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ARCHIVE_READ(3)	       FreeBSD Library Functions Manual	       ARCHIVE_READ(3)

NAME
     archive_read_new, archive_read_set_filter_options,
     archive_read_set_format_options, archive_read_set_options,
     archive_read_support_compression_all,
     archive_read_support_compression_bzip2,
     archive_read_support_compression_compress,
     archive_read_support_compression_gzip,
     archive_read_support_compression_lzma,
     archive_read_support_compression_none,
     archive_read_support_compression_xz,
     archive_read_support_compression_program,
     archive_read_support_compression_program_signature,
     archive_read_support_format_all, archive_read_support_format_ar,
     archive_read_support_format_cpio, archive_read_support_format_empty,
     archive_read_support_format_iso9660, archive_read_support_format_mtree,
     archive_read_support_format_raw, archive_read_support_format_tar,
     archive_read_support_format_zip, archive_read_open, archive_read_open2,
     archive_read_open_fd, archive_read_open_FILE, archive_read_open_filename,
     archive_read_open_memory, archive_read_next_header,
     archive_read_next_header2,	archive_read_data, archive_read_data_block,
     archive_read_data_skip, archive_read_data_into_buffer,
     archive_read_data_into_fd,	archive_read_extract, archive_read_extract2,
     archive_read_extract_set_progress_callback, archive_read_close,
     archive_read_free -- functions for	reading	streaming archives

SYNOPSIS
     #include <archive.h>

     struct archive *
     archive_read_new(void);

     int
     archive_read_support_compression_all(struct archive *);

     int
     archive_read_support_compression_bzip2(struct archive *);

     int
     archive_read_support_compression_compress(struct archive *);

     int
     archive_read_support_compression_gzip(struct archive *);

     int
     archive_read_support_compression_lzma(struct archive *);

     int
     archive_read_support_compression_none(struct archive *);

     int
     archive_read_support_compression_xz(struct	archive	*);

     int
     archive_read_support_compression_program(struct archive *,
	 const char *cmd);

     int
     archive_read_support_compression_program_signature(struct archive *,
	 const char *cmd, const	void *signature, size_t	signature_length);

     int
     archive_read_support_format_all(struct archive *);

     int
     archive_read_support_format_ar(struct archive *);

     int
     archive_read_support_format_cpio(struct archive *);

     int
     archive_read_support_format_empty(struct archive *);

     int
     archive_read_support_format_iso9660(struct	archive	*);

     int
     archive_read_support_format_mtree(struct archive *);

     int
     archive_read_support_format_raw(struct archive *);

     int
     archive_read_support_format_tar(struct archive *);

     int
     archive_read_support_format_zip(struct archive *);

     int
     archive_read_set_filter_options(struct archive *, const char *);

     int
     archive_read_set_format_options(struct archive *, const char *);

     int
     archive_read_set_options(struct archive *,	const char *);

     int
     archive_read_open(struct archive *, void *client_data,
	 archive_open_callback *, archive_read_callback	*,
	 archive_close_callback	*);

     int
     archive_read_open2(struct archive *, void *client_data,
	 archive_open_callback *, archive_read_callback	*,
	 archive_skip_callback *, archive_close_callback *);

     int
     archive_read_open_FILE(struct archive *, FILE *file);

     int
     archive_read_open_fd(struct archive *, int	fd, size_t block_size);

     int
     archive_read_open_filename(struct archive *, const	char *filename,
	 size_t	block_size);

     int
     archive_read_open_memory(struct archive *,	void *buff, size_t size);

     int
     archive_read_next_header(struct archive *,	struct archive_entry **);

     int
     archive_read_next_header2(struct archive *, struct	archive_entry *);

     ssize_t
     archive_read_data(struct archive *, void *buff, size_t len);

     int
     archive_read_data_block(struct archive *, const void **buff, size_t *len,
	 off_t *offset);

     int
     archive_read_data_skip(struct archive *);

     int
     archive_read_data_into_buffer(struct archive *, void *, ssize_t len);

     int
     archive_read_data_into_fd(struct archive *, int fd);

     int
     archive_read_extract(struct archive *, struct archive_entry *,
	 int flags);

     int
     archive_read_extract2(struct archive *src,	struct archive_entry *,
	 struct	archive	*dest);

     void
     archive_read_extract_set_progress_callback(struct archive *,
	 void (*func)(void *), void *user_data);

     int
     archive_read_close(struct archive *);

     int
     archive_read_free(struct archive *);

