Bzip2 Class

Properties   Methods   Events   Config Settings   Errors  

The Bzip2 class implements a bzip2 compressor and decompressor. It is compliant with bzip2 specification.

Syntax

class ipworkszip.Bzip2

Remarks

The bzip2 file format is typically used only to archive a single file. Accordingly, the operation of the class is simpler than that of the other classs.

To compress with the class, set archive_file to the name of the bzip2 file to be created, and file_decompressed_name to the name of the file to be compressed. Finally, invoke compress. To extract the file, set archive_file to the bzip2 archive and file_decompressed_name to the file where the class should extract. Finally, invoke the extract or compress method.

Example (Creating a Bzip2 File)

ZipControl.ArchiveFile = "c:\test.bz2" ZipControl.FileDecompressedName = "c:\test.txt" ZipControl.Compress() Example (Extracting from a Bzip2 File)

ZipControl.ArchiveFile = "c:\test.bz2" ZipControl.FileDecompressedName = "c:\test.txt" ZipControl.Extract()

This class is an implementation based on Julian Seward's bzip2 library (http://www.bzip.org).

Property List

---

The following is the full list of the properties of the class with short descriptions. Click on the links for further details.

Method List

---

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

Event List

---

The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.

Config Settings

---

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

archive_file Property

The name of the zip, gzip, tar, or jar archive.

Syntax

def get_archive_file() -> str: ...
def set_archive_file(value: str) -> None: ...

archive_file = property(get_archive_file, set_archive_file)

Default Value

""

Remarks

This property specifies the name of the archive to be read or written. This property is required when extracting files.

When scan, extract, or extract_all is invoked, the file specified by archive_file will be opened for read. If the file does not exist, a trappable error will be generated.

When compress is called, the file named by archive_file will be written; if a file of this name already exists the on_overwrite event will be fired. If archive_file is set to the empty string (""), the archive will not be written to disk, and will be provided only through the on_progress event.

The filename may be specified with or without a path. Paths may be relative or absolute, and should be specified in the format native to the host operating system. The filename should be specified with the appropriate extension (such as "zip"); an extension will not automatically be appended by the class.

If the file cannot be read, or written, as appropriate, a trappable error will be generated.

Example (Creating an Archive)

ZipControl.ArchiveFile = "c:\test.zip" ZipControl.RecurseSubdirectories = true ZipControl.IncludeFiles("c:\foo\*") ZipControl.Compress()

Note: an archive already open for read may be closed by setting archive_file to the empty string ("").

bzip_2_data Property

(Decompression only) The bzip2 file contents as a byte array.

Syntax

def set_bzip_2_data(value: bytes) -> None: ...

bzip_2_data = property(None, set_bzip_2_data)

Default Value

""

Remarks

Normally you should set archive_file before invoking scan or extract. If you prefer to read the bzip2 file from memory you may set bzip_2_data instead. bzip_2_data should be set to the entire contents of the bzip2 file; this will allow you to read from the bzip2 without writing any temporary files to disk.

If you would like to extract data from the archive without ever writing to disk you should also set WriteToProgressEvent to true, and after invoking scan, you should set the value of file_decompressed_name to an empty string. Then, when you invoke extract (or extract_all) the data will be provided in the on_progress event.

This property is write-only. Note that modifying a bzip2 file stored in bzip_2_data is not supported, so append will throw exceptions.

This property is write-only.

extract_to_path Property

A base path to decompress to.

Syntax

def get_extract_to_path() -> str: ...
def set_extract_to_path(value: str) -> None: ...

extract_to_path = property(get_extract_to_path, set_extract_to_path)

Default Value

""

Remarks

Setting the extract_to_path property affects the operation of the extract and extract_all methods. Setting this property to a nonempty string will cause all decompressed files to be written to the specified path. If pathnames are given in the values of file_decompressed_name they will be regarded as relative to extract_to_path.

If the specified directory does not exist, it will be created when extraction is done.

extract_to_path should always be specified in the format native to the host operating system, and with a trailing slash or backslash. If the path is specified otherwise, it will be immediately converted and stored in the converted format. For example, "/temp" would be immediately converted to "\temp\" on a Windows system.

file_decompressed_name Property

File name to decompress to, or compress from.

Syntax

def get_file_decompressed_name() -> str: ...
def set_file_decompressed_name(value: str) -> None: ...

file_decompressed_name = property(get_file_decompressed_name, set_file_decompressed_name)

Default Value

""

Remarks

file_decompressed_name contains the name of the file in the archive, as stored on the file system, outside the archive.

When compressing a file, this property should be specified with a path, if necessary, to allow the file to be found by the class. If the file cannot be found when compress is called, a trappable error will be generated, and the archive will not be correctly written.

