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"""GDB support for WebKit types.

Add this to your gdb by amending your ~/.gdbinit as follows:

  python

  import sys

  sys.path.insert(0, "/path/to/tools/gdb/")

  import webcore

"""

import gdb

import struct

def ustring_to_string(ptr, length=None):

    """Convert a pointer to UTF-16 data into a Python Unicode string.

    ptr and length are both gdb.Value objects.

    If length is unspecified, will guess at the length."""

    extra = ''

    if length is None:

        # Try to guess at the length.

        for i in xrange(0, 2048):

            if int((ptr + i).dereference()) == 0:

                length = i

                break

        if length is None:

            length = 256

            extra = u' (no trailing NUL found)'

    else:

        length = int(length)

    char_vals = [int((ptr + i).dereference()) for i in xrange(length)]

    string = struct.pack('H' * length, *char_vals).decode('utf-16', 'replace')

    return string + extra

class StringPrinter(object):

    "Shared code between different string-printing classes"

    def __init__(self, val):

        self.val = val

    def display_hint(self):

        return 'string'

class UCharStringPrinter(StringPrinter):

    "Print a UChar*; we must guess at the length"

    def to_string(self):

        return ustring_to_string(self.val)

class WebCoreAtomicStringPrinter(StringPrinter):

    "Print a WebCore::AtomicString"

    def to_string(self):

        return self.val['m_string']

class WebCoreStringPrinter(StringPrinter):

    "Print a WebCore::String"

    def get_length(self):

        if not self.val['m_impl']['m_ptr']:

            return 0

        return self.val['m_impl']['m_ptr']['m_length']

    def to_string(self):

        if self.get_length() == 0:

            return '(null)'

        return ustring_to_string(self.val['m_impl']['m_ptr']['m_data'],

                                 self.get_length())

class WebCoreQualifiedNamePrinter(StringPrinter):

    "Print a WebCore::QualifiedName"

    def __init__(self, val):

        super(WebCoreQualifiedNamePrinter, self).__init__(val)

        self.prefix_length = 0

        self.length = 0

        if self.val['m_impl']:

            self.prefix_printer = WebCoreStringPrinter(

                self.val['m_impl']['m_prefix']['m_string'])

            self.local_name_printer = WebCoreStringPrinter(

                self.val['m_impl']['m_localName']['m_string'])

            self.prefix_length = self.prefix_printer.get_length()

            if self.prefix_length > 0:

                self.length = (self.prefix_length + 1 +

                    self.local_name_printer.get_length())

            else:

                self.length = self.local_name_printer.get_length()

    def get_length(self):

        return self.length

    def to_string(self):

        if self.get_length() == 0:

            return "(null)"

        else:

            if self.prefix_length > 0:

                return (self.prefix_printer.to_string() + ":" +

                    self.local_name_printer.to_string())

            else:

                return self.local_name_printer.to_string()

def lookup_function(val):

    """Function used to load pretty printers; will be passed to GDB."""

    lookup_tag = val.type.tag

    printers = {

        "WebCore::AtomicString": WebCoreAtomicStringPrinter,

        "WebCore::String": WebCoreStringPrinter,

        "WebCore::QualifiedName": WebCoreQualifiedNamePrinter,

    }

    name = val.type.tag

    if name in printers:

        return printers[name](val)

    if val.type.code == gdb.TYPE_CODE_PTR:

        name = str(val.type.target().unqualified())

        if name == 'UChar':

            return UCharStringPrinter(val)

    return None

gdb.pretty_printers.append(lookup_function)

class PrintPathToRootCommand(gdb.Command):

  """Command for printing WebKit Node trees.

Usage: printpathtoroot variable_name

"""

  def __init__(self):

      super(PrintPathToRootCommand, self).__init__("printpathtoroot",

          gdb.COMMAND_SUPPORT,

          gdb.COMPLETE_NONE)

  def invoke(self, arg, from_tty):

      element_type = gdb.lookup_type('WebCore::Element')

      node_type = gdb.lookup_type('WebCore::Node')

      frame = gdb.selected_frame()

      try:

          val = gdb.Frame.read_var(frame, arg)

      except:

          print "No such variable, or invalid type"

          return

      target_type = str(val.type.target().strip_typedefs())

      if target_type == str(node_type):

          stack = []

          while val:

              stack.append([val,

                  val.cast(element_type.pointer()).dereference()['m_tagName']])

              val = val.dereference()['m_parent']

          padding = ''

          while len(stack) > 0:

              pair = stack.pop()

              print padding, pair[1], pair[0]

              padding = padding + '  '

      else:

          print 'Sorry: I don\'t know how to deal with %s yet.' % target_type

PrintPathToRootCommand()