Stream DataFlex 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

// (Dataflex programs use the 32-bit Chilkat ActiveX)
Handle hoStream
Get Create(RefClass(cComChilkatStream)) to hoStream

Properties

AbortCurrent
Function ComAbortCurrent Returns Boolean
Procedure Set ComAbortCurrent Boolean value
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
Function ComCanRead Returns Boolean
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
Function ComCanWrite Returns Boolean
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
Function ComDataAvailable Returns Boolean
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
Function ComDebugLogFilePath Returns String
Procedure Set ComDebugLogFilePath String value

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
Function ComDefaultChunkSize Returns Integer
Procedure Set ComDefaultChunkSize Integer value
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
Function ComEndOfStream Returns Boolean
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
Function ComIsWriteClosed Returns Boolean
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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LastBinaryResult
Function ComLastBinaryResult Returns Variant
Introduced in version 9.5.0.52

The binary data returned by the last (binary data returning) method called. Only available if Chilkat.Global.KeepBinaryResult is set to True. This provides a means for obtaining large varbinary results in the SQL Server environment (where limitations exist in getting large amounts of data returned by method calls, but where temp tables can be used for binary properties).

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LastErrorHtml
Function ComLastErrorHtml Returns String

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
Function ComLastErrorText Returns String

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
Function ComLastErrorXml Returns String

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
Function ComLastMethodSuccess Returns Boolean
Procedure Set ComLastMethodSuccess Boolean value
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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LastStringResult
Function ComLastStringResult Returns String
Introduced in version 9.5.0.52

The string return value of the last (string returning) method called. Only available if Chilkat.Global.KeepStringResult is set to True. This provides a means for obtaining large string results in the SQL Server environment (where limitations exist in getting long strings returned by method calls, but where temp tables can be used for string properties).

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LastStringResultLen
Function ComLastStringResultLen Returns Integer
Introduced in version 9.5.0.53

The length, in characters, of the string contained in the LastStringResult property.

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Length
Function ComLength Returns Integer
Procedure Set ComLength Integer value
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
Function ComLength32 Returns Integer
Procedure Set ComLength32 Integer value
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
Function ComNumReceived Returns Integer
Introduced in version 9.5.0.56

The number of bytes received by the stream.

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NumSent
Function ComNumSent Returns Integer
Introduced in version 9.5.0.56

The number of bytes sent by the stream.

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ReadFailReason
Function ComReadFailReason Returns Integer
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
Function ComReadTimeoutMs Returns Integer
Procedure Set ComReadTimeoutMs Integer value
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
Function ComSinkFile Returns String
Procedure Set ComSinkFile String value
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
Function ComSourceFile Returns String
Procedure Set ComSourceFile String value
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
Function ComSourceFilePart Returns Integer
Procedure Set ComSourceFilePart Integer value
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
Function ComSourceFilePartSize Returns Integer
Procedure Set ComSourceFilePartSize Integer value
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
Function ComStringBom Returns Boolean
Procedure Set ComStringBom Boolean value
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
Function ComStringCharset Returns String
Procedure Set ComStringCharset String value
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
Function ComVerboseLogging Returns Boolean
Procedure Set ComVerboseLogging Boolean value

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
Function ComVersion Returns String

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

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WriteFailReason
Function ComWriteFailReason Returns Integer
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
Function ComWriteTimeoutMs Returns Integer
Procedure Set ComWriteTimeoutMs Integer value
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
Function ComReadBd cComChilkatBinData binData Returns 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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ReadBdAsync (1)
Function ComReadBdAsync cComChilkatBinData binData Returns cComChilkatTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the ReadBd method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

More Information and Examples
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ReadBytes
Function ComReadBytes Returns Variant
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 null on failure

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ReadBytesAsync (1)
Function ComReadBytesAsync Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadBytes method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadBytesENC
Function ComReadBytesENC String encoding Returns 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 null on failure

More Information and Examples
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ReadBytesENCAsync (1)
Function ComReadBytesENCAsync String encoding Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadBytesENC method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadNBytes
Function ComReadNBytes Integer numBytes Returns Variant
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 null on failure

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ReadNBytesAsync (1)
Function ComReadNBytesAsync Integer numBytes Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadNBytes method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadNBytesENC
Function ComReadNBytesENC Integer numBytes String encoding Returns 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 null on failure

More Information and Examples
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ReadNBytesENCAsync (1)
Function ComReadNBytesENCAsync Integer numBytes String encoding Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadNBytesENC method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadSb
Function ComReadSb cComChilkatStringBuilder sb Returns 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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ReadSbAsync (1)
Function ComReadSbAsync cComChilkatStringBuilder sb Returns cComChilkatTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the ReadSb method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

More Information and Examples
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ReadString
Function ComReadString Returns 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 null on failure

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ReadStringAsync (1)
Function ComReadStringAsync Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadString method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadToCRLF
Function ComReadToCRLF Returns 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 null on failure

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ReadToCRLFAsync (1)
Function ComReadToCRLFAsync Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadToCRLF method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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ReadUntilMatch
Function ComReadUntilMatch String matchStr Returns 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 null on failure

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ReadUntilMatchAsync (1)
Function ComReadUntilMatchAsync String matchStr Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the ReadUntilMatch method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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Reset
Procedure ComReset
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
Function ComRunStream Returns 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.

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RunStreamAsync (1)
Function ComRunStreamAsync Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the RunStream method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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SetSinkStream
Function ComSetSinkStream cComChilkatStream strm Returns 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 ComSetSourceBytes Variant sourceData Returns 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 ComSetSourceStream cComChilkatStream strm Returns 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.

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SetSourceString
Function ComSetSourceString String srcStr String charset Returns 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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ToDecimalStr
Function ComToDecimalStr String propertyName Returns String
Introduced in version 9.5.0.56

Some programming languages do not support 64-bit integers. The following properties are implemented as 64-bit ints: Length, NumReceived, NumSent. The value of these properties can be retrieved in decimal string form by passing the property name in propertyName.

Returns null on failure

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WriteBd
Function ComWriteBd cComChilkatBinData binData Returns 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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WriteBdAsync (1)
Function ComWriteBdAsync cComChilkatBinData binData Returns cComChilkatTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the WriteBd method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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WriteByte
Function ComWriteByte Integer byteVal Returns 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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WriteByteAsync (1)
Function ComWriteByteAsync Integer byteVal Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the WriteByte method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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WriteBytes
Function ComWriteBytes Variant byteData Returns 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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WriteBytesAsync (1)
Function ComWriteBytesAsync Variant byteData Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the WriteBytes method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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WriteBytesENC
Function ComWriteBytesENC String byteData String encoding Returns 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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WriteBytesENCAsync (1)
Function ComWriteBytesENCAsync String byteData String encoding Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the WriteBytesENC method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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WriteClose
Function ComWriteClose Returns 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
Function ComWriteSb cComChilkatStringBuilder sb Returns 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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WriteSbAsync (1)
Function ComWriteSbAsync cComChilkatStringBuilder sb Returns cComChilkatTask
Introduced in version 9.5.0.67

Creates an asynchronous task to call the WriteSb method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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WriteString
Function ComWriteString String str Returns 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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WriteStringAsync (1)
Function ComWriteStringAsync String str Returns cComChilkatTask
Introduced in version 9.5.0.56

Creates an asynchronous task to call the WriteString method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns null on failure

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