.\" Copyright (c) 2003-2011 Tim Kientzle
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.\" $FreeBSD$
.\"
.Dd February 2, 2012
.Dt ARCHIVE_READ_DATA 3
.Os
.Sh NAME
.Nm archive_read_data
.Nm archive_read_data_block ,
.Nm archive_read_data_skip ,
.Nm archive_read_data_into_fd
.Nd functions for reading streaming archives
.Sh LIBRARY
Streaming Archive Library (libarchive, -larchive)
.Sh SYNOPSIS
.In archive.h
.Ft la_ssize_t
.Fn archive_read_data "struct archive *" "void *buff" "size_t len"
.Ft int
.Fo archive_read_data_block
.Fa "struct archive *"
.Fa "const void **buff"
.Fa "size_t *len"
.Fa "off_t *offset"
.Fc
.Ft int
.Fn archive_read_data_skip "struct archive *"
.Ft int
.Fn archive_read_data_into_fd "struct archive *" "int fd"
.\"
.Sh DESCRIPTION
.Bl -tag -compact -width indent
.It Fn archive_read_data
Read data associated with the header just read.
Internally, this is a convenience function that calls
.Fn archive_read_data_block
and fills any gaps with nulls so that callers see a single
continuous stream of data.
.It Fn archive_read_data_block
Return the next available block of data for this entry.
Unlike
.Fn archive_read_data ,
the
.Fn archive_read_data_block
function avoids copying data and allows you to correctly handle
sparse files, as supported by some archive formats.
The library guarantees that offsets will increase and that blocks
will not overlap.
Note that the blocks returned from this function can be much larger
than the block size read from disk, due to compression
and internal buffer optimizations.
.It Fn archive_read_data_skip
A convenience function that repeatedly calls
.Fn archive_read_data_block
to skip all of the data for this archive entry.
Note that this function is invoked automatically by
.Fn archive_read_next_header2
if the previous entry was not completely consumed.
.It Fn archive_read_data_into_fd
A convenience function that repeatedly calls
.Fn archive_read_data_block
to copy the entire entry to the provided file descriptor.
.El
.\"
.Sh RETURN VALUES
Most functions return zero on success, non-zero on error.
The possible return codes include:
.Cm ARCHIVE_OK
(the operation succeeded),
.Cm ARCHIVE_WARN
(the operation succeeded but a non-critical error was encountered),
.Cm ARCHIVE_EOF
(end-of-archive was encountered),
.Cm ARCHIVE_RETRY
(the operation failed but can be retried),
and
.Cm ARCHIVE_FATAL
(there was a fatal error; the archive should be closed immediately).
.Pp
.Fn archive_read_data
returns a count of bytes actually read or zero at the end of the entry.
On error, a value of
.Cm ARCHIVE_FATAL ,
.Cm ARCHIVE_WARN ,
or
.Cm ARCHIVE_RETRY
is returned.
.\"
.Sh ERRORS
Detailed error codes and textual descriptions are available from the
.Fn archive_errno
and
.Fn archive_error_string
functions.
.\"
.Sh SEE ALSO
.Xr tar 1 ,
.Xr libarchive 3 ,
.Xr archive_read 3 ,
.Xr archive_read_extract 3 ,
.Xr archive_read_filter 3 ,
.Xr archive_read_format 3 ,
.Xr archive_read_header 3 ,
.Xr archive_read_open 3 ,
.Xr archive_read_set_options 3 ,
.Xr archive_util 3 ,
.Xr tar 5