Refactor serialization helpers from impl/memory -> service/datastore/serialize

impl/memory/datastore_query.go

 // 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 memory
 
 import (
         "bytes"
         "encoding/base64"
         "errors"
@@ skipping 227 matching lines @@
         ret.numCols = len(ret.suffixFormat)
         for prop, vals := range ret.eqFilters {
                 if len(ret.suffixFormat) == 1 && prop == "__ancestor__" {
                         continue
                 }
                 ret.numCols += vals.Len()
         }
 
         return ret, nil
 }
+
+var invert = serialize.Invert

[Vadim Sh., 2015/09/24 19:06:14]

same here. why?

[iannucci, 2015/09/24 19:43:41]

same :)

+
+func increment(bstr []byte) []byte {
+        ret, overflow := serialize.Increment(bstr)
+        if overflow {
+                // This byte string was ALL 0xFF's. The only safe incrementation to do here
+                // would be to add a new byte to the beginning of bstr with the value 0x01,
+                // and a byte to the beginning OF ALL OTHER []byte's which bstr may be
+                // compared with. This is obviously impossible to do here, so panic. If we
+                // hit this, then we would need to add a spare 0 byte before every index
+                // column.
+                //
+                // Another way to think about this is that we just accumulated a 'carry' bit,
+                // and the new value has overflowed this representation.
+                //
+                // Fortunately, the first byte of a serialized index column entry is a
+                // PropertyType byte, and the only valid values that we'll be incrementing
+                // are never equal to 0xFF, since they have the high bit set (so either they're
+                // 0x8*, or 0x7*, depending on if it's inverted).
+                impossible(fmt.Errorf("incrementing %v would require more sigfigs", bstr))
+        }
+        return ret
+}