examples/synthetic/unordered_multi.py

import lldb

_map_capping_size = 255

class libcxx_hash_table_SynthProvider:
	def __init__(self, valobj, dict):
		self.valobj = valobj
		self.num_elements = None
		self.next_element = None
		self.bucket_count = None

	def update(self):
		logger = lldb.formatters.Logger.Logger()
		self.num_elements = None
		self.next_element = None
		self.bucket_count = None
		try:
			# unordered_map is made up a a hash_map, which has 4 pieces in it:
			#   bucket list :
			#      array of buckets
			#   p1 (pair):
			#      first - pointer to first loaded element
			#   p2 (pair):
			#      first - number of elements
			#      second - hash function
			#   p3 (pair):
			#      first - max_load_factor
			#      second - equality operator function
			#
			# For display, we actually dont need to go inside the buckets, since 'p1' has a way to iterate over all
			# the elements directly.
			#
			# We will calculate other values about the map because they will be useful for the summary.
			#
			table = self.valobj.GetChildMemberWithName('__table_')

			bl_ptr = table.GetChildMemberWithName('__bucket_list_').GetChildMemberWithName('__ptr_')
			self.bucket_array_ptr = bl_ptr.GetChildMemberWithName('__first_').GetValueAsUnsigned(0)
			self.bucket_count = bl_ptr.GetChildMemberWithName('__second_').GetChildMemberWithName('__data_').GetChildMemberWithName('__first_').GetValueAsUnsigned(0)
			logger >> "Bucket count = %r" % self.bucket_count

			self.begin_ptr = table.GetChildMemberWithName('__p1_').GetChildMemberWithName('__first_').GetChildMemberWithName('__next_')

			self.num_elements    = table.GetChildMemberWithName('__p2_').GetChildMemberWithName('__first_').GetValueAsUnsigned(0)
			self.max_load_factor = table.GetChildMemberWithName('__p3_').GetChildMemberWithName('__first_').GetValueAsUnsigned(0)
			logger >> "Num elements = %r" % self.num_elements

			# save the pointers as we get them
			#   -- dont access this first element if num_element==0!
			self.elements_cache = []
			if self.num_elements:
				self.next_element = self.begin_ptr
			else:
				self.next_element = None
		except Exception, e:
			logger >> "Caught exception: %r" % e
			pass

	def num_children(self):
		global _map_capping_size
		num_elements = self.num_elements
		if num_elements is not None:
			if num_elements > _map_capping_size:
				num_elements = _map_capping_size
		return num_elements

	def has_children(self):
		return True

	def get_child_index(self,name):
		logger = lldb.formatters.Logger.Logger()
		try:
			return int(name.lstrip('[').rstrip(']'))
		except:
			return -1

	def get_child_at_index(self,index):
		logger = lldb.formatters.Logger.Logger()
		logger >> "Retrieving child " + str(index)
		if index < 0:
			return None
		if index >= self.num_children():
			return None

		# extend
		logger >> " : cache size starts with %d elements" % len(self.elements_cache)
		while index >= len(self.elements_cache):
			# if we hit the end before we get the index, give up:
			if not self.next_element:
				logger >> " : hit end of list"
				return None

			node = self.next_element.Dereference()

			value = node.GetChildMemberWithName('__value_')
			hash_value = node.GetChildMemberWithName('__hash_').GetValueAsUnsigned()
			self.elements_cache.append((value, hash_value))

			self.next_element = node.GetChildMemberWithName('__next_')
			if not self.next_element.GetValueAsUnsigned(0):
				self.next_element = None

		# hit the index! so we have the value
		logger >> " : cache size ends with %d elements" % len(self.elements_cache)
		value, hash_value = self.elements_cache[index]
		return self.valobj.CreateValueFromData('[%d] <hash %d>'%(index,hash_value), value.GetData(), value.GetType())


def __lldb_init_module(debugger,dict):
	debugger.HandleCommand('type synthetic add -l unordered_multi.libcxx_hash_table_SynthProvider -x "^(std::__1::)unordered_(multi)?(map|set)<.+> >$" -w libcxx')