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// Copyright 2022 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.
// Code copied from
// https://github.com/golang/go/blob/2ebe77a2fda1ee9ff6fd9a3e08933ad1ebaea039/src/cmd/go/internal/web/url.go
// TODO(https://go.dev/issue/32456): if accepted, use the new API.
package web
import (
"errors"
"net/url"
"path/filepath"
"runtime"
"strings"
)
var errNotAbsolute = errors.New("path is not absolute")
// URLToFilePath converts a file-scheme url to a file path.
func URLToFilePath(u *url.URL) (string, error) {
if u.Scheme != "file" {
return "", errors.New("non-file URL")
}
checkAbs := func(path string) (string, error) {
if !filepath.IsAbs(path) {
return "", errNotAbsolute
}
return path, nil
}
if u.Path == "" {
if u.Host != "" || u.Opaque == "" {
return "", errors.New("file URL missing path")
}
return checkAbs(filepath.FromSlash(u.Opaque))
}
path, err := convertFileURLPath(u.Host, u.Path)
if err != nil {
return path, err
}
return checkAbs(path)
}
// URLFromFilePath converts the given absolute path to a URL.
func URLFromFilePath(path string) (*url.URL, error) {
if !filepath.IsAbs(path) {
return nil, errNotAbsolute
}
// If path has a Windows volume name, convert the volume to a host and prefix
// per https://blogs.msdn.microsoft.com/ie/2006/12/06/file-uris-in-windows/.
if vol := filepath.VolumeName(path); vol != "" {
if strings.HasPrefix(vol, `\\`) {
path = filepath.ToSlash(path[2:])
i := strings.IndexByte(path, '/')
if i < 0 {
// A degenerate case.
// \\host.example.com (without a share name)
// becomes
// file://host.example.com/
return &url.URL{
Scheme: "file",
Host: path,
Path: "/",
}, nil
}
// \\host.example.com\Share\path\to\file
// becomes
// file://host.example.com/Share/path/to/file
return &url.URL{
Scheme: "file",
Host: path[:i],
Path: filepath.ToSlash(path[i:]),
}, nil
}
// C:\path\to\file
// becomes
// file:///C:/path/to/file
return &url.URL{
Scheme: "file",
Path: "/" + filepath.ToSlash(path),
}, nil
}
// /path/to/file
// becomes
// file:///path/to/file
return &url.URL{
Scheme: "file",
Path: filepath.ToSlash(path),
}, nil
}
func convertFileURLPath(host, path string) (string, error) {
if runtime.GOOS == "windows" {
return convertFileURLPathWindows(host, path)
}
switch host {
case "", "localhost":
default:
return "", errors.New("file URL specifies non-local host")
}
return filepath.FromSlash(path), nil
}
func convertFileURLPathWindows(host, path string) (string, error) {
if len(path) == 0 || path[0] != '/' {
return "", errNotAbsolute
}
path = filepath.FromSlash(path)
// We interpret Windows file URLs per the description in
// https://blogs.msdn.microsoft.com/ie/2006/12/06/file-uris-in-windows/.
// The host part of a file URL (if any) is the UNC volume name,
// but RFC 8089 reserves the authority "localhost" for the local machine.
if host != "" && host != "localhost" {
// A common "legacy" format omits the leading slash before a drive letter,
// encoding the drive letter as the host instead of part of the path.
// (See https://blogs.msdn.microsoft.com/freeassociations/2005/05/19/the-bizarre-and-unhappy-story-of-file-urls/.)
// We do not support that format, but we should at least emit a more
// helpful error message for it.
if filepath.VolumeName(host) != "" {
return "", errors.New("file URL encodes volume in host field: too few slashes?")
}
return `\\` + host + path, nil
}
// If host is empty, path must contain an initial slash followed by a
// drive letter and path. Remove the slash and verify that the path is valid.
if vol := filepath.VolumeName(path[1:]); vol == "" || strings.HasPrefix(vol, `\\`) {
return "", errors.New("file URL missing drive letter")
}
return path[1:], nil
}
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