Source file src/net/url/url.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:generate go run gen_encoding_table.go
     6  
     7  // Package url parses URLs and implements query escaping.
     8  //
     9  // See RFC 3986. This package generally follows RFC 3986, except where
    10  // it deviates for compatibility reasons.
    11  // RFC 6874 followed for IPv6 zone literals.
    12  package url
    13  
    14  // When sending changes, first  search old issues for history on decisions.
    15  // Unit tests should also contain references to issue numbers with details.
    16  
    17  import (
    18  	"bytes"
    19  	"errors"
    20  	"fmt"
    21  	"internal/godebug"
    22  	"net/netip"
    23  	"path"
    24  	"slices"
    25  	"strconv"
    26  	"strings"
    27  	_ "unsafe" // for linkname
    28  )
    29  
    30  var urlstrictcolons = godebug.New("urlstrictcolons")
    31  
    32  // Error reports an error and the operation and URL that caused it.
    33  type Error struct {
    34  	Op  string
    35  	URL string
    36  	Err error
    37  }
    38  
    39  func (e *Error) Unwrap() error { return e.Err }
    40  func (e *Error) Error() string { return fmt.Sprintf("%s %q: %s", e.Op, e.URL, e.Err) }
    41  
    42  func (e *Error) Timeout() bool {
    43  	t, ok := e.Err.(interface {
    44  		Timeout() bool
    45  	})
    46  	return ok && t.Timeout()
    47  }
    48  
    49  func (e *Error) Temporary() bool {
    50  	t, ok := e.Err.(interface {
    51  		Temporary() bool
    52  	})
    53  	return ok && t.Temporary()
    54  }
    55  
    56  const upperhex = "0123456789ABCDEF"
    57  
    58  func ishex(c byte) bool {
    59  	return table[c]&hexChar != 0
    60  }
    61  
    62  // Precondition: ishex(c) is true.
    63  func unhex(c byte) byte {
    64  	return 9*(c>>6) + (c & 15)
    65  }
    66  
    67  type EscapeError string
    68  
    69  func (e EscapeError) Error() string {
    70  	return "invalid URL escape " + strconv.Quote(string(e))
    71  }
    72  
    73  type InvalidHostError string
    74  
    75  func (e InvalidHostError) Error() string {
    76  	return "invalid character " + strconv.Quote(string(e)) + " in host name"
    77  }
    78  
    79  // See the reference implementation in gen_encoding_table.go.
    80  func shouldEscape(c byte, mode encoding) bool {
    81  	return table[c]&mode == 0
    82  }
    83  
    84  // QueryUnescape does the inverse transformation of [QueryEscape],
    85  // converting each 3-byte encoded substring of the form "%AB" into the
    86  // hex-decoded byte 0xAB.
    87  // It returns an error if any % is not followed by two hexadecimal
    88  // digits.
    89  func QueryUnescape(s string) (string, error) {
    90  	return unescape(s, encodeQueryComponent)
    91  }
    92  
    93  // PathUnescape does the inverse transformation of [PathEscape],
    94  // converting each 3-byte encoded substring of the form "%AB" into the
    95  // hex-decoded byte 0xAB. It returns an error if any % is not followed
    96  // by two hexadecimal digits.
    97  //
    98  // PathUnescape is identical to [QueryUnescape] except that it does not
    99  // unescape '+' to ' ' (space).
   100  func PathUnescape(s string) (string, error) {
   101  	return unescape(s, encodePathSegment)
   102  }
   103  
   104  // unescape unescapes a string; the mode specifies
   105  // which section of the URL string is being unescaped.
   106  func unescape(s string, mode encoding) (string, error) {
   107  	// Count %, check that they're well-formed.
   108  	n := 0
   109  	hasPlus := false
   110  	for i := 0; i < len(s); {
   111  		switch s[i] {
   112  		case '%':
   113  			n++
   114  			if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
   115  				s = s[i:]
   116  				if len(s) > 3 {
   117  					s = s[:3]
   118  				}
   119  				return "", EscapeError(s)
   120  			}
   121  			// Per https://tools.ietf.org/html/rfc3986#page-21
   122  			// in the host component %-encoding can only be used
   123  			// for non-ASCII bytes.
   124  			// But https://tools.ietf.org/html/rfc6874#section-2
   125  			// introduces %25 being allowed to escape a percent sign
   126  			// in IPv6 scoped-address literals. Yay.
   127  			if mode == encodeHost && unhex(s[i+1]) < 8 && s[i:i+3] != "%25" {
   128  				return "", EscapeError(s[i : i+3])
   129  			}
   130  			if mode == encodeZone {
   131  				// RFC 6874 says basically "anything goes" for zone identifiers
   132  				// and that even non-ASCII can be redundantly escaped,
   133  				// but it seems prudent to restrict %-escaped bytes here to those
   134  				// that are valid host name bytes in their unescaped form.
   135  				// That is, you can use escaping in the zone identifier but not
   136  				// to introduce bytes you couldn't just write directly.
   137  				// But Windows puts spaces here! Yay.
   138  				v := unhex(s[i+1])<<4 | unhex(s[i+2])
   139  				if s[i:i+3] != "%25" && v != ' ' && shouldEscape(v, encodeHost) {
   140  					return "", EscapeError(s[i : i+3])
   141  				}
   142  			}
   143  			i += 3
   144  		case '+':
   145  			hasPlus = mode == encodeQueryComponent
   146  			i++
   147  		default:
   148  			if (mode == encodeHost || mode == encodeZone) && s[i] < 0x80 && shouldEscape(s[i], mode) {
   149  				return "", InvalidHostError(s[i : i+1])
   150  			}
   151  			i++
   152  		}
   153  	}
   154  
   155  	if n == 0 && !hasPlus {
   156  		return s, nil
   157  	}
   158  
   159  	var unescapedPlusSign byte
   160  	switch mode {
   161  	case encodeQueryComponent:
   162  		unescapedPlusSign = ' '
   163  	default:
   164  		unescapedPlusSign = '+'
   165  	}
   166  	var t strings.Builder
   167  	t.Grow(len(s) - 2*n)
   168  	for i := 0; i < len(s); i++ {
   169  		switch s[i] {
   170  		case '%':
   171  			// In the loop above, we established that unhex's precondition is
   172  			// fulfilled for both s[i+1] and s[i+2].
