Adding upstream version 2.5.1.

Signed-off-by: Daniel Baumann <daniel@debian.org>

index/upsidedown/row_merge.go

@@ -0,0 +1,76 @@
+//  Copyright (c) 2014 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package upsidedown
+
+import (
+	"encoding/binary"
+)
+
+var mergeOperator upsideDownMerge
+
+var dictionaryTermIncr []byte
+var dictionaryTermDecr []byte
+
+func init() {
+	dictionaryTermIncr = make([]byte, 8)
+	binary.LittleEndian.PutUint64(dictionaryTermIncr, uint64(1))
+	dictionaryTermDecr = make([]byte, 8)
+	var negOne = int64(-1)
+	binary.LittleEndian.PutUint64(dictionaryTermDecr, uint64(negOne))
+}
+
+type upsideDownMerge struct{}
+
+func (m *upsideDownMerge) FullMerge(key, existingValue []byte, operands [][]byte) ([]byte, bool) {
+	// set up record based on key
+	dr, err := NewDictionaryRowK(key)
+	if err != nil {
+		return nil, false
+	}
+	if len(existingValue) > 0 {
+		// if existing value, parse it
+		err = dr.parseDictionaryV(existingValue)
+		if err != nil {
+			return nil, false
+		}
+	}
+
+	// now process operands
+	for _, operand := range operands {
+		next := int64(binary.LittleEndian.Uint64(operand))
+		if next < 0 && uint64(-next) > dr.count {
+			// subtracting next from existing would overflow
+			dr.count = 0
+		} else if next < 0 {
+			dr.count -= uint64(-next)
+		} else {
+			dr.count += uint64(next)
+		}
+	}
+
+	return dr.Value(), true
+}
+
+func (m *upsideDownMerge) PartialMerge(key, leftOperand, rightOperand []byte) ([]byte, bool) {
+	left := int64(binary.LittleEndian.Uint64(leftOperand))
+	right := int64(binary.LittleEndian.Uint64(rightOperand))
+	rv := make([]byte, 8)
+	binary.LittleEndian.PutUint64(rv, uint64(left+right))
+	return rv, true
+}
+
+func (m *upsideDownMerge) Name() string {
+	return "upsideDownMerge"
+}