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gforth mmap - can't connect?

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  gforth mmap - can't connect? Jan Coombs <Jan-54 <jenfhaomndgfwutc@murmic.plus.com>> - 2015-04-03 12:07 +0100
    Re: gforth mmap - can't connect? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2015-04-03 12:03 +0000

#37881 — gforth mmap - can't connect?

I want to connect support tools for Forth chips like the 
b16 and j1 to my development tools, so that I can 
interactively write code and debug on a simulation of the 
hardware. The tools can the be later connected to the 
FPGA hardware to continue testing at higher speed. 

Small FPGA boards often include a USB comm port for debug, 
so there is no problem connecting tools to real chip, but 
in order to connect up for simulation I need a byte-wide 
bi-directional pipe. To make this easy to port to Windows 
I chose to implement this myself using mmap. 

Getting this working at the chip tools end, in Python, was 
not too difficult, but I cannot seem to get it connecting 
in gforth.  The mmap'd file has only one writer. 


This is the read end setup in Python:

import os
fd_in = os.open('/home/jan/tmp/mmaptest', os.O_RDONLY)
buf = mmap.mmap(fd_in, mmap.PAGESIZE, mmap.MAP_SHARED, mmap.PROT_READ)


This is my gforth read setup:

include mmap_0.7.9.fs
s" /home/jan/tmp/mmaptest"  r/o open-file throw  Value fd_in
here >pagealign here - allot 
here pagesize allot  constant buf
\ buf pagesize PROT_READ MAP_SHARED fd_in  off  mmap      
\ buf pagesize PROT_READ MAP_SHARED fd_in  -1   mmap      
  buf pagesize PROT_READ MAP_SHARED fd_in   0   mmap      

I do not know what 'iff' is, and having looked at mmap docs 
for C still can't guess. Or perhaps my problem is elsewhere?  
I'm not seeing any errors, but buff remains empty, while I 
can see another receiver working correctly. 


The gforth version is Gforth 0.7.0, running under ubuntu. 
Any ideas, updated source or docs, would be appreciated. 


Jan Coombs
-- 
email valid, else fix dots and hyphen
jan4clf2014@murrayhyphenmicroftdotcodotuk

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#37883

Jan Coombs <Jan-54 <jenfhaomndgfwutc@murmic.plus.com>> writes:
>This is my gforth read setup:
>
>include mmap_0.7.9.fs
>s" /home/jan/tmp/mmaptest"  r/o open-file throw  Value fd_in
>here >pagealign here - allot 
>here pagesize allot  constant buf
>\ buf pagesize PROT_READ MAP_SHARED fd_in  off  mmap      
>\ buf pagesize PROT_READ MAP_SHARED fd_in  -1   mmap      
>  buf pagesize PROT_READ MAP_SHARED fd_in   0   mmap      
>
>I do not know what 'iff' is, and having looked at mmap docs 
>for C still can't guess.

If your question is what the offset parameter of mmap is, the
documentation says this:

  The contents of a file mapping (as opposed to an anonymous mapping; see
  MAP_ANONYMOUS  below),  are  initialized using length bytes starting at
  offset offset in the file (or other object) referred  to  by  the  file
  descriptor  fd.

0 is probably what you want.

> Or perhaps my problem is elsewhere?  

open-file returns a FILE *, not an int.  You need fileno to convert it
into an int, or you open the file with the system call open.

You probably should specify 0 instead of buf (so the OS can select a
free address region).  The address of the mapping is returned as
result.

Depending on how mmap is defined, offset might be expected to be a
double; if so, use 0. instead of 0 for the offset parameter.

>I'm not seeing any errors

Do you get a non-zero result out of mmap?

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
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