src

url.go (3968B)

---

 // 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
 }