Stream Lianja Reference Documentation

Stream

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

loObject = createobject("CkStream")

Properties

AbortCurrent As Boolean

Introduced in version 9.5.0.58

When set to .T., 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 .F. when the next method is called. When the abort occurs, this property is reset to .F.. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

CanRead As Boolean (read-only)

Introduced in version 9.5.0.56

.T. if the stream supports reading. Otherwise .F..

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

CanWrite As Boolean (read-only)

Introduced in version 9.5.0.56

.T. if the stream supports writing. Otherwise .F..

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

DataAvailable As Boolean (read-only)

Introduced in version 9.5.0.56

.T. if it is known for sure that data is ready and waiting to be read. .F. 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).

DebugLogFilePath As Character

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.

DefaultChunkSize As Numeric

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.

EndOfStream As Boolean (read-only)

Introduced in version 9.5.0.56

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

IsWriteClosed As Boolean (read-only)

Introduced in version 9.5.0.56

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

LastErrorHtml As Character (read-only)

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.

LastErrorText As Character (read-only)

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.

Concept of LastErrorText

LastErrorText Standard Information

LastErrorXml As Character (read-only)

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.

LastMethodSuccess As Boolean

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of .T. indicates success, a value of .F. 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 = .T. and failure = .F..
  • 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 .T.. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

Length As Numeric

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.

Length32 As Numeric

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).

NumReceived As Numeric (read-only)

Introduced in version 9.5.0.56

The number of bytes received by the stream.

NumSent As Numeric (read-only)

Introduced in version 9.5.0.56

The number of bytes sent by the stream.

ReadFailReason As Numeric (read-only)

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).

ReadTimeoutMs As Numeric

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.

SinkFile As Character

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.

Copy a File using a Stream

SourceFile As Character

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.

Copy a File using a Stream

SourceFilePart As Numeric

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.

S3 Upload the Parts for a Multipart Upload

SourceFilePartSize As Numeric

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.

S3 Upload the Parts for a Multipart Upload

StringBom As Boolean

Introduced in version 9.5.0.56

If .T., 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 .T., then include the BOM when writing a string via the WriteString method. The default value of this property is .F..

StringCharset As Character

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".

Charsets Supported by Chilkat

VerboseLogging As Boolean

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

Version As Character (read-only)

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

WriteFailReason As Numeric (read-only)

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).

WriteTimeoutMs As Numeric

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.

Methods

ReadBd(binData As CkBinData) As 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 .T. for success, .F. for failure.

Unzip Binary File to Stream

ReadBdAsync(binData As CkBinData) As CkTask

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 .F. on failure

FTP Download Binary File to a Stream

ReadBytesENC(encoding As Character) As Character

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 .F. on failure

Binary Encodings Supported by Chilkat

ReadBytesENCAsync(encoding As Character) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

ReadNBytesENC(numBytes As Numeric, encoding As Character) As Character

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 .F. on failure

Binary Encodings Supported by Chilkat

ReadNBytesENCAsync(numBytes As Numeric, encoding As Character) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

ReadSb(sb As CkStringBuilder) As 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 .T. for success, .F. for failure.

ReadSbAsync(sb As CkStringBuilder) As CkTask

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 .F. on failure

Unzip One File to a Stream

ReadString() As Character

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 .F. on failure

ReadStringAsync() As CkTask

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 .F. on failure

How to Run an Asynchronous Task

ReadToCRLF() As Character

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 .F. on failure

ReadToCRLFAsync() As CkTask

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 .F. on failure

How to Run an Asynchronous Task

ReadUntilMatch(matchStr As Character) As Character

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 .F. on failure

Firebase Receive Server-Sent Events (text/event-stream)

ReadUntilMatchAsync(matchStr As Character) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

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.

RunStream() As 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 .T. for success, .F. for failure.

Chaining Asynchronous Streams

RunStreamAsync() As CkTask

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 .F. on failure

How to Run an Asynchronous Task

SaveLastError(path As Character) As Boolean

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns .T. for success, .F. for failure.

SetSinkStream(strm As CkStream) 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 .T. for success, .F. for failure.

SetSourceStream(strm As CkStream) 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 .T. for success, .F. for failure.

Chaining Asynchronous Streams

SetSourceString(srcStr As Character, charset As Character) 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 .T. for success, .F. for failure.

WriteBd(binData As CkBinData) As Boolean

Introduced in version 9.5.0.67

Writes the contents of binData to the stream.

Returns .T. for success, .F. for failure.

WriteBdAsync(binData As CkBinData) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

WriteByte(byteVal As Numeric) As 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 .T. for success, .F. for failure.

WriteByteAsync(byteVal As Numeric) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

WriteBytesENC(byteData As Character, encoding As Character) As 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 .T. for success, .F. for failure.

Binary Encodings Supported by Chilkat

WriteBytesENCAsync(byteData As Character, encoding As Character) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

WriteClose() As Boolean

Introduced in version 9.5.0.56

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

Returns .T. for success, .F. for failure.

WriteSb(sb As CkStringBuilder) As 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 .T. for success, .F. for failure.

WriteSbAsync(sb As CkStringBuilder) As CkTask

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 .F. on failure

How to Run an Asynchronous Task

WriteString(str As Character) As 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 .T. for success, .F. for failure.

WriteStringAsync(str As Character) As CkTask

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 .F. on failure

How to Run an Asynchronous Task