1 files changed, 131 insertions, 0 deletions
diff --git a/src/os/signal/signal.go b/src/os/signal/signal.go
new file mode 100644
index 000000000..300427549
--- /dev/null
+++ b/src/os/signal/signal.go
@@ -0,0 +1,131 @@
+// Copyright 2012 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 signal implements access to incoming signals.
+package signal
+
+// BUG(rsc): This package is not yet implemented on Plan 9.
+
+import (
+	"os"
+	"sync"
+)
+
+var handlers struct {
+	sync.Mutex
+	m   map[chan<- os.Signal]*handler
+	ref [numSig]int64
+}
+
+type handler struct {
+	mask [(numSig + 31) / 32]uint32
+}
+
+func (h *handler) want(sig int) bool {
+	return (h.mask[sig/32]>>uint(sig&31))&1 != 0
+}
+
+func (h *handler) set(sig int) {
+	h.mask[sig/32] |= 1 << uint(sig&31)
+}
+
+// Notify causes package signal to relay incoming signals to c.
+// If no signals are listed, all incoming signals will be relayed to c.
+// Otherwise, just the listed signals will.
+//
+// Package signal will not block sending to c: the caller must ensure
+// that c has sufficient buffer space to keep up with the expected
+// signal rate.  For a channel used for notification of just one signal value,
+// a buffer of size 1 is sufficient.
+//
+// It is allowed to call Notify multiple times with the same channel:
+// each call expands the set of signals sent to that channel.
+// The only way to remove signals from the set is to call Stop.
+//
+// It is allowed to call Notify multiple times with different channels
+// and the same signals: each channel receives copies of incoming
+// signals independently.
+func Notify(c chan<- os.Signal, sig ...os.Signal) {
+	if c == nil {
+		panic("os/signal: Notify using nil channel")
+	}
+
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	h := handlers.m[c]
+	if h == nil {
+		if handlers.m == nil {
+			handlers.m = make(map[chan<- os.Signal]*handler)
+		}
+		h = new(handler)
+		handlers.m[c] = h
+	}
+
+	add := func(n int) {
+		if n < 0 {
+			return
+		}
+		if !h.want(n) {
+			h.set(n)
+			if handlers.ref[n] == 0 {
+				enableSignal(n)
+			}
+			handlers.ref[n]++
+		}
+	}
+
+	if len(sig) == 0 {
+		for n := 0; n < numSig; n++ {
+			add(n)
+		}
+	} else {
+		for _, s := range sig {
+			add(signum(s))
+		}
+	}
+}
+
+// Stop causes package signal to stop relaying incoming signals to c.
+// It undoes the effect of all prior calls to Notify using c.
+// When Stop returns, it is guaranteed that c will receive no more signals.
+func Stop(c chan<- os.Signal) {
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	h := handlers.m[c]
+	if h == nil {
+		return
+	}
+	delete(handlers.m, c)
+
+	for n := 0; n < numSig; n++ {
+		if h.want(n) {
+			handlers.ref[n]--
+			if handlers.ref[n] == 0 {
+				disableSignal(n)
+			}
+		}
+	}
+}
+
+func process(sig os.Signal) {
+	n := signum(sig)
+	if n < 0 {
+		return
+	}
+
+	handlers.Lock()
+	defer handlers.Unlock()
+
+	for c, h := range handlers.m {
+		if h.want(n) {
+			// send but do not block for it
+			select {
+			case c <- sig:
+			default:
+			}
+		}
+	}
+}