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.TH "fileutil::magic::rt" n 1.0 fumagic "file utilities"
.BS
.SH NAME
fileutil::magic::rt \- Runtime core for file type recognition engines written in pure Tcl
.SH SYNOPSIS
package require \fBTcl  8.4\fR
.sp
package require \fBfileutil::magic::rt  ?1.0?\fR
.sp
\fB::fileutil::magic::rt::open\fR \fIfilename\fR
.sp
\fB::fileutil::magic::rt::close\fR
.sp
\fB::fileutil::magic::rt::file_start\fR \fIname\fR
.sp
\fB::fileutil::magic::rt::result\fR ?\fImsg\fR?
.sp
\fB::fileutil::magic::rt::resultv\fR ?\fImsg\fR?
.sp
\fB::fileutil::magic::rt::emit\fR \fImsg\fR
.sp
\fB::fileutil::magic::rt::offset\fR \fIwhere\fR
.sp
\fB::fileutil::magic::rt::Nv\fR \fItype\fR \fIoffset\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::N\fR \fItype\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::Nvx\fR \fIatlevel\fR \fItype\fR \fIoffset\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::Nx\fR \fIatlevel\fR \fItype\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::S\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::Sx\fR \fIatlevel\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
.sp
\fB::fileutil::magic::rt::L\fR \fInewlevel\fR
.sp
\fB::fileutil::magic::rt::I\fR \fIbase\fR \fItype\fR \fIdelta\fR
.sp
\fB::fileutil::magic::rt::R\fR \fIoffset\fR
.sp
.BE
.SH DESCRIPTION
.PP
This package provides the runtime core for file type recognition
engines written in pure Tcl and is thus used by all other packages in
this module, i.e. the two frontend packages
\fBfileutil::magic::mimetypes\fR and
\fBfileutil::magic::filetypes\fR, and the two engine compiler
packages \fBfileutil::magic::cgen\fR and
\fBfileutil::magic::cfront\fR.
.SH COMMANDS
.TP
\fB::fileutil::magic::rt::open\fR \fIfilename\fR
This command initializes the runtime and prepares the file
\fIfilename\fR for use by the system.
This command has to be invoked first, before any other command of this
package.
.sp
The command returns the channel handle of the opened file as its
result.
.TP
\fB::fileutil::magic::rt::close\fR
This command closes the last file opened via
\fB::fileutil::magic::rt::open\fR and shuts the runtime down.
This command has to be invoked last, after the file has been dealt
with completely.
Afterward another invokation of \fB::fileutil::magic::rt::open\fR  is
required to process another file.
.sp
This command returns the empty string as its result.
.TP
\fB::fileutil::magic::rt::file_start\fR \fIname\fR
This command marks the start of a magic file when debugging. It
returns the empty string as its result.
.TP
\fB::fileutil::magic::rt::result\fR ?\fImsg\fR?
This command returns the current result and stops processing.
.sp
If \fImsg\fR is specified its text is added to the result before it is
returned. See \fB::fileutil::magic::rt::emit\fR for the allowed
special character sequences.
.TP
\fB::fileutil::magic::rt::resultv\fR ?\fImsg\fR?
This command returns the current result.
In contrast to \fB::fileutil::magic::rt::result\fR processing
continues.
.sp
If \fImsg\fR is specified its text is added to the result before it is
returned. See \fB::fileutil::magic::rt::emit\fR for the allowed
special character sequences.
.TP
\fB::fileutil::magic::rt::emit\fR \fImsg\fR
This command adds the text \fImsg\fR to the result buffer. The
message may contain the following special character sequences. They
will be replaced with buffered values before the message is added to
the result. The command returns the empty string as its result.
.RS
.TP
\fB\\b\fR
This sequence is removed
.TP
\fB%s\fR
Replaced with the last buffered string value.
.TP
\fB%ld\fR
Replaced with the last buffered numeric value.
.TP
\fB%d\fR
See above.
.RE
.TP
\fB::fileutil::magic::rt::Nv\fR \fItype\fR \fIoffset\fR ?\fIqual\fR?
This command fetches the numeric value with \fItype\fR from the
absolute location \fIoffset\fR and returns it as its result. The
fetched value is further stored in the numeric buffer.
.sp
If \fIqual\fR is specified it is considered to be a mask and applied
to the fetched value before it is stored and returned. It has to have
the form of a partial Tcl bit-wise expression, i.e.
.nf

