common.h

#pragma once

#include "feature.h"

#define unlikely(x) __builtin_expect((x), 0)
#define likely(x) __builtin_expect((x), 1)

#define UNUSED __attribute__((unused))

#define MASK(n) (~((~0U << (n))))

#define ARRAY_SIZE(a) (sizeof(a) / sizeof(*(a)))

/* Ensure that __builtin_clz is never called with 0 argument */
static inline int ilog2(int x)
{
    return 31 - __builtin_clz(x | 1);
}

#define MIN(a, b) (((a) < (b)) ? (a) : (b))

/* Range check
 * For any variable range checking:
 *     if (x >= minx && x <= maxx) ...
 * it is faster to use bit operation:
 *     if ((signed)((x - minx) | (maxx - x)) >= 0) ...
 */
#define RANGE_CHECK(x, minx, size) \
    ((int32_t) ((x - minx) | (minx + size - 1 - x)) >= 0)

/* Packed macro */
#if defined(__GNUC__) || defined(__clang__)
#define PACKED(name) name __attribute__((packed))
#elif defined(_MSC_VER)
#define PACKED(name) __pragma(pack(push, 1)) name __pragma(pack(pop))
#else /* unsupported compilers */
#define PACKED(name)
#endif

/* Pattern Matching for C macros.
 * https://github.com/pfultz2/Cloak/wiki/C-Preprocessor-tricks,-tips,-and-idioms
 */

/* In Visual Studio, __VA_ARGS__ is treated as a separate parameter. */
#define FIX_VC_BUG(x) x

/* catenate */
#define PRIMITIVE_CAT(a, ...) FIX_VC_BUG(a##__VA_ARGS__)

#define IIF(c) PRIMITIVE_CAT(IIF_, c)
/* run the 2nd parameter */
#define IIF_0(t, ...) __VA_ARGS__
/* run the 1st parameter */
#define IIF_1(t, ...) t