github.com/linchen2chris/hugo@v0.0.0-20230307053224-cec209389705/markup/highlight/chromalexers/chromalexers.go (about)

     1  // Copyright 2022 The Hugo Authors. All rights reserved.
     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  // 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 chromalexers
    15  
    16  import (
    17  	"sync"
    18  
    19  	"github.com/alecthomas/chroma/v2"
    20  	"github.com/alecthomas/chroma/v2/lexers"
    21  )
    22  
    23  type lexersMap struct {
    24  	lexers map[string]chroma.Lexer
    25  	mu     sync.RWMutex
    26  }
    27  
    28  var lexerCache = &lexersMap{lexers: make(map[string]chroma.Lexer)}
    29  
    30  // Get returns a lexer for the given language name, nil if not found.
    31  // This is just a wrapper around chromalexers.Get that caches the result.
    32  // Reasoning for this is that chromalexers.Get is slow in the case where the lexer is not found,
    33  // which is a common case in Hugo.
    34  func Get(name string) chroma.Lexer {
    35  	lexerCache.mu.RLock()
    36  	lexer, found := lexerCache.lexers[name]
    37  	lexerCache.mu.RUnlock()
    38  
    39  	if found {
    40  		return lexer
    41  	}
    42  
    43  	lexer = lexers.Get(name)
    44  
    45  	lexerCache.mu.Lock()
    46  	lexerCache.lexers[name] = lexer
    47  	lexerCache.mu.Unlock()
    48  
    49  	return lexer
    50  }