Pipes

[Sather User]

Hello, all.  In too much of a tizz to look in since my last super
roughie. Sorry about it.  I quickly abandoned libtiff.  I decided that
re-implementation in Sather directly was a better approach than
digesting the libtiff documentation.  For example several TIFF tag
values are rationals and Sather has a rational type (RAT) but C does
not so libtiff does a workaround and you never seen the numerator and
denominator of an XResolution, for example, only a floating point value.

To hastily move on, here is an addition you can make to
Library/IO/file.sa.  You can put it anywhere, but that's what I did.
I needed to look up the date from Sather, you see, to put the DateTime
tag into TIFF files, and I had to do that by running the shell
command, date, and reading the response.

This, I guess, is another roughie.  It works, that's all I know.

-------------------------------------------------------------------
partial class FILE_PIPE is
   -- Things common to both
   readonly attr fp:EXT_OB;      -- The FILE pointer readonly attr

   get_char:CHAR pre ~void(fp) is
      return RUNTIME::fgetc(fp);
   end;

   get_str:STR is
      -- A string containing the characters up to the next newline.
      return get_line.str;
   end;

   get_line:FSTR is
      -- A string buffer containing the characters up to the next newline.
      res::=#FSTR;
      loop
          c::=get_char;
          if eof then return res end;
          -- Next 2 lines reversed mtw Sep 2011
          until!(c='\n');
          res:=res.push(c);
      end;
      return res;
   end;

   get(s:STR):FLIST{STR} is
      p::=open_for_read(s);
      if p.error then raise "oops" end;
      ans::=#FLIST{STR};
      loop
         t::=p.get_str;
         while!(~p.eof);
         ans:=ans.push(t)
      end;
      p.close;
      return ans
   end;



end;

class PIPE is
   -- Not < $OSTREAM because no plus...
   -- MTW Oct 2011
   -- The stdin/stdout of FILE maybe should be here.
   --
   -- Example:
   -- class MAIN is
   --    main is
   --       p::=PIPE::open_for_read("date +'%Y:%m:%d %H:%M:%S'");
   --       s:STR:=p.get_str;
   --       p.close;
   --       #OUT+s+"\n"; -- prints formatted date
   --    end
   -- end
   --
   include FILE_PIPE;

   open_for_read(command:STR):SAME is
      -- Open pipe for reading.
      r::=new;
      r.fp:=RUNTIME::popen(command,"r");
      return r
   end;

   close pre ~void(fp) is
      -- Close the pipe corresponding to self.
      RUNTIME::pclose(fp)
   end;

   error:BOOL is
      -- true is an error has occurred with this file.  Cleared by "clear".
      return void(fp) or RUNTIME::ferror(fp)
   end;


   eof:BOOL pre ~void(fp) is
      -- true if EOF has been encountered.  Cleared by "clear".
      return RUNTIME::feof(fp)
   end;

end;

class FILE < $OSTREAM is ... etc

-------------------------------------------------------------

Library/System/runtime.sa:

external class RUNTIME is
        ...
        popen(nm:STR,tp:STR):EXT_OB;
        pclose(fp:EXT_OB);
        ...

---------------------------------------------------------------------

Hope I haven't missed anything there.  You can see from the commented
example that it's easy as pie, just one of the loose ends left undone
in ICSI Sather.

Merry Christmas to all.

--Mike


-- 
Michael Talbot-Wilson