Stream VB.NET WinRT Reference Documentation

Stream

Current Version: 9.5.0.73

Provides a generic class for streaming from a source to a sink. Streams can be connected together where the sink of one feeds to the source of another.

Note: This class was added in Chilkat v9.5.0.56. Initially it will seem somewhat useless, but over time, streaming functionality will be added to existing Chilkat classes and will be prevalent in new Chilkat classes.

Object Creation

Dim obj As New Chilkat.Stream()

Properties

AbortCurrent
AbortCurrent As Boolean
Introduced in version 9.5.0.58

When set to True, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to False when the next method is called. When the abort occurs, this property is reset to False. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

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CanRead
CanRead As Boolean (ReadOnly)
Introduced in version 9.5.0.56

True if the stream supports reading. Otherwise False.

Note: A stream that supports reading, which has already reached the end-of-stream, will still have a CanRead value of True. This property indicates the stream's inherent ability, and not whether or not the stream can be read at a particular moment in time.

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CanWrite
CanWrite As Boolean (ReadOnly)
Introduced in version 9.5.0.56

True if the stream supports writing. Otherwise False.

Note: A stream that supports writing, which has already been closed for write, will still have a CanWrite value of True. This property indicates the stream's inherent ability, and not whether or not the stream can be written at a particular moment in time.

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DataAvailable
DataAvailable As Boolean (ReadOnly)
Introduced in version 9.5.0.56

True if it is known for sure that data is ready and waiting to be read. False if it is not known for sure (it may be that data is immediately available, but reading the stream with a ReadTimeoutMs of 0, which is to poll the stream, is the way to find out).

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DebugLogFilePath
DebugLogFilePath As String

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

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DefaultChunkSize
DefaultChunkSize As Integer
Introduced in version 9.5.0.56

The default internal chunk size for reading or writing. The default value is 65536. If this property is set to 0, it will cause the default chunk size (65536) to be used. Note: The chunk size can have significant performance impact. If performance is an issue, be sure to experiment with different chunk sizes.

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EndOfStream
EndOfStream As Boolean (ReadOnly)
Introduced in version 9.5.0.56

True if the end-of-stream has already been reached. When the stream has already ended, all calls to Read* methods will return False with the ReadFailReason set to 3 (already at end-of-stream).

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IsWriteClosed
IsWriteClosed As Boolean (ReadOnly)
Introduced in version 9.5.0.56

True if the stream is closed for writing. Once closed, no more data may be written to the stream.

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LastErrorHtml
LastErrorHtml As String (ReadOnly)

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorText
LastErrorText As String (ReadOnly)

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastErrorXml
LastErrorXml As String (ReadOnly)

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

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LastMethodSuccess
LastMethodSuccess As Boolean
Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of True indicates success, a value of False indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = True and failure = False.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to True. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

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Length
Length As Int64
Introduced in version 9.5.0.56

The length (in bytes) of the stream's source. If unknown, then this property will have a value of -1. This property may be set by the application if it knows in advance the length of the stream.

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Length32
Length32 As Integer
Introduced in version 9.5.0.58

The length (in bytes) of the stream's source. If unknown, then this property will have a value of -1. This property may be set by the application if it knows in advance the length of the stream.

Setting this property also sets the Length property (which is a 64-bit integer).

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NumReceived
NumReceived As Int64 (ReadOnly)
Introduced in version 9.5.0.56

The number of bytes received by the stream.

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NumSent
NumSent As Int64 (ReadOnly)
Introduced in version 9.5.0.56

The number of bytes sent by the stream.

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ReadFailReason
ReadFailReason As Integer (ReadOnly)
Introduced in version 9.5.0.56

This property is automatically set when a Read* method is called. It indicates the reason for failure. Possible values are:

  1. No failure (success)
  2. Timeout, or no data is immediately available for a polling read.
  3. Aborted by an application callback.
  4. Already at end-of-stream.
  5. Fatal stream error.
  6. Out-of-memory error (this is very unlikely).

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ReadTimeoutMs
ReadTimeoutMs As Integer
Introduced in version 9.5.0.56

The maximum number of seconds to wait while reading. The default value is 30 seconds (i.e. 30000ms). A value of 0 indicates a poll. (A polling read is to return with a timeout if no data is immediately available.)

Important: For most Chilkat timeout related properties, a value of 0 indicates an infinite timeout. For this property, a value of 0 indicates a poll. If setting a timeout related property (or method argument) to zero, be sure to understand if 0 means "wait forever" or "poll".

The timeout value is not a total timeout. It is the maximum time to wait while no additional data is forthcoming.

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SinkFile
SinkFile As String
Introduced in version 9.5.0.56

Sets the sink to the path of a file. The file does not need to exist at the time of setting this property. The sink file will be automatically opened on demand, when the stream is first written.

Note: This property takes priority over other potential sinks. Make sure this property is set to an empty string if the stream's sink is to be something else.

More Information and Examples
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SourceFile
SourceFile As String
Introduced in version 9.5.0.56

Sets the source to the path of a file. The file does not need to exist at the time of setting this property. The source file will be automatically opened on demand, when the stream is first read.

