def __init__(self, **kwargs):
buffer = kwargs.get("buffer", None)
self.flags = kwargs.get("flags", b'\x00')
self.pageCapacity = kwargs.get("pageCapacity", len(buffer))
self.tupleSize = kwargs.get("tupleSize", None)
self.bitmap = kwargs.get("bitmap", None)
if buffer == None:
raise ValueError(
"No backing buffer supplied for SlottedPageHeader")
if self.bitmap == None:
headerSizeWithoutBitmap = struct.Struct("cHHH").size
tupleCapacity = math.floor(
(8 * (self.pageCapacity - headerSizeWithoutBitmap)) /
(1 + (8 * self.tupleSize)))
bString = '0b' + ('0' * tupleCapacity)
self.bitmap = BitArray(bString)
self.binrepr = struct.Struct("cHHH" +
str(math.ceil(len(self.bitmap))) + 's')
self.size = self.binrepr.size
self.freeSpaceOffset = self.size
buffer[0:self.size] = self.pack()
def unpack(cls, buffer):
binrepr1 = struct.Struct("cHHH")
values1 = binrepr1.unpack_from(buffer)
headerSizeWithoutBitmap = binrepr1.size
tupleCapacity = math.floor(
(8 * (values1[3] - headerSizeWithoutBitmap)) / (1 +
(8 * values1[1])))
binrepr2 = struct.Struct("cHHH" + str(math.ceil(tupleCapacity)) + 's')
values2 = binrepr2.unpack_from(buffer)
bString = '0b' + ('0' * tupleCapacity)
bitmap = BitArray(bString)
index = 0
for bit in values2[4]:
if index >= tupleCapacity:
break
if bit:
bitmap[index] = '0b1'
else:
bitmap[index] = '0b0'
index = index + 1
if len(values2) == 5:
return cls(buffer=buffer,
flags=values2[0],
tupleSize=values2[1],
freeSpaceOffset=values2[2],
pageCapacity=values2[3],
bitmap=bitmap)
def __init__(self, **kwargs):
buffer=kwargs.get("buffer", None)
self.flags = kwargs.get("flags", b'\x00')
self.pageCapacity = kwargs.get("pageCapacity", len(buffer))
self.tupleSize = kwargs.get("tupleSize", None)
self.bitmap=kwargs.get("bitmap", None)
if buffer == None:
raise ValueError("No backing buffer supplied for SlottedPageHeader")
if self.bitmap == None:
headerSizeWithoutBitmap = struct.Struct("cHHH").size
tupleCapacity = math.floor((8*(self.pageCapacity-headerSizeWithoutBitmap))/(1+(8*self.tupleSize)))
bString = '0b' + ('0' * tupleCapacity)
self.bitmap = BitArray(bString)
self.binrepr = struct.Struct("cHHH" + str(math.ceil(len(self.bitmap))) + 's')
self.size = self.binrepr.size
self.freeSpaceOffset = self.size
buffer[0:self.size] = self.pack()
class SlottedPageHeader(PageHeader):
"""
A slotted page header implementation. This should store a slot bitmap
implemented as a memoryview on the byte buffer backing the page
associated with this header. Additionally this header object stores
the number of slots in the array, as well as the index of the next
available slot.
The binary representation of this header object is: (numSlots, nextSlot, slotBuffer)
>>> import io
>>> buffer = io.BytesIO(bytes(4096))
>>> ph = SlottedPageHeader(buffer=buffer.getbuffer(), tupleSize=16)
>>> ph2 = SlottedPageHeader.unpack(buffer.getbuffer())
>>> ph == ph2
True
## Dirty bit tests
>>> ph.isDirty()
False
>>> ph.setDirty(True)
>>> ph.isDirty()
True
>>> ph.setDirty(False)
>>> ph.isDirty()
False
## Tuple count tests
>>> ph.hasFreeTuple()
True
# First tuple allocated should be at the first slot.
# Notice this is a slot index, not an offset as with contiguous pages.
>>> ph.nextFreeTuple() == 0
True
>>> ph.numTuples()
1
>>> tuplesToTest = 10
>>> [ph.nextFreeTuple() for i in range(0, tuplesToTest)]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> ph.numTuples() == tuplesToTest+1
True
>>> ph.hasFreeTuple()
True
# Check space utilization
>>> ph.usedSpace() == (tuplesToTest+1)*ph.tupleSize
True
>>> ph.freeSpace() == 4096 - (ph.headerSize() + ((tuplesToTest+1) * ph.tupleSize))
True
>>> remainingTuples = int(ph.freeSpace() / ph.tupleSize)
# Fill the page.
>>> [ph.nextFreeTuple() for i in range(0, remainingTuples)] # doctest:+ELLIPSIS
[11, 12, ...]
