github.com/nats-io/nats-server/v2@v2.11.0-preview.2/server/stree/util.go (about)

     1  // Copyright 2023-2024 The NATS Authors
     2  // Licensed under the Apache License, Version 2.0 (the "License");
     3  // you may not use this file except in compliance with the License.
     4  // You may obtain a copy of the License at
     5  //
     6  // http://www.apache.org/licenses/LICENSE-2.0
     7  //
     8  // Unless required by applicable law or agreed to in writing, software
     9  // distributed under the License is distributed on an "AS IS" BASIS,
    10  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    11  // See the License for the specific language governing permissions and
    12  // limitations under the License.
    13  
    14  package stree
    15  
    16  // For subject matching.
    17  const (
    18  	pwc  = '*'
    19  	fwc  = '>'
    20  	tsep = '.'
    21  )
    22  
    23  // Determine index of common prefix. No match at all is 0, etc.
    24  func commonPrefixLen(s1, s2 []byte) int {
    25  	limit := min(len(s1), len(s2))
    26  	var i int
    27  	for ; i < limit; i++ {
    28  		if s1[i] != s2[i] {
    29  			break
    30  		}
    31  	}
    32  	return min(i, maxPrefixLen)
    33  }
    34  
    35  // Helper to copy bytes.
    36  func copyBytes(src []byte) []byte {
    37  	if len(src) == 0 {
    38  		return nil
    39  	}
    40  	dst := make([]byte, len(src))
    41  	copy(dst, src)
    42  	return dst
    43  }
    44  
    45  type position interface{ int | uint16 }
    46  
    47  // Can return 0 if we have all the subject as prefixes.
    48  func pivot[N position](subject []byte, pos N) byte {
    49  	if int(pos) >= len(subject) {
    50  		return 0
    51  	}
    52  	return subject[pos]
    53  }
    54  
    55  // TODO(dlc) - Can be removed with Go 1.21 once server is on Go 1.22.
    56  func min(a, b int) int {
    57  	if a < b {
    58  		return a
    59  	}
    60  	return b
    61  }