   173  			t.WriteByte(unhex(s[i+1])<<4 | unhex(s[i+2]))
   174  			i += 2
   175  		case '+':
   176  			t.WriteByte(unescapedPlusSign)
   177  		default:
   178  			t.WriteByte(s[i])
   179  		}
   180  	}
   181  	return t.String(), nil
   182  }
   183  
   184  // QueryEscape escapes the string so it can be safely placed
   185  // inside a [URL] query.
   186  func QueryEscape(s string) string {
   187  	return escape(s, encodeQueryComponent)
   188  }
   189  
   190  // PathEscape escapes the string so it can be safely placed inside a [URL] path segment,
   191  // replacing special characters (including /) with %XX sequences as needed.
   192  func PathEscape(s string) string {
   193  	return escape(s, encodePathSegment)
   194  }
   195  
   196  func escape(s string, mode encoding) string {
   197  	spaceCount, hexCount := 0, 0
   198  	for _, c := range []byte(s) {
   199  		if shouldEscape(c, mode) {
   200  			if c == ' ' && mode == encodeQueryComponent {
   201  				spaceCount++
   202  			} else {
   203  				hexCount++
   204  			}
   205  		}
   206  	}
   207  
   208  	if spaceCount == 0 && hexCount == 0 {
   209  		return s
   210  	}
   211  
   212  	var buf [64]byte
   213  	var t []byte
   214  
   215  	required := len(s) + 2*hexCount
   216  	if required <= len(buf) {
   217  		t = buf[:required]
   218  	} else {
   219  		t = make([]byte, required)
   220  	}
   221  
   222  	if hexCount == 0 {
   223  		copy(t, s)
   224  		for i := 0; i < len(s); i++ {
   225  			if s[i] == ' ' {
   226  				t[i] = '+'
   227  			}
   228  		}
   229  		return string(t)
   230  	}
   231  
   232  	j := 0
   233  	for _, c := range []byte(s) {
   234  		switch {
   235  		case c == ' ' && mode == encodeQueryComponent:
   236  			t[j] = '+'
   237  			j++
   238  		case shouldEscape(c, mode):
   239  			t[j] = '%'
   240  			t[j+1] = upperhex[c>>4]
   241  			t[j+2] = upperhex[c&15]
   242  			j += 3
   243  		default:
   244  			t[j] = c
   245  			j++
   246  		}
   247  	}
   248  	return string(t)
   249  }
   250  
   251  // A URL represents a parsed URL (technically, a URI reference).
   252  //
   253  // The general form represented is:
   254  //
   255  //	[scheme:][//[userinfo@]host][/]path[?query][#fragment]
   256  //
   257  // URLs that do not start with a slash after the scheme are interpreted as:
   258  //
   259  //	scheme:opaque[?query][#fragment]
   260  //
   261  // The Host field contains the host and port subcomponents of the URL.
   262  // When the port is present, it is separated from the host with a colon.
   263  // When the host is an IPv6 address, it must be enclosed in square brackets:
   264  // "[fe80::1]:80". The [net.JoinHostPort] function combines a host and port
   265  // into a string suitable for the Host field, adding square brackets to
   266  // the host when necessary.
   267  //
   268  // Note that the Path field is stored in decoded form: /%47%6f%2f becomes /Go/.
   269  // A consequence is that it is impossible to tell which slashes in the Path were
   270  // slashes in the raw URL and which were %2f. This distinction is rarely important,
   271  // but when it is, the code should use the [URL.EscapedPath] method, which preserves
   272  // the original encoding of Path. The Fragment field is also stored in decoded form,
   273  // use [URL.EscapedFragment] to retrieve the original encoding.
   274  //
   275  // The [URL.String] method uses the [URL.EscapedPath] method to obtain the path.
   276  type URL struct {
   277  	Scheme   string
   278  	Opaque   string    // encoded opaque data
   279  	User     *Userinfo // username and password information
   280  	Host     string    // "host" or "host:port" (see Hostname and Port methods)
   281  	Path     string    // path (relative paths may omit leading slash)
   282  	Fragment string    // fragment for references (without '#')
   283  
   284  	// RawQuery contains the encoded query values, without the initial '?'.
   285  	// Use URL.Query to decode the query.
   286  	RawQuery string
   287  
   288  	// RawPath is an optional field containing an encoded path hint.
   289  	// See the EscapedPath method for more details.
   290  	//
   291  	// In general, code should call EscapedPath instead of reading RawPath.
   292  	RawPath string
   293  
   294  	// RawFragment is an optional field containing an encoded fragment hint.
   295  	// See the EscapedFragment method for more details.
   296  	//
   297  	// In general, code should call EscapedFragment instead of reading RawFragment.
   298  	RawFragment string
   299  
   300  	// ForceQuery indicates whether the original URL contained a query ('?') character.
   301  	// When set, the String method will include a trailing '?', even when RawQuery is empty.
   302  	ForceQuery bool
   303  
   304  	// OmitHost indicates the URL has an empty host (authority).
   305  	// When set, the String method will not include the host when it is empty.
   306  	OmitHost bool
   307  }
   308  
   309  // User returns a [Userinfo] containing the provided username
   310  // and no password set.
   311  func User(username string) *Userinfo {
   312  	return &Userinfo{username, "", false}
   313  }
   314  
   315  // UserPassword returns a [Userinfo] containing the provided username
   316  // and password.
   317  //
   318  // This functionality should only be used with legacy web sites.
   319  // RFC 2396 warns that interpreting Userinfo this way
   320  // “is NOT RECOMMENDED, because the passing of authentication
   321  // information in clear text (such as URI) has proven to be a
   322  // security risk in almost every case where it has been used.”
   323  func UserPassword(username, password string) *Userinfo {
   324  	return &Userinfo{username, password, true}
   325  }
   326  
   327  // The Userinfo type is an immutable encapsulation of username and
   328  // password details for a [URL]. An existing Userinfo value is guaranteed
   329  // to have a username set (potentially empty, as allowed by RFC 2396),
   330  // and optionally a password.
