struct.unpack less than 1 byte

[cprogrammer]

hello all,

i need to read from a file a struct like this [1byte, 12bits, 12bits]
reading 1 byte or more is not a problem ... but the 12 bits values
are ...

thanks

 

[Guilherme Polo]

hello all,

i need to read from a file a struct like this [1byte, 12bits, 12bits]
reading 1 byte or more is not a problem ... but the 12 bits values
are ...

thanks

12bits, 12bits == 3 byes

 

[Michal Bozon]

You are able to read single bits from file in C ?

You'll have to read the bytes and than perform some bitwise operations on
them to extract the bits

 

[John Machin]

i need to read from a file a struct like this [1byte, 12bits, 12bits]
reading 1 byte or more is not a problem ... but the 12 bits values
are ...

12bits, 12bits == 3 byes

and 8 + 12 + 12 = 32

Assuming little-endianess and that all 3 items are unsigned:

import struct
bytes = "\x21\x43\xba\xdc"
i32 = struct.unpack("<I", bytes)[0]
hex(i32) '0xdcba4321L'
fields = map(int, (i32 & 0xff, (i32 >> 8) & 0xfff, i32 >> 20))
fields [33, 2627, 3531]
map(hex, fields) ['0x21', '0xa43', '0xdcb']

 

[Stargaming]

i need to read from a file a struct like this [1byte, 12bits, 12bits]
reading 1 byte or more is not a problem ... but the 12 bits values
are ...

12bits, 12bits == 3 byes

and 8 + 12 + 12 = 32

[snipped bitfiddling]

Or, if you're doing more of those parsing tasks (or just dislike bit
shifting), you could have a look into `construct`_::
... Octet("spam"), # synonym for BitField("spam", 8)
... BitField("ham", 12),
... BitField("eggs", 12)
... ) Container(eggs = 4095, ham = 4095, spam = 255)

Cheers,
Stargaming

... _construct: http://construct.wikispaces.com/