litex/gen/migen/sim/vcd.py

   1 from itertools import count
   2
   3 from migen.fhdl.namer import build_namespace
   4
   5
   6 def vcd_codes():
   7     codechars = [chr(i) for i in range(33, 127)]
   8     for n in count():
   9         q, r = divmod(n, len(codechars))
  10         code = codechars[r]
  11         while q > 0:
  12             q, r = divmod(q, len(codechars))
  13             code = codechars[r] + code
  14         yield code
  15
  16
  17 class VCDWriter:
  18     def __init__(self, filename, signals):
  19         self.fo = open(filename, "w")
  20         self.codes = dict()
  21         self.signal_values = dict()
  22         self.t = 0
  23
  24         try:
  25             ns = build_namespace(signals)
  26             codes = vcd_codes()
  27             for signal in signals:
  28                 name = ns.get_name(signal)
  29                 code = next(codes)
  30                 self.codes[signal] = code
  31                 self.fo.write("$var wire {len} {code} {name} $end\n"
  32                               .format(name=name, code=code, len=len(signal)))
  33             self.fo.write("$dumpvars\n")
  34             for signal in signals:
  35                 value = signal.reset.value
  36                 self._write_value(signal, value)
  37                 self.signal_values[signal] = value
  38             self.fo.write("$end\n")
  39             self.fo.write("#0\n")
  40         except:
  41             self.close()
  42             raise
  43
  44     def _write_value(self, signal, value):
  45         l = len(signal)
  46         if value < 0:
  47             value += 2**l
  48         if l > 1:
  49             fmtstr = "b{:0" + str(l) + "b} {}\n"
  50         else:
  51             fmtstr = "{}{}\n"
  52         self.fo.write(fmtstr.format(value, self.codes[signal]))
  53
  54     def set(self, signal, value):
  55         if self.signal_values[signal] != value:
  56             self._write_value(signal, value)
  57             self.signal_values[signal] = value
  58
  59     def delay(self, delay):
  60         self.t += delay
  61         self.fo.write("#{}\n".format(self.t))
  62
  63     def close(self):
  64         self.fo.close()
  65
  66
  67 class DummyVCDWriter:
  68     def set(self, signal, value):
  69         pass
  70
  71     def delay(self, delay):
  72         pass
  73
  74     def close(self):
  75         pass