cosmopolitan/libc/calls/getpriority.c

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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi
Copyright 2020 Justine Alexandra Roberts Tunney
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Permission to use, copy, modify, and/or distribute this software for
any purpose with or without fee is hereby granted, provided that the
above copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
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*/
#include "libc/calls/calls.h"
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#include "libc/calls/syscall-nt.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/asmflag.h"
#include "libc/intrin/describeflags.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/limits.h"
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/**
* Returns nice value of thing.
*
* Since -1 might be a valid return value for this API, it's necessary
* to clear `errno` beforehand and see if it changed, in order to truly
* determine if an error happened.
*
* On Windows, there's only six priority classes. We define them as -16
* (realtime), -10 (high), -5 (above), 0 (normal), 5 (below), 15 (idle)
* which are the only values that'll roundtrip getpriority/setpriority.
*
* @param which can be one of:
* - `PRIO_PROCESS` is supported universally
* - `PRIO_PGRP` is supported on unix
* - `PRIO_USER` is supported on unix
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* @param who is the pid, pgid, or uid (0 means current)
* @return value [-NZERO,NZERO) or -1 w/ errno
* @raise EINVAL if `which` was invalid or unsupported
* @raise EPERM if access to process was denied
* @raise ESRCH if no such process existed
* @see setpriority()
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*/
int getpriority(int which, unsigned who) {
int rc;
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#ifdef __x86_64__
char cf;
if (IsLinux()) {
asm volatile("syscall"
: "=a"(rc)
: "0"(140), "D"(which), "S"(who)
: "rcx", "r11", "memory");
if (rc >= 0) {
rc = NZERO - rc;
} else {
errno = -rc;
rc = -1;
}
} else if (IsBsd()) {
asm volatile(CFLAG_ASM("syscall")
: CFLAG_CONSTRAINT(cf), "=a"(rc)
: "1"((IsXnu() ? 0x2000000 : 0) | 100), "D"(which), "S"(who)
: "rcx", "rdx", "r8", "r9", "r10", "r11", "memory");
if (cf) {
errno = rc;
rc = -1;
}
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} else {
rc = sys_getpriority_nt(which, who);
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}
#else
rc = sys_getpriority(which, who);
if (rc != -1) {
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rc = NZERO - rc;
}
#endif
STRACE("getpriority(%s, %u) → %d% m", DescribeWhichPrio(which), who, rc);
return rc;
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}