>>> ph.hasFreeTuple()
False
# No value is returned when trying to exceed the page capacity.
>>> ph.nextFreeTuple() == None
True
>>> ph.freeSpace() < ph.tupleSize
True
"""
def __init__(self, **kwargs):
buffer=kwargs.get("buffer", None)
self.flags = kwargs.get("flags", b'\x00')
self.pageCapacity = kwargs.get("pageCapacity", len(buffer))
self.tupleSize = kwargs.get("tupleSize", None)
self.bitmap=kwargs.get("bitmap", None)
if buffer == None:
raise ValueError("No backing buffer supplied for SlottedPageHeader")
if self.bitmap == None:
headerSizeWithoutBitmap = struct.Struct("cHHH").size
tupleCapacity = math.floor((8*(self.pageCapacity-headerSizeWithoutBitmap))/(1+(8*self.tupleSize)))
bString = '0b' + ('0' * tupleCapacity)
self.bitmap = BitArray(bString)
self.binrepr = struct.Struct("cHHH" + str(math.ceil(len(self.bitmap))) + 's')
self.size = self.binrepr.size
self.freeSpaceOffset = self.size
buffer[0:self.size] = self.pack()
# super().__init__(buffer=buffer, flags=kwargs.get("flags", b'\x00'), self.tupleSize)
def __eq__(self, other):
return ( self.flags == other.flags
and self.tupleSize == other.tupleSize
and self.pageCapacity == other.pageCapacity
and self.freeSpaceOffset == other.freeSpaceOffset
and self.bitmap == other.bitmap)
def __hash__(self):
return hash((self.flags, self.tupleSize, self.pageCapacity, self.freeSpaceOffset, self.bitmap))
def headerSize(self):
return self.size
# Flag operations.
def flag(self, mask):
return (ord(self.flags) & mask) > 0
def setFlag(self, mask, set):
if set:
self.flags = bytes([ord(self.flags) | mask])
else:
self.flags = bytes([ord(self.flags) & ~mask])
# Dirty bit accessors
def isDirty(self):
return self.flag(PageHeader.dirtyMask)
def setDirty(self, dirty):
self.setFlag(PageHeader.dirtyMask, dirty)
def numTuples(self):
return self.bitmap.count(1)
# Returns the space available in the page associated with this header.
def freeSpace(self):
return self.pageCapacity - (self.size + (self.numTuples() * self.tupleSize))
# Returns the space used in the page associated with this header.
def usedSpace(self):
return (self.numTuples() * self.tupleSize)
# Slot operations.
def offsetOfSlot(self, slot):
return slot * self.tupleSize + self.size
def hasSlot(self, slotIndex):
return slotIndex < len(self.bitmap)
def getSlot(self, slotIndex):
return self.bitmap[slotIndex] == '0b1'
def setSlot(self, slotIndex, slot):
if not self.hasSlot(slotIndex):
return
if slot == True:
self.bitmap[slotIndex] = '0b1'
elif slot == False:
self.bitmap[slotIndex] = '0b0'
def resetSlot(self, slotIndex):
self.setSlot(slotIndex, False)
def freeSlots(self):
freeList = []
for i in range(len(self.bitmap)):
if self.bitmap[i] == '0b0':
freeList.append(i)
return freeList
def usedSlots(self):
usedList = []
for i in range(len(self.bitmap)):
if self.bitmap[i] == '0b1':
usedList.append(i)
return usedList
# Tuple allocation operations.
# Returns whether the page has any free space for a tuple.
def hasFreeTuple(self):
return self.freeSpace() >= self.tupleSize
# findTuple = self.bitmap.find('0b0')
# if findTuple == ():
# return False
# else:
# return True
# Returns the tupleIndex of the next free tuple.
# This should also "allocate" the tuple, such that any subsequent call
# does not yield the same tupleIndex.
def nextFreeTuple(self):
#nextTuple = self.bitmap.find('0b0')
#if nextTuple == ():
# return None
#headerSizeWithoutBitmap = struct.Struct("cHHH").size
#tupleCapacity = math.floor((8*(self.pageCapacity-headerSizeWithoutBitmap))/(1+(8*self.tupleSize)))
#if nextTuple[0] >= tupleCapacity:
# return None
#self.bitmap[nextTuple[0]] = '0b1'
#return nextTuple[0]
if self.hasFreeTuple():
nextTuple = self.bitmap.find('0b0')
self.bitmap[nextTuple[0]] = '0b1'
return nextTuple[0]
else:
return None
def nextTupleRange(self):
start = self.nextFreeTuple()
end = start + self.tupleSize
index = (start - self.size)//self.tupleSize
return (index, start, end)
