retro-imager/dependencies/libarchive-3.5.2/doc/text/archive_write_open.3.txt

ARCHIVE_WRITE_OPEN(3)	 BSD Library Functions Manual	 ARCHIVE_WRITE_OPEN(3)

NAME
     archive_write_open, archive_write_open2, archive_write_open_fd,
     archive_write_open_FILE, archive_write_open_filename,
     archive_write_open_memory — functions for creating archives

LIBRARY
     Streaming Archive Library (libarchive, -larchive)

SYNOPSIS
     #include <archive.h>

     int
     archive_write_open(struct archive *, void *client_data,
	 archive_open_callback *, archive_write_callback *,
	 archive_close_callback *);

     int
     archive_write_open2(struct archive *, void *client_data,
	 archive_open_callback *, archive_write_callback *,
	 archive_close_callback *, archive_free_callback *);

     int
     archive_write_open_fd(struct archive *, int fd);

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

     int
     archive_write_open_filename(struct archive *, const char *filename);

     int
     archive_write_open_memory(struct archive *, void *buffer,
	 size_t bufferSize, size_t *outUsed);

DESCRIPTION
     archive_write_open()
	     Freeze the settings, open the archive, and prepare for writing
	     entries.  This is the most generic form of this function, which
	     accepts pointers to three callback functions which will be in‐
	     voked by the compression layer to write the constructed archive.
	     This does not alter the default archive padding.

     archive_write_open2()
	     Same as archive_write_open() with an additional fourth free call‐
	     back. This function should be preferred to archive_write_open().

     archive_write_open_fd()
	     A convenience form of archive_write_open() that accepts a file
	     descriptor.  The archive_write_open_fd() function is safe for use
	     with tape drives or other block-oriented devices.

     archive_write_open_FILE()
	     A convenience form of archive_write_open() that accepts a FILE *
	     pointer.  Note that archive_write_open_FILE() is not safe for
	     writing to tape drives or other devices that require correct
	     blocking.

     archive_write_open_file()
	     A deprecated synonym for archive_write_open_filename().

     archive_write_open_filename()
	     A convenience form of archive_write_open() that accepts a file‐
	     name.  A NULL argument indicates that the output should be writ‐
	     ten to standard output; an argument of “-” will open a file with
	     that name.  If you have not invoked
	     archive_write_set_bytes_in_last_block(), then
	     archive_write_open_filename() will adjust the last-block padding
	     depending on the file: it will enable padding when writing to
	     standard output or to a character or block device node, it will
	     disable padding otherwise.  You can override this by manually in‐
	     voking archive_write_set_bytes_in_last_block() before calling
	     archive_write_open2().  The archive_write_open_filename() func‐
	     tion is safe for use with tape drives or other block-oriented de‐
	     vices.

     archive_write_open_memory()
	     A convenience form of archive_write_open2() that accepts a
	     pointer to a block of memory that will receive the archive.  The
	     final size_t * argument points to a variable that will be updated
	     after each write to reflect how much of the buffer is currently
	     in use.  You should be careful to ensure that this variable re‐
	     mains allocated until after the archive is closed.  This function
	     will disable padding unless you have specifically set the block
	     size.
     More information about the struct archive object and the overall design
     of the library can be found in the libarchive(3) overview.

     Note that the convenience forms above vary in how they block the output.
     See archive_write_blocksize(3) if you need to control the block size used
     for writes or the end-of-file padding behavior.

CLIENT CALLBACKS
     To use this library, you will need to define and register callback func‐
     tions that will be invoked to write data to the resulting archive.  These
     functions are registered by calling archive_write_open2():

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

     The open callback is invoked by archive_write_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 er‐
     ror code and message and return ARCHIVE_FATAL.  Please note that if open
     fails, close is not called and resources must be freed inside the open
     callback or with the free callback.

	   typedef la_ssize_t archive_write_callback(struct archive *,
	   void *client_data, const void *buffer, size_t length)

     The write callback is invoked whenever the library needs to write raw
     bytes to the archive.  For correct blocking, each call to the write call‐
     back function should translate into a single write(2) system call.  This
     is especially critical when writing archives to tape drives.  On success,
     the write callback should return the number of bytes actually written.
     On error, the callback should invoke archive_set_error() to register an
     error code and message and return -1.

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

     The close callback is invoked by archive_close when the archive process‐
     ing is complete. If the open callback fails, the close callback is not
     invoked.  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

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

     The free callback is always invoked on archive_free.  The return code of
     this callback is not processed.

     Note that if the client-provided write callback function returns a non-
     zero value, that error will be propagated back to the caller through
     whatever API function resulted in that call, which may include
     archive_write_header(), archive_write_data(), archive_write_close(),
     archive_write_finish(), or archive_write_free().  The client callback can
     call archive_set_error() to provide values that can then be retrieved by
     archive_errno() and archive_error_string().

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_write(3), archive_write_blocksize(3),
     archive_write_filter(3), archive_write_format(3), archive_write_new(3),
     archive_write_set_options(3), libarchive(3), cpio(5), mtree(5), tar(5)

BSD			       November 12, 2020			   BSD