Compression Chilkat2 Java Reference Documentation
Compression
Current Version: 11.7.0
Markdown version of this page for AI tools (v 11.7.0) · all AI docs
Chilkat.Compression
Supports
Work with byte arrays, strings,
Process data incrementally with
Return compressed bytes as text using encodings such as
Compress or decompress large files and streams with stable memory usage.
Combine compression and encryption in file workflows with integrated methods.
For an extended overview, see
Compression Class Overview.
See also
Binary Encodings
for supported encoded output formats.
Compress and decompress bytes, text, files, and streams with a flexible API.
Chilkat.Compression provides a general-purpose API for compressing
and decompressing data in memory, files, and streams. It supports multiple
algorithms, text charset conversion, encoded output, chunked processing, and
streaming operations for large data.
Multiple algorithms
deflate, zlib,
bzip2, and lzw.
Flexible data types
BinData,
StringBuilder, files, and streams.
Chunked processing
FirstChunk and
LastChunk for chunk-aware methods.
Encoded output
base64, hex, and others.
Streaming support
Compression + encryption
Charset = "utf-8" unless
another encoding is required. For encoded compressed data, set
EncodingMode to the desired output format.
Object Creation
import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Compression;
try (Compression compression = new Compression()) {
// ... use compression ...
} catch (ChilkatException e) {
System.out.println(e.getMessage()); // "Compression.someMethod failed: <reason>"
System.out.println(e.getLastErrorText()); // the full log of the failed call
}Creates the underlying native Chilkat object. The native library (chilkat2java) is loaded the first time any Chilkat2 object is created; see the README in the download for where it is looked for (-Dchilkat2.library.path, a classpath resource, or java.library.path).
Releases the native object (Compression is AutoCloseable, so try-with-resources calls it). Calling it again does nothing; any other method or property accessor called afterwards throws IllegalStateException. An object that is never closed is freed by a background cleaner once it becomes unreachable, but the garbage collector does not see native memory, so closing is the normal path. Objects returned by methods are owned by the caller too.
Returns true once close() has been called.
Errors
A method that fails throws ChilkatException, an unchecked exception carrying getClassName(), getMethodName(), getReason() (one line, also in the message) and getLastErrorText() (the full log, captured at the moment of the failure). The object remains usable. Methods that look something up and find nothing return null instead of throwing (each such method says so), and methods that answer a question (hasMember, isUnlocked, ...) return a plain boolean. Property accessors do not throw for Chilkat reasons.
A null string or object argument throws NullPointerException naming the parameter (except where a method documents that null is accepted), and a string containing U+0000 throws IllegalArgumentException.
Use an object from one thread at a time; it may be handed from one thread to another. The one cross-thread operation is setting setAbortCurrent(true) on an object that is busy in another thread (on the classes that have AbortCurrent). Unlocking: call new Global().unlockBundle("...") once at startup.
Properties
Algorithm
String getAlgorithm()
void setAlgorithm(String value)
Specifies the compression algorithm to use. Supported values are
deflate, zlib, gzip, bzip2, and lzw.
The zlib option is the deflate algorithm with a zlib header.
The gzip option (starting in v11.7.0) is the deflate algorithm in the gzip format (RFC 1952): a gzip
header, the deflate data, and a trailer with the CRC-32 and size of the uncompressed data. When decompressing in one
call, the CRC-32 and size are checked. Before v11.7.0, gzip was not recognized and was treated as
deflate.
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
String getCharset()
void setCharset(String value)
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
String getDebugLogFilePath()
void setDebugLogFilePath(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.
DeflateLevel
int getDeflateLevel()
void setDeflateLevel(int value)
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
String getEncodingMode()
void setEncodingMode(String value)
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
boolean getFirstChunk()
void setFirstChunk(boolean value)
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
int getHeartbeatMs()
void setHeartbeatMs(int value)
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
boolean getLastChunk()
void setLastChunk(boolean value)
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
String getLastErrorHtml()
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 getLastErrorText()
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 getLastErrorXml()
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
boolean getLastMethodSuccess()
void setLastMethodSuccess(boolean 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.
UncommonOptions
String getUncommonOptions()
void setUncommonOptions(String value)
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
boolean getVerboseLogging()
void setVerboseLogging(boolean value)
If set to true, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is false. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.
Version
String getVersion()
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
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.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
DecryptDecompressFile
Decrypts and decompresses a file, writing the restored data to a destination file.
This is the reverse operation of CompressEncryptFile.
Throws ChilkatException on failure; e.getLastErrorText() (or the object's getLastErrorText()) explains why, and the object remains usable.
Events
All Chilkat methods are synchronous: the call returns when the work is done. During a long-running call, Compression reports progress through a ProgressListener, an interface with three methods, each with a default, so you override only what you need:
import com.chilkatsoft.chilkat2.ProgressListener;
compression.setProgressListener(new ProgressListener() {
@Override public boolean percentDone(int pctDone) {
System.out.println(pctDone + "%");
return false; // return true to abort the method in progress
}
@Override public void progressInfo(String name, String value) {
System.out.println(name + ": " + value);
}
});
compression.setHeartbeatMs(250); // abortCheck 4 times per secondFor a single callback, a lambda is shorter:
compression.onPercentDone(pct -> { System.out.println(pct + "%"); return false; });Installs listener as the receiver of this object's events, replacing any listener or lambda installed before; null removes it.
Returns the installed listener, or null.
Each installs a listener whose only callback is the given lambda (from java.util.function). Like setProgressListener, each replaces the listener installed before, so to handle more than one event, implement ProgressListener. null removes the listener.
abortCheck is called at the interval set by the HeartbeatMs property (0, the default, disables it); percentDone is called when an operation's completion percentage is known; progressInfo delivers named progress values. Returning true from abortCheck or percentDone aborts the running method, which then throws ChilkatException.
Callbacks run on the thread that called the method, before it returns. Inside a callback, property accessors of the object (such as setAbortCurrent(true)) and other objects may be used, but calling a method of the same object throws IllegalStateException. An exception thrown by a callback aborts the running method and is rethrown from it; the object remains usable.
AbortCheck
boolean abortCheck()
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
import java.util.concurrent.atomic.AtomicBoolean;
final AtomicBoolean stop = new AtomicBoolean(false); // another thread may call stop.set(true)
compression.setHeartbeatMs(250); // call abortCheck 4 times per second
compression.onAbortCheck(() -> stop.get());PercentDone
boolean percentDone(int pctDone)
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
compression.onPercentDone(pct -> {
// pct ranges from 0 to 100.
System.out.println("Percent done: " + pct);
return false; // return true to abort the method in progress
});ProgressInfo
void progressInfo(String name, String value)
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
compression.onProgressInfo((name, value) -> System.out.println(name + ": " + value));