Re: reversing a byte


Charles Mills wrote:
Ajay wrote:
Hi all,can you please tell the most efficient method to reverse a
byte.Function should return a byte that is reversed.

Use a look up table (untested generated code below):

static unsigned char
reverse_byte(unsigned char b)
{
static const unsigned char b_tbl[] = {
---8<---- sniped totally wrong lookup table ---8<----
};
return b_tbl[b];
}

-Charlie

probably want something like this:
static const unsigned char b_tbl[] = {
0x0, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
...,
0xf, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff
};

you can fill in the blanks.

-Charlie

.