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## Introduction

I've been developing software using C/C++ for a very long time yet I still have to think twice when I encounter
bitwise operations, let alone when I have to explain them to somebody else! For example:

unsigned const STAT_ONE = 0x0001;
unsigned const STAT_TWO = 0x0002;
unsigned status = 0x0001;
if(status & (STAT_ONE | STAT_TWO)) DoSomething();

We all know that the preceding statement checks if both `STAT_ONE`

and `STAT_TWO`

bits are
set then `DoSomething()`

will be executed... or is it if either `STAT_ONE`

or `STAT_TWO`

bits are set? Lets see:

0001 or 0010 ----
0011 and 0001 ----
0001

Because the result is non-zero then `DoSomething()`

will be executed. I think this can be very tricky,
especially if the expressions get too complex. Isn't the intent of the following code easier to understand and less
error-prone?

unsigned const STAT_ONE = 0x0001;
unsigned const STAT_TWO = 0x0002;
unsigned status = 0x0001;
if(isAnyBitSet(status, STAT_ONE | STAT_TWO)) DoSomething();

if(areAllBitsSet(status, STAT_ONE | STAT_TWO)) DoSomething();

Also it's very convenient to access a bit's value by its position like this:

if(isBitSetByPos(status, 5))
bitClearByPos(status, 5);

All the functions provided in the *BitTools.h* header are inlined so there is no size or run-time speed
tradeoffs to worry about.

## Templates

### Bitmask-based functions

template <class T, class U>
bool isAnyBitSet(T value, U mask)

Returns `true`

if any of the bits in `mask`

is set in `value`

. Defined as:
`(value & mask) != 0`

1010 and 0110 ----
0010

template <class T, class U>
bool areAllBitsSet(T value, U mask)

Returns `true`

if all the bits in `mask`

are set in `value`

. Defined as:
`(value & mask) == mask`

1010 and 1110 ----
1010

template <class T, class U>
bool areAllBitsClear(T value, U mask)

Returns `true`

if all the bits in `mask`

are cleared in `value`

. Defined as:
`(value & mask) == 0`

1010 and 0101 ----
0000

template <class T, class U>
T setBits(T value, U mask)

Returns `value`

with the `mask`

bits set. Defined as: `value | mask`

1000 or 0110 ----
1110

template <class T, class U>
T setBitsExcept(T value, U mask)

Returns `value`

with the all the bits set except the `mask`

bits. Defined as:
`value | ~mask`

1001 not ----
0110 or 0001 ----
0111

template <class T, class U>
T clearBits(T value, U mask)

Returns `value`

with the `mask`

bits cleared. Defined as: `value & ~mask`

1001 not ----
0110 and 1111 ----
0110

template <class T, class U>
T clearBitsExcept(T value, U mask)

Returns `value`

with the all the bits cleared except the `mask`

bits. Defined as:
`value & mask`

0010 and 0110 ----
0010

template <class T, class U>
T setClearBits(T value, U add, U remove)

Returns `value`

with the `add`

bits set and the `remove`

bits cleared.
Defined as: `(value | add) & ~remove`

1101 or 0101 ----
0111
0001 not ----
1110 and 0111 ----
0110

template <class T, class U, class V>
T setBits(T value, U mask, V set)

Returns `value`

with the `mask`

bits set or cleared depending on the value of
`set`

.

### Position-based functions

template <class T>
T setBitByPos(T value, unsigned char n)

Returns `value`

with the `n`

th bit set. Defined as `value | (1 << n)`

template <class T>
T clearBitByPos(T value, unsigned char n)

Returns `value`

with the `n`

th bit cleared. Defined as `value & ~(1 << n)`

template <class T>
bool isBitSetByPos(T value, unsigned char n)

Returns `true`

if `value`

has the the `n`

th bit set. Defined as
`(value & (1 << n)) != 0`

template <class T>
bool isBitClearByPos(T value, unsigned char n)

Returns `true`

if `value`

has the the `n`

th bit cleared. Defined as
`(value & (1 << n)) == 0`

## Conclusion

The templates contained in *BitTools.h* provide an easier and less error-prone way of expressing bitwise
operations with no performance or size penalties compared to hand written code. I hope you find these functions
as useful and easy to use as I did.