Compression Xojo Plugin Reference Documentation
Compression
Current Version: 11.4.0
Provides a flexible and efficient API for compressing and decompressing data in memory, files, and streams. It supports multiple compression algorithms, chunked processing for large data, and optional encoding for easy transport or storage.
Key Features
- Multiple Compression Algorithms
deflatezlib(deflate with header)bzip2lzw
- Flexible Data Types
- Byte arrays
- Strings (with configurable charset)
BinDataandStringBuilder- Files and streams
- Streaming Support
- Compress/decompress arbitrarily large data with constant memory usage
- Ideal for files, sockets, or continuous data streams
- Chunked Processing
- Process data incrementally using
FirstChunkandLastChunk - Replace older Begin/More/End patterns
- Process data incrementally using
- Encoded Output Options
- Return compressed data as:
- Base64
- Hex
- 20+ other encodings
- Return compressed data as:
- Integrated Compression + Encryption
- Combine compression and encryption in a single operation
Object Creation
Dim compression As New Chilkat.Compression
Properties
Algorithm
Specifies the compression algorithm to use. Supported values are
deflate, zlib, bzip2, and lzw.
The zlib option is the deflate algorithm with a zlib header.
Note: ppmd is deprecated and should not be used.
It was only available on 32-bit systems and specifically used the J variant.
New applications should use one of the supported algorithms listed above.
Charset
Specifies the character encoding used when converting text to bytes before compression, and bytes back to text after decompression.
The current default is the computer’s ANSI charset, such as Windows-1252 on many
Western Windows systems. However, most modern applications should explicitly set
this property to utf-8.
Recommendation: Set Charset = "utf-8" unless you
specifically need compatibility with another encoding.
DebugLogFilePath
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.
DeflateLevel
Sets the compression level used by the deflate and zlib
algorithms.
0means no compression.9means maximum compression.- The default value is
6.
Higher values may produce smaller output but can require more processing time.
topEncodingMode
Specifies the text encoding used by methods whose names end in ENC,
such as CompressBytesENC and DecompressStringENC.
Compression methods ending in ENC return compressed binary data as
an encoded string. Decompression methods ending in ENC expect the
input string to use this same encoding.
Valid values include:
base64hexurlquoted-printable
FirstChunk
Indicates that the next chunk-aware compression or decompression call is the first chunk in a sequence.
The default value is True
When both FirstChunk and LastChunk are
True
HeartbeatMs
Specifies the interval, in milliseconds, between AbortCheck event
callbacks.
This allows an application to periodically check whether a long-running operation should be aborted.
The default value is 0, which disables AbortCheck
callbacks.
LastChunk
Indicates that the next chunk-aware compression or decompression call is the final chunk in a sequence.
The default value is True
When both FirstChunk and LastChunk are
True
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
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
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
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.
UncommonOptions
Provides a way to enable specialized or uncommon behavior. This property normally remains empty.
It may be set to a comma-separated list of keywords.
Supported option:
-
Crypt2CompressHdr— Duplicates the compression/decompression header behavior used by the deprecated and removed Crypt2 compression functions.
VerboseLogging
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
Methods
CompressBd
Compresses the data contained in a BinData object.
The BinData object is modified to contain the compressed result.
This method is not FirstChunk / LastChunk aware.
Returns True for success, False for failure.
CompressBdAsync (1)
Creates an asynchronous task to call the CompressBd method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressBd2
Compresses the data in one BinData object and appends the
compressed output to another BinData object.
The input BinData is not modified.
This method is FirstChunk / LastChunk aware.
Returns True for success, False for failure.
CompressBd2Async (1)
Creates an asynchronous task to call the CompressBd2 method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressBytes
Compresses a byte array and returns the compressed bytes.
This method is FirstChunk / LastChunk aware.
Returns Nil on failure
CompressBytesAsync (1)
Creates an asynchronous task to call the CompressBytes method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressBytesENC
Compresses a byte array and returns the compressed result as an encoded string.
The output encoding is controlled by EncodingMode.
This method is not FirstChunk / LastChunk aware.
Returns Nil on failure
CompressBytesENCAsync (1)
Creates an asynchronous task to call the CompressBytesENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressEncryptFile
Compresses and encrypts a file, writing the result to a destination file.
The compression and encryption are performed internally in streaming mode, so files of any size can be processed without loading the entire file into memory.
Returns True for success, False for failure.
