Reading and Writing to a file simultaneously

问题

I have a module in written in System Verilog that dumps the contents of the SRAM into a file. I would like to read from this file and use the data in a separate program written in python, but in real time. I don't have much control over the writing from the verilog code. Is it possible to somehow manage the two read and writes? Currently when it reads from the file, there is a (seemingly) random number inserted at the start of every line and that throws off the parsing. I assume these prefixes only appear when they are reading and writing at the same time because if I run them both very slowly it works fine.

window = Tk()
canvas = Canvas(window, width=WIDTH, height=HEIGHT, bg="#000000")
canvas.pack()
img = PhotoImage(width=WIDTH, height=HEIGHT)
canvas.create_image((WIDTH/2, HEIGHT/2), image=img, state="normal")

def redraw():
fp = open('test_data.txt','r')
lines=fp.readlines()
for i in range(len(lines)):
        #do stuff
fp.close()
window.after(35,redraw)  

window.after(35,redraw)
mainloop()

This is what is reading.

Any suggestions are appreciated.

回答1:

Reading and writing a file from multiple processes is likely to be unpredictable.

If you are running on a Unix-like system, you could use mkfifo to make a file-like object which you can write to and read from simultaneously and the data will stay in the correct order.

On Windows you need a NamedPipe - which you could create from Python and then connect to by opening as a normal file in SystemVerilog (I believe!)

http://docs.activestate.com/activepython/2.4/pywin32/win32pipe.html

回答2:

I would suggest using VPI to directly access the contents of the SRAM straight from the simulation. This also opens the possibility of dynamically adjusting your stimulus (e.g. sending data until a FIFO is full) rather than relying on files for input/output.

Since you're using Python you could look into Cocotb, an open-source Python cosimulation framework. Basically you can use the python 'dot' notation to traverse the design hierarchy and pull out values:

# Pull out the values from the simulation
for index in range(len(dut.path.through.hierarchy.ram)):
    val = dut.path.through.hierarchy.ram[index].value.integer
    # do stuff

I created a quick example on EDA Playground with a simplistic example: http://www.edaplayground.com/s/57/565

Disclaimer: I'm one of the Cocotb developers.

回答3:

You can use pipe, in this example a cmd (windows) command line writes in the pipe, then the program shows its output from the same pipe:

import subprocess,sys

p = subprocess.Popen("netsatat",shell=False ,stdout=subprocess.PIPE)
while True:
    out = p.stdout.readline()
    if out == '' and p.poll() != None:
        break
    if out != b'':
        print(out.decode('ascii','backslashreplace'))
    else :
        break;

来源：https://stackoverflow.com/questions/15992375/reading-and-writing-to-a-file-simultaneously

标签

python

file-io

system-verilog