1"""Abstraction layer for different ABIs."""
2
3import re
4import symbol
5
6def UnpackLittleEndian(word):
7  """Split a hexadecimal string in little endian order."""
8  return [word[x:x+2] for x in range(len(word) - 2, -2, -2)]
9
10
11ASSEMBLE = 'as'
12DISASSEMBLE = 'objdump'
13LINK = 'ld'
14UNPACK = 'unpack'
15
16OPTIONS = {
17    'x86': {
18        ASSEMBLE: ['--32'],
19        LINK: ['-melf_i386']
20    }
21}
22
23
24class Architecture(object):
25  """Creates an architecture abstraction for a given ABI.
26
27  Args:
28    name: The abi name, as represented in a tombstone.
29  """
30
31  def __init__(self, name):
32    symbol.ARCH = name
33    self.toolchain = symbol.FindToolchain()
34    self.options = OPTIONS.get(name, {})
35
36  def Assemble(self, args):
37    """Generates an assembler command, appending the given args."""
38    return [symbol.ToolPath(ASSEMBLE)] + self.options.get(ASSEMBLE, []) + args
39
40  def Link(self, args):
41    """Generates a link command, appending the given args."""
42    return [symbol.ToolPath(LINK)] + self.options.get(LINK, []) + args
43
44  def Disassemble(self, args):
45    """Generates a disassemble command, appending the given args."""
46    return ([symbol.ToolPath(DISASSEMBLE)] + self.options.get(DISASSEMBLE, []) +
47            args)
48
49  def WordToBytes(self, word):
50    """Unpacks a hexadecimal string in the architecture's byte order.
51
52    Args:
53      word: A string representing a hexadecimal value.
54
55    Returns:
56      An array of hexadecimal byte values.
57    """
58    return self.options.get(UNPACK, UnpackLittleEndian)(word)
59