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D Programming Language 2.0

Last update Thu Oct 28 17:54:29 2010

core.bitop

This module contains a collection of bit-level operations.

License:
Boost License 1.0.

Authors:
Don Clugston, Sean Kelly, Walter Bright

Copyright Don Clugston 2005 - 2009. Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at

http:
//www.boost.org/LICENSE_1_0.txt)

int bsf(uint v);
Scans the bits in v starting with bit 0, looking for the first set bit.

Returns:
The bit number of the first bit set. The return value is undefined if v is zero.

int bsr(uint v);
Scans the bits in v from the most significant bit to the least significant bit, looking for the first set bit.

Returns:
The bit number of the first bit set. The return value is undefined if v is zero.

Example:
 import core.bitop;

 int main()
 {
     uint v;
     int x;

     v = 0x21;
     x = bsf(v);
     printf("bsf(x%x) = %d\n", v, x);
     x = bsr(v);
     printf("bsr(x%x) = %d\n", v, x);
     return 0;
 }

Output:
bsf(x21) = 0
bsr(x21) = 5

int bt(uint* p, uint bitnum);
Tests the bit.

int btc(uint* p, uint bitnum);
Tests and complements the bit.

int btr(uint* p, uint bitnum);
Tests and resets (sets to 0) the bit.

int bts(uint* p, uint bitnum);
Tests and sets the bit.

Parameters:
uint* p a non-NULL pointer to an array of uints.
index a bit number, starting with bit 0 of p[0], and progressing. It addresses bits like the expression:
    p[index / (uint.sizeof*8)] & (1 << (index & ((uint.sizeof*8) - 1)))

Returns:
A non-zero value if the bit was set, and a zero if it was clear.

Example:
    import core.bitop;

    int main()
    {
        uint array[2];

        array[0] = 2;
        array[1] = 0x100;

        printf("btc(array, 35) = %d\n", <b>btc</b>(array, 35));
        printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);

        printf("btc(array, 35) = %d\n", <b>btc</b>(array, 35));
        printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);

        printf("bts(array, 35) = %d\n", <b>bts</b>(array, 35));
        printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);

        printf("btr(array, 35) = %d\n", <b>btr</b>(array, 35));
        printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);

        printf("bt(array, 1) = %d\n", <b>bt</b>(array, 1));
        printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);

        return 0;
    }

Output:
    btc(array, 35) = 0
    array = [0]:x2, [1]:x108
    btc(array, 35) = -1
    array = [0]:x2, [1]:x100
    bts(array, 35) = 0
    array = [0]:x2, [1]:x108
    btr(array, 35) = -1
    array = [0]:x2, [1]:x100
    bt(array, 1) = -1
    array = [0]:x2, [1]:x100
    

uint bswap(uint v);
Swaps bytes in a 4 byte uint end-to-end, i.e. byte 0 becomes byte 3, byte 1 becomes byte 2, byte 2 becomes byte 1, byte 3 becomes byte 0.

ubyte inp(uint port_address);
ushort inpw(uint port_address);
uint inpl(uint port_address);
Reads I/O port at port_address.

ubyte outp(uint port_address, ubyte value);
ushort outpw(uint port_address, ushort value);
uint outpl(uint port_address, uint value);
Writes and returns value to I/O port at port_address.

int popcnt(uint x);
Calculates the number of set bits in a 32-bit integer.

uint bitswap(uint x);
Reverses the order of bits in a 32-bit integer.