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# synthetic children provider for CFString
# (and related NSString class)
import lldb
class CFStringSynthProvider:
def __init__(self,valobj,dict):
self.valobj = valobj;
self.update()
# children other than "content" are for debugging only and must not be used in production code
def num_children(self):
if self.invalid:
return 0;
return 6;
def read_unicode(self, pointer):
process = self.valobj.GetTarget().GetProcess()
error = lldb.SBError()
pystr = u''
# cannot do the read at once because the length value has
# a weird encoding. better play it safe here
while True:
content = process.ReadMemory(pointer, 2, error)
new_bytes = bytearray(content)
b0 = new_bytes[0]
b1 = new_bytes[1]
pointer = pointer + 2
if b0 == 0 and b1 == 0:
break
# rearrange bytes depending on endianness
# (do we really need this or is Cocoa going to
# use Windows-compatible little-endian even
# if the target is big endian?)
if self.is_little:
value = b1 * 256 + b0
else:
value = b0 * 256 + b1
pystr = pystr + unichr(value)
return pystr
# handle the special case strings
# only use the custom code for the tested LP64 case
def handle_special(self):
if self.lp64 == False:
# for 32bit targets, use safe ObjC code
return self.handle_unicode_string_safe()
offset = 12
pointer = self.valobj.GetValueAsUnsigned(0) + offset
pystr = self.read_unicode(pointer)
return self.valobj.CreateValueFromExpression("content",
"(char*)\"" + pystr.encode('utf-8') + "\"")
# last resort call, use ObjC code to read; the final aim is to
# be able to strip this call away entirely and only do the read
# ourselves
def handle_unicode_string_safe(self):
return self.valobj.CreateValueFromExpression("content",
"(char*)\"" + self.valobj.GetObjectDescription() + "\"");
def handle_unicode_string(self):
# step 1: find offset
if self.inline:
pointer = self.valobj.GetValueAsUnsigned(0) + self.size_of_cfruntime_base();
if self.explicit == False:
# untested, use the safe code path
return self.handle_unicode_string_safe();
else:
# not sure why 8 bytes are skipped here
# (lldb) mem read -c 50 0x00000001001154f0
# 0x1001154f0: 98 1a 85 71 ff 7f 00 00 90 07 00 00 01 00 00 00 ...q?...........
# 0x100115500: 03 00 00 00 00 00 00 00 *c3 03 78 00 78 00 00 00 ........?.x.x...
# 0x100115510: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
# 0x100115520: 00 00 ..
# content begins at * (i.e. 8 bytes into variants, skipping void* buffer in
# __notInlineImmutable1 entirely, while the length byte is correctly located
# for an inline string)
pointer = pointer + 8;
else:
pointer = self.valobj.GetValueAsUnsigned(0) + self.size_of_cfruntime_base();
# read 8 bytes here and make an address out of them
vopointer = self.valobj.CreateChildAtOffset("dummy",
pointer,self.valobj.GetType().GetBasicType(lldb.eBasicTypeChar).GetPointerType());
pointer = vopointer.GetValueAsUnsigned(0)
# step 2: read Unicode data at pointer
pystr = self.read_unicode(pointer)
# step 3: return it
return self.valobj.CreateValueFromExpression("content",
"(char*)\"" + pystr.encode('utf-8') + "\"")
# we read at "the right place" into the __CFString object instead of running code
# we are replicating the functionality of __CFStrContents in CFString.c here
def handle_UTF8_inline(self):
offset = int(self.valobj.GetValue(), 0) + self.size_of_cfruntime_base();
if self.explicit == False:
offset = offset + 1;
return self.valobj.CreateValueFromAddress("content",
offset, self.valobj.GetType().GetBasicType(lldb.eBasicTypeChar));
def handle_UTF8_not_inline(self):
offset = self.size_of_cfruntime_base();
return self.valobj.CreateChildAtOffset("content",
offset,self.valobj.GetType().GetBasicType(lldb.eBasicTypeChar).GetPointerType());
def get_child_at_index(self,index):
if index == 0:
return self.valobj.CreateValueFromExpression("mutable",
