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 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.

     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 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.

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)