CompressEncryptFileAsync (1)
Creates an asynchronous task to call the CompressEncryptFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressFile
Compresses a source file and writes the compressed data to a destination file.
The file is processed internally in streaming mode, allowing files of any size to be compressed with stable memory usage.
Returns True for success, False for failure.
CompressFileAsync (1)
Creates an asynchronous task to call the CompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressSb
Compresses the text contained in a StringBuilder and appends the
compressed bytes to a BinData object.
Text is converted to bytes according to the Charset property.
This method is FirstChunk / LastChunk aware.
Returns True for success, False for failure.
CompressSbAsync (1)
Creates an asynchronous task to call the CompressSb method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressStr
Compresses a string and appends the compressed bytes to a BinData
object.
The string is converted to bytes using the charset specified by the
Charset property.
This method is FirstChunk / LastChunk aware.
Returns True for success, False for failure.
topCompressStrAsync (1)
Creates an asynchronous task to call the CompressStr method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressStream
Compresses data from a stream source and writes the compressed data to the stream sink.
The operation is performed in streaming mode, making it suitable for very large or even continuous streams while maintaining stable memory usage.
Returns True for success, False for failure.
CompressStreamAsync (1)
Creates an asynchronous task to call the CompressStream method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressString
Compresses a string and returns the compressed bytes.
The string is converted to bytes using the Charset property.
This method is FirstChunk / LastChunk aware.
Returns Nil on failure
CompressStringAsync (1)
Creates an asynchronous task to call the CompressString method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
CompressStringENC
Compresses a string and returns the compressed result as an encoded string.
The string is first converted to bytes using Charset, then
compressed, and finally encoded according to EncodingMode.
This method is not FirstChunk / LastChunk aware.
Returns Nil on failure
CompressStringENCAsync (1)
Creates an asynchronous task to call the CompressStringENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressBd
Decompresses the compressed data contained in a BinData object.
The BinData object is modified to contain the decompressed result.
This method is not FirstChunk / LastChunk aware.
Returns True for success, False for failure.
DecompressBdAsync (1)
Creates an asynchronous task to call the DecompressBd method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressBd2
Decompresses the data in one BinData object and appends the
decompressed output to another BinData object.
The input BinData is not modified.
This method is FirstChunk / LastChunk aware.
Returns True for success, False for failure.
DecompressBd2Async (1)
Creates an asynchronous task to call the DecompressBd2 method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressBytes
Decompresses compressed byte data and returns the decompressed bytes.
This method is FirstChunk / LastChunk aware.
Returns Nil on failure
DecompressBytesAsync (1)
Creates an asynchronous task to call the DecompressBytes method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressBytesENC
Decompresses compressed data supplied as an encoded string and returns the decompressed bytes.
The input string is decoded according to EncodingMode before being
decompressed.
Returns Nil on failure
DecompressBytesENCAsync (1)
Creates an asynchronous task to call the DecompressBytesENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressFile
Decompresses a source file and writes the decompressed data to a destination file.
The file is processed internally in streaming mode, allowing files of any size to be decompressed without loading the entire file into memory.
Returns True for success, False for failure.
DecompressFileAsync (1)
Creates an asynchronous task to call the DecompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressSb
Decompresses compressed data from a BinData object and appends the
resulting text to a StringBuilder.
The decompressed bytes are converted to text using the Charset
property.
This method is FirstChunk / LastChunk aware.
Returns True for success, False for failure.
DecompressSbAsync (1)
Creates an asynchronous task to call the DecompressSb method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressStream
Decompresses data from a stream source and writes the decompressed data to the stream sink.
The operation is performed in streaming mode, making it suitable for very large or continuous streams while maintaining stable memory usage.
Returns True for success, False for failure.
DecompressStreamAsync (1)
Creates an asynchronous task to call the DecompressStream method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecompressString
Decompresses compressed byte data and returns the resulting string.
The decompressed bytes are converted to text using the Charset
property.
This method is FirstChunk / LastChunk aware.
Returns Nil on failure
DecompressStringENC
Decompresses compressed data supplied as an encoded string and returns the resulting text.
The input string is decoded according to EncodingMode, then
decompressed. The resulting bytes are converted to text using
Charset.
This method is not FirstChunk / LastChunk aware.
Returns Nil on failure
DecompressStringENCAsync (1)
Creates an asynchronous task to call the DecompressStringENC method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
DecryptDecompressFile
Decrypts and decompresses a file, writing the restored data to a destination file.
