github.com/camlistore/go4@v0.0.0-20200104003542-c7e774b10ea0/strutil/intern.go (about)

     1  /*
     2  Copyright 2013 The Perkeep Authors
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8       http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package strutil
    18  
    19  var internStr = map[string]string{}
    20  
    21  // RegisterCommonString adds common strings to the interned string
    22  // table.  This should be called during init from the main
    23  // goroutine, not later at runtime.
    24  func RegisterCommonString(s ...string) {
    25  	for _, v := range s {
    26  		internStr[v] = v
    27  	}
    28  }
    29  
    30  // StringFromBytes returns string(v), minimizing copies for common values of v
    31  // as previously registered with RegisterCommonString.
    32  func StringFromBytes(v []byte) string {
    33  	// In Go 1.3, this string conversion in the map lookup does not allocate
    34  	// to make a new string. We depend on Go 1.3, so this is always free:
    35  	if s, ok := internStr[string(v)]; ok {
    36  		return s
    37  	}
    38  	return string(v)
    39  }