github.com/df-mc/goleveldb@v1.1.9/leveldb/comparer/bytes_comparer.go (about)

     1  // Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
     2  // All rights reserved.
     3  //
     4  // Use of this source code is governed by a BSD-style license that can be
     5  // found in the LICENSE file.
     6  
     7  package comparer
     8  
     9  import "bytes"
    10  
    11  type bytesComparer struct{}
    12  
    13  func (bytesComparer) Compare(a, b []byte) int {
    14  	return bytes.Compare(a, b)
    15  }
    16  
    17  func (bytesComparer) Name() string {
    18  	return "leveldb.BytewiseComparator"
    19  }
    20  
    21  func (bytesComparer) Separator(dst, a, b []byte) []byte {
    22  	i, n := 0, len(a)
    23  	if n > len(b) {
    24  		n = len(b)
    25  	}
    26  	for ; i < n && a[i] == b[i]; i++ {
    27  	}
    28  	if i >= n {
    29  		// Do not shorten if one string is a prefix of the other
    30  	} else if c := a[i]; c < 0xff && c+1 < b[i] {
    31  		dst = append(dst, a[:i+1]...)
    32  		dst[len(dst)-1]++
    33  		return dst
    34  	}
    35  	return nil
    36  }
    37  
    38  func (bytesComparer) Successor(dst, b []byte) []byte {
    39  	for i, c := range b {
    40  		if c != 0xff {
    41  			dst = append(dst, b[:i+1]...)
    42  			dst[len(dst)-1]++
    43  			return dst
    44  		}
    45  	}
    46  	return nil
    47  }
    48  
    49  // DefaultComparer are default implementation of the Comparer interface.
    50  // It uses the natural ordering, consistent with bytes.Compare.
    51  var DefaultComparer = bytesComparer{}