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core.bitop

This module contains a collection of bit-level operations.

License:
Boost License 1.0

Authors:
Don Clugston, Sean Kelly, Walter Bright, Alex Rønne Petersen

Source:
core/bitop.d

pure nothrow @safe int bsf(size_t 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.

Example:
import core.bitop;

int main()
{
    assert(bsf(0x21) == 0);
    return 0;
}

pure nothrow @safe int bsr(size_t 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()
{
    assert(bsr(0x21) == 5);
    return 0;
}

pure nothrow @system int bt(in size_t* p, size_t bitnum);
Tests the bit. (No longer an intrisic - the compiler recognizes the patterns in the body.)

Examples:
size_t array[2];

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

assert(bt(array.ptr, 1));
assert(array[0] == 2);
assert(array[1] == 0x100);

pure nothrow @system int btc(size_t* p, size_t bitnum);
Tests and complements the bit.

pure nothrow @system int btr(size_t* p, size_t bitnum);
Tests and resets (sets to 0) the bit.

pure nothrow @system int bts(size_t* p, size_t bitnum);
Tests and sets the bit.

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

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

Examples:
size_t array[2];

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

assert(btc(array.ptr, 35) == 0);
if (size_t.sizeof == 8)
{
    assert(array[0] == 0x8_0000_0002);
    assert(array[1] == 0x100);
}
else
{
    assert(array[0] == 2);
    assert(array[1] == 0x108);
}

assert(btc(array.ptr, 35));
assert(array[0] == 2);
assert(array[1] == 0x100);

assert(bts(array.ptr, 35) == 0);
if (size_t.sizeof == 8)
{
    assert(array[0] == 0x8_0000_0002);
    assert(array[1] == 0x100);
}
else
{
    assert(array[0] == 2);
    assert(array[1] == 0x108);
}

assert(btr(array.ptr, 35));
assert(array[0] == 2);
assert(array[1] == 0x100);

pure nothrow @safe 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.

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

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

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

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