Compression Excel Class Module Reference Documentation

Compression

Current Version: 9.5.0.80

Data compression component implementing the PPMD, Bzip2, Deflate, and LZW compression algorithms. .NET, ActiveX, and C++ implementations provide progress monitoring and abort capabilities. Provides a unified API for all supported compression algorithms.

Object Creation

Dim oCompression As Chilkat.Compression
Set oCompression = Chilkat.NewCompression

Properties

Algorithm
Algorithm As String

The compression algorithm to be used. Should be set to either "ppmd", "deflate", "zlib", "bzip2", or "lzw".

Note: The PPMD compression algorithm is only available for 32-bit builds. It is not available for 64-bit implementations. Also, this PPMD implementation is the "J" variant.

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Charset
Charset As String

Only applies to methods that compress or decompress strings. This specifies the character encoding that the string should be converted to before compression. Many programming languages use Unicode (2 bytes per char) for representing characters. This property allows for the string to be converted to a 1-byte per char encoding prior to compression.

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DebugLogFilePath
DebugLogFilePath As String

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.

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DeflateLevel
DeflateLevel As Long
Introduced in version 9.5.0.73

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.

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EncodingMode
EncodingMode As String

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.

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LastErrorHtml
LastErrorHtml As String (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.

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LastErrorText
LastErrorText As String (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.

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LastErrorXml
LastErrorXml As String (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.

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LastMethodSuccess
LastMethodSuccess As Long
Introduced in version 9.5.0.52

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

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VerboseLogging
VerboseLogging As Long

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.

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Version
Version As String (read only)

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

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Methods

BeginCompressStringENC
BeginCompressStringENC(str As String) As String

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 Nothing on failure

More Information and Examples
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BeginDecompressStringENC
BeginDecompressStringENC(str As String) As String

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 Nothing on failure

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CompressBd
CompressBd(binData As BinData) As Long
Introduced in version 9.5.0.66

Compresses the data contained in a BinData object.

Returns True for success, False for failure.

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CompressFile
CompressFile(srcPath As String, destPath As String) As Long

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.

More Information and Examples
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CompressSb
CompressSb(sb As StringBuilder, binData As BinData) As Long
Introduced in version 9.5.0.73

Compresses the contents of sb and appends the compressed bytes to binData.

Returns True for success, False for failure.

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CompressStream
CompressStream(strm As Stream) As Long
Introduced in version 9.5.0.56

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.

More Information and Examples
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CompressStringENC
CompressStringENC(str As String) As String

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 Nothing on failure

More Information and Examples
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DecompressBd
DecompressBd(binData As BinData) As Long
Introduced in version 9.5.0.66

Decompresses the data contained in a BinData object.

Returns True for success, False for failure.

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DecompressFile
DecompressFile(srcPath As String, destPath As String) As Long

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.

More Information and Examples
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DecompressSb
DecompressSb(binData As BinData, sb As StringBuilder) As Long
Introduced in version 9.5.0.73

Decompresses the contents of binData and appends the decompressed string to sb.

Returns True for success, False for failure.

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DecompressStream
DecompressStream(strm As Stream) As Long
Introduced in version 9.5.0.56

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.

More Information and Examples
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DecompressStringENC
DecompressStringENC(encodedCompressedData As String) As String

The opposite of CompressStringENC. encodedCompressedData contains the compressed data as an encoded string (hex, base64, etc) as specified by the EncodingMode property setting.

Returns Nothing on failure

More Information and Examples
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EndCompressBytesENC
EndCompressBytesENC() As String

Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.

(See BeginCompressBytesENC)

Returns Nothing on failure

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EndCompressStringENC
EndCompressStringENC() As String

Must be callled to finalize a compression stream. Returns any remaining (buffered) compressed data.

(See BeginCompressStringENC)

Returns Nothing on failure

More Information and Examples
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EndDecompressString
EndDecompressString() As String

Called to finalize the decompression stream and return any remaining (buffered) decompressed data.

(See BeginDecompressString)

Returns Nothing on failure

More Information and Examples
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EndDecompressStringENC
EndDecompressStringENC() As String

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 Nothing on failure

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MoreCompressStringENC
MoreCompressStringENC(str As String) As String

(See BeginCompressStringENC)

Returns Nothing on failure

More Information and Examples
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MoreDecompressStringENC
MoreDecompressStringENC(str As String) As String

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 Nothing on failure

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UnlockComponent
UnlockComponent(unlockCode As String) As Long

Unlocks the component allowing for the full functionality to be used. The component may be used fully-functional for the 1st 30-days after download by passing an arbitrary string to this method. If for some reason you do not receive the full 30-day trial, send email to support@chilkatsoft.com for a temporary unlock code w/ an explicit expiration date. Upon purchase, a purchased unlock code is provided which should replace the temporary/arbitrary string passed to this method.

Returns True for success, False for failure.

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