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121 lines
2.8 KiB
121 lines
2.8 KiB
// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package kv
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import (
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"bytes"
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"encoding/hex"
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)
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// Key represents high-level Key type.
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type Key []byte
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// Next returns the next key in byte-order.
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func (k Key) Next() Key {
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// add 0x0 to the end of key
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buf := make([]byte, len(k)+1)
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copy(buf, []byte(k))
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return buf
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}
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// PrefixNext returns the next prefix key.
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//
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// Assume there are keys like:
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//
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// rowkey1
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// rowkey1_column1
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// rowkey1_column2
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// rowKey2
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//
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// If we seek 'rowkey1' Next, we will get 'rowkey1_column1'.
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// If we seek 'rowkey1' PrefixNext, we will get 'rowkey2'.
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func (k Key) PrefixNext() Key {
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buf := make([]byte, len(k))
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copy(buf, []byte(k))
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var i int
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for i = len(k) - 1; i >= 0; i-- {
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buf[i]++
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if buf[i] != 0 {
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break
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}
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}
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if i == -1 {
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copy(buf, k)
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buf = append(buf, 0)
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}
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return buf
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}
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// Cmp returns the comparison result of two key.
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// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
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func (k Key) Cmp(another Key) int {
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return bytes.Compare(k, another)
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}
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// HasPrefix tests whether the Key begins with prefix.
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func (k Key) HasPrefix(prefix Key) bool {
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return bytes.HasPrefix(k, prefix)
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}
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// Clone returns a deep copy of the Key.
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func (k Key) Clone() Key {
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ck := make([]byte, len(k))
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copy(ck, []byte(k))
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return ck
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}
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// String implements fmt.Stringer interface.
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func (k Key) String() string {
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return hex.EncodeToString(k)
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}
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// KeyRange represents a range where StartKey <= key < EndKey.
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type KeyRange struct {
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StartKey Key
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EndKey Key
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}
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// IsPoint checks if the key range represents a point.
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func (r *KeyRange) IsPoint() bool {
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if len(r.StartKey) != len(r.EndKey) {
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// Works like
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// return bytes.Equal(r.StartKey.Next(), r.EndKey)
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startLen := len(r.StartKey)
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return startLen+1 == len(r.EndKey) &&
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r.EndKey[startLen] == 0 &&
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bytes.Equal(r.StartKey, r.EndKey[:startLen])
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}
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// Works like
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// return bytes.Equal(r.StartKey.PrefixNext(), r.EndKey)
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i := len(r.StartKey) - 1
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for ; i >= 0; i-- {
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if r.StartKey[i] != 255 {
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break
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}
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if r.EndKey[i] != 0 {
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return false
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}
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}
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if i < 0 {
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// In case all bytes in StartKey are 255.
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return false
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}
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// The byte at diffIdx in StartKey should be one less than the byte at diffIdx in EndKey.
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// And bytes in StartKey and EndKey before diffIdx should be equal.
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diffOneIdx := i
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return r.StartKey[diffOneIdx]+1 == r.EndKey[diffOneIdx] &&
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bytes.Equal(r.StartKey[:diffOneIdx], r.EndKey[:diffOneIdx])
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}
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