/* SPDX-License-Identifier: MIT */
/* Copyright © 2026 Intel Corporation */

#ifndef _PICK_H_
#define _PICK_H_

/*
 * Given the first two numbers __a and __b of arbitrarily many evenly spaced
 * numbers, pick the 0-based __index'th value.
 *
 * Always prefer this over _PICK() if the numbers are evenly spaced.
 */
#define _PICK_EVEN(__index, __a, __b) ((__a) + (__index) * ((__b) - (__a)))

/*
 * Like _PICK_EVEN(), but supports 2 ranges of evenly spaced address offsets.
 * @__c_index corresponds to the index in which the second range starts to be
 * used. Using math interval notation, the first range is used for indexes [ 0,
 * @__c_index), while the second range is used for [ @__c_index, ... ). Example:
 *
 * #define _FOO_A                       0xf000
 * #define _FOO_B                       0xf004
 * #define _FOO_C                       0xf008
 * #define _SUPER_FOO_A                 0xa000
 * #define _SUPER_FOO_B                 0xa100
 * #define FOO(x)                       _MMIO(_PICK_EVEN_2RANGES(x, 3,          \
 *                                            _FOO_A, _FOO_B,                   \
 *                                            _SUPER_FOO_A, _SUPER_FOO_B))
 *
 * This expands to:
 *      0: 0xf000,
 *      1: 0xf004,
 *      2: 0xf008,
 *      3: 0xa000,
 *      4: 0xa100,
 *      5: 0xa200,
 *      ...
 */
#define _PICK_EVEN_2RANGES(__index, __c_index, __a, __b, __c, __d)              \
        (BUILD_BUG_ON_ZERO(!__is_constexpr(__c_index)) +                        \
         ((__index) < (__c_index) ? _PICK_EVEN(__index, __a, __b) :             \
                                   _PICK_EVEN((__index) - (__c_index), __c, __d)))

/*
 * Given the arbitrary numbers in varargs, pick the 0-based __index'th number.
 *
 * Always prefer _PICK_EVEN() over this if the numbers are evenly spaced.
 */
#define _PICK(__index, ...) (((const u32 []){ __VA_ARGS__ })[__index])

#endif