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# Useful gdb string convenience functions.

# Copyright (C) 2012 Free Software Foundation, Inc.

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 3 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""$_memeq, $_strlen, $_streq, $_regex"""

import gdb

import re

class _MemEq(gdb.Function):

  """$_memeq - compare bytes of memory

Usage:

  $_memeq(a, b, len)

Returns:

  True if len bytes at a and b compare equally.

"""

  def __init__(self):

    super(_MemEq, self).__init__("_memeq")

  def invoke(self, a, b, length):

    if length < 0:

      raise ValueError("length must be non-negative")

    if length == 0:

      return True

    # The argument(s) to vector are [low_bound,]high_bound.

    byte_vector = gdb.lookup_type("char").vector(length - 1)

    ptr_byte_vector = byte_vector.pointer()

    a_ptr = a.reinterpret_cast(ptr_byte_vector)

    b_ptr = b.reinterpret_cast(ptr_byte_vector)

    return a_ptr.dereference() == b_ptr.dereference()

class _StrLen(gdb.Function):

  """$_strlen - compute string length

Usage:

  $_strlen(a)

Returns:

  Length of string a, assumed to be a string in the current language.

"""

  def __init__(self):

    super(_StrLen, self).__init__("_strlen")

  def invoke(self, a):

    s = a.string()

    return len(s)

class _StrEq(gdb.Function):

  """$_streq - check string equality

Usage:

  $_streq(a, b)

Returns:

  True if a and b are identical strings in the current language.

Example (amd64-linux):

  catch syscall open

  cond $bpnum $_streq((char*) $rdi, "foo")

"""

  def __init__(self):

    super(_StrEq, self).__init__("_streq")

  def invoke(self, a, b):

    return a.string() == b.string()

class _RegEx(gdb.Function):

  """$_regex - check if a string matches a regular expression

Usage:

  $_regex(string, regex)

Returns:

  True if string str (in the current language) matches the

  regular expression regex.

"""

  def __init__(self):

    super(_RegEx, self).__init__("_regex")

  def invoke(self, string, regex):

    s = string.string()

    r = re.compile(regex.string())

    return bool(r.match(s))

# GDB will import us automagically via gdb/__init__.py.

_MemEq()

_StrLen()

_StrEq()

_RegEx()