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<p><i>ARCHIVE_READ_OPEN</i>(3) Library Functions Manual
<i>ARCHIVE_READ_OPEN</i>(3)</p>
<p style="margin-top: 1em"><b>NAME</b></p>
<p style="margin-left:9%;">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</p>
<p style="margin-top: 1em"><b>LIBRARY</b></p>
<p style="margin-left:9%;">Streaming Archive Library
(libarchive, -larchive)</p>
<p style="margin-top: 1em"><b>SYNOPSIS</b></p>
<p style="margin-left:9%;"><b>#include
<archive.h></b></p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p><b>archive_read_open</b>(<i>struct archive *</i>,
<i>void *client_data</i>,
<i>archive_open_callback *</i>,
<i>archive_read_callback *</i>,
<i>archive_close_callback *</i>);</p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p><b>archive_read_open2</b>(<i>struct archive *</i>,
<i>void *client_data</i>,
<i>archive_open_callback *</i>,
<i>archive_read_callback *</i>,
<i>archive_skip_callback *</i>,
<i>archive_close_callback *</i>);</p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p style="margin-left:14%;"><b>archive_read_open_FILE</b>(<i>struct archive *</i>,
<i>FILE *file</i>);</p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p style="margin-left:14%;"><b>archive_read_open_fd</b>(<i>struct archive *</i>,
<i>int fd</i>, <i>size_t block_size</i>);</p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p><b>archive_read_open_filename</b>(<i>struct archive *</i>,
<i>const char *filename</i>,
<i>size_t block_size</i>);</p>
<p style="margin-left:9%; margin-top: 1em"><i>int</i></p>
<p style="margin-left:14%;"><b>archive_read_open_memory</b>(<i>struct archive *</i>,
<i>const void *buff</i>,
<i>size_t size</i>);</p>
<p style="margin-top: 1em"><b>DESCRIPTION <br>
archive_read_open</b>()</p>
<p style="margin-left:19%;">The same as
<b>archive_read_open2</b>(), except that the skip callback
is assumed to be NULL.</p>
<p><b>archive_read_open2</b>()</p>
<p style="margin-left:19%;">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
<b>archive_read_open_filename</b>(),
<b>archive_read_open_FILE</b>(),
<b>archive_read_open_fd</b>(), or
<b>archive_read_open_memory</b>() instead. The library
invokes the client-provided functions to obtain raw bytes
from the archive.</p>
<p><b>archive_read_open_FILE</b>()</p>
<p style="margin-left:19%;">Like
<b>archive_read_open</b>(), except that it accepts a <i>FILE
*</i> pointer. This function should not be used with tape
drives or other devices that require strict I/O
blocking.</p>
<p><b>archive_read_open_fd</b>()</p>
<p style="margin-left:19%;">Like
<b>archive_read_open</b>(), 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.</p>
<p><b>archive_read_open_file</b>()</p>
<p style="margin-left:19%;">This is a deprecated synonym
for <b>archive_read_open_filename</b>().</p>
<p><b>archive_read_open_filename</b>()</p>
<p style="margin-left:19%;">Like
<b>archive_read_open</b>(), 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.</p>
<p><b>archive_read_open_memory</b>()</p>
<p style="margin-left:19%;">Like
<b>archive_read_open</b>(), except that it accepts a pointer
and size of a block of memory containing the archive
data.</p>
<p style="margin-left:9%; margin-top: 1em">A complete
description of the struct archive and struct archive_entry
objects can be found in the overview manual page for
<i>libarchive</i>(3).</p>
<p style="margin-top: 1em"><b>CLIENT CALLBACKS</b></p>
<p style="margin-left:9%;">The callback functions must
match the following prototypes:</p>
<p style="margin-left:17%; margin-top: 1em"><i>typedef
la_ssize_t</i></p>
<p><b>archive_read_callback</b>(<i>struct archive *</i>,
<i>void *client_data</i>,
<i>const void **buffer</i>)</p>
<p style="margin-left:17%; margin-top: 1em"><i>typedef
la_int64_t</i></p>
<p><b>archive_skip_callback</b>(<i>struct archive *</i>,
<i>void *client_data</i>,
<i>off_t request</i>)</p>
<p style="margin-left:17%; margin-top: 1em"><i>typedef
int</i> <b>archive_open_callback</b>(<i>struct archive
*</i>, <i>void *client_data</i>)</p>
<p style="margin-left:17%; margin-top: 1em"><i>typedef
int</i> <b>archive_close_callback</b>(<i>struct archive
*</i>, <i>void *client_data</i>)</p>
<p style="margin-left:9%; margin-top: 1em">The open
callback is invoked by <b>archive_open</b>(). It should
return <b>ARCHIVE_OK</b> if the underlying file or data
source is successfully opened. If the open fails, it should
call <b>archive_set_error</b>() to register an error code
and message and return <b>ARCHIVE_FATAL</b>.</p>
<p style="margin-left:9%; margin-top: 1em">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 <b>const void **buffer</b> 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
<b>archive_set_error</b>() to register an error code and
message and return -1.</p>
<p style="margin-left:9%; margin-top: 1em">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.</p>
<p style="margin-left:9%; margin-top: 1em">The close
callback is invoked by archive_close when the archive
processing is complete. The callback should return
<b>ARCHIVE_OK</b> on success. On failure, the callback
should invoke <b>archive_set_error</b>() to register an
error code and message and return <b>ARCHIVE_FATAL</b>.</p>
<p style="margin-top: 1em"><b>RETURN VALUES</b></p>
<p style="margin-left:9%;">These functions return
<b>ARCHIVE_OK</b> on success, or <b>ARCHIVE_FATAL</b>.</p>
<p style="margin-top: 1em"><b>ERRORS</b></p>
<p style="margin-left:9%;">Detailed error codes and textual
descriptions are available from the <b>archive_errno</b>()
and <b>archive_error_string</b>() functions.</p>
<p style="margin-top: 1em"><b>SEE ALSO</b></p>
<p style="margin-left:9%;"><i>tar</i>(1),
<i>archive_read</i>(3), <i>archive_read_data</i>(3),
<i>archive_read_filter</i>(3),
<i>archive_read_format</i>(3),
<i>archive_read_set_options</i>(3), <i>archive_util</i>(3),
<i>libarchive</i>(3), <i>tar</i>(5) Debian February 2, 2012
<i>ARCHIVE_READ_OPEN</i>(3)</p>
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