# Create a binary representation of a slotted page header.
# The binary representation should include the slot contents.
def pack(self):
byteArray = bytearray(self.bitmap)
packed = self.binrepr.pack(
self.flags, self.tupleSize,
self.freeSpaceOffset, self.pageCapacity, byteArray)
unpacked = self.binrepr.unpack_from(packed)
return self.binrepr.pack(
self.flags, self.tupleSize,
self.freeSpaceOffset, self.pageCapacity, byteArray)
# Create a slotted page header instance from a binary representation held in the given buffer.
@classmethod
def unpack(cls, buffer):
binrepr1 = struct.Struct("cHHH")
values1 = binrepr1.unpack_from(buffer)
headerSizeWithoutBitmap = binrepr1.size
tupleCapacity = math.floor((8*(values1[3]-headerSizeWithoutBitmap))/(1+(8*values1[1])))
binrepr2 = struct.Struct("cHHH" + str(math.ceil(tupleCapacity)) + 's')
values2 = binrepr2.unpack_from(buffer)
bString = '0b' + ('0' * tupleCapacity)
bitmap = BitArray(bString)
index = 0
for bit in values2[4]:
if index >= tupleCapacity:
break
if bit:
bitmap[index] = '0b1'
else:
bitmap[index] = '0b0'
index = index + 1
if len(values2) == 5:
return cls(buffer=buffer, flags=values2[0], tupleSize=values2[1],
freeSpaceOffset=values2[2], pageCapacity=values2[3],
bitmap=bitmap)
class SlottedPageHeader(PageHeader):
"""
A slotted page header implementation. This should store a slot bitmap
implemented as a memoryview on the byte buffer backing the page
associated with this header. Additionally this header object stores
the number of slots in the array, as well as the index of the next
available slot.
The binary representation of this header object is: (numSlots, nextSlot, slotBuffer)
>>> import io
>>> buffer = io.BytesIO(bytes(4096))
>>> ph = SlottedPageHeader(buffer=buffer.getbuffer(), tupleSize=16)
>>> ph2 = SlottedPageHeader.unpack(buffer.getbuffer())
>>> ph == ph2
True
## Dirty bit tests
>>> ph.isDirty()
False
>>> ph.setDirty(True)
>>> ph.isDirty()
True
>>> ph.setDirty(False)
>>> ph.isDirty()
False
## Tuple count tests
>>> ph.hasFreeTuple()
True
# First tuple allocated should be at the first slot.
# Notice this is a slot index, not an offset as with contiguous pages.
>>> ph.nextFreeTuple() == 0
True
>>> ph.numTuples()
1
>>> tuplesToTest = 10
>>> [ph.nextFreeTuple() for i in range(0, tuplesToTest)]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>> ph.numTuples() == tuplesToTest+1
True
>>> ph.hasFreeTuple()
True
# Check space utilization
>>> ph.usedSpace() == (tuplesToTest+1)*ph.tupleSize
True
>>> ph.freeSpace() == 4096 - (ph.headerSize() + ((tuplesToTest+1) * ph.tupleSize))
True
>>> remainingTuples = int(ph.freeSpace() / ph.tupleSize)
# Fill the page.
>>> [ph.nextFreeTuple() for i in range(0, remainingTuples)] # doctest:+ELLIPSIS
[11, 12, ...]
>>> ph.hasFreeTuple()
False
# No value is returned when trying to exceed the page capacity.
>>> ph.nextFreeTuple() == None
True
>>> ph.freeSpace() < ph.tupleSize
True
"""
def __init__(self, **kwargs):
buffer = kwargs.get("buffer", None)
self.flags = kwargs.get("flags", b'\x00')
self.pageCapacity = kwargs.get("pageCapacity", len(buffer))
self.tupleSize = kwargs.get("tupleSize", None)
self.bitmap = kwargs.get("bitmap", None)
if buffer == None:
raise ValueError(
"No backing buffer supplied for SlottedPageHeader")
if self.bitmap == None:
headerSizeWithoutBitmap = struct.Struct("cHHH").size
tupleCapacity = math.floor(
(8 * (self.pageCapacity - headerSizeWithoutBitmap)) /
(1 + (8 * self.tupleSize)))
bString = '0b' + ('0' * tupleCapacity)
self.bitmap = BitArray(bString)
self.binrepr = struct.Struct("cHHH" +
str(math.ceil(len(self.bitmap))) + 's')
self.size = self.binrepr.size
self.freeSpaceOffset = self.size
buffer[0:self.size] = self.pack()
# super().__init__(buffer=buffer, flags=kwargs.get("flags", b'\x00'), self.tupleSize)
def __eq__(self, other):
return (self.flags == other.flags and self.tupleSize == other.tupleSize
and self.pageCapacity == other.pageCapacity
and self.freeSpaceOffset == other.freeSpaceOffset
and self.bitmap == other.bitmap)
def __hash__(self):
return hash((self.flags, self.tupleSize, self.pageCapacity,
self.freeSpaceOffset, self.bitmap))
def headerSize(self):
