nanogui: Re: [FIX] add alpha channel into GdDrawImage software handling
Subject:
RE: Re: [nanogui] Re: Re: [FIX] add alpha channel into GdDrawImage software handling
From:
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Date:
12 Mar 2010 11:17:59 -0000
Message-Id: <c4bc14e563bcc2cdb8e7be0196428d25@a51105>
Endian confuse me. I am studing again.
> You are saying that
> struct {
> unsigned char r:5;
> };
> allocates the TOP (MSB) bits in big endian?
Yes, in case 11110000(b)=0xF0 , r is 0x1e.
please refer to http://www.linuxjournal.com/node/6788/print.
> I don't think so.
> I agree it allocates the top BYTE in big endian, but the
> bits in the byte are still allocated from 0 up, not 7 down.
> This will still allocate the LOWER 5 bits in either endian,I think.
> So the issue is that bytes are re-ordered, but NOT bits, in little vs big endian.
typedef union
{
struct { unsigned char r:5 } r;
unsigned char v;
} BF
BF c;
c.v = 0xF0; // 11110000
then,
in a big endian c.f.r = 0x1e
in a little endian c.f.r = 0x10
It is tested on QEMU with arm big-endian.
( $ qemu-armeb a.out )
Regards,
Sung Joo
