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.\" 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_DATA 3
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.Os
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.Sh NAME
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.Nm archive_read_data ,
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.Nm archive_read_data_block ,
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.Nm archive_read_data_skip ,
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.Nm archive_read_data_into_fd
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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 la_ssize_t
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.Fn archive_read_data "struct archive *" "void *buff" "size_t len"
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.Ft int
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.Fo archive_read_data_block
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.Fa "struct archive *"
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.Fa "const void **buff"
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.Fa "size_t *len"
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.Fa "off_t *offset"
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.Fc
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.Ft int
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.Fn archive_read_data_skip "struct archive *"
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.Ft int
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.Fn archive_read_data_into_fd "struct archive *" "int fd"
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.\"
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.Sh DESCRIPTION
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.Bl -tag -compact -width indent
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.It Fn archive_read_data
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Read data associated with the header just read.
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Internally, this is a convenience function that calls
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.Fn archive_read_data_block
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and fills any gaps with nulls so that callers see a single
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continuous stream of data.
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.It Fn archive_read_data_block
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Return the next available block of data for this entry.
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Unlike
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.Fn archive_read_data ,
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the
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.Fn archive_read_data_block
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function avoids copying data and allows you to correctly handle
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sparse files, as supported by some archive formats.
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The library guarantees that offsets will increase and that blocks
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will not overlap.
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Note that the blocks returned from this function can be much larger
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than the block size read from disk, due to compression
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and internal buffer optimizations.
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.It Fn archive_read_data_skip
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A convenience function that repeatedly calls
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.Fn archive_read_data_block
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to skip all of the data for this archive entry.
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Note that this function is invoked automatically by
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.Fn archive_read_next_header2
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if the previous entry was not completely consumed.
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.It Fn archive_read_data_into_fd
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A convenience function that repeatedly calls
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.Fn archive_read_data_block
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to copy the entire entry to the provided file descriptor.
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.El
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.\"
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.Sh RETURN VALUES
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Most functions return zero on success, non-zero on error.
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The possible return codes include:
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.Cm ARCHIVE_OK
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(the operation succeeded),
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.Cm ARCHIVE_WARN
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(the operation succeeded but a non-critical error was encountered),
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.Cm ARCHIVE_EOF
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(end-of-archive was encountered),
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.Cm ARCHIVE_RETRY
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(the operation failed but can be retried),
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and
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.Cm ARCHIVE_FATAL
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(there was a fatal error; the archive should be closed immediately).
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.Pp
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.Fn archive_read_data
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returns a count of bytes actually read or zero at the end of the entry.
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On error, a value of
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.Cm ARCHIVE_FATAL ,
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.Cm ARCHIVE_WARN ,
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or
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.Cm ARCHIVE_RETRY
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is returned.
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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 archive_read 3 ,
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.Xr archive_read_extract 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_header 3 ,
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.Xr archive_read_open 3 ,
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.Xr archive_read_set_options 3 ,
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.Xr archive_util 3 ,
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.Xr libarchive 3 ,
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.Xr tar 5
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