Note: This property takes priority over other potential sources. Make sure this property is set to an empty string if the stream's source is to be something else.

More Information and Examples
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SourceFilePart
SourceFilePart As Integer
Introduced in version 9.5.0.59

If the source is a file, then this property can be used to stream one part of the file. The SourceFilePartSize property defines the size (in bytes) of each part. The SourceFilePart and SourceFilePartSize have default values of 0, which means the entire SourceFile is streamed.

This property is a 0-based index. For example, if the SourceFilePartSize is 1000, then part 0 is for bytes 0 to 999, part 1 is for bytes 1000 to 1999, etc.

More Information and Examples
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SourceFilePartSize
SourceFilePartSize As Integer
Introduced in version 9.5.0.59

If the source is a file, then this property, in conjunction with the SourceFilePart property, can be used to stream a single part of the file. This property defines the size (in bytes) of each part. The SourceFilePart and SourceFilePartSize have default values of 0, which means that by default, the entire SourceFile is streamed.

More Information and Examples
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StringBom
StringBom As Boolean
Introduced in version 9.5.0.56

If True, then include the BOM when creating a string source via SetSourceString where the charset is utf-8, utf-16, etc. (The term "BOM" stands for Byte Order Mark, also known as the preamble.) Also, if True, then include the BOM when writing a string via the WriteString method. The default value of this property is False.

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StringCharset
StringCharset As String
Introduced in version 9.5.0.56

Indicates the expected character encoding, such as utf-8, windows-1256, utf-16, etc. for methods that read text such as: ReadString, ReadToCRLF, ReadUntilMatch. Also controls the character encoding when writing strings with the WriteString method. The supported charsets are indicated at the link below.

The default value is "utf-8".

More Information and Examples
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VerboseLogging
VerboseLogging As Boolean

If set to True, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is False. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

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Version
Version As String (ReadOnly)

Version of the component/library, such as "9.5.0.63"

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WriteFailReason
WriteFailReason As Integer (ReadOnly)
Introduced in version 9.5.0.56

This property is automatically set when a Write* method is called. It indicates the reason for failure. Possible values are:

  1. No failure (success)
  2. Timeout, or unable to immediately write when the WriteTimeoutMs is 0.
  3. Aborted by an application callback.
  4. The stream has already ended.
  5. Fatal stream error.
  6. Out-of-memory error (this is very unlikely).

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WriteTimeoutMs
WriteTimeoutMs As Integer
Introduced in version 9.5.0.56

The maximum number of seconds to wait while writing. The default value is 30 seconds (i.e. 30000ms). A value of 0 indicates to return immediately if it is not possible to write to the sink immediately.

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Methods

ReadBd
<Awaitable> Function ReadBdAsyncAsync(ByVal binData As BinData) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.67

Read as much data as is immediately available on the stream. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive. The incoming data is appended to binData.

Returns True for success, False for failure.

More Information and Examples
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ReadBytes
<Awaitable> Function ReadBytesAsyncAsync() As IAsyncOperation(Of Byte())
Introduced in version 9.5.0.56

Read as much data as is immediately available on the stream. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive.

Returns an empty byte array on failure

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ReadBytesENC
<Awaitable> Function ReadBytesENCAsyncAsync(ByVal encoding As String) As IAsyncOperation(Of String)
Introduced in version 9.5.0.56

The same as ReadBytes, except returns the received bytes in encoded string form. The encoding argument indicates the encoding, which can be "base64", "hex", or any of the multitude of encodings indicated in the link below.

Returns Nothing on failure

More Information and Examples
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ReadNBytes
<Awaitable> Function ReadNBytesAsyncAsync(ByVal numBytes As Integer) As IAsyncOperation(Of Byte())
Introduced in version 9.5.0.56

Reads exactly numBytes bytes from the stream. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive.

Returns an empty byte array on failure

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ReadNBytesENC
<Awaitable> Function ReadNBytesENCAsyncAsync(ByVal numBytes As Integer, ByVal encoding As String) As IAsyncOperation(Of String)
Introduced in version 9.5.0.56

The same as ReadNBytes, except returns the received bytes in encoded string form. The encoding argument indicates the encoding, which can be "base64", "hex", or any of the multitude of encodings indicated in the link below.

Returns Nothing on failure

More Information and Examples
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ReadSb
<Awaitable> Function ReadSbAsyncAsync(ByVal sb As StringBuilder) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.67

Read as much data as is immediately available on the stream. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive. The data is appended to sb. The incoming bytes are interpreted according to the StringCharset property. For example, if utf-8 bytes are expected, then StringCharset should be set to "utf-8" prior to calling ReadSb.

Returns True for success, False for failure.

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ReadString
<Awaitable> Function ReadStringAsyncAsync() As IAsyncOperation(Of String)
Introduced in version 9.5.0.56

Read as much data as is immediately available on the stream. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive. The data is returned as a string. The incoming bytes are interpreted according to the StringCharset property. For example, if utf-8 bytes are expected, then StringCharset should be set to "utf-8" prior to calling ReadString.