return self.size
# Flag operations.
def flag(self, mask):
return (ord(self.flags) & mask) > 0
def setFlag(self, mask, set):
if set:
self.flags = bytes([ord(self.flags) | mask])
else:
self.flags = bytes([ord(self.flags) & ~mask])
# Dirty bit accessors
def isDirty(self):
return self.flag(PageHeader.dirtyMask)
def setDirty(self, dirty):
self.setFlag(PageHeader.dirtyMask, dirty)
def numTuples(self):
return self.bitmap.count(1)
# Returns the space available in the page associated with this header.
def freeSpace(self):
return self.pageCapacity - (self.size +
(self.numTuples() * self.tupleSize))
# Returns the space used in the page associated with this header.
def usedSpace(self):
return (self.numTuples() * self.tupleSize)
# Slot operations.
def offsetOfSlot(self, slot):
return slot * self.tupleSize + self.size
def hasSlot(self, slotIndex):
return slotIndex < len(self.bitmap)
def getSlot(self, slotIndex):
return self.bitmap[slotIndex] == '0b1'
def setSlot(self, slotIndex, slot):
if not self.hasSlot(slotIndex):
return
if slot == True:
self.bitmap[slotIndex] = '0b1'
elif slot == False:
self.bitmap[slotIndex] = '0b0'
def resetSlot(self, slotIndex):
self.setSlot(slotIndex, False)
def freeSlots(self):
freeList = []
for i in range(len(self.bitmap)):
if self.bitmap[i] == '0b0':
freeList.append(i)
return freeList
def usedSlots(self):
usedList = []
for i in range(len(self.bitmap)):
if self.bitmap[i] == '0b1':
usedList.append(i)
return usedList
# Tuple allocation operations.
# Returns whether the page has any free space for a tuple.
def hasFreeTuple(self):
return self.freeSpace() >= self.tupleSize
# findTuple = self.bitmap.find('0b0')
# if findTuple == ():
# return False
# else:
# return True
# Returns the tupleIndex of the next free tuple.
# This should also "allocate" the tuple, such that any subsequent call
# does not yield the same tupleIndex.
def nextFreeTuple(self):
#nextTuple = self.bitmap.find('0b0')
#if nextTuple == ():
# return None
#headerSizeWithoutBitmap = struct.Struct("cHHH").size
#tupleCapacity = math.floor((8*(self.pageCapacity-headerSizeWithoutBitmap))/(1+(8*self.tupleSize)))
#if nextTuple[0] >= tupleCapacity:
# return None
#self.bitmap[nextTuple[0]] = '0b1'
#return nextTuple[0]
if self.hasFreeTuple():
nextTuple = self.bitmap.find('0b0')
self.bitmap[nextTuple[0]] = '0b1'
return nextTuple[0]
else:
return None
def nextTupleRange(self):
start = self.nextFreeTuple()
end = start + self.tupleSize
index = (start - self.size) // self.tupleSize
return (index, start, end)
# Create a binary representation of a slotted page header.
# The binary representation should include the slot contents.
def pack(self):
byteArray = bytearray(self.bitmap)
packed = self.binrepr.pack(self.flags, self.tupleSize,
self.freeSpaceOffset, self.pageCapacity,
byteArray)
unpacked = self.binrepr.unpack_from(packed)
return self.binrepr.pack(self.flags, self.tupleSize,
self.freeSpaceOffset, self.pageCapacity,
byteArray)
# Create a slotted page header instance from a binary representation held in the given buffer.
@classmethod
def unpack(cls, buffer):
binrepr1 = struct.Struct("cHHH")
values1 = binrepr1.unpack_from(buffer)
headerSizeWithoutBitmap = binrepr1.size
tupleCapacity = math.floor(
(8 * (values1[3] - headerSizeWithoutBitmap)) / (1 +
(8 * values1[1])))
binrepr2 = struct.Struct("cHHH" + str(math.ceil(tupleCapacity)) + 's')
values2 = binrepr2.unpack_from(buffer)
bString = '0b' + ('0' * tupleCapacity)
bitmap = BitArray(bString)
index = 0
for bit in values2[4]:
if index >= tupleCapacity:
break
if bit:
bitmap[index] = '0b1'
else:
bitmap[index] = '0b0'
index = index + 1
if len(values2) == 5:
return cls(buffer=buffer,
flags=values2[0],
tupleSize=values2[1],
freeSpaceOffset=values2[2],
pageCapacity=values2[3],
bitmap=bitmap)
