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NetBSD 6.1.5 - man page for archive_read_open_memory (netbsd section 3)

archive_read(3) 		   BSD 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_finish -- 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_finish(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 ar-
	     chive.
     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 conjunction 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 specified 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 available 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 dis-
			     able.
     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 block-
	     ing.
     archive_read_open_fd()
	     Like archive_read_open(), except that it accepts a file descriptor 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 filename 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 continuous 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 cor-
	     rectly handle sparse files, as supported by some archive formats.	The library guar-
	     antees 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 archive 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 provided file descriptor.
     archive_read_extract(), archive_read_extract_set_skip_file()
	     A convenience function that wraps the corresponding archive_write_disk(3) inter-
	     faces.  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 trans-
	     parently 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 function 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 ref-
	     erence 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_finish()
	     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 appropriate decompression.  It also automatically detects the ar-
     chive 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 underly-
     ing 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 processing 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 func-
     tions 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_finish(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 operation 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() functions.

     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 ar-
     chive from being properly read, thus most I/O errors eventually 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 archives.  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.

BSD					  April 13, 2009				      BSD


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