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Hex Dump Exec Script

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sigma7:
A script to dump a few bytes from a file in hex.

Excruciatingly slowly prints some bytes from a file in hexadecimal. I cobbled this trying to figure out what was happening when uploading text files that have characters with the high bit set. I don't think it is particularly useful, but it does serve as a warning about trying something so ambitious.

WARNINGS:
Do not casually ask for more than say 256 bytes, or to dump at an offset more than that. If you do, you will be resetting the machine or waiting...
As written, the script cannot be interrupted (other than dropping into the debugger, but I don't know what you would do next).

To use this:

* Put the code listed below into a text file with some name, eg. "HD.TEXT" (case does not matter)
* From the main menu of the Workshop, type "r" for run. (If you do it in a different menu, you will be renaming a file or suffer some other punishment.)
* Type "<HD(filename,start,count,output)" and return
You must type the "<" character for the Workshop to recognize it is an Exec file.
You can leave .TEXT off of the name of the Exec script to run
filename is required and must be complete, eg. N68K.ERR - it does not need to be a text file, but it is unclear what the results mean
you may enter a question mark as the filename to see terse instructions about parameters
start is optional, it will default to 1 (which is the first byte in the file)
count is optional, it will default to 16
output is optional, it will default to -CONSOLE
examples:
r<HD(n68k.err)                 dump 16 bytes starting at the first one to the console
r<HD.TEXT(diff.obj,,32)     dump 32 bytes starting at the first one to the console
r<hd(n68k.err,8,2)            dump 2 bytes starting at the eighth one to the console
r<hd(n68k.err,,99999,N68k.err.hexdump.text)            dump many bytes to the file "N68k.err.hexdump.text"


--- Code: ---EXEC (filename,start,count,outfile)
  IF filename = '?' THEN
    WRITELN 'Parameters: (filename,start[1],count[16],outfile[-console])'
    WRITELN 'Dump "count" bytes from "filename" to "outfile" in hex beginning at byte number "start"'
    HALT
  ENDIF
  DEFAULT start to 1
  DEFAULT count to 16
  DEFAULT outfile to '-console'
  WRITELN 'Hex dump of ',count,' bytes from ',filename,', to ',outfile,', starting at byte #',start
  RESET fref,filename
  REWRITE outref,outfile
  IF IORESULT <> '' THEN
    HALT IORESULT
  ENDIF
  SET %3 TO 1
  WHILE %3 LT start DO
    READCH (fref) %4
    if %4 = 'EOF' THEN
      WRITELN 'EOF reached prematurely at ',%3,' bytes'
      HALT
    ELSEIF IORESULT <> '' THEN
      HALT IORESULT
    ENDIF
    SET %3 to EVAL(%3 + 1)
  ENDWHILE
  SET %3 TO 0
  SET %9 to count
  WHILE %3 LT %9 DO
    READCH (fref) %4
    if %4 = 'EOF' THEN
      WRITELN 'EOF reached after ',%3,' bytes were dumped'
      HALT
    ELSEIF IORESULT <> '' THEN
      HALT IORESULT
    ENDIF
    SET %5 TO ORD (%4)
    SET %6 TO EVAL (%5 MOD 16 + 1)
    SET %7 TO EVAL (%5 / 16 + 1)
    SET %8 TO CONCAT ( COPY ('0123456789ABCDEF',%7,1), COPY ('0123456789ABCDEF',%6,1))
    WRITE (outref) %8,' '
    IF IORESULT <> '' THEN
      HALT IORESULT
    ENDIF
    SET %3 to EVAL(%3 + 1)
    SET %5 to EVAL (%3 MOD 16)
    IF %5 EQ 0 THEN
      WRITELN (outref) ' '
    ENDIF
    IF %3 GE %9 THEN
      IF outfile = '-console' THEN
        WRITE ' -- Enter space to dump ',count,' more, '
        REQUEST %1 WITH 'anything else to cancel...'
        IF %1 = ' ' THEN
          SET %9 TO EVAL(count + %9)
        ELSE
          CLOSE fref
          HALT 'Done'
        ENDIF
      ELSE
        CLOSE fref
        CLOSE outref
        HALT 'Done'     
      ENDIF
    ENDIF
  ENDWHILE
ENDEXEC

--- End code ---

BUGS etc.:

* It doesn't seem to recognize the end of a file - fixed I think
* No obvious way to stop it if you give it ambitious parameters and realize your mistake
edit: fixed EOF, implemented output to a file

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