library: os, syscall

internal/lib/syscall/syscall_linux.go

@@ -11,6 +11,65 @@
 
 package syscall
 
+type WaitStatus uint32
+
+// Wait status is 7 bits at bottom, either 0 (exited),
+// 0x7F (stopped), or a signal number that caused an exit.
+// The 0x80 bit is whether there was a core dump.
+// An extra number (exit code, signal causing a stop)
+// is in the high bits. At least that's the idea.
+// There are various irregularities. For example, the
+// "continued" status is 0xFFFF, distinguishing itself
+// from stopped via the core dump bit.
+
+const (
+	mask    = 0x7F
+	core    = 0x80
+	exited  = 0x00
+	stopped = 0x7F
+	shift   = 8
+)
+
+func (w WaitStatus) Exited() bool { return w&mask == exited }
+
+func (w WaitStatus) Signaled() bool { return w&mask != stopped && w&mask != exited }
+
+func (w WaitStatus) Stopped() bool { return w&0xFF == stopped }
+
+func (w WaitStatus) Continued() bool { return w == 0xFFFF }
+
+func (w WaitStatus) CoreDump() bool { return w.Signaled() && w&core != 0 }
+
+func (w WaitStatus) ExitStatus() int {
+	if !w.Exited() {
+		return -1
+	}
+	return int(w>>shift) & 0xFF
+}
+
+func (w WaitStatus) Signal() Signal {
+	if !w.Signaled() {
+		return -1
+	}
+	return Signal(w & mask)
+}
+
+func (w WaitStatus) StopSignal() Signal {
+	if !w.Stopped() {
+		return -1
+	}
+	return Signal(w>>shift) & 0xFF
+}
+
+/* TODO(xsw):
+func (w WaitStatus) TrapCause() int {
+	if w.StopSignal() != SIGTRAP {
+		return -1
+	}
+	return int(w>>shift) >> 8
+}
+*/
+
 func Faccessat(dirfd int, path string, mode uint32, flags int) (err error) {
 	panic("todo: syscall.Faccessat")
 }