Returns Nothing on failure

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ReadToCRLF
<Awaitable> Function ReadToCRLFAsyncAsync() As IAsyncOperation(Of String)
Introduced in version 9.5.0.56

Reads the stream until a CRLF is received. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive. The data is returned as a string. The incoming bytes are interpreted according to the StringCharset property. For example, if utf-8 bytes are expected, then StringCharset should be set to "utf-8" prior to calling ReadString.

Note: If the end-of-stream is reached prior to receiving the CRLF, then the remaining data is returned, and the ReadFailReason property will be set to 3 (to indicate end-of-file). This is the only case where as string would be returned that does not end with CRLF.

Returns Nothing on failure

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ReadUntilMatch
<Awaitable> Function ReadUntilMatchAsyncAsync(ByVal matchStr As String) As IAsyncOperation(Of String)
Introduced in version 9.5.0.56

Reads the stream until the string indicated by matchStr is received. If no data is immediately available, it waits up to ReadTimeoutMs milliseconds for data to arrive. The data is returned as a string. The incoming bytes are interpreted according to the StringCharset property. For example, if utf-8 bytes are expected, then StringCharset should be set to "utf-8" prior to calling ReadString.

Note: If the end-of-stream is reached prior to receiving the match string, then the remaining data is returned, and the ReadFailReason property will be set to 3 (to indicate end-of-file). This is the only case where as string would be returned that does not end with the desired match string.

Returns Nothing on failure

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Reset
Sub Reset()
Introduced in version 9.5.0.56

Resets the stream. If a source or sink is open, then it is closed. Properties such as EndOfStream and IsWriteClose are reset to default values.

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RunStream
<Awaitable> Function RunStreamAsyncAsync() As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.56

Runs the stream to completion. This method should only be called when the source of the string has been set by any of the following methods: SetSourceBytes, SetSourceString, or SetSourceStream, or when the SourceFile property has been set (giving the stream a file source).

This method will read the stream source and forward to the sink until the end-of-stream is reached, and all data has been written to the sink.

Returns True for success, False for failure.

More Information and Examples
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SetSinkStream
Function SetSinkStream(ByVal strm As Stream) As Boolean
Introduced in version 9.5.0.56

Sets the stream's sink to strm. Any data written to this stream's sink will become available to strm on its source.

Returns True for success, False for failure.

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SetSourceBytes
Function SetSourceBytes(ByVal sourceData As Byte()) As Boolean
Introduced in version 9.5.0.56

Sets the stream's source to the contents of sourceData.

Returns True for success, False for failure.

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SetSourceStream
Function SetSourceStream(ByVal strm As Stream) As Boolean
Introduced in version 9.5.0.56

Sets the stream's source to be the sink of strm. Any data written to strm's sink will become available on this stream's source.

Returns True for success, False for failure.

More Information and Examples
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SetSourceString
Function SetSourceString(ByVal srcStr As String, ByVal charset As String) As Boolean
Introduced in version 9.5.0.56

Sets the stream's source to the contents of srcStr. The charset indicates the character encoding to be used for the byte representation of the srcStr.

Returns True for success, False for failure.

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WriteBd
<Awaitable> Function WriteBdAsyncAsync(ByVal binData As BinData) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.67

Writes the contents of binData to the stream.

Returns True for success, False for failure.

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WriteByte
<Awaitable> Function WriteByteAsyncAsync(ByVal byteVal As Integer) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.56

Writes a single byte to the stream. The byteVal must have a value from 0 to 255.

Returns True for success, False for failure.

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WriteBytes
<Awaitable> Function WriteBytesAsyncAsync(ByVal byteData As Byte()) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.56

Writes binary bytes to a stream.

Returns True for success, False for failure.

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WriteBytesENC
<Awaitable> Function WriteBytesENCAsyncAsync(ByVal byteData As String, ByVal encoding As String) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.56

Writes binary bytes to a stream. The byte data is passed in encoded string form, where the encoding can be "base64", "hex", or any of the supported binary encodings listed at the link below.

Returns True for success, False for failure.

More Information and Examples
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WriteClose
Function WriteClose() As Boolean
Introduced in version 9.5.0.56

Indicates that no more data will be written to the stream.

Returns True for success, False for failure.

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WriteSb
<Awaitable> Function WriteSbAsyncAsync(ByVal sb As StringBuilder) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.67

Writes the contents of sb to the stream. The actual bytes written are the byte representation of the string as indicated by the StringCharset property. For example, to write utf-8 bytes, first set StringCharset equal to "utf-8" and then call WriteSb.

Returns True for success, False for failure.

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WriteString
<Awaitable> Function WriteStringAsyncAsync(ByVal str As String) As IAsyncOperation(Of Boolean)
Introduced in version 9.5.0.56

Writes a string to a stream. The actual bytes written are the byte representation of the string as indicated by the StringCharset property. For example, to write utf-8 bytes, first set StringCharset equal to "utf-8" and then call WriteString.

Returns True for success, False for failure.

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Events