64 строки
1.6 KiB
Go
64 строки
1.6 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package web
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import (
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"io/fs"
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"path"
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"strings"
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"unicode/utf8"
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)
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// isText reports whether a significant prefix of s looks like correct UTF-8;
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// that is, if it is likely that s is human-readable text.
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func isText(s []byte) bool {
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const max = 1024 // at least utf8.UTFMax
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if len(s) > max {
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s = s[0:max]
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}
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for i, c := range string(s) {
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if i+utf8.UTFMax > len(s) {
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// last char may be incomplete - ignore
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break
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}
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if c == 0xFFFD || c < ' ' && c != '\n' && c != '\t' && c != '\f' {
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// decoding error or control character - not a text file
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return false
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}
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}
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return true
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}
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// isTextFile reports whether the file has a known extension indicating
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// a text file, or if a significant chunk of the specified file looks like
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// correct UTF-8; that is, if it is likely that the file contains human-
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// readable text.
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func isTextFile(fsys fs.FS, filename string) bool {
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// Various special cases must be served raw, not converted to nice HTML.
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if filename == "robots.txt" || strings.HasPrefix(filename, "doc/play/") {
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return false
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}
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switch path.Ext(filename) {
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case ".css", ".js", ".svg", ".ts":
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return false
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}
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// the extension is not known; read an initial chunk
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// of the file and check if it looks like text
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f, err := fsys.Open(filename)
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if err != nil {
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return false
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}
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defer f.Close()
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var buf [1024]byte
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n, err := f.Read(buf[0:])
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if err != nil {
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return false
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}
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return isText(buf[0:n])
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}
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