A client/server helper wrapper for endpoints in Go.

go/src/infra/gae/epservice/example/service_add.go

Index: go/src/infra/gae/epservice/example/service_add.go
diff --git a/go/src/infra/gae/epservice/example/service_add.go b/go/src/infra/gae/epservice/example/service_add.go
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+++ b/go/src/infra/gae/epservice/example/service_add.go
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+// Copyright 2015 The Chromium 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 example
+
+import (
+	"golang.org/x/net/context"
+	"infra/gae/libs/wrapper"
+	"infra/gae/libs/wrapper/gae"
+	"infra/gae/libs/wrapper/gae/commonErrors"
+
+	"github.com/GoogleCloudPlatform/go-endpoints/endpoints"
+)
+
+// AddReq describes the input parameters to the 'Add' RPC. Name is required,
+// which makes it show up in the REST path, and Delta will be encoded in the
+// request body as JSON.
+type AddReq struct {
+	Name string `endpoints:"required"`
+
+	Delta int64 `json:",string"`
+}
+
+// AddRsp describes the return value from the 'Add' RPC. Prev is the previous
+// value, and Cur is the post-increment value.
+type AddRsp struct {
+	Prev int64 `json:",string"`
+	Cur  int64 `json:",string"`
+}
+
+// Add adds a value to the current counter, and returns the old+new values. It
+// may cause a counter to come into existance.
+func (Example) Add(c endpoints.Context, r *AddReq) (rsp *AddRsp, err error) {
+	rsp = &AddRsp{}
+
+	ds := wrapper.GetDS(gae.Use(context.Background(), c))
+	err = ds.RunInTransaction(func(context.Context) error {
+		ctr := &Counter{ID: r.Name}
+		if err := ds.Get(ctr); err != nil && err != commonErrors.ErrNoSuchEntityDS {
+			return err
+		}
+		rsp.Prev = ctr.Val
+		ctr.Val += r.Delta
+		rsp.Cur = ctr.Val
+		_, err := ds.Put(ctr)
+		return err
+	}, nil)
+	return
+}
+
+func init() {
+	mi["Add"] = &endpoints.MethodInfo{
+		Path: "counter/{Name}",
+		Desc: "Add an an amount to a particular counter",
+	}
+}