   331  type Userinfo struct {
   332  	username    string
   333  	password    string
   334  	passwordSet bool
   335  }
   336  
   337  // Username returns the username.
   338  func (u *Userinfo) Username() string {
   339  	if u == nil {
   340  		return ""
   341  	}
   342  	return u.username
   343  }
   344  
   345  // Password returns the password in case it is set, and whether it is set.
   346  func (u *Userinfo) Password() (string, bool) {
   347  	if u == nil {
   348  		return "", false
   349  	}
   350  	return u.password, u.passwordSet
   351  }
   352  
   353  // String returns the encoded userinfo information in the standard form
   354  // of "username[:password]".
   355  func (u *Userinfo) String() string {
   356  	if u == nil {
   357  		return ""
   358  	}
   359  	s := escape(u.username, encodeUserPassword)
   360  	if u.passwordSet {
   361  		s += ":" + escape(u.password, encodeUserPassword)
   362  	}
   363  	return s
   364  }
   365  
   366  // Maybe rawURL is of the form scheme:path.
   367  // (Scheme must be [a-zA-Z][a-zA-Z0-9+.-]*)
   368  // If so, return scheme, path; else return "", rawURL.
   369  func getScheme(rawURL string) (scheme, path string, err error) {
   370  	for i := 0; i < len(rawURL); i++ {
   371  		c := rawURL[i]
   372  		switch {
   373  		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
   374  		// do nothing
   375  		case '0' <= c && c <= '9' || c == '+' || c == '-' || c == '.':
   376  			if i == 0 {
   377  				return "", rawURL, nil
   378  			}
   379  		case c == ':':
   380  			if i == 0 {
   381  				return "", "", errors.New("missing protocol scheme")
   382  			}
   383  			return rawURL[:i], rawURL[i+1:], nil
   384  		default:
   385  			// we have encountered an invalid character,
   386  			// so there is no valid scheme
   387  			return "", rawURL, nil
   388  		}
   389  	}
   390  	return "", rawURL, nil
   391  }
   392  
   393  // Parse parses a raw url into a [URL] structure.
   394  //
   395  // The url may be relative (a path, without a host) or absolute
   396  // (starting with a scheme). Trying to parse a hostname and path
   397  // without a scheme is invalid but may not necessarily return an
   398  // error, due to parsing ambiguities.
   399  func Parse(rawURL string) (*URL, error) {
   400  	// Cut off #frag
   401  	u, frag, _ := strings.Cut(rawURL, "#")
   402  	url, err := parse(u, false)
   403  	if err != nil {
   404  		return nil, &Error{"parse", u, err}
   405  	}
   406  	if frag == "" {
   407  		return url, nil
   408  	}
   409  	if err = url.setFragment(frag); err != nil {
   410  		return nil, &Error{"parse", rawURL, err}
   411  	}
   412  	return url, nil
   413  }
   414  
   415  // MustParse calls [Parse](rawURL) and panics on error.
   416  // It is intended for use with hard-coded strings representing valid urls.
   417  func MustParse(rawURL string) *URL {
   418  	url, err := Parse(rawURL)
   419  	if err != nil {
   420  		panic(err)
   421  	}
   422  	return url
   423  }
   424  
   425  // ParseRequestURI parses a raw url into a [URL] structure. It assumes that
   426  // url was received in an HTTP request, so the url is interpreted
   427  // only as an absolute URI or an absolute path.
   428  // The string url is assumed not to have a #fragment suffix.
   429  // (Web browsers strip #fragment before sending the URL to a web server.)
   430  func ParseRequestURI(rawURL string) (*URL, error) {
   431  	url, err := parse(rawURL, true)
   432  	if err != nil {
   433  		return nil, &Error{"parse", rawURL, err}
   434  	}
   435  	return url, nil
   436  }
   437  
   438  // parse parses a URL from a string in one of two contexts. If
   439  // viaRequest is true, the URL is assumed to have arrived via an HTTP request,
   440  // in which case only absolute URLs or path-absolute relative URLs are allowed.
   441  // If viaRequest is false, all forms of relative URLs are allowed.
   442  func parse(rawURL string, viaRequest bool) (*URL, error) {
   443  	var rest string
   444  	var err error
   445  
   446  	if stringContainsCTLByte(rawURL) {
   447  		return nil, errors.New("net/url: invalid control character in URL")
   448  	}
   449  
   450  	if rawURL == "" && viaRequest {
   451  		return nil, errors.New("empty url")
   452  	}
   453  	url := new(URL)
   454  
   455  	if rawURL == "*" {
   456  		url.Path = "*"
   457  		return url, nil
   458  	}
   459  
   460  	// Split off possible leading "http:", "mailto:", etc.
   461  	// Cannot contain escaped characters.
   462  	if url.Scheme, rest, err = getScheme(rawURL); err != nil {
   463  		return nil, err
   464  	}
   465  	url.Scheme = strings.ToLower(url.Scheme)
   466  
   467  	if strings.HasSuffix(rest, "?") && strings.Count(rest, "?") == 1 {
   468  		url.ForceQuery = true
   469  		rest = rest[:len(rest)-1]
   470  	} else {
   471  		rest, url.RawQuery, _ = strings.Cut(rest, "?")
   472  	}
   473  
   474  	if !strings.HasPrefix(rest, "/") {
   475  		if url.Scheme != "" {
   476  			// We consider rootless paths per RFC 3986 as opaque.
   477  			url.Opaque = rest
   478  			return url, nil
   479  		}
   480  		if viaRequest {
   481  			return nil, errors.New("invalid URI for request")
   482  		}
   483  
   484  		// Avoid confusion with malformed schemes, like cache_object:foo/bar.
   485  		// See golang.org/issue/16822.
   486  		//
   487  		// RFC 3986, §3.3:
   488  		// In addition, a URI reference (Section 4.1) may be a relative-path reference,
   489  		// in which case the first path segment cannot contain a colon (":") character.
   490  		if segment, _, _ := strings.Cut(rest, "/"); strings.Contains(segment, ":") {
   491  			// First path segment has colon. Not allowed in relative URL.
