119 lines
3 KiB
Go
119 lines
3 KiB
Go
/*
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* mime-db: Mime Database, (C) 2015 Minio, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// Package contentdb is a database of file extension to mime content-type.
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// Definitions are imported from NodeJS mime-db project under MIT license.
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package contentdb
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import (
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"errors"
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"fmt"
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"strings"
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"sync"
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"encoding/json"
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)
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var (
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// Internal lock.
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mutex = &sync.Mutex{}
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// Make note of initialization.
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isInitialized = false
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// Database of extension:content-type.
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extDB map[string]string
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)
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// Load JSON data from gobindata and parse them into extDB.
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func loadDB() error {
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// Structure of JSON data from mime-db project.
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type dbEntry struct {
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Source string `json:"source"`
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Compressible bool `json:"compresible"`
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Extensions []string `json:"extensions"`
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}
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// Access embedded "db.json" inside go-bindata.
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jsonDB, e := Asset("db/db.json")
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if e != nil {
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return e
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}
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// Convert db.json into go's typed structure.
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db := make(map[string]dbEntry)
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if e := json.Unmarshal(jsonDB, &db); e != nil {
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return e
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}
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// Generate a new database from mime-db.
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for key, val := range db {
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if len(val.Extensions) > 0 {
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/* Denormalize - each extension has its own
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unique content-type now. Looks will be fast. */
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for _, ext := range val.Extensions {
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/* Single extension type may map to
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multiple content-types. In that case,
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simply prefer the longest content-type
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to maintain some level of
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consistency. Only guarantee is,
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whatever content type is assigned, it
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is appropriate and valid type. */
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if strings.Compare(extDB[ext], key) < 0 {
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extDB[ext] = key
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}
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}
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}
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}
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return nil
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}
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// Init initializes contentdb for lookups. JSON structure is parsed into a simple map of extension and content-type.
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func Init() error {
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mutex.Lock()
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defer mutex.Unlock()
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if !isInitialized {
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var e error
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extDB = make(map[string]string)
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if !isInitialized {
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e = loadDB()
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}
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isInitialized = true
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return e
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}
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return nil
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}
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// Lookup returns matching content-type for known types of file extensions.
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func Lookup(extension string) (contentType string, e error) {
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if !isInitialized {
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return "", errors.New("contentdb is not initialized")
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}
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return extDB[extension], e
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}
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// MustLookup returns matching content-type for known types of file extensions. In case of error, it panics.
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func MustLookup(extension string) (contentType string) {
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var e error
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if contentType, e = Lookup(extension); e != nil {
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panic(fmt.Sprintf("Lookup failed: %s\n", e))
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}
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return contentType
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}
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