str(int(self.mutable)));
if index == 1:
return self.valobj.CreateValueFromExpression("inline",
str(int(self.inline)));
if index == 2:
return self.valobj.CreateValueFromExpression("explicit",
str(int(self.explicit)));
if index == 3:
return self.valobj.CreateValueFromExpression("unicode",
str(int(self.unicode)));
if index == 4:
return self.valobj.CreateValueFromExpression("special",
str(int(self.special)));
if index == 5:
if self.unicode == True:
return self.handle_unicode_string();
elif self.special == True:
return self.handle_special();
elif self.inline == True:
return self.handle_UTF8_inline();
else:
return self.handle_UTF8_not_inline();
def get_child_index(self,name):
if name == "content":
return self.num_children() - 1;
if name == "mutable":
return 0;
if name == "inline":
return 1;
if name == "explicit":
return 2;
if name == "unicode":
return 3;
if name == "special":
return 4;
def is_64bit(self):
return self.valobj.GetTarget().GetProcess().GetAddressByteSize() == 8
def is_little_endian(self):
return self.valobj.GetTarget().GetProcess().GetByteOrder() == lldb.eByteOrderLittle
# CFRuntimeBase is defined as having an additional
# 4 bytes (padding?) on LP64 architectures
# to get its size we add up sizeof(pointer)+4
# and then add 4 more bytes if we are on a 64bit system
def size_of_cfruntime_base(self):
if self.lp64 == True:
return 8+4+4;
else:
return 4+4;
# the info bits are part of the CFRuntimeBase structure
# to get at them we have to skip a uintptr_t and then get
# at the least-significant byte of a 4 byte array. If we are
# on big-endian this means going to byte 3, if we are on
# little endian (OSX & iOS), this means reading byte 0
def offset_of_info_bits(self):
if self.lp64 == True:
offset = 8;
else:
offset = 4;
if self.is_little == False:
offset = offset + 3;
return offset;
def read_info_bits(self):
cfinfo = self.valobj.CreateChildAtOffset("cfinfo",
self.offset_of_info_bits(),
self.valobj.GetType().GetBasicType(lldb.eBasicTypeChar));
cfinfo.SetFormat(11)
info = cfinfo.GetValue();
if info != None:
self.invalid = False;
return int(info,0);
else:
self.invalid = True;
return None;
# calculating internal flag bits of the CFString object
# this stuff is defined and discussed in CFString.c
def is_mutable(self):
return (self.info_bits & 1) == 1;
def is_inline(self):
return (self.info_bits & 0x60) == 0;
# this flag's name is ambiguous, it turns out
# we must skip a length byte to get at the data
# when this flag is False
def has_explicit_length(self):
return (self.info_bits & (1 | 4)) != 4;
# probably a subclass of NSString. obtained this from [str pathExtension]
# here info_bits = 0 and Unicode data at the start of the padding word
# in the long run using the isa value might be safer as a way to identify this
# instead of reading the info_bits
def is_special_case(self):
return self.info_bits == 0;
def is_unicode(self):
return (self.info_bits & 0x10) == 0x10;
# preparing ourselves to read into memory
# by adjusting architecture-specific info
def adjust_for_architecture(self):
self.lp64 = self.is_64bit();
self.is_little = self.is_little_endian();
# reading info bits out of the CFString and computing
# useful values to get at the real data
def compute_flags(self):
self.info_bits = self.read_info_bits();
if self.info_bits == None:
return;
self.mutable = self.is_mutable();
self.inline = self.is_inline();
self.explicit = self.has_explicit_length();
self.unicode = self.is_unicode();
self.special = self.is_special_case();
def update(self):
self.adjust_for_architecture();
self.compute_flags();
def CFString_SummaryProvider (valobj,dict):
provider = CFStringSynthProvider(valobj,dict);
if provider.invalid == False:
return provider.get_child_at_index(provider.get_child_index("content")).GetSummary();
return ''
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