zip.pl -- Access resource ZIP archives

This library provides access to ZIP files. ZIP files are used to store SWI-Prolog resources. Ths library provides more high level access and documentation in addition to the low level access provided as built in as it is needed to bootstrap SWI-Prolog.

Access to a zip file is provided by means of a zipper object. This is a blob that is subject to atom garbage collection. Collecting a zipper closes the underlying OS access.

A zipper is a stateful object. We recognise the following states: idle, scan, read_entry, write_entry and close. The interface raise a permission_error when trying to make an illegal state transition.

Being stateful, a zipper cannot be used simultaneously from multiple threads. The zipper becomes owned by a thread when moving to scan using zipper_goto/2. It is released after zipper_open_current/3 followed by closing the stream.

zip_open(+File, +Mode, -Zipper, +Options) is det

Create a Zipper, providing access to File. Mode is one of read or write. The Options list is currently ignored.

zip_close(+Zipper) is det

zip_close(+Zipper, +Options) is det

Close a zipper. Options processed:

comment(+Comment): If the zipper is open for writing, set the global comment for the zip file.

zipper_goto(+Zipper, +Where) is semidet

Seek Zipper to a specified entry. Where is one of

first: Go to the first entry. Fails if the zip is empty.
next: Go to the next entry. Fails if there is no next entry.
file(Name): Go to the entry with the specified name.

zipper_open_current(+Zipper, -Stream, +Options) is det

Open the current entry as an input stream. Before this call the caller must use zipper_goto/2 to position to archive. Options:

type(+Type)
encoding(+Encoding)
bom(+Boolean): Determine type and encoding of the stream. The semantics is the same as for open/4.
release(+Boolean): If true (default), release te archive for access by other threads after the entry is closed.

It is allowed to call zip_close/1 immediately after this call, in which case the archive is closed when the entry is closed.

with_zipper(+Zipper, :Goal)

Run Goal while holding ownership over Zipper.

zipper_members(+Zipper, -Members:list(atom)) is det

True when Members is the list of file names in the Zipper.

zipper_file_info(+Zipper, -Name, -Attrs) is det

Obtain information about the current zip entry. Name is an atom representing the name of the entry. Attrs is a dict holding:

compressed_size:Bytes: Size in the archive
uncompressed_size:Bytes: Bytes after decompression
time:Stamp: Numeric time stamp in Prolog native format (float expressing seconds since Jan 1, 1970). Note that the resolution of time in zip archives is one second.
extra:Extra
comment:Extra: Optional additional fields.
offset:Offset: Direct pointer to this entry. May be used with zip_goto/2.

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

zipper_open_new_file_in_zip(Arg1, Arg2, Arg3, Arg4)
zip_close(Arg1, Arg2)