Bit fields (as in C)

This module allows you to define bit fields over words. For instance, you can have a Word16 split into 3 fields X, Y and Z composed of 5, 9 and 2 bits respectively.

X Y Z w :: Word16 |0 0 0 0 0|0 0 0 0 0 0 0 0 0|0 0|

You define it as follows:

{--}

w :: BitFields Word16 '[ BitField 5 X Word8 
                       , BitField 9 Y Word16
                       , BitField 2 Z Word8
                       ]
w = BitFields 0x0102

Note that each field has its own associated type (e.g. Word8 for X and Z) that must be large enough to hold the number of bits for the field.

Operations on BitFields expect that the cumulated size of the fields is equal to the whole word size: use a padding field if necessary. Otherwise you can use unsafe versions of the functions: extractField', updateField', withField'.

You can extract and update the value of a field by its name:

x = extractField X w
z = extractField Z w
w' = updateField @Y 0x16 w

Fields can also be BitSet or EnumField:

{--}

data A = A0 | A1 | A2 | A3 deriving (Enum,CEnum)

data B = B0 | B1 deriving (Enum,BitOffset)

w :: BitFields Word16 '[ BitField 5 X (EnumField Word8 A)
                       , BitField 9 Y Word16
                       , BitField 2 Z (BitSet Word8 B)
                       ]
w = BitFields 0x0102