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

1 files changed, 10 insertions, 0 deletions

diff --git a/src/lib/http/triv.go b/src/lib/http/triv.go
index daf5eb8c0c..48e345e5e8 100644
--- a/src/lib/http/triv.go
+++ b/src/lib/http/triv.go
@@ -6,6 +6,7 @@ package main
 
 import (
 	"bufio";
+	"exvar";
 	"flag";
 	"fmt";
 	"http";
@@ -17,15 +18,23 @@ import (
 
 // hello world, the web server
 func HelloServer(c *http.Conn, req *http.Request) {
+	exvar.Increment("hello-requests", 1);
 	io.WriteString(c, "hello, world!\n");
 }
 
+// Handler for /exvar requests.
+func ExvarServer(c *http.Conn, req *http.Request) {
+	c.SetHeader("content-type", "text/plain; charset=utf-8");
+	io.WriteString(c, exvar.String());
+}
+
 // simple counter server
 type Counter struct {
 	n int;
 }
 
 func (ctr *Counter) ServeHTTP(c *http.Conn, req *http.Request) {
+	exvar.Increment("counter-requests", 1);
 	fmt.Fprintf(c, "counter = %d\n", ctr.n);
 	ctr.n++;
 }
@@ -92,6 +101,7 @@ func main() {
 	http.Handle("/args", http.HandlerFunc(ArgServer));
 	http.Handle("/go/hello", http.HandlerFunc(HelloServer));
 	http.Handle("/chan", ChanCreate());
+	http.Handle("/exvar", http.HandlerFunc(ExvarServer));
 	err := http.ListenAndServe(":12345", nil);
 	if err != nil {
 		panic("ListenAndServe: ", err.String())