Compression Xojo Plugin Reference Documentation
Compression
Current Version: 11.0.0
Implements the Bzip2, Deflate, and LZW compression algorithms.
Object Creation
Dim compression As New Chilkat.Compression
Properties
Algorithm
Specifies the compression algorithm: "deflate", "zlib", "bzip2", or "lzw". Note that "ppmd" is deprecated and should not be used. It was only available for 32-bit systems and specifically used the "J" variant. Please transition to one of the recommended algorithms.
topCharset
Specifies the character encoding for compressing or decompressing strings. Options include utf-8 (default), windows-1252, Shift_JIS, iso-8859-2, and others.
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
This property allows for customization of the compression level for the "deflate" and "zlib" compression algoirthms. ("zlib" is just the deflate algorithm with a zlib header.) A value of 0 = no compression, while 9 = maximum compression. The default is 6.
topEncodingMode
Controls the encoding expected by methods ending in "ENC", such as CompressBytesENC. Valid values are "base64", "hex", "url", and "quoted-printable". Compression methods ending in ENC return the binary compressed data as an encoded string using this encoding. Decompress methods expect the input string to be this encoding.
topFirstChunk
This property applies to FirstChunk and LastChunk aware compression and decompression methods. It signifies that the data being compressed is the first of multiple chunks.
The default value is True.
When both FirstChunk and LastChunk, it means the entire amount of data to be compressed or decompressed is presented in a single call.
HeartbeatMs
The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort any method call prior to completion. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire.
topLastChunk
This property applies to FirstChunk and LastChunk aware compression and decompression methods. It signifies that the data being compressed is the last of multiple chunks.
The default value is True.
When both FirstChunk and LastChunk, it means the entire amount of data to be compressed or decompressed is presented in a single call.
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.
UncommonOptions
This is a catch-all property to be used for uncommon needs. This property defaults to the empty string and should typically remain empty.
Can be set to a list of the following comma separated keywords:
Crypt2CompressHdr- Duplicates the compression and decompression as implemented in 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 bd. 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
This method compresses the data in bdIn without modifying it and appends the compressed data to bdOut. It is also FirstChunk/LastChunk aware.
Returns True for success, False for failure.
topCompressBd2Async (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 byte data.
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
CompressEncryptFile
Performs file-to-file compression and encryption. Files of any size may be compressed because the file is compressed and encrypted internally in streaming mode.
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
Performs file-to-file compression. Files of any size may be compressed because the file is compressed internally in streaming mode.
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 contents of sb and appends the compressed bytes to binData.
This method is FirstChunk/LastChunk aware.
Returns True for success, False for failure.
topCompressSbAsync (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 to bd. The byte representation (character encoding) of the actual bytes to be compressed is determined 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 a stream. Internally, the strm's source is read, compressed, and the compressed data written to the strm's sink. It does this in streaming fashion. Extremely large or even infinite streams can be compressed with stable ungrowing 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.
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 data encoded to a string. The output encoding (hex, base64, etc.) is determined by the EncodingMode property setting.
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 data contained in bd. 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
This method decompresses the data in bdIn without modifying it and appends the decompressed data to bdOut. It is also FirstChunk/LastChunk aware.
Returns True for success, False for failure.
topDecompressBd2Async (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
This method decompresses 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
DecompressFile
Performs file-to-file decompression (the opposite of CompressFile). Internally the file is decompressed in streaming mode which allows files of any size to be decompressed.
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 the contents of binData and appends the decompressed string to sb.
This method is FirstChunk/LastChunk aware.
Returns True for success, False for failure.
topDecompressSbAsync (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 a stream. Internally, the strm's source is read, decompressed, and the decompressed data written to the strm's sink. It does this in streaming fashion. Extremely large or even infinite streams can be decompressed with stable ungrowing 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
DecryptDecompressFile
Performs file-to-file decryption and decompression.
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
Provides the opportunity for a method call to be aborted. The AbortCheck event is fired periodically based on the value of the HeartbeatMs property. If HeartbeatMs is 0, then no AbortCheck events will fire. As an example, to fire 5 AbortCheck events per second, set the HeartbeatMs property equal to 200.
PercentDone
Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This event is only fired when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For operations (Chilkat method calls) that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).
The PercentDone callback counts as an AbortCheck event. For method calls that complete quickly such that PercentDone events fire, it may be that AbortCheck events don't fire because the opportunity to abort is already provided in the PercentDone callback. For time consuming operations, where the amount of time between PercentDone callbacks are long, AbortCheck callbacks may be used to allow for the operation to be aborted in a more responsive manner.
The abort output argument provides a means for aborting the operation. Setting it to True will cause the method to abort and return a failed status (or whatever return value indicates failure).
ProgressInfo
A general name/value event that provides information about what is happening during a method call. To find out what information is available, write code to handle this event and log the name/value pairs. Most are self-explanatory.
TaskCompleted
Called in the background thread when an asynchronous task completes.
Deprecated
BeginCompressBytes
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
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
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
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
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 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
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 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
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytes)
Returns Nil on failure
EndCompressBytesENC
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressBytesENC)
Returns Nil on failure
EndCompressString
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressString)
Returns Nil on failure
EndCompressStringENC
Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.
(See BeginCompressStringENC)
Returns Nil on failure
EndDecompressBytes
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressBytes)
Returns Nil on failure
EndDecompressBytesENC
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
Called to finalize the decompression stream and return any remaining (buffered) decompressed data.
(See BeginDecompressString)
Returns Nil on failure
EndDecompressStringENC
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