/* SPDX-License-Identifier: MIT */

#ifndef HELPERS_H
#define HELPERS_H

// Ideally, we'd use `__has_attribute` and `__has_builtin`, but these were only introduced in GCC 9
#ifdef __GNUC__ // GCC or compatible
	#define format_(archetype, str_index, first_arg) \
		__attribute__((format(archetype, str_index, first_arg)))
	#define attr_(...) __attribute__((__VA_ARGS__))
	// In release builds, define "unreachable" as such, but trap in debug builds
	#ifdef NDEBUG
		#define unreachable_ __builtin_unreachable
	#else
		#define unreachable_ __builtin_trap
	#endif
#else
	// Unsupported, but no need to throw a fit
	#define format_(archetype, str_index, first_arg)
	#define attr_(...)
// This seems to generate similar code to __builtin_unreachable, despite different semantics
// Note that executing this is undefined behavior (declared [[noreturn]], but does return)
[[noreturn]] static inline void unreachable_() {
}
#endif

// Use builtins whenever possible, and shim them otherwise
#ifdef __GNUC__ // GCC or compatible
	#define ctz __builtin_ctz
	#define clz __builtin_clz

#elif defined(_MSC_VER)
	#include <assert.h>
	#include <intrin.h>
	#pragma intrinsic(_BitScanReverse, _BitScanForward)
static inline int ctz(unsigned int x) {
	unsigned long cnt;

	assert(x != 0);
	_BitScanForward(&cnt, x);
	return cnt;
}
static inline int clz(unsigned int x) {
	unsigned long cnt;

	assert(x != 0);
	_BitScanReverse(&cnt, x);
	return 31 - cnt;
}

#else
	#include <limits.h>
static inline int ctz(unsigned int x) {
	int cnt = 0;

	while (!(x & 1)) {
		x >>= 1;
		cnt++;
	}
	return cnt;
}

static inline int clz(unsigned int x) {
	int cnt = 0;

	while (x <= UINT_MAX / 2) {
		x <<= 1;
		cnt++;
	}
	return cnt;
}
#endif

// Macros for stringification
#define STR(x)            #x
#define EXPAND_AND_STR(x) STR(x)

// Obtaining the size of an array; `arr` must be an expression, not a type!
// (Having two instances of `arr` is OK because the contents of `sizeof` are not evaluated.)
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof *(arr))

// For lack of <ranges>, this adds some more brevity
#define RANGE(s) std::begin(s), std::end(s)

// Convenience feature for visiting variants.
template<typename... Ts>
struct Visitor : Ts... {
	using Ts::operator()...;
};
template<typename... Ts>
Visitor(Ts...) -> Visitor<Ts...>;

#endif // HELPERS_H