mirror of git://gcc.gnu.org/git/gcc.git
132 lines
2.7 KiB
Go
132 lines
2.7 KiB
Go
// Copyright 2012 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package signal implements access to incoming signals.
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package signal
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// BUG(rsc): This package is not yet implemented on Plan 9.
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import (
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"os"
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"sync"
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)
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var handlers struct {
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sync.Mutex
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m map[chan<- os.Signal]*handler
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ref [numSig]int64
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}
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type handler struct {
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mask [(numSig + 31) / 32]uint32
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}
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func (h *handler) want(sig int) bool {
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return (h.mask[sig/32]>>uint(sig&31))&1 != 0
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}
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func (h *handler) set(sig int) {
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h.mask[sig/32] |= 1 << uint(sig&31)
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}
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// Notify causes package signal to relay incoming signals to c.
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// If no signals are listed, all incoming signals will be relayed to c.
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// Otherwise, just the listed signals will.
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//
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// Package signal will not block sending to c: the caller must ensure
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// that c has sufficient buffer space to keep up with the expected
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// signal rate. For a channel used for notification of just one signal value,
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// a buffer of size 1 is sufficient.
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//
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// It is allowed to call Notify multiple times with the same channel:
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// each call expands the set of signals sent to that channel.
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// The only way to remove signals from the set is to call Stop.
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//
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// It is allowed to call Notify multiple times with different channels
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// and the same signals: each channel receives copies of incoming
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// signals independently.
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func Notify(c chan<- os.Signal, sig ...os.Signal) {
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if c == nil {
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panic("os/signal: Notify using nil channel")
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}
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handlers.Lock()
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defer handlers.Unlock()
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h := handlers.m[c]
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if h == nil {
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if handlers.m == nil {
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handlers.m = make(map[chan<- os.Signal]*handler)
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}
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h = new(handler)
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handlers.m[c] = h
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}
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add := func(n int) {
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if n < 0 {
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return
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}
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if !h.want(n) {
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h.set(n)
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if handlers.ref[n] == 0 {
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enableSignal(n)
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}
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handlers.ref[n]++
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}
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}
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if len(sig) == 0 {
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for n := 0; n < numSig; n++ {
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add(n)
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}
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} else {
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for _, s := range sig {
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add(signum(s))
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}
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}
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}
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// Stop causes package signal to stop relaying incoming signals to c.
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// It undoes the effect of all prior calls to Notify using c.
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// When Stop returns, it is guaranteed that c will receive no more signals.
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func Stop(c chan<- os.Signal) {
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handlers.Lock()
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defer handlers.Unlock()
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h := handlers.m[c]
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if h == nil {
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return
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}
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delete(handlers.m, c)
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for n := 0; n < numSig; n++ {
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if h.want(n) {
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handlers.ref[n]--
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if handlers.ref[n] == 0 {
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disableSignal(n)
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}
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}
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}
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}
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func process(sig os.Signal) {
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n := signum(sig)
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if n < 0 {
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return
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}
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handlers.Lock()
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defer handlers.Unlock()
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for c, h := range handlers.m {
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if h.want(n) {
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// send but do not block for it
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select {
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case c <- sig:
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default:
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}
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}
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}
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}
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