Memory Alignment

Fast, bitwise macros for aligning pointers and sizes to powers of 2. More...

Macros
#define	ALIGN_UP_POW2(x, p)
	Aligns a value UP to the nearest multiple of p (must be power of 2).
#define	ALIGN_DOWN_POW2(x, p)
	Aligns a value DOWN to the nearest multiple of p (must be power of 2).
#define	IS_POW2_OR_ZERO(x)
	Checks if a given integer is a power of 2 or zero.
#define	IS_POW2(x)
	Checks if a given integer is a strictly positive power of 2.
#define	SHIFT8(T, x, s)
	Shifts a byte value to a specific bit position.
#define	PACK_U32_LE(a, b, c, d)
	Packs 4 bytes into a 32-bit unsigned integer (little-endian order).

Detailed Description

Fast, bitwise macros for aligning pointers and sizes to powers of 2.

Macro Definition Documentation

ALIGN_DOWN_POW2

#define ALIGN_DOWN_POW2	(		x,
			p )

Value:

((x) & ~((p) - 1))

Aligns a value DOWN to the nearest multiple of p (must be power of 2).

Example:

usize size = ALIGN_DOWN_POW2(13, 8); // 8
usize size = ALIGN_DOWN_POW2(16, 8); // 16 (already aligned)

Parameters

x	The value to align.
p	The alignment boundary (must be a power of 2).

Returns

The largest multiple of p that is <= x.

Definition at line 483 of file base_macros.h.

ALIGN_UP_POW2

#define ALIGN_UP_POW2	(		x,
			p )

Value:

(((x) + (p) - 1) & ~((p) - 1))

Aligns a value UP to the nearest multiple of p (must be power of 2).

Example:

usize size = ALIGN_UP_POW2(13, 8);  // 16
usize size = ALIGN_UP_POW2(16, 8);  // 16 (already aligned)
usize size = ALIGN_UP_POW2(1,  64); // 64

Parameters

x	The value to align.
p	The alignment boundary (must be a power of 2).

Returns

The smallest multiple of p that is >= x.

Definition at line 468 of file base_macros.h.

IS_POW2

#define IS_POW2

(

x

)

Value:

((x) != 0 && (((x) & ((x) - 1)) == 0))

Checks if a given integer is a strictly positive power of 2.

Unlike IS_POW2_OR_ZERO(), returns 0 for zero. Use this when validating alignment values since an alignment of 0 is never valid.

Example:

IS_POW2(0)  // 0 (false — zero is not a valid alignment)
IS_POW2(1)  // 1 (true)
IS_POW2(16) // 1 (true)
IS_POW2(15) // 0 (false)

Parameters

x	The value to check.

Returns

1 if x > 0 and is a power of 2, 0 otherwise.

Definition at line 518 of file base_macros.h.

IS_POW2_OR_ZERO

#define IS_POW2_OR_ZERO

(

x

)

Value:

(((x) & ((x) - 1)) == 0)

Checks if a given integer is a power of 2 or zero.

Example:

IS_POW2_OR_ZERO(0)  // 1 (true)
IS_POW2_OR_ZERO(1)  // 1 (true)
IS_POW2_OR_ZERO(16) // 1 (true)
IS_POW2_OR_ZERO(15) // 0 (false)

Parameters

x	The value to check.

Returns

1 if it is a power of 2 or zero, 0 otherwise.

Definition at line 499 of file base_macros.h.

PACK_U32_LE

#define PACK_U32_LE	(		a,
			b,
			c,
			d )

Value:

(SHIFT8(U32, a, 0) | SHIFT8(U32, b, 8) | SHIFT8(U32, c, 16) | SHIFT8(U32, d, 24))

Packs 4 bytes into a 32-bit unsigned integer (little-endian order).

Parameters

a	Least significant byte.
b	Second byte.
c	Third byte.
d	Most significant byte.

Returns

A packed U32 value.

Definition at line 536 of file base_macros.h.

SHIFT8

#define SHIFT8	(		T,
			x,
			s )

Value:

((T)(x) << (s))

Shifts a byte value to a specific bit position.

Parameters

T	Target type (e.g., U32).
x	Value to shift.
s	Bit position (0, 8, 16, 24).

Definition at line 526 of file base_macros.h.