// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import "unsafe"

//extern pipe
func libcPipe([2]int32) int32

func pipe() (r, w int32, e int32) {
	var p [2]int32
	r := libcPipe(noescape(unsafe.Pointer(&p)))
	if r < 0 {
		e = int32(errno())
	}
	return p[0], p[1], e
}

//go:nosplit
func setNonblock(fd int32) {
	flags := fcntlUintptr(uintptr(fd), _F_GETFL, 0)
	fcntlUintptr(uintptr(fd), _F_SETFL, flags|_O_NONBLOCK)
}

type mOS struct {
	initialized bool
	mutex       pthreadmutex
	cond        pthreadcond
	count       int
}

func unimplemented(name string) {
	println(name, "not implemented")
	*(*int)(unsafe.Pointer(uintptr(1231))) = 1231
}

//go:nosplit
func semacreate(mp *m) {
	if mp.initialized {
		return
	}
	mp.initialized = true
	if err := pthread_mutex_init(&mp.mutex, nil); err != 0 {
		throw("pthread_mutex_init")
	}
	if err := pthread_cond_init(&mp.cond, nil); err != 0 {
		throw("pthread_cond_init")
	}
}

//go:nosplit
func semasleep(ns int64) int32 {
	var start int64
	if ns >= 0 {
		start = nanotime()
	}
	mp := getg().m
	pthread_mutex_lock(&mp.mutex)
	for {
		if mp.count > 0 {
			mp.count--
			pthread_mutex_unlock(&mp.mutex)
			return 0
		}
		if ns >= 0 {
			spent := nanotime() - start
			if spent >= ns {
				pthread_mutex_unlock(&mp.mutex)
				return -1
			}
			var t timespec
			t.set_nsec(ns - spent)
			err := pthread_cond_timedwait_relative_np(&mp.cond, &mp.mutex, &t)
			if err == _ETIMEDOUT {
				pthread_mutex_unlock(&mp.mutex)
				return -1
			}
		} else {
			pthread_cond_wait(&mp.cond, &mp.mutex)
		}
	}
}

//go:nosplit
func semawakeup(mp *m) {
	pthread_mutex_lock(&mp.mutex)
	mp.count++
	if mp.count > 0 {
		pthread_cond_signal(&mp.cond)
	}
	pthread_mutex_unlock(&mp.mutex)
}

// The read and write file descriptors used by the sigNote functions.
var sigNoteRead, sigNoteWrite int32

// sigNoteSetup initializes an async-signal-safe note.
//
// The current implementation of notes on Darwin is not async-signal-safe,
// because the functions pthread_mutex_lock, pthread_cond_signal, and
// pthread_mutex_unlock, called by semawakeup, are not async-signal-safe.
// There is only one case where we need to wake up a note from a signal
// handler: the sigsend function. The signal handler code does not require
// all the features of notes: it does not need to do a timed wait.
// This is a separate implementation of notes, based on a pipe, that does
// not support timed waits but is async-signal-safe.
func sigNoteSetup(*note) {
	if sigNoteRead != 0 || sigNoteWrite != 0 {
		throw("duplicate sigNoteSetup")
	}
	var errno int32
	sigNoteRead, sigNoteWrite, errno = pipe()
	if errno != 0 {
		throw("pipe failed")
	}
	closeonexec(sigNoteRead)
	closeonexec(sigNoteWrite)

	// Make the write end of the pipe non-blocking, so that if the pipe
	// buffer is somehow full we will not block in the signal handler.
	// Leave the read end of the pipe blocking so that we will block
	// in sigNoteSleep.
	setNonblock(sigNoteWrite)
}

// sigNoteWakeup wakes up a thread sleeping on a note created by sigNoteSetup.
func sigNoteWakeup(*note) {
	var b byte
	write(uintptr(sigNoteWrite), unsafe.Pointer(&b), 1)
}

// sigNoteSleep waits for a note created by sigNoteSetup to be woken.
func sigNoteSleep(*note) {
	entersyscallblock()
	var b byte
	read(sigNoteRead, unsafe.Pointer(&b), 1)
	exitsyscall()
}

// BSD interface for threading.
func osinit() {
	// pthread_create delayed until end of goenvs so that we
	// can look at the environment first.

	ncpu = getncpu()
	physPageSize = getPageSize()
}