   492  			return nil, errors.New("first path segment in URL cannot contain colon")
   493  		}
   494  	}
   495  
   496  	if (url.Scheme != "" || !viaRequest && !strings.HasPrefix(rest, "///")) && strings.HasPrefix(rest, "//") {
   497  		var authority string
   498  		authority, rest = rest[2:], ""
   499  		if i := strings.Index(authority, "/"); i >= 0 {
   500  			authority, rest = authority[:i], authority[i:]
   501  		}
   502  		url.User, url.Host, err = parseAuthority(url.Scheme, authority)
   503  		if err != nil {
   504  			return nil, err
   505  		}
   506  	} else if url.Scheme != "" && strings.HasPrefix(rest, "/") {
   507  		// OmitHost is set to true when rawURL has an empty host (authority).
   508  		// See golang.org/issue/46059.
   509  		url.OmitHost = true
   510  	}
   511  
   512  	// Set Path and, optionally, RawPath.
   513  	// RawPath is a hint of the encoding of Path. We don't want to set it if
   514  	// the default escaping of Path is equivalent, to help make sure that people
   515  	// don't rely on it in general.
   516  	if err := url.setPath(rest); err != nil {
   517  		return nil, err
   518  	}
   519  	return url, nil
   520  }
   521  
   522  func parseAuthority(scheme, authority string) (user *Userinfo, host string, err error) {
   523  	i := strings.LastIndex(authority, "@")
   524  	if i < 0 {
   525  		host, err = parseHost(scheme, authority)
   526  	} else {
   527  		host, err = parseHost(scheme, authority[i+1:])
   528  	}
   529  	if err != nil {
   530  		return nil, "", err
   531  	}
   532  	if i < 0 {
   533  		return nil, host, nil
   534  	}
   535  	userinfo := authority[:i]
   536  	if !validUserinfo(userinfo) {
   537  		return nil, "", errors.New("net/url: invalid userinfo")
   538  	}
   539  	if !strings.Contains(userinfo, ":") {
   540  		if userinfo, err = unescape(userinfo, encodeUserPassword); err != nil {
   541  			return nil, "", err
   542  		}
   543  		user = User(userinfo)
   544  	} else {
   545  		username, password, _ := strings.Cut(userinfo, ":")
   546  		if username, err = unescape(username, encodeUserPassword); err != nil {
   547  			return nil, "", err
   548  		}
   549  		if password, err = unescape(password, encodeUserPassword); err != nil {
   550  			return nil, "", err
   551  		}
   552  		user = UserPassword(username, password)
   553  	}
   554  	return user, host, nil
   555  }
   556  
   557  // parseHost parses host as an authority without user
   558  // information. That is, as host[:port].
   559  func parseHost(scheme, host string) (string, error) {
   560  	if openBracketIdx := strings.LastIndex(host, "["); openBracketIdx > 0 {
   561  		return "", errors.New("invalid IP-literal")
   562  	} else if openBracketIdx == 0 {
   563  		// Parse an IP-Literal in RFC 3986 and RFC 6874.
   564  		// E.g., "[fe80::1]", "[fe80::1%25en0]", "[fe80::1]:80".
   565  		closeBracketIdx := strings.LastIndex(host, "]")
   566  		if closeBracketIdx < 0 {
   567  			return "", errors.New("missing ']' in host")
   568  		}
   569  
   570  		colonPort := host[closeBracketIdx+1:]
   571  		if !validOptionalPort(colonPort) {
   572  			return "", fmt.Errorf("invalid port %q after host", colonPort)
   573  		}
   574  		unescapedColonPort, err := unescape(colonPort, encodeHost)
   575  		if err != nil {
   576  			return "", err
   577  		}
   578  
   579  		hostname := host[openBracketIdx+1 : closeBracketIdx]
   580  		var unescapedHostname string
   581  		// RFC 6874 defines that %25 (%-encoded percent) introduces
   582  		// the zone identifier, and the zone identifier can use basically
   583  		// any %-encoding it likes. That's different from the host, which
   584  		// can only %-encode non-ASCII bytes.
   585  		// We do impose some restrictions on the zone, to avoid stupidity
   586  		// like newlines.
   587  		zoneIdx := strings.Index(hostname, "%25")
   588  		if zoneIdx >= 0 {
   589  			hostPart, err := unescape(hostname[:zoneIdx], encodeHost)
   590  			if err != nil {
   591  				return "", err
   592  			}
   593  			zonePart, err := unescape(hostname[zoneIdx:], encodeZone)
   594  			if err != nil {
   595  				return "", err
   596  			}
   597  			unescapedHostname = hostPart + zonePart
   598  		} else {
   599  			var err error
   600  			unescapedHostname, err = unescape(hostname, encodeHost)
   601  			if err != nil {
   602  				return "", err
   603  			}
   604  		}
   605  
   606  		// Per RFC 3986, only a host identified by a valid
   607  		// IPv6 address can be enclosed by square brackets.
   608  		// This excludes any IPv4, but notably not IPv4-mapped addresses.
   609  		addr, err := netip.ParseAddr(unescapedHostname)
   610  		if err != nil {
   611  			return "", fmt.Errorf("invalid host: %w", err)
   612  		}
   613  		if addr.Is4() {
   614  			return "", errors.New("invalid IP-literal")
   615  		}
   616  		return "[" + unescapedHostname + "]" + unescapedColonPort, nil
   617  	} else if i := strings.Index(host, ":"); i != -1 {
   618  		lastColon := strings.LastIndex(host, ":")
   619  		if lastColon != i {
   620  			// RFC 3986 does not allow colons to appear in the host subcomponent.
   621  			//
   622  			// However, a number of databases including PostgreSQL and MongoDB
   623  			// permit a comma-separated list of hosts (with optional ports) in the
   624  			// host subcomponent.
   625  			//
   626  			// Since we historically permitted colons to appear in the host,
   627  			// enforce strict colons only for http and https URLs.
   628  			//
   629  			// See https://go.dev/issue/75223 and https://go.dev/issue/78077.
