[milo] Add BuildSummary and common models.

milo/appengine/common/model/manifest_link.go

+// Copyright 2017 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package model
+
+import (
+        "bytes"
+
+        ds "github.com/luci/gae/service/datastore"
+        "github.com/luci/luci-go/common/data/cmpbin"
+)
+
+// ManifestLink is an in-MILO link to a named source manifest.
+type ManifestLink struct {
+        // The name of the manifest as the build annotated it.
+        Name string
+
+        // The manifest ID (sha256).
+        ID []byte
+}
+
+var _ ds.PropertyConverter = (*ManifestLink)(nil)
+
+// FromProperty implements ds.PropertyConverter
+func (m *ManifestLink) FromProperty(p ds.Property) (err error) {
+        val, err := p.Project(ds.PTBytes)
+        if err != nil {
+                return err
+        }
+        buf := bytes.NewReader(val.([]byte))
+        if m.Name, _, err = cmpbin.ReadString(buf); err != nil {
+                return
+        }
+        m.ID, _, err = cmpbin.ReadBytes(buf)
+        return
+}
+
+// ToProperty implements ds.PropertyConverter
+func (m *ManifestLink) ToProperty() (ds.Property, error) {
+        buf := bytes.NewBuffer(nil)
+        cmpbin.WriteString(buf, m.Name)

[Ryan Tseng, 2017/06/17 00:44:29]

These functions return errors, should probably propagate them

[iannucci, 2017/06/17 01:30:04]

They only return errors if the write returns an error. bytes.Buffer writes can't
return errors :)

+        cmpbin.WriteBytes(buf, m.ID)
+        return ds.MkProperty(buf.Bytes()), nil
+}