.TH dtp 1L "Mar 1995"
.SH NAME
dtp \- extract/list the contents of a Unix dtp archive
.SH SYNOPSIS
.B dtp
[
.B t|x
] 
.I filename
.SH DESCRIPTION
.B dtp
takes the filename of a Unix dtp archive as its second argument, and either
lists the contents of the archive, or extracts the contents of the archive
to the current directory. The first argument is either a
.B t
or an
.B x.
.SH OPTIONS
.TP
.B t
Produce a table of contents.
.TP
.B x
Extract the archive's contents to the current directory.
.SH ARCHIVE FORMAT
A
.I dtp
archive is broken up into a number of 512-byte blocks. Block 0 contains
the offset of the actual files' data, stored in a uint16_t at bytes 6 and 7. 
This value is converted to an offset in bytes as follows:
.PP
.nf
offset = 64 * (256 * byte[6] + byte[7]);
.fi
.PP
Block 1 begins the archive's table of contents. The table of contents is
made up of a number of records with the following C structure:
.PP
.nf
/* dtp tape directory entry */
struct tpdir {
    char pathname[114];       /* Filename of file */
    uint16_t mode;            /* Unix mode */
    uint8_t uid;              /* Owner of file */
    uint8_t gid;              /* Group of file */
    uint8_t unused1;
    uint8_t size[3];          /* Size in bytes */
    uint8_t modtime[4];       /* Time of last modification */
    uint16_t tapeaddr;        /* Beginning block on tape */
};
.fi
.PP
where
.I uintXX_t
indicates an unsigned integer
.I XX
bits wide.
.PP
The table of contents extends from Block 1 up to the data offset
calculated above. Alternatively,
the last record in the table of contents may be indicated by a 0 in the
first byte of the
.I pathname
string. All blocks following this block contain the files in the archive.
The
.I tapeaddr
field in each file entry points to the first block after the offset 
which contains the
data for that file. Files are stored contiguously. Where a file is
not a multiple of the block-size in size, it is padded with bytes
so that it is a integral number of blocks.
.SH BUGS
.B dtp
does not use the
.I checksum
field in the table of contents records.
.PP
.I mkdir -p
is used to recursively make directory hierachies if they are needed.
.SH "SEE ALSO"
.BR tap (1L),
.BR tp (1L),
.BR itp (1L),
.BR mkdir (1)
.SH AUTHOR
Warren Toomey wkt@cs.adfa.edu.au