   630  			if scheme == "http" || scheme == "https" {
   631  				if urlstrictcolons.Value() == "0" {
   632  					urlstrictcolons.IncNonDefault()
   633  					i = lastColon
   634  				}
   635  			} else {
   636  				i = lastColon
   637  			}
   638  		}
   639  		colonPort := host[i:]
   640  		if !validOptionalPort(colonPort) {
   641  			return "", fmt.Errorf("invalid port %q after host", colonPort)
   642  		}
   643  	}
   644  
   645  	var err error
   646  	if host, err = unescape(host, encodeHost); err != nil {
   647  		return "", err
   648  	}
   649  	return host, nil
   650  }
   651  
   652  // setPath sets the Path and RawPath fields of the URL based on the provided
   653  // escaped path p. It maintains the invariant that RawPath is only specified
   654  // when it differs from the default encoding of the path.
   655  // For example:
   656  // - setPath("/foo/bar")   will set Path="/foo/bar" and RawPath=""
   657  // - setPath("/foo%2fbar") will set Path="/foo/bar" and RawPath="/foo%2fbar"
   658  // setPath will return an error only if the provided path contains an invalid
   659  // escaping.
   660  //
   661  // setPath should be an internal detail,
   662  // but widely used packages access it using linkname.
   663  // Notable members of the hall of shame include:
   664  //   - github.com/sagernet/sing
   665  //
   666  // Do not remove or change the type signature.
   667  // See go.dev/issue/67401.
   668  //
   669  //go:linkname badSetPath net/url.(*URL).setPath
   670  func (u *URL) setPath(p string) error {
   671  	path, err := unescape(p, encodePath)
   672  	if err != nil {
   673  		return err
   674  	}
   675  	u.Path = path
   676  	if escp := escape(path, encodePath); p == escp {
   677  		// Default encoding is fine.
   678  		u.RawPath = ""
   679  	} else {
   680  		u.RawPath = p
   681  	}
   682  	return nil
   683  }
   684  
   685  // for linkname because we cannot linkname methods directly
   686  func badSetPath(*URL, string) error
   687  
   688  // EscapedPath returns the escaped form of u.Path.
   689  // In general there are multiple possible escaped forms of any path.
   690  // EscapedPath returns u.RawPath when it is a valid escaping of u.Path.
   691  // Otherwise EscapedPath ignores u.RawPath and computes an escaped
   692  // form on its own.
   693  // The [URL.String] and [URL.RequestURI] methods use EscapedPath to construct
   694  // their results.
   695  // In general, code should call EscapedPath instead of
   696  // reading u.RawPath directly.
   697  func (u *URL) EscapedPath() string {
   698  	if u.RawPath != "" && validEncoded(u.RawPath, encodePath) {
   699  		p, err := unescape(u.RawPath, encodePath)
   700  		if err == nil && p == u.Path {
   701  			return u.RawPath
   702  		}
   703  	}
   704  	if u.Path == "*" {
   705  		return "*" // don't escape (Issue 11202)
   706  	}
   707  	return escape(u.Path, encodePath)
   708  }
   709  
   710  // validEncoded reports whether s is a valid encoded path or fragment,
   711  // according to mode.
   712  // It must not contain any bytes that require escaping during encoding.
   713  func validEncoded(s string, mode encoding) bool {
   714  	for i := 0; i < len(s); i++ {
   715  		// RFC 3986, Appendix A.
   716  		// pchar = unreserved / pct-encoded / sub-delims / ":" / "@".
   717  		// shouldEscape is not quite compliant with the RFC,
   718  		// so we check the sub-delims ourselves and let
   719  		// shouldEscape handle the others.
   720  		switch s[i] {
   721  		case '!', '$', '&', '\'', '(', ')', '*', '+', ',', ';', '=', ':', '@':
   722  			// ok
   723  		case '[', ']':
   724  			// ok - not specified in RFC 3986 but left alone by modern browsers
   725  		case '%':
   726  			// ok - percent encoded, will decode
   727  		default:
   728  			if shouldEscape(s[i], mode) {
   729  				return false
   730  			}
   731  		}
   732  	}
   733  	return true
   734  }
   735  
   736  // setFragment is like setPath but for Fragment/RawFragment.
   737  func (u *URL) setFragment(f string) error {
   738  	frag, err := unescape(f, encodeFragment)
   739  	if err != nil {
   740  		return err
   741  	}
   742  	u.Fragment = frag
   743  	if escf := escape(frag, encodeFragment); f == escf {
   744  		// Default encoding is fine.
   745  		u.RawFragment = ""
   746  	} else {
   747  		u.RawFragment = f
   748  	}
   749  	return nil
   750  }
   751  
   752  // EscapedFragment returns the escaped form of u.Fragment.
   753  // In general there are multiple possible escaped forms of any fragment.
   754  // EscapedFragment returns u.RawFragment when it is a valid escaping of u.Fragment.
   755  // Otherwise EscapedFragment ignores u.RawFragment and computes an escaped
   756  // form on its own.
   757  // The [URL.String] method uses EscapedFragment to construct its result.
   758  // In general, code should call EscapedFragment instead of
   759  // reading u.RawFragment directly.
   760  func (u *URL) EscapedFragment() string {
   761  	if u.RawFragment != "" && validEncoded(u.RawFragment, encodeFragment) {
   762  		f, err := unescape(u.RawFragment, encodeFragment)
   763  		if err == nil && f == u.Fragment {
   764  			return u.RawFragment
   765  		}
   766  	}
   767  	return escape(u.Fragment, encodeFragment)
   768  }
   769  
   770  // validOptionalPort reports whether port is either an empty string
   771  // or matches /^:\d*$/
   772  func validOptionalPort(port string) bool {
   773  	if port == "" {
   774  		return true
   775  	}
   776  	if port[0] != ':' {
   777  		return false
   778  	}
   779  	for _, b := range port[1:] {
   780  		if b < '0' || b > '9' {
   781  			return false
   782  		}
   783  	}
   784  	return true
   785  }
   786  
   787  // String reassembles the [URL] into a valid URL string.
   788  // The general form of the result is one of:
   789  //
   790  //	scheme:opaque?query#fragment
   791  //	scheme://userinfo@host/path?query#fragment
   792  //
   793  // If u.Opaque is non-empty, String uses the first form;
   794  // otherwise it uses the second form.
   795  // Any non-ASCII characters in host are escaped.
   796  // To obtain the path, String uses u.EscapedPath().
