Fix memory corruption bug in impl/memory

impl/memory/gkvlite_iter_test.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"
         "testing"
 
@@ skipping 16 matching lines @@
         ret, _, err := cmpbin.ReadInt(bytes.NewBuffer(data))
         memoryCorruption(err)
 
         return ret
 }
 
 func TestIterator(t *testing.T) {
         t.Parallel()
 
         s := newMemStore()
-        c := s.SetCollection("zup", nil)
+        c := s.GetOrCreateCollection("zup")
         prev := []byte{}
         for i := 5; i < 100; i++ {
                 data := mkNum(int64(i))
                 c.Set(data, prev)
                 prev = data
         }
+        c = s.Snapshot().GetCollection("zup")
 
         get := func(c C, t *iterator) interface{} {
                 ret := interface{}(nil)
                 t.next(nil, func(i *gkvlite.Item) {
                         if i != nil {
                                 ret = readNum(i.Key)
                         }
                 })
                 return ret
         }
@@ skipping 130 matching lines @@
         for i, nms := range otherVals {
                 numbs := make([][]byte, len(nms))
                 for i, n := range nms {
                         numbs[i] = mkNum(n)
                 }
                 otherValBytes[i] = serialize.Join(numbs...)
         }
 
         Convey("Test MultiIterator", t, func() {
                 s := newMemStore()
-                c := s.SetCollection("zup1", nil)
+                c := s.GetOrCreateCollection("zup1")
                 for _, row := range valBytes {
                         c.Set(row, []byte{})
                 }
-                c2 := s.SetCollection("zup2", nil)
+                c2 := s.GetOrCreateCollection("zup2")
                 for _, row := range otherValBytes {
                         c2.Set(row, []byte{})
                 }
+                c = s.Snapshot().GetCollection("zup1")
+                c2 = s.Snapshot().GetCollection("zup2")
 
                 Convey("can join the same collection twice", func() {
                         // get just the (1, *)
                         // starting at (1, 2) (i.e. >= 2)
                         // ending at (1, 4) (i.e. < 7)
                         defs := []*iterDefinition{
                                 {c: c, prefix: mkNum(1), prefixLen: len(mkNum(1)), start: mkNum(2), end: mkNum(7)},
                                 {c: c, prefix: mkNum(1), prefixLen: len(mkNum(1)), start: mkNum(2), end: mkNum(7)},
                         }
 
@@ skipping 59 matching lines @@
                                 So(readNum(suffix), ShouldEqual, vals[i][1])
                                 i++
                                 return datastore.Stop
                         }), shouldBeSuccessful)
                         So(i, ShouldEqual, 1)
                 })
 
         })
 
 }