DESCRIPTION
     These functions provide a complete	API for	reading	streaming archives.
     The general process is to first create the	struct archive object, set
     options, initialize the reader, iterate over the archive headers and
     associated	data, then close the archive and release all resources.	 The
     following summary describes the functions in approximately	the order they
     would be used:
     archive_read_new()
	     Allocates and initializes a struct	archive	object suitable	for
	     reading from an archive.
     archive_read_support_compression_bzip2(),
	     archive_read_support_compression_compress(),
	     archive_read_support_compression_gzip(),
	     archive_read_support_compression_lzma(),
	     archive_read_support_compression_none(),
	     archive_read_support_compression_xz()
	     Enables auto-detection code and decompression support for the
	     specified compression.  Returns ARCHIVE_OK	if the compression is
	     fully supported, or ARCHIVE_WARN if the compression is supported
	     only through an external program.	Note that decompression	using
	     an	external program is usually slower than	decompression through
	     built-in libraries.  Note that ``none'' is	always enabled by
	     default.
     archive_read_support_compression_all()
	     Enables all available decompression filters.
     archive_read_support_compression_program()
	     Data is fed through the specified external	program	before being
	     dearchived.  Note that this disables automatic detection of the
	     compression format, so it makes no	sense to specify this in con-
	     junction with any other decompression option.
     archive_read_support_compression_program_signature()
	     This feeds	data through the specified external program but	only
	     if	the initial bytes of the data match the	specified signature
	     value.
     archive_read_support_format_all(),	archive_read_support_format_ar(),
	     archive_read_support_format_cpio(),
	     archive_read_support_format_empty(),
	     archive_read_support_format_iso9660(),
	     archive_read_support_format_mtree(),
	     archive_read_support_format_tar(),
	     archive_read_support_format_zip()
	     Enables support---including auto-detection	code---for the speci-
	     fied archive format.  For example,
	     archive_read_support_format_tar() enables support for a variety
	     of	standard tar formats, old-style	tar, ustar, pax	interchange
	     format, and many common variants.	For convenience,
	     archive_read_support_format_all() enables support for all avail-
	     able formats.  Only empty archives	are supported by default.
     archive_read_support_format_raw()
	     The ``raw'' format	handler	allows libarchive to be	used to	read
	     arbitrary data.  It treats	any data stream	as an archive with a
	     single entry.  The	pathname of this entry is ``data''; all	other
	     entry fields are unset.  This is not enabled by
	     archive_read_support_format_all() in order	to avoid erroneous
	     handling of damaged archives.
     archive_read_set_filter_options(),	archive_read_set_format_options(),
	     archive_read_set_options()
	     Specifies options that will be passed to currently-registered
	     filters (including	decompression filters) and/or format readers.
	     The argument is a comma-separated list of individual options.
	     Individual	options	have one of the	following forms:
	     option=value
		     The option/value pair will	be provided to every module.
		     Modules that do not accept	an option with this name will
		     ignore it.
	     option  The option	will be	provided to every module with a	value
		     of	``1''.
	     !option
		     The option	will be	provided to every module with a	NULL
		     value.
	     module:option=value, module:option, module:!option
		     As	above, but the corresponding option and	value will be
		     provided only to modules whose name matches module.
	     The return	value will be ARCHIVE_OK if any	module accepts the
	     option, or	ARCHIVE_WARN if	no module accepted the option, or
	     ARCHIVE_FATAL if there was	a fatal	error while attempting to
	     process the option.

