add enum support for generating perf event data struct (iovisor#2199)

Add enum type support so that scripts like tools/dcsnoop.py could be
simplied.

src/python/bcc/table.py

@@ -575,6 +575,7 @@ def _get_event_class(self):
  'u16' : ct.c_ushort,
  'int' : ct.c_int,
  's32' : ct.c_int,
+ 'enum' : ct.c_int,
  'unsigned int' : ct.c_uint,
  'u32' : ct.c_uint,
  'long' : ct.c_long,
@@ -599,6 +600,9 @@ def _get_event_class(self):
  field_name = m.group(1)
  field_type = m.group(2)
 
+ if re.match(r"enum .*", field_type):
+ field_type = "enum"
+
  m = array_type.match(field_type)
  try:
  if m:

tools/dcsnoop.py

@@ -23,7 +23,6 @@
 from __future__ import print_function
 from bcc import BPF
 import argparse
-import ctypes as ct
 import re
 import time
 
@@ -123,17 +122,6 @@
 }
 """
 
-TASK_COMM_LEN = 16 # linux/sched.h
-MAX_FILE_LEN = 64 # see inline C
-
-class Data(ct.Structure):
- _fields_ = [
- ("pid", ct.c_uint),
- ("type", ct.c_int),
- ("comm", ct.c_char * TASK_COMM_LEN),
- ("filename", ct.c_char * MAX_FILE_LEN),
- ]
-
 if args.ebpf:
  print(bpf_text)
  exit()
@@ -151,7 +139,7 @@ class Data(ct.Structure):
 start_ts = time.time()
 
 def print_event(cpu, data, size):
- event = ct.cast(data, ct.POINTER(Data)).contents
+ event = b["events"].event(data)
  print("%-11.6f %-6d %-16s %1s %s" % (
  time.time() - start_ts, event.pid,
  event.comm.decode('utf-8', 'replace'), mode_s[event.type],