47 lines
2.5 KiB
C
47 lines
2.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ 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 License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/conv/conv.h"
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#include "libc/sysv/consts/prio.h"
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static int clamp(int p) { return max(-NZERO, min(NZERO - 1, p)); }
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/**
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* Changes process priority.
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*
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* @param delta is added to current priority w/ clamping
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* @return new priority, or -1 w/ errno
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* @see Linux claims ioprio_set() is tuned automatically by this
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*/
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int nice(int delta) {
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int p;
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if (abs(delta) >= NZERO * 2) {
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p = delta;
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} else {
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delta = clamp(delta);
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if ((p = getpriority(PRIO_PROCESS, 0)) == -1) return -1;
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p += delta;
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}
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p = clamp(p);
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if (setpriority(PRIO_PROCESS, 0, p) == -1) return -1;
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return p;
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}
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