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// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package util contains utility types and functions for godoc.
package util // import "golang.org/x/tools/godoc/util"
import (
pathpkg "path"
"sync"
"time"
"unicode/utf8"
"golang.org/x/tools/godoc/vfs"
)
// An RWValue wraps a value and permits mutually exclusive
// access to it and records the time the value was last set.
type RWValue struct {
mutex sync.RWMutex
value interface{}
timestamp time.Time // time of last set()
}
func (v *RWValue) Set(value interface{}) {
v.mutex.Lock()
v.value = value
v.timestamp = time.Now()
v.mutex.Unlock()
}
func (v *RWValue) Get() (interface{}, time.Time) {
v.mutex.RLock()
defer v.mutex.RUnlock()
return v.value, v.timestamp
}
// IsText reports whether a significant prefix of s looks like correct UTF-8;
// that is, if it is likely that s is human-readable text.
func IsText(s []byte) bool {
const max = 1024 // at least utf8.UTFMax
if len(s) > max {
s = s[0:max]
}
for i, c := range string(s) {
if i+utf8.UTFMax > len(s) {
// last char may be incomplete - ignore
break
}
if c == 0xFFFD || c < ' ' && c != '\n' && c != '\t' && c != '\f' {
// decoding error or control character - not a text file
return false
}
}
return true
}
// textExt[x] is true if the extension x indicates a text file, and false otherwise.
var textExt = map[string]bool{
".css": false, // must be served raw
".js": false, // must be served raw
".svg": false, // must be served raw
}
// IsTextFile reports whether the file has a known extension indicating
// a text file, or if a significant chunk of the specified file looks like
// correct UTF-8; that is, if it is likely that the file contains human-
// readable text.
func IsTextFile(fs vfs.Opener, filename string) bool {
// if the extension is known, use it for decision making
if isText, found := textExt[pathpkg.Ext(filename)]; found {
return isText
}
// the extension is not known; read an initial chunk
// of the file and check if it looks like text
f, err := fs.Open(filename)
if err != nil {
return false
}
defer f.Close()
var buf [1024]byte
n, err := f.Read(buf[0:])
if err != nil {
return false
}
return IsText(buf[0:n])
}
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