When decompressing files, this property may be set prior to calling extract. If this property is set to the empty string when extract is called, extract will automatically set this property to an appropriate value.

Paths on the local file system should be specified in the format native to the host operating system. They may also be specified in standard (UNIX) format, in which case they will be immediately converted.

file_input_data Property

The data of the file to be compressed.

Syntax

def get_file_input_data() -> bytes: ...
def set_file_input_data(value: bytes) -> None: ...

file_input_data = property(get_file_input_data, set_file_input_data)

Default Value

""

Remarks

When this property is set, the class will read in the data from this property instead of reading from the file contained in the file_decompressed_name property.

has_more_data Property

Shows whether or not there is more data in the bzip2 archive.

Syntax

def get_has_more_data() -> bool: ...

has_more_data = property(get_has_more_data, None)

Default Value

FALSE

Remarks

The bzip2 format allows multiple bzip2 data members to be concatenated into a single file. However, due to the nature of the algorithm it is impossible to determine the number of data members until after the entire archive has been decompressed. The has_more_data property can be used to cycle through the archive and extract each file.

Simply set the archive_file and extract_to_path properties, then call extract as long as the class has available data.

Note: the class will not update file_decompressed_name unless you manually set file_decompressed_name on each loop before calling extract.

Example (Extracting Multiple Files)

ZipControl.ArchiveFile = "c:\temp.bz2" ZipControl.ExtractToPath = "c:\extracted\" Do //here you may set the file name in file_decompressed_name prior to extraction ZipControl.Extract() While ZipControl.HasMoreData

This property is read-only.

abort Method

Aborts the current operation.

Syntax

def abort() -> None: ...

Remarks

abort may be used to immediately interrupt compression or decompression. Any files partially written by the class will be deleted.

append Method

Adds specified file to an existing archive.

Syntax

def append() -> None: ...

Remarks

The file contained in the file_decompressed_name property will be appended to the archive specified by archive_file.

This method may only be used to add files to an existing archive. To add files to a new archive, compress method should be used.

compress Method

Creates the compressed bzip2 archive.

Syntax

def compress() -> None: ...

Remarks

Invoking compress creates the archive specified by archive_file. When the method is called, the file specified by file_decompressed_name will be opened, and the file specified by archive_file will contain the compressed output.

As the data is compressed the on_progress event will be fired at regular intervals. This event may be used to stream out the bzip2 file, or to display a progress bar to the user.

config Method

Sets or retrieves a configuration setting.

Syntax

def config(configuration_string: str) -> str: ...

Remarks

config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

extract Method

Extracts the compressed file from the bzip2 archive.

Syntax

def extract() -> None: ...

Remarks

Invoking extract decompresses the archive specified by archive_file. The compressed file will be extracted, and written to disk.

If file_decompressed_name is set to a nonempty string the file will be written there. Otherwise the class will automatically set file_decompressed_name to an appropriate value:

If archive_file ends in ".bz2", this filename, less the ".bz2" extension will be used.

If this condition does not hold, ".unzipped" will be appended to archive_file.

extract_all Method

Extracts all files from the compressed archive.

Syntax

def extract_all() -> None: ...

Remarks

extract_all extracts all files from the archive. The file(s) will be extracted to the directory specified by extract_to_path, and given the names specified by file_decompressed_name.

The on_begin_file and on_end_file events will be fired before and after each file is extracted, and the on_progress event will be fired as the data is extracted. If WriteToProgressEvent is set to true, the decompressed data will be streamed out through the on_progress event.

reset Method

Resets the class.

Syntax

def reset() -> None: ...

Remarks

reset resets the state of the class. All properties will be set to their default values, and any files open will be closed.

scan Method

Scans the compressed archive.

Syntax

def scan() -> None: ...

Remarks

This method will scan the bzip archive specified by archive_file. The archive will be read, and the header will be checked.

Unlike in the Zip, Tar, and Jar classs, it is never necessary to invoke this method, and it will not be automatically invoked by extract. Suggested uses for this method would be to check that the file is a bzip file.

on_begin_file Event

Fired before a file is processed.

Syntax

class Bzip2BeginFileEventParams(object):
  @property
  def index() -> int: ...

  @property
  def skip() -> bool: ...
  @skip.setter
  def skip(value) -> None: ...

# In class Bzip2:
@property
def on_begin_file() -> Callable[[Bzip2BeginFileEventParams], None]: ...
@on_begin_file.setter
def on_begin_file(event_hook: Callable[[Bzip2BeginFileEventParams], None]) -> None: ...

Remarks

on_begin_file is fired before compression or decompression begins. Index will contain 0.

You may use the Skip parameter to tell the class to skip the file when appending or decompressing.

on_end_file Event

Fired after a file is processed.

Syntax

class Bzip2EndFileEventParams(object):
  @property
  def index() -> int: ...

