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numeric.go
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numeric.go
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// Copyright 2014, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package vindexes
import (
"bytes"
"encoding/binary"
"fmt"
)
// Numeric defines a bit-pattern mapping of a uint64 to the KeyspaceId.
// It's Unique and Reversible.
type Numeric struct {
name string
}
// NewNumeric creates a Numeric vindex.
func NewNumeric(name string, _ map[string]string) (Vindex, error) {
return &Numeric{name: name}, nil
}
// String returns the name of the vindex.
func (vind *Numeric) String() string {
return vind.name
}
// Cost returns the cost of this vindex as 0.
func (*Numeric) Cost() int {
return 0
}
// Verify returns true if ids and ksids match.
func (*Numeric) Verify(_ VCursor, ids []interface{}, ksids [][]byte) (bool, error) {
if len(ids) != len(ksids) {
return false, fmt.Errorf("Numeric.Verify: length of ids %v doesn't match length of ksids %v", len(ids), len(ksids))
}
for rowNum := range ids {
var keybytes [8]byte
num, err := getNumber(ids[rowNum])
if err != nil {
return false, fmt.Errorf("Numeric.Verify: %v", err)
}
binary.BigEndian.PutUint64(keybytes[:], uint64(num))
if bytes.Compare(keybytes[:], ksids[rowNum]) != 0 {
return false, nil
}
}
return true, nil
}
// Map returns the associated keyspace ids for the given ids.
func (*Numeric) Map(_ VCursor, ids []interface{}) ([][]byte, error) {
out := make([][]byte, 0, len(ids))
for _, id := range ids {
num, err := getNumber(id)
if err != nil {
return nil, fmt.Errorf("Numeric.Map: %v", err)
}
var keybytes [8]byte
binary.BigEndian.PutUint64(keybytes[:], uint64(num))
out = append(out, keybytes[:])
}
return out, nil
}
// ReverseMap returns the associated ids for the ksids.
func (*Numeric) ReverseMap(_ VCursor, ksids [][]byte) ([]interface{}, error) {
var reverseIds = make([]interface{}, len(ksids))
for rownum, keyspaceID := range ksids {
if len(keyspaceID) != 8 {
return nil, fmt.Errorf("Numeric.ReverseMap: length of keyspaceId is not 8: %d", len(keyspaceID))
}
reverseIds[rownum] = binary.BigEndian.Uint64([]byte(keyspaceID))
}
return reverseIds, nil
}
func init() {
Register("numeric", NewNumeric)
}