1
0
mirror of https://github.com/moparisthebest/SickRage synced 2024-12-15 12:32:18 -05:00
SickRage/lib/hachoir_core/field/float.py

100 lines
3.5 KiB
Python
Raw Normal View History

from lib.hachoir_core.field import Bit, Bits, FieldSet
from lib.hachoir_core.endian import BIG_ENDIAN, LITTLE_ENDIAN
import struct
# Make sure that we use right struct types
assert struct.calcsize("f") == 4
assert struct.calcsize("d") == 8
assert struct.unpack("<d", "\x1f\x85\xebQ\xb8\x1e\t@")[0] == 3.14
assert struct.unpack(">d", "\xc0\0\0\0\0\0\0\0")[0] == -2.0
class FloatMantissa(Bits):
def createValue(self):
value = Bits.createValue(self)
return 1 + float(value) / (2 ** self.size)
def createRawDisplay(self):
return unicode(Bits.createValue(self))
class FloatExponent(Bits):
def __init__(self, parent, name, size):
Bits.__init__(self, parent, name, size)
self.bias = 2 ** (size-1) - 1
def createValue(self):
return Bits.createValue(self) - self.bias
def createRawDisplay(self):
return unicode(self.value + self.bias)
def floatFactory(name, format, mantissa_bits, exponent_bits, doc):
size = 1 + mantissa_bits + exponent_bits
class Float(FieldSet):
static_size = size
__doc__ = doc
def __init__(self, parent, name, description=None):
assert parent.endian in (BIG_ENDIAN, LITTLE_ENDIAN)
FieldSet.__init__(self, parent, name, description, size)
if format:
if self._parent.endian == BIG_ENDIAN:
self.struct_format = ">"+format
else:
self.struct_format = "<"+format
else:
self.struct_format = None
def createValue(self):
"""
Create float value: use struct.unpack() when it's possible
(32 and 64-bit float) or compute it with :
mantissa * (2.0 ** exponent)
This computation may raise an OverflowError.
"""
if self.struct_format:
raw = self._parent.stream.readBytes(
self.absolute_address, self._size//8)
try:
return struct.unpack(self.struct_format, raw)[0]
except struct.error, err:
raise ValueError("[%s] conversion error: %s" %
(self.__class__.__name__, err))
else:
try:
value = self["mantissa"].value * (2.0 ** float(self["exponent"].value))
if self["negative"].value:
return -(value)
else:
return value
except OverflowError:
raise ValueError("[%s] floating point overflow" %
self.__class__.__name__)
def createFields(self):
yield Bit(self, "negative")
yield FloatExponent(self, "exponent", exponent_bits)
if 64 <= mantissa_bits:
yield Bit(self, "one")
yield FloatMantissa(self, "mantissa", mantissa_bits-1)
else:
yield FloatMantissa(self, "mantissa", mantissa_bits)
cls = Float
cls.__name__ = name
return cls
# 32-bit float (standart: IEEE 754/854)
Float32 = floatFactory("Float32", "f", 23, 8,
"Floating point number: format IEEE 754 int 32 bit")
# 64-bit float (standart: IEEE 754/854)
Float64 = floatFactory("Float64", "d", 52, 11,
"Floating point number: format IEEE 754 in 64 bit")
# 80-bit float (standart: IEEE 754/854)
Float80 = floatFactory("Float80", None, 64, 15,
"Floating point number: format IEEE 754 in 80 bit")