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135 lines
4.0 KiB
135 lines
4.0 KiB
5 years ago
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"""
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Debugging utilities for constructs
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"""
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from __future__ import print_function
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import sys
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import traceback
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import pdb
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import inspect
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from .core import Construct, Subconstruct
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from .lib import HexString, Container, ListContainer
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class Probe(Construct):
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"""
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A probe: dumps the context, stack frames, and stream content to the screen
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to aid the debugging process.
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See also Debugger.
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Parameters:
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* name - the display name
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* show_stream - whether or not to show stream contents. default is True.
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the stream must be seekable.
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* show_context - whether or not to show the context. default is True.
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* show_stack - whether or not to show the upper stack frames. default
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is True.
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* stream_lookahead - the number of bytes to dump when show_stack is set.
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default is 100.
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Example:
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Struct("foo",
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UBInt8("a"),
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Probe("between a and b"),
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UBInt8("b"),
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)
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"""
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__slots__ = [
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"printname", "show_stream", "show_context", "show_stack",
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"stream_lookahead"
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]
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counter = 0
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def __init__(self, name = None, show_stream = True,
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show_context = True, show_stack = True,
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stream_lookahead = 100):
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Construct.__init__(self, None)
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if name is None:
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Probe.counter += 1
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name = "<unnamed %d>" % (Probe.counter,)
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self.printname = name
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self.show_stream = show_stream
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self.show_context = show_context
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self.show_stack = show_stack
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self.stream_lookahead = stream_lookahead
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def __repr__(self):
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return "%s(%r)" % (self.__class__.__name__, self.printname)
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def _parse(self, stream, context):
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self.printout(stream, context)
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def _build(self, obj, stream, context):
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self.printout(stream, context)
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def _sizeof(self, context):
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return 0
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def printout(self, stream, context):
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obj = Container()
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if self.show_stream:
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obj.stream_position = stream.tell()
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follows = stream.read(self.stream_lookahead)
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if not follows:
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obj.following_stream_data = "EOF reached"
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else:
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stream.seek(-len(follows), 1)
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obj.following_stream_data = HexString(follows)
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print
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if self.show_context:
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obj.context = context
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if self.show_stack:
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obj.stack = ListContainer()
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frames = [s[0] for s in inspect.stack()][1:-1]
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frames.reverse()
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for f in frames:
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a = Container()
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a.__update__(f.f_locals)
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obj.stack.append(a)
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print("=" * 80)
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print("Probe", self.printname)
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print(obj)
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print("=" * 80)
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class Debugger(Subconstruct):
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"""
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A pdb-based debugger. When an exception occurs in the subcon, a debugger
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will appear and allow you to debug the error (and even fix on-the-fly).
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Parameters:
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* subcon - the subcon to debug
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Example:
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Debugger(
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Enum(UBInt8("foo"),
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a = 1,
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b = 2,
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c = 3
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)
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)
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"""
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__slots__ = ["retval"]
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def _parse(self, stream, context):
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try:
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return self.subcon._parse(stream, context)
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except Exception:
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self.retval = NotImplemented
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self.handle_exc("(you can set the value of 'self.retval', "
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"which will be returned)")
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if self.retval is NotImplemented:
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raise
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else:
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return self.retval
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def _build(self, obj, stream, context):
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try:
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self.subcon._build(obj, stream, context)
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except Exception:
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self.handle_exc()
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def handle_exc(self, msg = None):
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print("=" * 80)
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print("Debugging exception of %s:" % (self.subcon,))
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print("".join(traceback.format_exception(*sys.exc_info())[1:]))
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if msg:
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print(msg)
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pdb.post_mortem(sys.exc_info()[2])
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print("=" * 80)
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