	& number

.fi
For example:
.nf

	Nv lelong 0 &0x8080ffff

.fi
For the possible types see section \fBNUMERIC TYPES\fR.
.TP
\fB::fileutil::magic::rt::N\fR \fItype\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
This command behaves mostly like \fB::fileutil::magic::rt::Nv\fR,
except that it compares the fetched and masked value against \fIval\fR
as specified with \fIcomp\fR and returns the result of that
comparison.
.sp
The argument \fIcomp\fR has to contain one of Tcl's comparison
operators, and the comparison made will be
.nf

	<val> <comp> <fetched-and-masked-value>

.fi
.sp
The special comparison operator \fBx\fR signals that no comparison
should be done, or, in other words, that the fetched value will always
match \fIval\fR.
.TP
\fB::fileutil::magic::rt::Nvx\fR \fIatlevel\fR \fItype\fR \fIoffset\fR ?\fIqual\fR?
This command behaves like \fB::fileutil::magic::rt::Nv\fR, except that
it additionally remembers the location in the file after the fetch in
the calling context, for the level \fIatlevel\fR, for later use by
\fB::fileutil::magic::rt::R\fR.
.TP
\fB::fileutil::magic::rt::Nx\fR \fIatlevel\fR \fItype\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
This command behaves like \fB::fileutil::magic::rt::N\fR, except that
it additionally remembers the location in the file after the fetch in
the calling context, for the level \fIatlevel\fR, for later use by
\fB::fileutil::magic::rt::R\fR.
.TP
\fB::fileutil::magic::rt::S\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
This command behaves like \fB::fileutil::magic::rt::N\fR, except that
it fetches and compares strings, not numeric data. The fetched value
is also stored in the internal string buffer instead of the numeric
buffer.
.TP
\fB::fileutil::magic::rt::Sx\fR \fIatlevel\fR \fIoffset\fR \fIcomp\fR \fIval\fR ?\fIqual\fR?
This command behaves like \fB::fileutil::magic::rt::S\fR, except that
it additionally remembers the location in the file after the fetch in
the calling context, for the level \fIatlevel\fR, for later use by
\fB::fileutil::magic::rt::R\fR.
.TP
\fB::fileutil::magic::rt::L\fR \fInewlevel\fR
This command sets the current level in the calling context to
\fInewlevel\fR. The command returns the empty string as its result.
.TP
\fB::fileutil::magic::rt::I\fR \fIbase\fR \fItype\fR \fIdelta\fR
This command handles base locations specified indirectly through the
contents of the inspected file. It returns the sum of \fIdelta\fR and
the value of numeric \fItype\fR fetched from the absolute location
\fIbase\fR.
.sp
For the possible types see section \fBNUMERIC TYPES\fR.
.TP
\fB::fileutil::magic::rt::R\fR \fIoffset\fR
This command handles base locations specified relative to the end of
the last field one level above.
.sp
In other words, the command computes an absolute location in the file
based on the relative \fIoffset\fR and returns it as its result. The
base the offset is added to is the last location remembered for the
level in the calling context.
.PP
.SH "NUMERIC TYPES"
.TP
\fBbyte\fR
8-bit integer
.TP
\fBshort\fR
16-bit integer, stored in native endianess
.TP
\fBbeshort\fR
see above, stored in big endian
.TP
\fBleshort\fR
see above, stored in small/little endian
.TP
\fBlong\fR
32-bit integer, stored in native endianess
.TP
\fBbelong\fR
see above, stored in big endian
.TP
\fBlelong\fR
see above, stored in small/little endian
.PP
All of the types above exit in an unsigned form as well. The type
names are the same, with the character "u" added as prefix.
.TP
\fBdate\fR
32-bit integer timestamp, stored in native endianess
.TP
\fBbedate\fR
see above, stored in big endian
.TP
\fBledate\fR
see above, stored in small/little endian
.TP
\fBldate\fR
32-bit integer timestamp, stored in native endianess
.TP
\fBbeldate\fR
see above, stored in big endian
.TP
\fBleldate\fR
see above, stored in small/little endian
.PP
.SH "BUGS, IDEAS, FEEDBACK"
This document, and the package it describes, will undoubtedly contain
bugs and other problems.
Please report such in the category \fIfileutil :: magic\fR of the
\fITcllib SF Trackers\fR [http://sourceforge.net/tracker/?group_id=12883].
Please also report any ideas for enhancements you may have for either
package and/or documentation.
.SH "SEE ALSO"
file(1), fileutil, magic(5)
.SH KEYWORDS
file recognition, file type, file utilities, mime, type