Stream Dart Reference Documentation
CkStream
Current Version: 11.6.1
Chilkat.Stream
Stream from a source file, byte array, string, or selected file part
without manually loading or copying all data first.
Write streamed data to a sink file, append to an existing file, or output
to
Read or write raw bytes, fixed byte counts, encoded byte strings,
individual bytes, or
Read and write strings using
Control read and write wait behavior, poll for immediately available
data, and inspect read or write failure reasons.
Track bytes sent and received, detect end-of-stream or write-closed
state, reset streams, close writing, and abort long-running operations.
Read, write, pipe, monitor, and control byte or text streams.
Chilkat.Stream is a general-purpose streaming object for moving
data between sources and sinks without requiring the entire payload to be
handled at once. A stream can read from files, byte arrays, strings, or other
sources; write to files, memory, BinData,
StringBuilder, or other sinks; handle binary and text data;
apply character-set rules for strings; process file parts; track bytes sent
and received; and support timeouts, polling, aborts, async task integration,
and end-of-stream handling.
File and memory sources
File and object sinks
BinData, StringBuilder, bytes, or strings.
Binary reads and writes
BinData content.
Text streaming
StringCharset, optionally use a
BOM, and read text until CRLF or a matching delimiter.
Timeouts and polling
Progress and lifecycle
BinData, or
StringBuilder. Check EndOfStream,
ReadFailReason, WriteFailReason,
NumReceived, NumSent, and
LastErrorText to understand stream progress and failures.
ReadTimeoutMs, a value of 0 means a polling
read, not an infinite timeout. For WriteTimeoutMs,
0 means return immediately if the stream cannot be written to
right away.
Object Creation
// pubspec.yaml:
// dependencies:
// chilkat: ^11.6.1
import 'package:chilkat/chilkat.dart';
// Once per process, before any other Chilkat call:
Chilkat.unlockBundle('Anything for 30-day trial'); // shorthand for CkGlobal().unlockBundle(..)
final stream = CkStream();
// ... the native object is released when `stream` is garbage collected, or now with stream.dispose().Creates the underlying native Chilkat object. Use a CkStream only from the isolate that created it: Chilkat objects cannot be sent between isolates. Every call is synchronous; in a Flutter app, run long operations (network, large files) inside Isolate.run, creating the Chilkat objects inside the isolate.
Releases the native object immediately instead of waiting for garbage collection (useful for a large CkBinData or an open socket). Calling it more than once is harmless; any other use of the object afterwards throws a StateError. isDisposed tells whether it has been called.
Errors
A method that can fail throws a ChilkatException: a method whose only outcome is success or failure returns void and throws on failure; a method producing a String or an object returns it and throws where Chilkat would have returned null. The exception carries the object's LastErrorText at the time of the failure (lastErrorText), the class and method names (className, methodName) and a one-line message. Properties never throw, and methods that answer a question (has..., is..., ...) return a plain bool.
try {
stream.someMethod(...);
} on ChilkatException catch (e) {
print(e); // CkStream.someMethod failed: <reason>
print(e.lastErrorText); // the full Chilkat log of the failed call
}Properties
AbortCurrent
bool get abortCurrent
set abortCurrent(bool value)
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.)
CanRead
bool get canRead
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.
CanWrite
bool get canWrite
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.
DataAvailable
bool get dataAvailable
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).
DebugLogFilePath
String get debugLogFilePath
set debugLogFilePath(String value)
If set to a file path, this property logs the LastErrorText of each Chilkat method or property call to the specified file. This logging helps identify the context and history of Chilkat calls leading up to any crash or hang, aiding in debugging.
Enabling the VerboseLogging property provides more detailed information. This property is mainly used for debugging rare instances where a Chilkat method call causes a hang or crash, which should generally not happen.
Possible causes of hangs include:
- A timeout property set to 0, indicating an infinite timeout.
- A hang occurring within an event callback in the application code.
- An internal bug in the Chilkat code causing the hang.
DefaultChunkSize
int get defaultChunkSize
set defaultChunkSize(int value)
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.
topEndOfStream
bool get endOfStream
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).
HeartbeatMs
int get heartbeatMs
set heartbeatMs(int value)
The interval in milliseconds between each AbortCheck event callback, which enables an application to abort certain method calls before they complete. By default, HeartbeatMs is set to 0, meaning no AbortCheck event callbacks will trigger.
IsWriteClosed
bool get isWriteClosed
true if the stream is closed for writing. Once closed, no more data may be written to the stream.
LastErrorHtml
String get lastErrorHtml
Provides HTML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastErrorText
String get lastErrorText
Provides plain text information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
LastErrorXml
String get lastErrorXml
Provides XML-formatted information about the last called method or property. If a method call fails or behaves unexpectedly, check this property for details. Note that information is available regardless of the method call's success.
topLastMethodSuccess
bool get lastMethodSuccess
set lastMethodSuccess(bool value)
Indicates the success or failure of the most recent method call: true means success, false means failure. This property remains unchanged by property setters or getters. This method is present to address challenges in checking for null or Nothing returns in certain programming languages. Note: This property does not apply to methods that return integer values or to boolean-returning methods where the boolean does not indicate success or failure.
Length
int get length
set length(int value)
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.
topLength32
int get length32
set length32(int value)
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).
topNumReceived
int get numReceived
The number of bytes received by the stream.
topNumSent
int get numSent
The number of bytes sent by the stream.
topReadFailReason
int get readFailReason
This property is automatically set when a Read* method is called. It indicates the reason for failure. Possible values are:
- 0>
- No failure (success)
- Timeout, or no data is immediately available for a polling read.
- Aborted by an application callback.
- Already at end-of-stream.
- Fatal stream error.
