github.com/insionng/yougam@v0.0.0-20170714101924-2bc18d833463/libraries/pingcap/tidb/kv/key.go (about)

     1  // Copyright 2015 PingCAP, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package kv
    15  
    16  import "bytes"
    17  
    18  // Key represents high-level Key type.
    19  type Key []byte
    20  
    21  // Next returns the next key in byte-order.
    22  func (k Key) Next() Key {
    23  	// add 0x0 to the end of key
    24  	buf := make([]byte, len([]byte(k))+1)
    25  	copy(buf, []byte(k))
    26  	return buf
    27  }
    28  
    29  // PrefixNext returns the next prefix key.
    30  //
    31  // Assume there are keys like:
    32  //
    33  //   rowkey1
    34  //   rowkey1_column1
    35  //   rowkey1_column2
    36  //   rowKey2
    37  //
    38  // If we seek 'rowkey1' Next, we will get 'rowkey1_colum1'.
    39  // If we seek 'rowkey1' PrefixNext, we will get 'rowkey2'.
    40  func (k Key) PrefixNext() Key {
    41  	buf := make([]byte, len([]byte(k)))
    42  	copy(buf, []byte(k))
    43  	var i int
    44  	for i = len(k) - 1; i >= 0; i-- {
    45  		buf[i]++
    46  		if buf[i] != 0 {
    47  			break
    48  		}
    49  	}
    50  	if i == -1 {
    51  		copy(buf, k)
    52  		buf = append(buf, 0)
    53  	}
    54  	return buf
    55  }
    56  
    57  // Cmp returns the comparison result of two key.
    58  // The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
    59  func (k Key) Cmp(another Key) int {
    60  	return bytes.Compare(k, another)
    61  }
    62  
    63  // HasPrefix tests whether the Key begins with prefix.
    64  func (k Key) HasPrefix(prefix Key) bool {
    65  	return bytes.HasPrefix(k, prefix)
    66  }
    67  
    68  // Clone returns a copy of the Key.
    69  func (k Key) Clone() Key {
    70  	return append([]byte(nil), k...)
    71  }
    72  
    73  // EncodedKey represents encoded key in low-level storage engine.
    74  type EncodedKey []byte
    75  
    76  // Cmp returns the comparison result of two key.
    77  // The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
    78  func (k EncodedKey) Cmp(another EncodedKey) int {
    79  	return bytes.Compare(k, another)
    80  }
    81  
    82  // Next returns the next key in byte-order.
    83  func (k EncodedKey) Next() EncodedKey {
    84  	return EncodedKey(bytes.Join([][]byte{k, Key{0}}, nil))
    85  }