   797  //
   798  // In the second form, the following rules apply:
   799  //   - if u.Scheme is empty, scheme: is omitted.
   800  //   - if u.User is nil, userinfo@ is omitted.
   801  //   - if u.Host is empty, host/ is omitted.
   802  //   - if u.Scheme and u.Host are empty and u.User is nil,
   803  //     the entire scheme://userinfo@host/ is omitted.
   804  //   - if u.Host is non-empty and u.Path begins with a /,
   805  //     the form host/path does not add its own /.
   806  //   - if u.RawQuery is empty, ?query is omitted.
   807  //   - if u.Fragment is empty, #fragment is omitted.
   808  func (u *URL) String() string {
   809  	var buf strings.Builder
   810  
   811  	n := len(u.Scheme)
   812  	if u.Opaque != "" {
   813  		n += len(u.Opaque)
   814  	} else {
   815  		if !u.OmitHost && (u.Scheme != "" || u.Host != "" || u.User != nil) {
   816  			username := u.User.Username()
   817  			password, _ := u.User.Password()
   818  			n += len(username) + len(password) + len(u.Host)
   819  		}
   820  		n += len(u.Path)
   821  	}
   822  	n += len(u.RawQuery) + len(u.RawFragment)
   823  	n += len(":" + "//" + "//" + ":" + "@" + "/" + "./" + "?" + "#")
   824  	buf.Grow(n)
   825  
   826  	if u.Scheme != "" {
   827  		buf.WriteString(u.Scheme)
   828  		buf.WriteByte(':')
   829  	}
   830  	if u.Opaque != "" {
   831  		buf.WriteString(u.Opaque)
   832  	} else {
   833  		if u.Scheme != "" || u.Host != "" || u.User != nil {
   834  			if u.OmitHost && u.Host == "" && u.User == nil {
   835  				// omit empty host
   836  			} else {
   837  				if u.Host != "" || u.Path != "" || u.User != nil {
   838  					buf.WriteString("//")
   839  				}
   840  				if ui := u.User; ui != nil {
   841  					buf.WriteString(ui.String())
   842  					buf.WriteByte('@')
   843  				}
   844  				if h := u.Host; h != "" {
   845  					buf.WriteString(escape(h, encodeHost))
   846  				}
   847  			}
   848  		}
   849  		path := u.EscapedPath()
   850  		if u.OmitHost && u.Host == "" && u.User == nil && strings.HasPrefix(path, "//") {
   851  			// Escape the first / in a path starting with "//" and no authority
   852  			// so that re-parsing the URL doesn't turn the path into an authority
   853  			// (e.g., Path="//host/p" producing "http://host/p").
   854  			buf.WriteString("%2F")
   855  			path = path[1:]
   856  		}
   857  		if path != "" && path[0] != '/' && u.Host != "" {
   858  			buf.WriteByte('/')
   859  		}
   860  		if buf.Len() == 0 {
   861  			// RFC 3986 §4.2
   862  			// A path segment that contains a colon character (e.g., "this:that")
   863  			// cannot be used as the first segment of a relative-path reference, as
   864  			// it would be mistaken for a scheme name. Such a segment must be
   865  			// preceded by a dot-segment (e.g., "./this:that") to make a relative-
   866  			// path reference.
   867  			if segment, _, _ := strings.Cut(path, "/"); strings.Contains(segment, ":") {
   868  				buf.WriteString("./")
   869  			}
   870  		}
   871  		buf.WriteString(path)
   872  	}
   873  	if u.ForceQuery || u.RawQuery != "" {
   874  		buf.WriteByte('?')
   875  		buf.WriteString(u.RawQuery)
   876  	}
   877  	if u.Fragment != "" {
   878  		buf.WriteByte('#')
   879  		buf.WriteString(u.EscapedFragment())
   880  	}
   881  	return buf.String()
   882  }
   883  
   884  // Redacted is like [URL.String] but replaces any password with "xxxxx".
   885  // Only the password in u.User is redacted.
   886  func (u *URL) Redacted() string {
   887  	if u == nil {
   888  		return ""
   889  	}
   890  
   891  	ru := *u
   892  	if _, has := ru.User.Password(); has {
   893  		ru.User = UserPassword(ru.User.Username(), "xxxxx")
   894  	}
   895  	return ru.String()
   896  }
   897  
   898  // Values maps a string key to a list of values.
   899  // It is typically used for query parameters and form values.
   900  // Unlike in the http.Header map, the keys in a Values map
   901  // are case-sensitive.
   902  type Values map[string][]string
   903  
   904  // Get gets the first value associated with the given key.
   905  // If there are no values associated with the key, Get returns
   906  // the empty string. To access multiple values, use the map
   907  // directly.
   908  func (v Values) Get(key string) string {
   909  	vs := v[key]
   910  	if len(vs) == 0 {
   911  		return ""
   912  	}
   913  	return vs[0]
   914  }
   915  
   916  // Set sets the key to value. It replaces any existing
   917  // values.
   918  func (v Values) Set(key, value string) {
   919  	v[key] = []string{value}
   920  }
   921  
   922  // Add adds the value to key. It appends to any existing
   923  // values associated with key.
   924  func (v Values) Add(key, value string) {
   925  	v[key] = append(v[key], value)
   926  }
   927  
   928  // Del deletes the values associated with key.
   929  func (v Values) Del(key string) {
   930  	delete(v, key)
   931  }
   932  
   933  // Has checks whether a given key is set.
   934  func (v Values) Has(key string) bool {
   935  	_, ok := v[key]
   936  	return ok
   937  }
   938  
   939  // Clone creates a deep copy of the subject [Values].
   940  func (vs Values) Clone() Values {
   941  	if vs == nil {
   942  		return nil
   943  	}
   944  
   945  	newVals := make(Values, len(vs))
   946  	for k, v := range vs {
   947  		newVals[k] = slices.Clone(v)
   948  	}
   949  	return newVals
   950  }
   951  
   952  // ParseQuery parses the URL-encoded query string and returns
   953  // a map listing the values specified for each key.
   954  // ParseQuery always returns a non-nil map containing all the
   955  // valid query parameters found; err describes the first decoding error
   956  // encountered, if any.
