xref: /freebsd-10.1-release/contrib/libarchive/README

README for libarchive bundle.

Questions?  Issues?
   * http://www.libarchive.org is the home for ongoing
     libarchive development, including documentation, and
     links to the libarchive mailing lists.
   * To report an issue, use the issue tracker at
     http://code.google.com/p/libarchive/issues/list
   * To submit an enhancement to libarchive, please submit
     a pull request via GitHub.
     https://github.com/libarchive/libarchive/pulls

This distribution bundle includes the following components:
   * libarchive: a library for reading and writing streaming archives
   * tar: the 'bsdtar' program is a full-featured 'tar'
          replacement built on libarchive
   * cpio: the 'bsdcpio' program is a different interface to
          essentially the same functionality
   * examples: Some small example programs that you may find useful.
   * examples/minitar: a compact sample demonstrating use of libarchive.
   * contrib:  Various items sent to me by third parties;
          please contact the authors with any questions.

The top-level directory contains the following information files:
   * NEWS - highlights of recent changes
   * COPYING - what you can do with this
   * INSTALL - installation instructions
   * README - this file
   * configure - configuration script, see INSTALL for details.
   * CMakeLists.txt - input for "cmake" build tool, see INSTALL

The following files in the top-level directory are used by the
'configure' script:
   * Makefile.am, aclocal.m4, configure.ac
       - used to build this distribution, only needed by maintainers
   * Makefile.in, config.h.in
	- templates used by configure script

Guide to Documentation installed by this system:
 * bsdtar.1 explains the use of the bsdtar program
 * bsdcpio.1 explains the use of the bsdcpio program
 * libarchive.3 gives an overview of the library as a whole
 * archive_read.3, archive_write.3, archive_write_disk.3, and
   archive_read_disk.3 provide detailed calling sequences for the read
   and write APIs
 * archive_entry.3 details the "struct archive_entry" utility class
 * archive_internals.3 provides some insight into libarchive's
   internal structure and operation.
 * libarchive-formats.5 documents the file formats supported by the library
 * cpio.5, mtree.5, and tar.5 provide detailed information about these
   popular archive formats, including hard-to-find details about
   modern cpio and tar variants.
The manual pages above are provided in the 'doc' directory in
a number of different formats.

You should also read the copious comments in "archive.h" and the
source code for the sample programs for more details.  Please let us
know about any errors or omissions you find.

Currently, the library automatically detects and reads the following fomats:
  * GNU tar format (including GNU long filenames, long link names, and sparse files)
  * Solaris 9 extended tar format (including ACLs)
  * Old V7 tar archives
  * POSIX ustar
  * POSIX pax interchange format
  * POSIX octet-oriented cpio
  * SVR4 ASCII cpio
  * POSIX octet-oriented cpio
  * Binary cpio (big-endian or little-endian)
  * ISO9660 CD-ROM images (with optional Rockridge or Joliet extensions)
  * ZIP archives (with uncompressed or "deflate" compressed entries)
  * GNU and BSD 'ar' archives
  * 'mtree' format
  * 7-Zip archives
  * Microsoft CAB format
  * LHA and LZH archives
  * RAR archives
  * XAR archives

The library also detects and handles any of the following before evaluating the archive:
  * uuencoded files
  * files with RPM wrapper
  * gzip compression
  * bzip2 compression
  * compress/LZW compression
  * lzma, lzip, and xz compression

The library can create archives in any of the following formats:
  * POSIX ustar
  * POSIX pax interchange format
  * "restricted" pax format, which will create ustar archives except for
    entries that require pax extensions (for long filenames, ACLs, etc).
  * Old GNU tar format
  * POSIX octet-oriented cpio
  * SVR4 "newc" cpio
  * shar archives
  * ZIP archives (with uncompressed or "deflate" compressed entries)
  * GNU and BSD 'ar' archives
  * 'mtree' format
  * ISO9660 format
  * 7-Zip archives
  * XAR archives

When creating archives, the result can be filtered with any of the following:
  * uuencode
  * gzip compression
  * bzip2 compression
  * compress/LZW compression
  * lzma, lzip, and xz compression

Notes about the library architecture:

 * This is a heavily stream-oriented system.  There is no direct
   support for in-place modification or random access.

 * The library is designed to be extended with new compression and
   archive formats.  The only requirement is that the format be
   readable or writable as a stream and that each archive entry be
   independent.  There are articles on the libarchive Wiki explaining
   how to extend libarchive.

 * On read, compression and format are always detected automatically.

 * I've attempted to minimize static link pollution.  If you don't
   explicitly invoke a particular feature (such as support for a
   particular compression or format), it won't get pulled in.
   In particular, if you don't explicitly enable a particular
   compression or decompression support, you won't need to link
   against the corresponding compression or decompression libraries.
   This also reduces the size of statically-linked binaries in
   environments where that matters.

 * On read, the library accepts whatever blocks you hand it.
   Your read callback is free to pass the library a byte at a time
   or mmap the entire archive and give it to the library at once.
   On write, the library always produces correctly-blocked output.

 * The object-style approach allows you to have multiple archive streams
   open at once.  bsdtar uses this in its "@archive" extension.

 * The archive itself is read/written using callback functions.
   You can read an archive directly from an in-memory buffer or
   write it to a socket, if you wish.  There are some utility
   functions to provide easy-to-use "open file," etc, capabilities.

 * The read/write APIs are designed to allow individual entries
   to be read or written to any data source:  You can create
   a block of data in memory and add it to a tar archive without
   first writing a temporary file.  You can also read an entry from
   an archive and write the data directly to a socket.  If you want
   to read/write entries to disk, there are convenience functions to
   make this especially easy.

 * Note: "pax interchange format" is really an extended tar format,
   despite what the name says.