160 lines
5.0 KiB
C
160 lines
5.0 KiB
C
/*
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* Copyright (C) 2007 Oracle. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public
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* License along with this program; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 021110-1307, USA.
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*/
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/*
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* All those macros are cross-ported from kernel's include/linux/minmax.h, with needed
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* dependency put here directly.
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*/
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#ifndef __INTERNAL_H__
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#define __INTERNAL_H__
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/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
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#define ___PASTE(a,b) a##b
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#define __PASTE(a,b) ___PASTE(a,b)
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/* Not-quite-unique ID. */
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#ifndef __UNIQUE_ID
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# define __UNIQUE_ID(prefix) __PASTE(__PASTE(__UNIQUE_ID_, prefix), __LINE__)
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#endif
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#ifdef __CHECKER__
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#define BUILD_BUG_ON_ZERO(e) (0)
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#else /* __CHECKER__ */
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/*
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* Force a compilation error if condition is true, but also produce a
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* result (of value 0 and type int), so the expression can be used
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* e.g. in a structure initializer (or where-ever else comma expressions
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* aren't permitted).
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*/
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#define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
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#endif /* __CHECKER__ */
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/*
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* This returns a constant expression while determining if an argument is
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* a constant expression, most importantly without evaluating the argument.
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* Glory to Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
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*/
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#define __is_constexpr(x) \
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(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
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/*
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* min()/max()/clamp() macros must accomplish three things:
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*
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* - avoid multiple evaluations of the arguments (so side-effects like
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* "x++" happen only once) when non-constant.
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* - perform strict type-checking (to generate warnings instead of
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* nasty runtime surprises). See the "unnecessary" pointer comparison
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* in __typecheck().
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* - retain result as a constant expressions when called with only
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* constant expressions (to avoid tripping VLA warnings in stack
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* allocation usage).
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*/
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#define __typecheck(x, y) \
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(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
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#define __no_side_effects(x, y) \
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(__is_constexpr(x) && __is_constexpr(y))
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#define __safe_cmp(x, y) \
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(__typecheck(x, y) && __no_side_effects(x, y))
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#define __cmp(x, y, op) ((x) op (y) ? (x) : (y))
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#define __cmp_once(x, y, unique_x, unique_y, op) ({ \
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typeof(x) unique_x = (x); \
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typeof(y) unique_y = (y); \
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__cmp(unique_x, unique_y, op); })
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#define __careful_cmp(x, y, op) \
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__builtin_choose_expr(__safe_cmp(x, y), \
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__cmp(x, y, op), \
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__cmp_once(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y), op))
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#define __clamp(val, lo, hi) \
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((val) >= (hi) ? (hi) : ((val) <= (lo) ? (lo) : (val)))
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#define __clamp_once(val, lo, hi, unique_val, unique_lo, unique_hi) ({ \
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typeof(val) unique_val = (val); \
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typeof(lo) unique_lo = (lo); \
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typeof(hi) unique_hi = (hi); \
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__clamp(unique_val, unique_lo, unique_hi); })
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#define __clamp_input_check(lo, hi) \
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(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
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__is_constexpr((lo) > (hi)), (lo) > (hi), false)))
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#define __careful_clamp(val, lo, hi) ({ \
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__clamp_input_check(lo, hi) + \
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__builtin_choose_expr(__typecheck(val, lo) && __typecheck(val, hi) && \
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__typecheck(hi, lo) && __is_constexpr(val) && \
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__is_constexpr(lo) && __is_constexpr(hi), \
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__clamp(val, lo, hi), \
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__clamp_once(val, lo, hi, __UNIQUE_ID(__val), \
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__UNIQUE_ID(__lo), __UNIQUE_ID(__hi))); })
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/**
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* min - return minimum of two values of the same or compatible types
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* @x: first value
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* @y: second value
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*/
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#define min(x, y) __careful_cmp(x, y, <)
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/**
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* max - return maximum of two values of the same or compatible types
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* @x: first value
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* @y: second value
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*/
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#define max(x, y) __careful_cmp(x, y, >)
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/**
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* clamp - return a value clamped to a given range with strict typechecking
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* @val: current value
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* @lo: lowest allowable value
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* @hi: highest allowable value
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*
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* This macro does strict typechecking of @lo/@hi to make sure they are of the
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* same type as @val. See the unnecessary pointer comparisons.
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*/
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#define clamp(val, lo, hi) __careful_clamp(val, lo, hi)
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/*
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* ..and if you can't take the strict
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* types, you can specify one yourself.
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*
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* Or not use min/max/clamp at all, of course.
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*/
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/**
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* min_t - return minimum of two values, using the specified type
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* @type: data type to use
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* @x: first value
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* @y: second value
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*/
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#define min_t(type, x, y) __careful_cmp((type)(x), (type)(y), <)
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/**
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* max_t - return maximum of two values, using the specified type
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* @type: data type to use
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* @x: first value
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* @y: second value
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*/
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#define max_t(type, x, y) __careful_cmp((type)(x), (type)(y), >)
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#endif
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