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fileutil::magic::rt(3tcl) file utilities fileutil::magic::rt(3tcl) 





NAME


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






SYNOPSIS


package require Tcl 8.5


package require fileutil::magic::rt ?2.0?


::fileutil::magic::rt::>


::fileutil::magic::rt::<


::fileutil::magic::rt::new chan named
    analyze


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


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


::fileutil::magic::rt::O where


::fileutil::magic::rt::R where


::fileutil::magic::rt::Nv type offset
    compinvert comp expected


::fileutil::magic::rt::N type offset
    testinvert compinvert mod mand comp
    expected


::fileutil::magic::rt::S type offset
    testinvert mod mand comp val


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


::fileutil::magic::rt::I offset it ioi
    ioo iir io


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


::fileutil::magic::rt::U fileindex name










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 such as fileutil::magic::filetype and the two compiler
    packages fileutil::magic::cgen and
  fileutil::magic::cfront.






COMMANDS



  
::fileutil::magic::rt::>

  
Increment the level and perform related housekeeping

  
::fileutil::magic::rt::<

  
Decrement the level and perform related housekeeping

  
::fileutil::magic::rt::new chan named
    analyze

  
Create a new command which returns one description of the file each time
      it is called, and a code of break when there are no more
      descriptions. chan is the channel containing the data to describe.
      The channel configuration is then managed as needed. named is a
      dictionary of named tests, as generated by
      fileutil::magic::cfront::compile. test is a command prefix
      for a routine composed of the list of commands as returned by
      fileutil::magic::cfront::compile.

  
::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::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.

  
${x:...?...}

  
Substitute one string if the file is executable, and another string
      otherwise.







  
::fileutil::magic::rt::O where

  
Produce an offset from where, relative to the cursor one level up.
      Produce an offset from where, relative to the offset one level
    up.

  
::fileutil::magic::rt::Nv type offset
    compinvert comp expected

  
A limited form of ::fileutile::magic::rt::N that only checks for
      equality and can't be told to invert the test.

  
::fileutil::magic::rt::N type offset
    testinvert compinvert mod mand comp
    expected

  
Fetch the numeric value with type from the absolute location
      offset, compare it with expected using comp as the
      comparision operator, and returns the result.
    
The argument comp must be one of Tcl's comparison
        operators.

  






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





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::S type offset
    testinvert mod mand comp val

  
Like ::fileutil::magic::rt::N except that it fetches and compares
      string types , not numeric data.

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

  
Sets the current level in the calling context to newlevel. The
      command returns the empty string as its result.

  
::fileutil::magic::rt::I offset it ioi
    ioo iir io

  
Calculates an offset based on an initial offset and the provided
      modifiers.

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

  
Given an initial offset, calculates an offset relative to the cursor at
      the next level up. The cursor is the position in the data one character
      after the data extracted from the file one level up.
    

  

  
::fileutil::magic::rt::U fileindex name

  
Add a level and use a named test script.








NUMERIC TYPES



  

  
8-bit integer

  

  
16-bit integer, stored in native endianess

  

  
see above, stored in big endian

  

  
see above, stored in small/little endian

  

  
32-bit integer, stored in native endianess

  

  
see above, stored in big endian

  

  
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.



  

  
32-bit integer timestamp, stored in native endianess

  

  
see above, stored in big endian

  

  
see above, stored in small/little endian

  

  
32-bit integer timestamp, stored in native endianess

  

  
see above, stored in big endian

  

  
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 Trackers
    [http://core.tcl.tk/tcllib/reportlist]. Please also report any ideas for
    enhancements you may have for either package and/or documentation.


When proposing code changes, please provide unified diffs,
    i.e the output of diff -u.


Note further that attachments are strongly preferred over
    inlined patches. Attachments can be made by going to the Edit form of
    the ticket immediately after its creation, and then using the left-most
    button in the secondary navigation bar.






SEE ALSO


file(1), fileutil, magic(5)






KEYWORDS


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






CATEGORY


Programming tools







  

    2.0
    tcllib