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234 lines
6.8 KiB
234 lines
6.8 KiB
.\" Copyright (c) 2003-2011 Tim Kientzle
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 2, 2012
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.Dt ARCHIVE_READ_OPEN 3
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.Os
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.Sh NAME
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.Nm archive_read_open ,
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.Nm archive_read_open2 ,
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.Nm archive_read_open_fd ,
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.Nm archive_read_open_FILE ,
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.Nm archive_read_open_filename ,
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.Nm archive_read_open_memory
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.Nd functions for reading streaming archives
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.Sh LIBRARY
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Streaming Archive Library (libarchive, -larchive)
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.Sh SYNOPSIS
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.In archive.h
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.Ft int
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.Fo archive_read_open
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.Fa "struct archive *"
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.Fa "void *client_data"
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.Fa "archive_open_callback *"
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.Fa "archive_read_callback *"
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.Fa "archive_close_callback *"
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.Fc
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.Ft int
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.Fo archive_read_open2
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.Fa "struct archive *"
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.Fa "void *client_data"
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.Fa "archive_open_callback *"
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.Fa "archive_read_callback *"
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.Fa "archive_skip_callback *"
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.Fa "archive_close_callback *"
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.Fc
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.Ft int
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.Fn archive_read_open_FILE "struct archive *" "FILE *file"
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.Ft int
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.Fn archive_read_open_fd "struct archive *" "int fd" "size_t block_size"
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.Ft int
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.Fo archive_read_open_filename
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.Fa "struct archive *"
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.Fa "const char *filename"
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.Fa "size_t block_size"
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.Fc
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.Ft int
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.Fn archive_read_open_memory "struct archive *" "const void *buff" "size_t size"
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.Sh DESCRIPTION
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.Bl -tag -compact -width indent
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.It Fn archive_read_open
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The same as
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.Fn archive_read_open2 ,
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except that the skip callback is assumed to be
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.Dv NULL .
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.It Fn archive_read_open2
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Freeze the settings, open the archive, and prepare for reading entries.
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This is the most generic version of this call, which accepts
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four callback functions.
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Most clients will want to use
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.Fn archive_read_open_filename ,
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.Fn archive_read_open_FILE ,
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.Fn archive_read_open_fd ,
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or
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.Fn archive_read_open_memory
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instead.
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The library invokes the client-provided functions to obtain
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raw bytes from the archive.
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.It Fn archive_read_open_FILE
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Like
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.Fn archive_read_open ,
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except that it accepts a
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.Ft "FILE *"
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pointer.
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This function should not be used with tape drives or other devices
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that require strict I/O blocking.
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.It Fn archive_read_open_fd
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Like
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.Fn archive_read_open ,
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except that it accepts a file descriptor and block size rather than
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a set of function pointers.
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Note that the file descriptor will not be automatically closed at
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end-of-archive.
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This function is safe for use with tape drives or other blocked devices.
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.It Fn archive_read_open_file
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This is a deprecated synonym for
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.Fn archive_read_open_filename .
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.It Fn archive_read_open_filename
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Like
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.Fn archive_read_open ,
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except that it accepts a simple filename and a block size.
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A NULL filename represents standard input.
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This function is safe for use with tape drives or other blocked devices.
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.It Fn archive_read_open_memory
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Like
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.Fn archive_read_open ,
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except that it accepts a pointer and size of a block of
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memory containing the archive data.
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.El
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.Pp
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A complete description of the
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.Tn struct archive
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and
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.Tn struct archive_entry
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objects can be found in the overview manual page for
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.Xr libarchive 3 .
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.Sh CLIENT CALLBACKS
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The callback functions must match the following prototypes:
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.Bl -item -offset indent
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.It
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.Ft typedef la_ssize_t
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.Fo archive_read_callback
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.Fa "struct archive *"
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.Fa "void *client_data"
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.Fa "const void **buffer"
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.Fc
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.It
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.Ft typedef la_int64_t
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.Fo archive_skip_callback
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.Fa "struct archive *"
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.Fa "void *client_data"
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.Fa "off_t request"
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.Fc
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.It
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.Ft typedef int
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.Fn archive_open_callback "struct archive *" "void *client_data"
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.It
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.Ft typedef int
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.Fn archive_close_callback "struct archive *" "void *client_data"
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.El
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.Pp
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The open callback is invoked by
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.Fn archive_open .
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It should return
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.Cm ARCHIVE_OK
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if the underlying file or data source is successfully
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opened.
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If the open fails, it should call
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.Fn archive_set_error
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to register an error code and message and return
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.Cm ARCHIVE_FATAL .
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.Pp
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The read callback is invoked whenever the library
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requires raw bytes from the archive.
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The read callback should read data into a buffer,
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set the
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.Li const void **buffer
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argument to point to the available data, and
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return a count of the number of bytes available.
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The library will invoke the read callback again
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only after it has consumed this data.
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The library imposes no constraints on the size
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of the data blocks returned.
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On end-of-file, the read callback should
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return zero.
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On error, the read callback should invoke
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.Fn archive_set_error
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to register an error code and message and
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return -1.
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.Pp
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The skip callback is invoked when the
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library wants to ignore a block of data.
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The return value is the number of bytes actually
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skipped, which may differ from the request.
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If the callback cannot skip data, it should return
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zero.
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If the skip callback is not provided (the
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function pointer is
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.Dv NULL ),
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the library will invoke the read function
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instead and simply discard the result.
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A skip callback can provide significant
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performance gains when reading uncompressed
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archives from slow disk drives or other media
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that can skip quickly.
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.Pp
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The close callback is invoked by archive_close when
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the archive processing is complete.
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The callback should return
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.Cm ARCHIVE_OK
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on success.
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On failure, the callback should invoke
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.Fn archive_set_error
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to register an error code and message and
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return
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.Cm ARCHIVE_FATAL.
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.\" .Sh EXAMPLE
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.\"
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.Sh RETURN VALUES
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These functions return
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.Cm ARCHIVE_OK
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on success, or
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.Cm ARCHIVE_FATAL .
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.\"
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.Sh ERRORS
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Detailed error codes and textual descriptions are available from the
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.Fn archive_errno
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and
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.Fn archive_error_string
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functions.
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.\"
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.Sh SEE ALSO
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.Xr tar 1 ,
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.Xr libarchive 3 ,
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.Xr archive_read 3 ,
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.Xr archive_read_data 3 ,
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.Xr archive_read_filter 3 ,
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.Xr archive_read_format 3 ,
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.Xr archive_read_set_options 3 ,
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.Xr archive_util 3 ,
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.Xr tar 5
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