mirror of
https://github.com/vivisect/vivisect
synced 2026-06-08 18:04:23 +00:00
James Gross
80de840881
A lot of cleanup things in prep for a python 3 transition. Getting rid of the old exception syntax, converting prints over to logging, cutting random scraps of code to be proper unit tests, cut away some older bits of code, etc. This still works in python2. It's just a lot of tidying up. There are no major functionality changes.
122 lines
3.4 KiB
Python
122 lines
3.4 KiB
Python
import binascii
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from vstruct import VStruct
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from vstruct.primitives import *
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class v_bits(v_number):
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def __init__(self, width):
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v_number.__init__(self)
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self._vs_bitwidth = width
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def vsSetValue(self, value):
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'''
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override base because we are not using the min or max val.
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'''
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self._vs_value = long(value)
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def vsSetBitWidth(self, width):
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self._vs_bitwidth = width
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class VBitField(VStruct):
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'''
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A VStruct *like* field which may contain v_bits
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children. To all VStruct related operations, we are
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a primitive, but we do have internal structure.
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Example:
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see vstruct/defs/swf.py
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NOTE: this object will pad itself to byte aligned bounds
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'''
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def __init__(self):
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VStruct.__init__(self)
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def vsIsPrim(self):
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return True
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def vsAddField(self, name, value):
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if not isinstance(value, v_bits):
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raise Exception('VBitField *must* use v_bits() kids!')
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return VStruct.vsAddField(self, name, value)
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def vsGetPrintInfo(self, offset=0, indent=0, top=True):
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ret = []
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if top:
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ret.append((offset, indent, self._vs_name, self))
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indent += 1
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bitoff = 0
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for fname,field in self.vsGetFields():
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# use vsSetBitWidth(0) to disable fields
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if field._vs_bitwidth == 0:
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continue
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bitname = '%s[%d:%d]' % (fname,bitoff,bitoff + field._vs_bitwidth)
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ret.append( (offset, indent, bitname, field) )
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bitoff += field._vs_bitwidth
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return ret
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def __len__(self):
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bits = sum([ f._vs_bitwidth for (n,f) in self.vsGetFields() ])
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bittobyte,bitoff = divmod(bits,8)
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if bitoff:
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bittobyte += 1
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return bittobyte
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def vsParse(self, bytez, offset=0):
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bitoff = 0
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for fname,field in self.vsGetFields():
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# use vsSetBitWidth(0) to disable fields
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if field._vs_bitwidth == 0:
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continue
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# adjust forward from last fields bits % 8
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startbyte,startbit = divmod(bitoff,8)
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#offset += bittobyte
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endbyte,endbit = divmod(bitoff + field._vs_bitwidth, 8)
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# if we have an endbit remainder, we need to grab
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# an additional byte...
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endround = 0
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endshift = 0
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if endbit:
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endshift = (8-endbit)
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endround = 1
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fieldbytes = bytez[offset + startbyte:offset+endbyte+endround]
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rawint = int(binascii.hexlify(fieldbytes), 16)
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if endshift:
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#if bitshift:
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rawint >>= endshift
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rawint &= (2**field._vs_bitwidth)-1
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field.vsSetValue(rawint)
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bitoff += field._vs_bitwidth
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self._vsFireCallbacks(fname)
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offbytes,offbits = divmod(bitoff,8)
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offset += offbytes
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# mop up any remaining bits int a byte boundary
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if offbits:
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offset += 1
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return offset
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def vsEmit(self):
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valu = 0
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width = 0
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for name,field in self.vsGetFields():
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width += field._vs_bitwidth
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valu = ( valu << field._vs_bitwidth ) | field._vs_value
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bytelen,bitrem = divmod(width,8)
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if bitrem:
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bytelen += 1
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valu <<= ( 8 - bitrem )
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return binascii.unhexlify(('%.' + str(bytelen*2) + 'x') % valu)
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