Initial cut at an "exported variables" (exvar) package.
This handles integer-valued vars in a singleton struct, and exports functions
for incrementing, setting and getting those vars, as well as rendering all the
vars in a standard format.
Demonstrate the use of the exvar package in the http/triv server.
R=dcross,r
APPROVED=r
DELTA=122 (122 added, 0 deleted, 0 changed)
OCL=27617
CL=27622
diff --git a/src/lib/exvar.go b/src/lib/exvar.go
new file mode 100644
index 0000000..ccfd34a
--- /dev/null
+++ b/src/lib/exvar.go
@@ -0,0 +1,60 @@
+// 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.
+
+// The exvar package provides a standardized interface to public variables,
+// such as operation counters in servers.
+package exvar
+
+import (
+ "fmt";
+ "sync";
+)
+
+// Global state.
+var (
+ mutex sync.Mutex;
+ intVars = make(map[string] int);
+ mapVars = make(map[string] map[string] int);
+ // TODO(dsymonds):
+ // - string-valued vars
+ // - docstrings
+ // - dynamic lookup vars (via chan)
+)
+
+// Increment adds inc to the var called name.
+func Increment(name string, inc int) {
+ mutex.Lock();
+ defer mutex.Unlock();
+
+ if x, ok := intVars[name]; ok {
+ intVars[name] += inc
+ } else {
+ intVars[name] = inc
+ }
+}
+
+// Set sets the var called name to value.
+func Set(name string, value int) {
+ intVars[name] = value
+}
+
+// Get retrieves an integer-valued var called name.
+func Get(name string) (x int, ok bool) {
+ x, ok = intVars[name];
+ return
+}
+
+// TODO(dsymonds): Functions for map-valued vars.
+
+// String produces a string of all the vars in textual format.
+func String() string {
+ mutex.Lock();
+ defer mutex.Unlock();
+
+ s := "";
+ for name, value := range intVars {
+ s += fmt.Sprintln(name, value)
+ }
+ return s
+}