# In class Bzip2:
@property
def on_end_file() -> Callable[[Bzip2EndFileEventParams], None]: ...
@on_end_file.setter
def on_end_file(event_hook: Callable[[Bzip2EndFileEventParams], None]) -> None: ...

Remarks

on_end_file is fired when compression or decompression finishes. Index will contain 0.

on_error Event

Information about non-fatal errors.

Syntax

class Bzip2ErrorEventParams(object):
  @property
  def description() -> str: ...

  @property
  def error_code() -> int: ...

  @property
  def index() -> int: ...

  @property
  def filename() -> str: ...

  @property
  def ignore() -> bool: ...
  @ignore.setter
  def ignore(value) -> None: ...

# In class Bzip2:
@property
def on_error() -> Callable[[Bzip2ErrorEventParams], None]: ...
@on_error.setter
def on_error(event_hook: Callable[[Bzip2ErrorEventParams], None]) -> None: ...

Remarks

The on_error event is fired when non-fatal errors occur during compression or decompression. Note that if this event is fired during decompression this may indicate that the archive is corrupt.

By default these errors will cause the component to fail with an exception. The exception may be overridden by setting Ignore to true. This will cause the error to be ignored, the file will be skipped if necessary, and the class will continue operation.

ErrorCode will correspond to one of the following errors:

Description contains a textual description of the error. Index and Filename contain the array index (where appropriate) and filename of the file being processed at the time of the error.

on_overwrite Event

Fired whenever a file exists and may be overwritten.

Syntax

class Bzip2OverwriteEventParams(object):
  @property
  def filename() -> str: ...
  @filename.setter
  def filename(value) -> None: ...

  @property
  def overwrite() -> bool: ...
  @overwrite.setter
  def overwrite(value) -> None: ...

# In class Bzip2:
@property
def on_overwrite() -> Callable[[Bzip2OverwriteEventParams], None]: ...
@on_overwrite.setter
def on_overwrite(event_hook: Callable[[Bzip2OverwriteEventParams], None]) -> None: ...

Remarks

on_overwrite is fired when a file is about to be overwritten, and would overwrite an existing file. The event is fired during decompression.

Filename contains the full name of the file, specified with its pathname.

Overwrite specifies whether or not the file will be overwritten. For Zip, Jar, and Tar, this is equal by default to the value of the overwrite_files property. For Gzip, this value defaults to true.

Either of the parameters may be changed when the event is fired. Changing the value of Overwrite will override the default behavior of the class, and cause the file to be overwritten or not overwritten, depending on the value set. If Filename is changed, the value of Overwrite will be ignored, and the file will be written with the specified name. If a file of the new name also exists this file will be silently overwritten.

on_progress Event

Fired as progress is made.

Syntax

class Bzip2ProgressEventParams(object):
  @property
  def data() -> bytes: ...

  @property
  def filename() -> str: ...

  @property
  def bytes_processed() -> int: ...

  @property
  def percent_processed() -> int: ...

# In class Bzip2:
@property
def on_progress() -> Callable[[Bzip2ProgressEventParams], None]: ...
@on_progress.setter
def on_progress(event_hook: Callable[[Bzip2ProgressEventParams], None]) -> None: ...

Remarks

The on_progress event is automatically fired as compression or decompression is performed. When WriteToProgressEvent is true, the output data is provided through the Data parameter, allowing for it to be streamed out.

Filename contains the name of the file being written. If no file is being written, Filename will contain an empty string, and the output data will be provided exclusively through this event.

BytesProcessed contains the total number of uncompressed bytes processed. PercentProcessed contains the percent of uncompressed bytes processed, corresponding roughly to the running time of the operation.

For Gzip extraction only, BytesProcessed and PercentProcessed will reflect the number of compressed bytes extracted, as it is generally impossible to predetermine the total uncompressed size.

If WriteToProgressEvent is false, Data will contain null.

Bzip2 Config Settings

The class accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the config method.

Bzip2 Config Settings

Base Config Settings

Bzip2 Errors

Errors

The following errors may be generated by the class. Note that frequently the error message will contain more specific information than what is listed here.

Note that some non-fatal errors may be trapped and explicitly ignored in the on_error event. This will allow the class to continue operation even in case of error.

Bzip2 Errors

	111   Can't open file for read.
	112   Can't open file for write.
	113   Can't create directory.
	114   The file is too large.
	115   Can't create empty archive.
	116   The archive must be scanned prior to attempting this operation.
	117   The array index is out of range.
	118   The maximum size of the archive has been exceeded.
	119   The archive must be specified, or streaming must be enabled.
	120   The component is busy.
	124   Must specify the compressed name.
	127   Bad CRC-32 checksum.
	128   Unable to set file date.
	133   File already exists in the archive.
	150   An I/O error has occurred (details follow).