   957  //
   958  // Query is expected to be a list of key=value settings separated by ampersands.
   959  // A setting without an equals sign is interpreted as a key set to an empty
   960  // value.
   961  // Settings containing a non-URL-encoded semicolon are considered invalid.
   962  func ParseQuery(query string) (Values, error) {
   963  	m := make(Values)
   964  	err := parseQuery(m, query)
   965  	return m, err
   966  }
   967  
   968  var urlmaxqueryparams = godebug.New("urlmaxqueryparams")
   969  
   970  // Keep this in sync with net/http/httputil.
   971  const defaultMaxParams = 10000
   972  
   973  func urlParamsWithinMax(params int) bool {
   974  	withinDefaultMax := params <= defaultMaxParams
   975  	if urlmaxqueryparams.Value() == "" {
   976  		return withinDefaultMax
   977  	}
   978  	customMax, err := strconv.Atoi(urlmaxqueryparams.Value())
   979  	if err != nil {
   980  		return withinDefaultMax
   981  	}
   982  	withinCustomMax := customMax == 0 || params < customMax
   983  	if withinDefaultMax != withinCustomMax {
   984  		urlmaxqueryparams.IncNonDefault()
   985  	}
   986  	return withinCustomMax
   987  }
   988  
   989  func parseQuery(m Values, query string) (err error) {
   990  	if !urlParamsWithinMax(strings.Count(query, "&") + 1) {
   991  		return errors.New("number of URL query parameters exceeded limit")
   992  	}
   993  	for query != "" {
   994  		var key string
   995  		key, query, _ = strings.Cut(query, "&")
   996  		if strings.Contains(key, ";") {
   997  			err = fmt.Errorf("invalid semicolon separator in query")
   998  			continue
   999  		}
  1000  		if key == "" {
  1001  			continue
  1002  		}
  1003  		key, value, _ := strings.Cut(key, "=")
  1004  		key, err1 := QueryUnescape(key)
  1005  		if err1 != nil {
  1006  			if err == nil {
  1007  				err = err1
  1008  			}
  1009  			continue
  1010  		}
  1011  		value, err1 = QueryUnescape(value)
  1012  		if err1 != nil {
  1013  			if err == nil {
  1014  				err = err1
  1015  			}
  1016  			continue
  1017  		}
  1018  		m[key] = append(m[key], value)
  1019  	}
  1020  	return err
  1021  }
  1022  
  1023  // Encode encodes the values into “URL encoded” form
  1024  // ("bar=baz&foo=quux") sorted by key.
  1025  func (v Values) Encode() string {
  1026  	if len(v) == 0 {
  1027  		return ""
  1028  	}
  1029  	var buf strings.Builder
  1030  	// To minimize allocations, we eschew iterators and pre-size the slice in
  1031  	// which we collect v's keys.
  1032  	keys := make([]string, len(v))
  1033  	var i int
  1034  	for k := range v {
  1035  		keys[i] = k
  1036  		i++
  1037  	}
  1038  	slices.Sort(keys)
  1039  	for _, k := range keys {
  1040  		vs := v[k]
  1041  		keyEscaped := QueryEscape(k)
  1042  		for _, v := range vs {
  1043  			if buf.Len() > 0 {
  1044  				buf.WriteByte('&')
  1045  			}
  1046  			buf.WriteString(keyEscaped)
  1047  			buf.WriteByte('=')
  1048  			buf.WriteString(QueryEscape(v))
  1049  		}
  1050  	}
  1051  	return buf.String()
  1052  }
  1053  
  1054  // resolvePath applies special path segments from refs and applies
  1055  // them to base, per RFC 3986.
  1056  func resolvePath(base, ref string) string {
  1057  	var full string
  1058  	if ref == "" {
  1059  		full = base
  1060  	} else if ref[0] != '/' {
  1061  		i := strings.LastIndex(base, "/")
  1062  		full = base[:i+1] + ref
  1063  	} else {
  1064  		full = ref
  1065  	}
  1066  	if full == "" {
  1067  		return ""
  1068  	}
  1069  
  1070  	dst := make([]byte, 0, len(full)+1)
  1071  	dst = append(dst, '/')
  1072  	elem := ""
  1073  	remaining := full
  1074  	found := true
  1075  	first := true
  1076  	for found {
  1077  		elem, remaining, found = strings.Cut(remaining, "/")
  1078  		switch elem {
  1079  		case ".":
  1080  			first = false
  1081  			continue
  1082  		case "..":
  1083  			if i := bytes.LastIndexByte(dst[1:], '/'); i >= 0 {
  1084  				dst = dst[:i+1]
  1085  			} else {
  1086  				dst = dst[:1]
  1087  			}
  1088  			first = len(dst) == 1
  1089  		default:
  1090  			if !first {
  1091  				dst = append(dst, '/')
  1092  			}
  1093  			dst = append(dst, elem...)
  1094  			first = false
  1095  		}
  1096  	}
  1097  
  1098  	if elem == "." || elem == ".." {
  1099  		dst = append(dst, '/')
  1100  	}
  1101  
  1102  	// We wrote an initial '/', but we don't want two.
  1103  	if len(dst) > 1 && dst[1] == '/' {
  1104  		return string(dst[1:])
  1105  	}
  1106  	return string(dst)
  1107  }
  1108  
  1109  // IsAbs reports whether the [URL] is absolute.
  1110  // Absolute means that it has a non-empty scheme.
  1111  func (u *URL) IsAbs() bool {
  1112  	return u.Scheme != ""
  1113  }
  1114  
  1115  // Parse parses a [URL] in the context of the receiver. The provided URL
  1116  // may be relative or absolute. Parse returns nil, err on parse
  1117  // failure, otherwise its return value is the same as [URL.ResolveReference].
  1118  func (u *URL) Parse(ref string) (*URL, error) {
  1119  	refURL, err := Parse(ref)
  1120  	if err != nil {
  1121  		return nil, err
  1122  	}
  1123  	return u.ResolveReference(refURL), nil
  1124  }
  1125  
  1126  // ResolveReference resolves a URI reference to an absolute URI from
  1127  // an absolute base URI u, per RFC 3986 Section 5.2. The URI reference
  1128  // may be relative or absolute. ResolveReference always returns a new
  1129  // [URL] instance, even if the returned URL is identical to either the
  1130  // base or reference. If ref is an absolute URL, then ResolveReference
  1131  // ignores base and returns a copy of ref.
