Re: question about bitfields to decode websocket header

[test via Digitalmars-d-learn]

On Wednesday, 7 November 2018 at 14:22:43 UTC, lithium iodate 
wrote:
On Wednesday, 7 November 2018 at 13:05:49 UTC, test wrote:
I am confused about the bitfields order.
The bitfields start with the least significant bits:
fin -> 1
rsv1 -> 0
rsv2 -> 0
rsv3 -> 0
opcode -> 1000 = 8

mask -> 1
_size -> 1000001 = 65

This order will likely be what you want:
mixin(bitfields!(
    opcode, "opcode", 4,
    bool,   "rsv3",   1,
    bool,   "rsv2",   1,
    bool,   "rsv1",   1,
    bool,   "fin",    1,

    ubyte,  "_size",  7,
    bool,   "mask",   1,
));

Also beware of endianness when mapping bytes to it.

After I use your code it working now.

my other question is: if the opcode bit cross byte, how do we 
define the bitfields ?

for example if the opcode is a 6 bit number instead 4bit :  
F1|R1|R1|R1|opcode6|Mask1|Size5

I has to split the opcode here ?

mixin(bitfields!(
     opcode, "opcode4", 4,
     bool,   "rsv3",   1,
     bool,   "rsv2",   1,
     bool,   "rsv1",   1,
     bool,   "fin",    1,

     ubyte,  "_size",  5,
     bool,   "mask",   1,
     bool,   "opcode2",   1,
 ));