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Karel Kočí
b9066e42bb
These macros are commonly provided on BSD systems. They are not part of C nor POSIX but these types of operations can be required in drivers implementation as well as in user space. The operations themself are simple but kind of cryptic when placed in the code as is. Thus having macro with an appropriate name is beneficial. The use of BSD naming here is only to cling to at least some other implementation instead of creating completelly NuttX specific one. Kudos to @hartmannathan for the source code documentation. Signed-off-by: Karel Kočí <kkoci@elektroline.cz>
110 lines
3.4 KiB
C
110 lines
3.4 KiB
C
/****************************************************************************
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* include/sys/param.h
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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#ifndef __INCLUDE_SYS_PARAM_H
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#define __INCLUDE_SYS_PARAM_H
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <limits.h>
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define MAXHOSTNAMELEN HOST_NAME_MAX
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/* Macros for min/max. */
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#ifndef MIN
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# define MIN(a,b) (((a) < (b)) ? (a) : (b))
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#endif /* MIN */
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#ifndef MAX
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# define MAX(a,b) (((a) > (b)) ? (a) : (b))
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#endif /* MAX */
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/* Macros for number of items.
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* (aka. ARRAY_SIZE, ArraySize, Size of an Array)
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*/
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#ifndef nitems
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# define nitems(_a) (sizeof(_a) / sizeof(0[(_a)]))
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#endif /* nitems */
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/* Macros for counting and rounding.
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*
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* These macros accept value to be rounded or checked as 'a' and base as 'b'.
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* They are consistent with those provided by some BSDs.
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*
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* howmany() calculates how many b fit into a.
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*
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* rounddown() and roundup() round a to the next b.
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*
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* rounddown2() and roundup2() are for powers of 2 only.
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*
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* powerof2() returns 1 if a is a power of 2, 0 otherwise.
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*
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* Warning: rounddown2() and roundup2() can be used only if b is power of 2,
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* otherwise they will produce wrong result.
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*
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* In all of these macros, outcome is undefined if b is 0.
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*
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* All parameters are assumed to be unsigned integers.
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*/
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#ifndef howmany
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# define howmany(a, b) (((a) + ((b) - 1)) / (b))
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#endif /* howmany */
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#ifndef rounddown
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# define rounddown(a, b) (((a) / (b)) * (b))
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#endif /* rounddown */
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#ifndef rounddown2
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# define rounddown2(a, b) ((a) & ~((b) - 1))
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#endif /* rounddown2 */
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#ifndef roundup
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# define roundup(a, b) ((((a) + ((b) - 1)) / (b)) * (b))
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#endif /* roundup */
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#ifndef roundup2
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# define roundup2(a, b) (((a) + ((b) - 1)) & ~((b) - 1))
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#endif /* roundup2 */
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#ifndef powerof2
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# define powerof2(a) (!(((a) - 1) & (a)))
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#endif /* powerof2 */
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/****************************************************************************
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* Public Type Definitions
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****************************************************************************/
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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#endif /* __INCLUDE_SYS_PARAM_H */
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