def byte_to_float(b, mantissabits=5, zeroexp=2):
"""Decodes a floating point number stored in a single byte.
"""
b = ord(b)
if b == 0:
return 0.0
bits = (b & 0xff) << (24 - mantissabits)
bits += (63 - zeroexp) << 24
return unpack("f", pack("i", bits))[0]
def byte_to_float(b, mantissabits=5, zeroexp=2):
"""Decodes a floating point number stored in a single byte.
"""
b = ord(b)
if b == 0:
return 0.0
bits = (b & 0xff) << (24 - mantissabits)
bits += (63 - zeroexp) << 24
return unpack("f", pack("i", bits))[0]
def float_to_byte(value, mantissabits=5, zeroexp=2):
"""Encodes a floating point number in a single byte.
"""
# Assume int size == float size
fzero = (63 - zeroexp) << mantissabits
bits = unpack("i", pack("f", value))[0]
smallfloat = bits >> (24 - mantissabits)
if smallfloat < fzero:
# Map negative numbers and 0 to 0
# Map underflow to next smallest non-zero number
if bits <= 0:
return chr(0)
else:
return chr(1)
elif smallfloat >= fzero + 0x100:
# Map overflow to largest number
return chr(255)
else:
return chr(smallfloat - fzero)
def float_to_byte(value, mantissabits=5, zeroexp=2):
"""Encodes a floating point number in a single byte.
"""
# Assume int size == float size
fzero = (63 - zeroexp) << mantissabits
bits = unpack("i", pack("f", value))[0]
smallfloat = bits >> (24 - mantissabits)
if smallfloat < fzero:
# Map negative numbers and 0 to 0
# Map underflow to next smallest non-zero number
if bits <= 0:
return chr(0)
else:
return chr(1)
elif smallfloat >= fzero + 0x100:
# Map overflow to largest number
return chr(255)
else:
return chr(smallfloat - fzero)