Fix lldb string formatter.

Tools/lldb/lldb_webkit.py

 # Copyright (C) 2012 Apple. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions
 # are met:
 # 1.  Redistributions of source code must retain the above copyright
 #     notice, this list of conditions and the following disclaimer.
 # 2.  Redistributions in binary form must reproduce the above copyright
 #     notice, this list of conditions and the following disclaimer in the
 #     documentation and/or other materials provided with the distribution.
@@ skipping 12 matching lines @@
 """
     LLDB Support for WebKit Types
 
     Add the following to your .lldbinit file to add WebKit Type summaries in LLDB and Xcode:
 
     command script import {Path to WebKit Root}/Tools/lldb/lldb_webkit.py
 
 """
 
 import lldb
+import struct
 
 
 def __lldb_init_module(debugger, dict):
     debugger.HandleCommand('type summary add --expand -F lldb_webkit.WTFString_SummaryProvider WTF::String')
     debugger.HandleCommand('type summary add --expand -F lldb_webkit.WTFStringImpl_SummaryProvider WTF::StringImpl')
     debugger.HandleCommand('type summary add --expand -F lldb_webkit.WTFAtomicString_SummaryProvider WTF::AtomicString')
     debugger.HandleCommand('type summary add --expand -F lldb_webkit.WTFVector_SummaryProvider -x "WTF::Vector<.+>$"')
     debugger.HandleCommand('type summary add --expand -F lldb_webkit.WTFHashTable_SummaryProvider -x "WTF::HashTable<.+>$"')
     debugger.HandleCommand('type synthetic add -x "WTF::Vector<.+>$" --python-class lldb_webkit.WTFVectorProvider')
     debugger.HandleCommand('type synthetic add -x "WTF::HashTable<.+>$" --python-class lldb_webkit.WTFHashTableProvider')
@@ skipping 24 matching lines @@
 
 # FIXME: Provide support for the following types:
 # def WTFVector_SummaryProvider(valobj, dict):
 # def WTFCString_SummaryProvider(valobj, dict):
 # def WebCoreKURLGooglePrivate_SummaryProvider(valobj, dict):
 # def WebCoreQualifiedName_SummaryProvider(valobj, dict):
 # def JSCIdentifier_SummaryProvider(valobj, dict):
 # def JSCJSString_SummaryProvider(valobj, dict):
 
 
-def guess_string_length(valobj, error):
-    if not valobj.GetValue():
-        return 0
-
-    for i in xrange(0, 2048):
-        if valobj.GetPointeeData(i, 1).GetUnsignedInt16(error, 0) == 0:
-            return i
-
-    return 256
-
-
-def ustring_to_string(valobj, error, length=None):
-    if length is None:
-        length = guess_string_length(valobj, error)
-    else:
-        length = int(length)
-
-    out_string = u""
-    for i in xrange(0, length):
-        char_value = valobj.GetPointeeData(i, 1).GetUnsignedInt16(error, 0)
-        out_string = out_string + unichr(char_value)
-
-    return out_string.encode('utf-8')
-
-
-def lstring_to_string(valobj, error, length=None):
-    if length is None:
-        length = guess_string_length(valobj, error)
-    else:
-        length = int(length)
-
-    out_string = u""
-    for i in xrange(0, length):
-        char_value = valobj.GetPointeeData(i, 1).GetUnsignedInt8(error, 0)
-        out_string = out_string + unichr(char_value)
-
-    return out_string.encode('utf-8')
-
-
 class WTFStringImplProvider:
     def __init__(self, valobj, dict):
         self.valobj = valobj
 
     def get_length(self):
         return self.valobj.GetChildMemberWithName('m_length').GetValueAsUnsigned(0)
 
+    def get_data(self, length):
+        offset = 12
+        # Try to get the address of the object.
+        addr = self.valobj.GetAddress()
+        # If address == 0 then the object is a pointer so we can use it's
+        # value instead. We need to offset the pointer so it points to
+        # raw string data.
+        ptr = (int(str(addr), 16) if addr else self.valobj.GetValueAsUnsigned(0)) + offset
+        error = lldb.SBError()
+        # Read the raw data from memory.
+        return self.valobj.GetTarget().GetProcess().ReadMemory(ptr, length, error)
+
     def get_data8(self):
-        return self.valobj.GetChildAtIndex(2).GetChildMemberWithName('m_data8')
+        return self.get_data(self.get_length())
 
     def get_data16(self):
-        return self.valobj.GetChildAtIndex(2).GetChildMemberWithName('m_data16')
+        length = self.get_length()
+        # Read raw string data.
+        data = self.get_data(2 * length)
+        # Create a list of length 2-byte unsigned integers from byte array.
+        ushort_list = struct.unpack(length * 'H', data)
+        # Return the string.
+        return u"".join(map(unichr, ushort_list))
 
     def to_string(self):
         error = lldb.SBError()
-        if self.is_8bit():
-            return lstring_to_string(self.get_data8(), error, self.get_length())
-        return ustring_to_string(self.get_data16(), error, self.get_length())
+        data = self.get_data8() if self.is_8bit() else self.get_data16()
+        return data.encode('utf-8')
 
     def is_8bit(self):
-        # FIXME: find a way to access WTF::StringImpl::s_hashFlag8BitBuffer
-        return bool(self.valobj.GetChildMemberWithName('m_hashAndFlags').GetValueAsUnsigned(0) \
-            & 1 << 6)
+        return bool(self.valobj.GetChildMemberWithName('m_is8Bit').GetValueAsUnsigned(0))
 
 
 class WTFStringProvider:
     def __init__(self, valobj, dict):
         self.valobj = valobj
 
     def stringimpl(self):
         impl_ptr = self.valobj.GetChildMemberWithName('m_impl').GetChildMemberWithName('m_ptr')
         return WTFStringImplProvider(impl_ptr, dict)
 
@@ skipping 94 matching lines @@
 
     def keyCount(self):
         return self.valobj.GetChildMemberWithName('m_keyCount').GetValueAsUnsigned(0)
 
     def update(self):
         self.data_type = self.valobj.GetType().GetTemplateArgumentType(0)
         self.data_size = self.data_type.GetByteSize()
 
     def has_children(self):
         return True