- Out-of-memory error (this is very unlikely).
ReadTimeoutMs
int get readTimeoutMs
set readTimeoutMs(int value)
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.
topSinkFile
String get sinkFile
set sinkFile(String value)
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.
topSinkFileAppend
bool get sinkFileAppend
set sinkFileAppend(bool value)
If true, the stream appends to the SinkFile rather than truncating and re-writing the sink file. The default value is false.
SourceFile
String get sourceFile
set sourceFile(String value)
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.
topSourceFilePart
int get sourceFilePart
set sourceFilePart(int value)
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.
SourceFilePartSize
int get sourceFilePartSize
set sourceFilePartSize(int value)
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.
StringBom
bool get stringBom
set stringBom(bool value)
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.
StringCharset
String get stringCharset
set stringCharset(String value)
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.
VerboseLogging
bool get verboseLogging
set verboseLogging(bool 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.
Version
String get version
WriteFailReason
int get writeFailReason
This property is automatically set when a Write* method is called. It indicates the reason for failure. Possible values are:
- 0>
- No failure (success)
- Timeout, or unable to immediately write when the WriteTimeoutMs is 0.
- Aborted by an application callback.
- The stream has already ended.
- Fatal stream error.
- Out-of-memory error (this is very unlikely).
WriteTimeoutMs
int get writeTimeoutMs
set writeTimeoutMs(int value)
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.
topMethods
ReadBd
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 normally on success; throws a ChilkatException on failure.
ReadBytesENC
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.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
ReadNBytesENC
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.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
ReadSb
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 normally on success; throws a ChilkatException on failure.
ReadString
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.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
ReadToCRLF
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.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
ReadUntilMatch
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.
Throws a ChilkatException on failure (where the description says null is returned, the Dart method throws instead).
Reset
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.
topSetSourceString
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 normally on success; throws a ChilkatException on failure.
WriteBd
Writes the contents of binData to the stream.
Returns normally on success; throws a ChilkatException on failure.
WriteByte
Writes a single byte to the stream. The byteVal must have a value from 0 to 255.
Returns normally on success; throws a ChilkatException on failure.
WriteBytes2
Writes binary bytes to a stream.
Returns normally on success; throws a ChilkatException on failure.
WriteBytesENC
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 normally on success; throws a ChilkatException on failure.
WriteClose
Indicates that no more data will be written to the stream.
Returns normally on success; throws a ChilkatException on failure.
WriteSb
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 normally on success; throws a ChilkatException on failure.
WriteString
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 normally on success; throws a ChilkatException on failure.
Events
All Chilkat methods are synchronous: the call returns when the work is done. During a call, CkStream raises three events so your application can show progress and offer a way out. Each event is a nullable callback property on the object; assign a function to receive it, or null to stop receiving it:
final stream = CkStream();
stream.onPercentDone = (pct) {
print('$pct%');
return false; // return true to abort the method in progress
};
stream.onProgressInfo = (name, value) => print('$name: $value');
stream.heartbeatMs = 250; // raise onAbortCheck 4 times per second during Chilkat calls
stream.onAbortCheck = () => _userPressedCancel;AbortCheck fires at regular intervals controlled by the HeartbeatMs property (0, the default, disables it); PercentDone fires when an operation's completion percentage is known; ProgressInfo delivers named progress values. Returning true from onAbortCheck or onPercentDone aborts the running method, which then throws a ChilkatException.
Events fire on the thread that called the method, before that method returns. An exception thrown inside a callback aborts the running method and is rethrown from it once the native library has returned. In a Flutter app the callbacks run inside the worker isolate that owns the object; forward progress to the UI through a SendPort, and let onAbortCheck read a flag the UI sets the same way.
AbortCheck
bool Function()? onAbortCheck
Enables a method call to be aborted by triggering the AbortCheck event at intervals defined by the HeartbeatMs property. If HeartbeatMs is set to its default value of 0, no events will occur. For instance, set HeartbeatMs to 200 to trigger 5 AbortCheck events per second.
Example:
stream.heartbeatMs = 250; // call onAbortCheck 4 times per second
var cancelRequested = false;
stream.onAbortCheck = () => cancelRequested;
// ... set cancelRequested = true (e.g. from a message received on a ReceivePort) to abort the method in progressPercentDone
bool Function(int pctDone)? onPercentDone
This provides the percentage completion for any method involving network communications or time-consuming processing, assuming the progress can be measured as a percentage. This event is triggered only when it's possible and logical to express the operation's progress as a percentage. The pctDone argument will range from 1 to 100. For methods that finish quickly, the number of PercentDone callbacks may vary, but the final callback will have pctDone equal to 100. For longer operations, callbacks will not exceed one per percentage point (e.g., 1, 2, 3, ..., 98, 99, 100).
The PercentDone callback also acts as an AbortCheck event. For fast methods where PercentDone fires, an AbortCheck event may not trigger since the PercentDone callback already provides an opportunity to abort. For longer operations, where time between PercentDone callbacks is extended, AbortCheck callbacks enable more responsive operation termination.
To abort the operation, set the abort output argument to true. This will cause the method to terminate and return a failure status or corresponding failure value.
Example:
stream.onPercentDone = (pct) {
// pct ranges from 1 to 100.
print('Percent done: $pct');
return false; // return true to abort the method in progress
};ProgressInfo
void Function(String name, String value)? onProgressInfo
This event callback provides tag name/value pairs that detail what occurs during a method call. To discover existing tag names, create code to handle the event, emit the pairs, and review them. Most tag names are self-explanatory.
Note: Some Chilkat methods don't fire any ProgressInfo events.
Example:
stream.onProgressInfo = (name, value) => print('$name: $value');