	     The currently supported options are:
	     Format iso9660
		     joliet  Support Joliet extensions.	 Defaults to enabled,
			     use !joliet to disable.
     archive_read_open()
	     The same as archive_read_open2(), except that the skip callback
	     is	assumed	to be NULL.
     archive_read_open2()
	     Freeze the	settings, open the archive, and	prepare	for reading
	     entries.  This is the most	generic	version	of this	call, which
	     accepts four callback functions.  Most clients will want to use
	     archive_read_open_filename(), archive_read_open_FILE(),
	     archive_read_open_fd(), or	archive_read_open_memory() instead.
	     The library invokes the client-provided functions to obtain raw
	     bytes from	the archive.
     archive_read_open_FILE()
	     Like archive_read_open(), except that it accepts a	FILE *
	     pointer.  This function should not	be used	with tape drives or
	     other devices that	require	strict I/O blocking.
     archive_read_open_fd()
	     Like archive_read_open(), except that it accepts a	file descrip-
	     tor and block size	rather than a set of function pointers.	 Note
	     that the file descriptor will not be automatically	closed at end-
	     of-archive.  This function	is safe	for use	with tape drives or
	     other blocked devices.
     archive_read_open_file()
	     This is a deprecated synonym for archive_read_open_filename().
     archive_read_open_filename()
	     Like archive_read_open(), except that it accepts a	simple file-
	     name and a	block size.  A NULL filename represents	standard
	     input.  This function is safe for use with	tape drives or other
	     blocked devices.
     archive_read_open_memory()
	     Like archive_read_open(), except that it accepts a	pointer	and
	     size of a block of	memory containing the archive data.
     archive_read_next_header()
	     Read the header for the next entry	and return a pointer to	a
	     struct archive_entry.  This is a convenience wrapper around
	     archive_read_next_header2() that reuses an	internal struct
	     archive_entry object for each request.
     archive_read_next_header2()
	     Read the header for the next entry	and populate the provided
	     struct archive_entry.
     archive_read_data()
	     Read data associated with the header just read.  Internally, this
	     is	a convenience function that calls archive_read_data_block()
	     and fills any gaps	with nulls so that callers see a single	con-
	     tinuous stream of data.
     archive_read_data_block()
	     Return the	next available block of	data for this entry.  Unlike
	     archive_read_data(), the archive_read_data_block()	function
	     avoids copying data and allows you	to correctly handle sparse
	     files, as supported by some archive formats.  The library guaran-
	     tees that offsets will increase and that blocks will not overlap.
	     Note that the blocks returned from	this function can be much
	     larger than the block size	read from disk,	due to compression and
	     internal buffer optimizations.
     archive_read_data_skip()
	     A convenience function that repeatedly calls
	     archive_read_data_block() to skip all of the data for this	ar-
	     chive entry.
     archive_read_data_into_buffer()
	     This function is deprecated and will be removed.  Use
	     archive_read_data() instead.
     archive_read_data_into_fd()
	     A convenience function that repeatedly calls
	     archive_read_data_block() to copy the entire entry	to the pro-
	     vided file	descriptor.
     archive_read_extract(), archive_read_extract_set_skip_file()
	     A convenience function that wraps the corresponding
	     archive_write_disk(3) interfaces.	The first call to
	     archive_read_extract() creates a restore object using
	     archive_write_disk_new(3) and
	     archive_write_disk_set_standard_lookup(3),	then transparently
	     invokes archive_write_disk_set_options(3),
	     archive_write_header(3), archive_write_data(3), and
	     archive_write_finish_entry(3) to create the entry on disk and
	     copy data into it.	 The flags argument is passed unmodified to
	     archive_write_disk_set_options(3).
     archive_read_extract2()
	     This is another version of	archive_read_extract() that allows you
	     to	provide	your own restore object.  In particular, this allows
	     you to override the standard lookup functions using
	     archive_write_disk_set_group_lookup(3), and
	     archive_write_disk_set_user_lookup(3).  Note that
	     archive_read_extract2() does not accept a flags argument; you
	     should use	archive_write_disk_set_options() to set	the restore
	     options yourself.
     archive_read_extract_set_progress_callback()
	     Sets a pointer to a user-defined callback that can	be used	for
	     updating progress displays	during extraction.  The	progress func-
	     tion will be invoked during the extraction	of large regular
	     files.  The progress function will	be invoked with	the pointer
	     provided to this call.  Generally,	the data pointed to should
	     include a reference to the	archive	object and the archive_entry
	     object so that various statistics can be retrieved	for the
	     progress display.
     archive_read_close()
	     Complete the archive and invoke the close callback.
     archive_read_free()
	     Invokes archive_read_close() if it	was not	invoked	manually, then
	     release all resources.  Note: In libarchive 1.x, this function
	     was declared to return void, which	made it	impossible to detect
	     certain errors when archive_read_close() was invoked implicitly
	     from this function.  The declaration is corrected beginning with
	     libarchive	2.0.

     Note that the library determines most of the relevant information about
     the archive by inspection.	 In particular,	it automatically detects
     gzip(1) or	bzip2(1) compression and transparently performs	the appropri-
     ate decompression.	 It also automatically detects the archive format.

     A complete	description of the struct archive and struct archive_entry
     objects can be found in the overview manual page for libarchive(3).

CLIENT CALLBACKS
     The callback functions must match the following prototypes:

	   typedef ssize_t archive_read_callback(struct	archive	*,
	   void	*client_data, const void **buffer)

	   typedef int archive_skip_callback(struct archive *,
	   void	*client_data, size_t request)

	   typedef int archive_open_callback(struct archive *, void
	   *client_data)

	   typedef int archive_close_callback(struct archive *,	void
	   *client_data)

     The open callback is invoked by archive_open().  It should	return
     ARCHIVE_OK	if the underlying file or data source is successfully opened.
     If	the open fails,	it should call archive_set_error() to register an
     error code	and message and	return ARCHIVE_FATAL.

     The read callback is invoked whenever the library requires	raw bytes from
     the archive.  The read callback should read data into a buffer, set the
     const void	**buffer argument to point to the available data, and return a
     count of the number of bytes available.  The library will invoke the read
     callback again only after it has consumed this data.  The library imposes
     no	constraints on the size	of the data blocks returned.  On end-of-file,
     the read callback should return zero.  On error, the read callback	should
     invoke archive_set_error()	to register an error code and message and
     return -1.

