key.go

// Copyright 2015 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package kv

import "bytes"

// Key represents high-level Key type.
type Key []byte

// Next returns the next key in byte-order.
func (k Key) Next() Key {
	// add 0x0 to the end of key
	buf := make([]byte, len([]byte(k))+1)
	copy(buf, []byte(k))
	return buf
}

// PrefixNext returns the next prefix key.
//
// Assume there are keys like:
//
//   rowkey1
//   rowkey1_column1
//   rowkey1_column2
//   rowKey2
//
// If we seek 'rowkey1' Next, we will get 'rowkey1_column1'.
// If we seek 'rowkey1' PrefixNext, we will get 'rowkey2'.
func (k Key) PrefixNext() Key {
	buf := make([]byte, len([]byte(k)))
	copy(buf, []byte(k))
	var i int
	for i = len(k) - 1; i >= 0; i-- {
		buf[i]++
		if buf[i] != 0 {
			break
		}
	}
	if i == -1 {
		copy(buf, k)
		buf = append(buf, 0)
	}
	return buf
}

// Cmp returns the comparison result of two key.
// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
func (k Key) Cmp(another Key) int {
	return bytes.Compare(k, another)
}

// HasPrefix tests whether the Key begins with prefix.
func (k Key) HasPrefix(prefix Key) bool {
	return bytes.HasPrefix(k, prefix)
}

// Clone returns a copy of the Key.
func (k Key) Clone() Key {
	return append([]byte(nil), k...)
}

// KeyRange represents a range where StartKey <= key < EndKey.
type KeyRange struct {
	StartKey Key
	EndKey   Key
}

// IsPoint checks if the key range represents a point.
func (r *KeyRange) IsPoint() bool {
	return bytes.Equal(r.StartKey.PrefixNext(), r.EndKey)
}

// EncodedKey represents encoded key in low-level storage engine.
type EncodedKey []byte

// Cmp returns the comparison result of two key.
// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
func (k EncodedKey) Cmp(another EncodedKey) int {
	return bytes.Compare(k, another)
}

// Next returns the next key in byte-order.
func (k EncodedKey) Next() EncodedKey {
	return EncodedKey(bytes.Join([][]byte{k, Key{0}}, nil))
}