.\" 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