     The skip callback is invoked when the library wants to ignore a block of
     data.  The	return value is	the number of bytes actually skipped, which
     may differ	from the request.  If the callback cannot skip data, it	should
     return zero.  If the skip callback	is not provided	(the function pointer
     is	NULL ),	the library will invoke	the read function instead and simply
     discard the result.  A skip callback can provide significant performance
     gains when	reading	uncompressed archives from slow	disk drives or other
     media that	can skip quickly.

     The close callback	is invoked by archive_close when the archive process-
     ing is complete.  The callback should return ARCHIVE_OK on	success.  On
     failure, the callback should invoke archive_set_error() to	register an
     error code	and message and	return ARCHIVE_FATAL.

EXAMPLE
     The following illustrates basic usage of the library.  In this example,
     the callback functions are	simply wrappers	around the standard open(2),
     read(2), and close(2) system calls.

	   void
	   list_archive(const char *name)
	   {
	     struct mydata *mydata;
	     struct archive *a;
	     struct archive_entry *entry;

	     mydata = malloc(sizeof(struct mydata));
	     a = archive_read_new();
	     mydata->name = name;
	     archive_read_support_compression_all(a);
	     archive_read_support_format_all(a);
	     archive_read_open(a, mydata, myopen, myread, myclose);
	     while (archive_read_next_header(a,	&entry)	== ARCHIVE_OK) {
	       printf("%s\n",archive_entry_pathname(entry));
	       archive_read_data_skip(a);
	     }
	     archive_read_free(a);
	     free(mydata);
	   }

	   ssize_t
	   myread(struct archive *a, void *client_data,	const void **buff)
	   {
	     struct mydata *mydata = client_data;

	     *buff = mydata->buff;
	     return (read(mydata->fd, mydata->buff, 10240));
	   }

	   int
	   myopen(struct archive *a, void *client_data)
	   {
	     struct mydata *mydata = client_data;

	     mydata->fd	= open(mydata->name, O_RDONLY);
	     return (mydata->fd	>= 0 ? ARCHIVE_OK : ARCHIVE_FATAL);
	   }

	   int
	   myclose(struct archive *a, void *client_data)
	   {
	     struct mydata *mydata = client_data;

	     if	(mydata->fd > 0)
	       close(mydata->fd);
	     return (ARCHIVE_OK);
	   }

RETURN VALUES
     Most functions return zero	on success, non-zero on	error.	The possible
     return codes include: ARCHIVE_OK (the operation succeeded), ARCHIVE_WARN
     (the operation succeeded but a non-critical error was encountered),
     ARCHIVE_EOF (end-of-archive was encountered), ARCHIVE_RETRY (the opera-
     tion failed but can be retried), and ARCHIVE_FATAL	(there was a fatal
     error; the	archive	should be closed immediately).	Detailed error codes
     and textual descriptions are available from the archive_errno() and
     archive_error_string() functions.

     archive_read_new()	returns	a pointer to a freshly allocated struct
     archive object.  It returns NULL on error.

     archive_read_data() returns a count of bytes actually read	or zero	at the
     end of the	entry.	On error, a value of ARCHIVE_FATAL, ARCHIVE_WARN, or
     ARCHIVE_RETRY is returned and an error code and textual description can
     be	retrieved from the archive_errno() and archive_error_string() func-
     tions.

     The library expects the client callbacks to behave	similarly.  If there
     is	an error, you can use archive_set_error() to set an appropriate	error
     code and description, then	return one of the non-zero values above.
     (Note that	the value eventually returned to the client may	not be the
     same; many	errors that are	not critical at	the level of basic I/O can
     prevent the archive from being properly read, thus	most I/O errors	even-
     tually cause ARCHIVE_FATAL	to be returned.)

SEE ALSO
     tar(1), archive(3), archive_util(3), tar(5)

HISTORY
     The libarchive library first appeared in FreeBSD 5.3.

AUTHORS
     The libarchive library was	written	by Tim Kientzle	<kientzle@acm.org>.

BUGS
     Many traditional archiver programs	treat empty files as valid empty ar-
     chives.  For example, many	implementations	of tar(1) allow	you to append
     entries to	an empty file.	Of course, it is impossible to determine the
     format of an empty	file by	inspecting the contents, so this library
     treats empty files	as having a special ``empty'' format.

FreeBSD	10.1			April 13, 2009			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | CLIENT CALLBACKS | EXAMPLE | RETURN VALUES | SEE ALSO | HISTORY | AUTHORS | BUGS

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