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regexpool.go
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regexpool.go
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// Copyright 2023 The PipeCD Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package regexpool
import (
"fmt"
"log"
"regexp"
"sync"
"github.com/pipe-cd/pipecd/pkg/cache/memorycache"
)
var (
defaultSize = 1000
defaultPool *Pool
)
// Pool is the representation of a pool of regular expression.
type Pool struct {
cache *memorycache.LRUCache
fails map[string]struct{}
mu sync.RWMutex
}
func init() {
var err error
if defaultPool, err = NewPool(defaultSize); err != nil {
log.Fatal(err)
}
}
// DefaultPool returns the default pool which was initialized at init by default.
func DefaultPool() *Pool {
return defaultPool
}
// NewPool initializes a new pool with a specified size.
func NewPool(size int) (*Pool, error) {
cache, err := memorycache.NewLRUCache(size)
if err != nil {
return nil, err
}
return &Pool{
fails: make(map[string]struct{}),
cache: cache,
}, nil
}
// Get retrieves the Regexp object from the pool or
// creates a new one if it does not exist.
func (p *Pool) Get(expr string) (*regexp.Regexp, error) {
regex, err := p.cache.Get(expr)
if err == nil {
return regex.(*regexp.Regexp), nil
}
// Check if the given expression was unable to compile before
// then return the error fast.
p.mu.RLock()
_, ok := p.fails[expr]
p.mu.RUnlock()
if ok {
return nil, fmt.Errorf("unable to compile: %s", expr)
}
// Compile the expression string and cache its result.
reg, err := regexp.Compile(expr)
if err == nil {
p.cache.Put(expr, reg)
return reg, nil
}
p.mu.Lock()
p.fails[expr] = struct{}{}
p.mu.Unlock()
return nil, fmt.Errorf("unable to compile: %s", expr)
}