48 lines
2.5 KiB
C
48 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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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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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/fmt/conv.h"
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#include "libc/sysv/consts/prio.h"
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static int clamp(int p) {
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return max(-NZERO, min(NZERO - 1, p));
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}
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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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