fileutil::magic::rt(n)          file utilities          fileutil::magic::rt(n)



______________________________________________________________________________

NAME
       fileutil::magic::rt - Runtime core for file type recognition engines
       written in pure Tcl

SYNOPSIS
       package require Tcl  8.4

       package require fileutil::magic::rt  ?1.0?

       ::fileutil::magic::rt::open filename

       ::fileutil::magic::rt::close

       ::fileutil::magic::rt::file_start name

       ::fileutil::magic::rt::result ?msg?

       ::fileutil::magic::rt::resultv ?msg?

       ::fileutil::magic::rt::emit msg

       ::fileutil::magic::rt::offset where

       ::fileutil::magic::rt::Nv type offset ?qual?

       ::fileutil::magic::rt::N type offset comp val ?qual?

       ::fileutil::magic::rt::Nvx atlevel type offset ?qual?

       ::fileutil::magic::rt::Nx atlevel type offset comp val ?qual?

       ::fileutil::magic::rt::S offset comp val ?qual?

       ::fileutil::magic::rt::Sx atlevel offset comp val ?qual?

       ::fileutil::magic::rt::L newlevel

       ::fileutil::magic::rt::I base type delta

       ::fileutil::magic::rt::R offset

_________________________________________________________________

DESCRIPTION
       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 fileutil::magic::mimetypes
       and fileutil::magic::filetypes, and the two engine compiler packages
       fileutil::magic::cgen and fileutil::magic::cfront.

COMMANDS
       ::fileutil::magic::rt::open filename
              This command initializes the runtime and prepares the file
              filename for use by the system.  This command has to be invoked
              first, before any other command of this package.

              The command returns the channel handle of the opened file as its
              result.

       ::fileutil::magic::rt::close
              This command closes the last file opened via
              ::fileutil::magic::rt::open and shuts the runtime down.  This
              command has to be invoked last, after the file has been dealt
              with completely.  Afterward another invokation of
              ::fileutil::magic::rt::open  is required to process another
              file.

              This command returns the empty string as its result.

       ::fileutil::magic::rt::file_start name
              This command marks the start of a magic file when debugging. It
              returns the empty string as its result.

       ::fileutil::magic::rt::result ?msg?
              This command returns the current result and stops processing.

              If msg is specified its text is added to the result before it is
              returned. See ::fileutil::magic::rt::emit for the allowed
              special character sequences.

       ::fileutil::magic::rt::resultv ?msg?
              This command returns the current result.  In contrast to
              ::fileutil::magic::rt::result processing continues.

              If msg is specified its text is added to the result before it is
              returned. See ::fileutil::magic::rt::emit for the allowed
              special character sequences.

       ::fileutil::magic::rt::emit msg
              This command adds the text msg 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.

              \b     This sequence is removed

              %s     Replaced with the last buffered string value.

              %ld    Replaced with the last buffered numeric value.

              %d     See above.

       ::fileutil::magic::rt::Nv type offset ?qual?
              This command fetches the numeric value with type from the
              absolute location offset and returns it as its result. The
              fetched value is further stored in the numeric buffer.

              If qual 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.


                & number


              For example:


                Nv lelong 0 &0x8080ffff


              For the possible types see section NUMERIC TYPES.

       ::fileutil::magic::rt::N type offset comp val ?qual?
              This command behaves mostly like ::fileutil::magic::rt::Nv,
              except that it compares the fetched and masked value against val
              as specified with comp and returns the result of that
              comparison.

              The argument comp has to contain one of Tcl's comparison
              operators, and the comparison made will be


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


       The special comparison operator x signals that no comparison should be
       done, or, in other words, that the fetched value will always match val.

       ::fileutil::magic::rt::Nvx atlevel type offset ?qual?
              This command behaves like ::fileutil::magic::rt::Nv, except that
              it additionally remembers the location in the file after the
              fetch in the calling context, for the level atlevel, for later
              use by ::fileutil::magic::rt::R.

       ::fileutil::magic::rt::Nx atlevel type offset comp val ?qual?
              This command behaves like ::fileutil::magic::rt::N, except that
              it additionally remembers the location in the file after the
              fetch in the calling context, for the level atlevel, for later
              use by ::fileutil::magic::rt::R.

       ::fileutil::magic::rt::S offset comp val ?qual?
              This command behaves like ::fileutil::magic::rt::N, 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.

       ::fileutil::magic::rt::Sx atlevel offset comp val ?qual?
              This command behaves like ::fileutil::magic::rt::S, except that
              it additionally remembers the location in the file after the
              fetch in the calling context, for the level atlevel, for later
              use by ::fileutil::magic::rt::R.

       ::fileutil::magic::rt::L newlevel
              This command sets the current level in the calling context to
              newlevel. The command returns the empty string as its result.

       ::fileutil::magic::rt::I base type delta
              This command handles base locations specified indirectly through
              the contents of the inspected file. It returns the sum of delta
              and the value of numeric type fetched from the absolute location
              base.

              For the possible types see section NUMERIC TYPES.

       ::fileutil::magic::rt::R offset
              This command handles base locations specified relative to the
              end of the last field one level above.

              In other words, the command computes an absolute location in the
              file based on the relative offset 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.

NUMERIC TYPES
       byte   8-bit integer

       short  16-bit integer, stored in native endianess

       beshort
              see above, stored in big endian

       leshort
              see above, stored in small/little endian

       long   32-bit integer, stored in native endianess

       belong see above, stored in big endian

       lelong see above, stored in small/little endian

       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.

       date   32-bit integer timestamp, stored in native endianess

       bedate see above, stored in big endian

       ledate see above, stored in small/little endian

       ldate  32-bit integer timestamp, stored in native endianess

       beldate
              see above, stored in big endian

       leldate
              see above, stored in small/little endian

BUGS, IDEAS, FEEDBACK
       This document, and the package it describes, will undoubtedly contain
       bugs and other problems.  Please report such in the category fileutil
       :: magic of the Tcllib SF Trackers
       [http://sourceforge.net/tracker/?group_id=12883].  Please also report
       any ideas for enhancements you may have for either package and/or
       documentation.

SEE ALSO
       file(1), fileutil, magic(5)

KEYWORDS
       file recognition, file type, file utilities, mime, type

CATEGORY
       Programming tools



fumagic                               1.0               fileutil::magic::rt(n)
