retro-imager/dependencies/libarchive-3.4.2/doc/text/archive_read_open.3.txt

ARCHIVE_READ_OPEN(3)	 BSD Library Functions Manual	  ARCHIVE_READ_OPEN(3)

NAME
     archive_read_open, archive_read_open2, archive_read_open_fd,
     archive_read_open_FILE, archive_read_open_filename,
     archive_read_open_memory -- functions for reading streaming archives

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

     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 *, const void *buff,
	 size_t size);

DESCRIPTION
     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.

     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 la_ssize_t archive_read_callback(struct archive *,
	   void *client_data, const void **buffer)

	   typedef la_int64_t archive_skip_callback(struct archive *,
	   void *client_data, off_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.

RETURN VALUES
     These functions return ARCHIVE_OK on success, or ARCHIVE_FATAL.

ERRORS
     Detailed error codes and textual descriptions are available from the
     archive_errno() and archive_error_string() functions.

SEE ALSO
     tar(1), archive_read(3), archive_read_data(3), archive_read_filter(3),
     archive_read_format(3), archive_read_set_options(3), archive_util(3),
     libarchive(3), tar(5)

BSD			       February 2, 2012 			   BSD