Defined by StreamExtensions)
	ReadDouble	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadGuid	Reads a Guid from the stream in Little Endian bytes. (Defined by StreamExtensions)
	ReadInt16	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadInt32	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadInt32Collection	Writes the supplied string to a Stream in UTF8 encoding. (Defined by StreamExtensions)
	ReadInt64	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadNextByte	Read a byte from the stream. Will throw an exception if the end of the stream has been reached. (Defined by StreamExtensions)
	ReadNullableString	Reads a string from a Stream that was encoded in UTF8. Value can be null and is prefixed with a boolean. (Defined by StreamExtensions)
	ReadObject	Reads an object from a stream. (Defined by StreamExtensions)
	ReadSByte	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadSingle	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadStream	Reads entire Stream contents, and returns Byte array of data. (Defined by StreamExtensions)
	ReadString	Reads a string from a Stream that was encoded in UTF8. (Defined by StreamExtensions)
	ReadStringCollection	Writes the supplied string to a Stream in UTF8 encoding. (Defined by StreamExtensions)
	ReadUInt16	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadUInt32	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	ReadUInt64	Reads the value from the stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to in little endian format. (Defined by StreamExtensions)
	Write	Writes the entire buffer to the stream (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied string to a Stream in UTF8 encoding. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes a guid in little endian bytes to the stream (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied string to a Stream in UTF8 encoding. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	Write	Writes the supplied value to stream in little endian format. (Defined by StreamExtensions)
	WriteCollection	Writes the supplied Collection to a Stream. (Defined by StreamExtensions)
	WriteCollection	Writes the supplied Collection to a Stream. (Defined by StreamExtensions)
	WriteNullable	Writes the supplied string to a Stream in UTF8 encoding with a prefix if the value is null (Defined by StreamExtensions)
	WriteObject	Encodes an object on a stream. (Defined by StreamExtensions)
	WriteWithLength	Writes the supplied value to stream along with prefixing the length so it can be properly read as a unit. (Defined by StreamExtensions)

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This class was developed as a wrapper around FileStream with the same basic functionality. This stream treats the file as a collection of contiguous blocks which can be loaded into an in-memory lookup table to greatly improve seek times. This class generally performs significantly better than the standard FileStream class when maintaining multiple file pointers and frequently seeking back and forth between them. For an example of a good use-case, consider copying a list of serialized objects from one location in the file to another without loading the whole list into memory.

This class likely will not perform significantly better or worse than the standard FileStream when performing strictly sequential reads or writes. For an example of a bad use-case, consider reading a list of objects into memory or simply appending new data to the end of the file. In both of these cases, it may be better to use the standard FileStream for less memory overhead and more predictable flush behavior.

Blocks are loaded into memory as they are used (for read/write operations) and will be kept in memory for as long as possible. Blocks can only be flushed from the cache by decreasing the cache size or by accessing a non-cached block when the cache is already full. In these cases, a least recently used algorithm is executed to determine which blocks should be removed from the cache either to decrease the size of the cache or to make room for a new block.

Write operations are also cached such that they will not be committed to the file until the block is removed from the cache or a call to Flush has been made. This can have some additional implications as compared to the standard FileStream. For instance, write operations may not be committed to the file in the order in which they were executed. Users of this class will need to be judicious about when and how often they call Flush.

Reference

GSF.IO Namespace