This is the reverse operation of CompressEncryptFile.
Returns True for success, False for failure.
DecryptDecompressFileAsync (1)
Creates an asynchronous task to call the DecryptDecompressFile method with the arguments provided.
Note: Async method event callbacks happen in the background thread. Accessing and updating UI elements existing in the main thread may require special considerations.
Returns Nil on failure
LoadTaskCaller
Events
To implement events, your application would define and implement a class that is a subclass of Chilkat.Compression. Your custom class would implement (i.e. override) some or all of the event methods.
For example:
class MyCompression
Inherits Chilkat.Compression
Function AbortCheck() As Boolean
Function PercentDone(pctDone As Int32) As Boolean
Sub ProgressInfo(name As String, value As String)
Sub TaskCompleted(task As Chilkat.Task)
End ClassAbortCheck
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.
PercentDone
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.
ProgressInfo
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.
TaskCompleted
Called from the background thread when an asynchronous task completes.
Deprecated
BeginCompressBytes
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2 .
Large amounts of binary byte data may be compressed in chunks by first calling BeginCompressBytes, followed by 0 or more calls to MoreCompressedBytes, and ending with a final call to EndCompressBytes. Each call returns 0 or more bytes of compressed data which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nil on failure
BeginCompressBytesENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Large amounts of binary byte data may be compressed in chunks by first calling BeginCompressBytesENC, followed by 0 or more calls to MoreCompressedBytesENC, and ending with a final call to EndCompressBytesENC. Each call returns 0 or more characters of compressed data (encoded as a string according to the EncodingMode property setting) which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nil on failure
BeginCompressString
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Large amounts of string data may be compressed in chunks by first calling BeginCompressString, followed by 0 or more calls to MoreCompressedString, and ending with a final call to EndCompressString. Each call returns 0 or more bytes of compressed data which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nil on failure
BeginCompressStringENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Large amounts of string data may be compressed in chunks by first calling BeginCompressStringENC, followed by 0 or more calls to MoreCompressedStringENC, and ending with a final call to EndCompressStringENC. Each call returns 0 or more characters of compressed data (encoded as a string according to the EncodingMode property setting) which may be output to a compressed data stream (such as a file, socket, etc.).
Returns Nil on failure
BeginDecompressBytes
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressBytes, followed by 0 or more calls to MoreDecompressedBytes, and ending with a final call to EndDecompressBytes. Each call returns 0 or more bytes of decompressed data.
Returns Nil on failure
BeginDecompressBytesENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressBytesENC, followed by 0 or more calls to MoreDecompressedBytesENC, and ending with a final call to EndDecompressBytesENC. Each call returns 0 or more bytes of decompressed data.
Returns Nil on failure
BeginDecompressString
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressString, followed by 0 or more calls to MoreDecompressedString, and ending with a final call to EndDecompressString. Each call returns 0 or more characters of decompressed text.
Returns Nil on failure
BeginDecompressStringENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
A compressed data stream may be decompressed in chunks by first calling BeginDecompressStringENC, followed by 0 or more calls to MoreDecompressedStringENC, and ending with a final call to EndDecompressStringENC. Each call returns 0 or more characters of decompressed text.
Returns Nil on failure
EndCompressBytes
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytes)
Returns Nil on failure
EndCompressBytesENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytesENC)
Returns Nil on failure
EndCompressString
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressString)
Returns Nil on failure
EndCompressStringENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressStringENC)
Returns Nil on failure
EndDecompressBytes
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressBytes)
Returns Nil on failure
EndDecompressBytesENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressBytesENC)
Returns Nil on failure
EndDecompressString
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressString)
Returns Nil on failure
EndDecompressStringENC
The Begin*, More*, and End* methods are replaced with the FirstChunk and LastChunk properties used in combination with FirstChunk/LastChunk aware methods, such as CompressStr and DecompressBd2.
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressStringENC)
Returns Nil on failure
MoreCompressBytes
MoreCompressBytesENC
MoreCompressString
MoreCompressStringENC
MoreDecompressBytes
MoreDecompressBytesENC
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressBytesENC)
Returns Nil on failure
MoreDecompressString
MoreDecompressStringENC
The input to this method is an encoded string containing compressed data. The EncodingMode property should be set prior to calling this method. The input string is decoded according to the EncodingMode (hex, base64, etc.) and then decompressed.
(See BeginDecompressStringENC)
Returns Nil on failure