  1132  func (u *URL) ResolveReference(ref *URL) *URL {
  1133  	url := *ref
  1134  	if ref.Scheme == "" {
  1135  		url.Scheme = u.Scheme
  1136  	}
  1137  	if ref.Scheme != "" || ref.Host != "" || ref.User != nil {
  1138  		// The "absoluteURI" or "net_path" cases.
  1139  		// We can ignore the error from setPath since we know we provided a
  1140  		// validly-escaped path.
  1141  		url.setPath(resolvePath(ref.EscapedPath(), ""))
  1142  		return &url
  1143  	}
  1144  	if ref.Opaque != "" {
  1145  		url.User = nil
  1146  		url.Host = ""
  1147  		url.Path = ""
  1148  		return &url
  1149  	}
  1150  	if ref.Path == "" && !ref.ForceQuery && ref.RawQuery == "" {
  1151  		url.RawQuery = u.RawQuery
  1152  		if ref.Fragment == "" {
  1153  			url.Fragment = u.Fragment
  1154  			url.RawFragment = u.RawFragment
  1155  		}
  1156  	}
  1157  	if ref.Path == "" && u.Opaque != "" {
  1158  		url.Opaque = u.Opaque
  1159  		url.User = nil
  1160  		url.Host = ""
  1161  		url.Path = ""
  1162  		return &url
  1163  	}
  1164  	// The "abs_path" or "rel_path" cases.
  1165  	url.Host = u.Host
  1166  	url.User = u.User
  1167  	url.setPath(resolvePath(u.EscapedPath(), ref.EscapedPath()))
  1168  	return &url
  1169  }
  1170  
  1171  // Query parses RawQuery and returns the corresponding values.
  1172  // It silently discards malformed value pairs.
  1173  // To check errors use [ParseQuery].
  1174  func (u *URL) Query() Values {
  1175  	v, _ := ParseQuery(u.RawQuery)
  1176  	return v
  1177  }
  1178  
  1179  // RequestURI returns the encoded path?query or opaque?query
  1180  // string that would be used in an HTTP request for u.
  1181  func (u *URL) RequestURI() string {
  1182  	result := u.Opaque
  1183  	if result == "" {
  1184  		result = u.EscapedPath()
  1185  		if result == "" {
  1186  			result = "/"
  1187  		}
  1188  	} else {
  1189  		if strings.HasPrefix(result, "//") {
  1190  			result = u.Scheme + ":" + result
  1191  		}
  1192  	}
  1193  	if u.ForceQuery || u.RawQuery != "" {
  1194  		result += "?" + u.RawQuery
  1195  	}
  1196  	return result
  1197  }
  1198  
  1199  // Hostname returns u.Host, stripping any valid port number if present.
  1200  //
  1201  // If the result is enclosed in square brackets, as literal IPv6 addresses are,
  1202  // the square brackets are removed from the result.
  1203  func (u *URL) Hostname() string {
  1204  	host, _ := splitHostPort(u.Host)
  1205  	return host
  1206  }
  1207  
  1208  // Port returns the port part of u.Host, without the leading colon.
  1209  //
  1210  // If u.Host doesn't contain a valid numeric port, Port returns an empty string.
  1211  func (u *URL) Port() string {
  1212  	_, port := splitHostPort(u.Host)
  1213  	return port
  1214  }
  1215  
  1216  // splitHostPort separates host and port. If the port is not valid, it returns
  1217  // the entire input as host, and it doesn't check the validity of the host.
  1218  // Unlike net.SplitHostPort, but per RFC 3986, it requires ports to be numeric.
  1219  func splitHostPort(hostPort string) (host, port string) {
  1220  	host = hostPort
  1221  
  1222  	colon := strings.LastIndexByte(host, ':')
  1223  	if colon != -1 && validOptionalPort(host[colon:]) {
  1224  		host, port = host[:colon], host[colon+1:]
  1225  	}
  1226  
  1227  	if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") {
  1228  		host = host[1 : len(host)-1]
  1229  	}
  1230  
  1231  	return
  1232  }
  1233  
  1234  // Marshaling interface implementations.
  1235  // Would like to implement MarshalText/UnmarshalText but that will change the JSON representation of URLs.
  1236  
  1237  func (u *URL) MarshalBinary() (text []byte, err error) {
  1238  	return u.AppendBinary(nil)
  1239  }
  1240  
  1241  func (u *URL) AppendBinary(b []byte) ([]byte, error) {
  1242  	return append(b, u.String()...), nil
  1243  }
  1244  
  1245  func (u *URL) UnmarshalBinary(text []byte) error {
  1246  	u1, err := Parse(string(text))
  1247  	if err != nil {
  1248  		return err
  1249  	}
  1250  	*u = *u1
  1251  	return nil
  1252  }
  1253  
  1254  // JoinPath returns a new [URL] with the provided path elements joined to
  1255  // any existing path and the resulting path cleaned of any ./ or ../ elements.
  1256  // Any sequences of multiple / characters will be reduced to a single /.
  1257  // Path elements must already be in escaped form, as produced by [PathEscape].
  1258  func (u *URL) JoinPath(elem ...string) *URL {
  1259  	url, _ := u.joinPath(elem...)
  1260  	return url
  1261  }
  1262  
  1263  func (u *URL) joinPath(elem ...string) (*URL, error) {
  1264  	elem = append([]string{u.EscapedPath()}, elem...)
  1265  	var p string
  1266  	if !strings.HasPrefix(elem[0], "/") {
  1267  		// Return a relative path if u is relative,
  1268  		// but ensure that it contains no ../ elements.
  1269  		elem[0] = "/" + elem[0]
  1270  		p = path.Join(elem...)[1:]
  1271  	} else {
  1272  		p = path.Join(elem...)
  1273  	}
  1274  	// path.Join will remove any trailing slashes.
  1275  	// Preserve at least one.
  1276  	if strings.HasSuffix(elem[len(elem)-1], "/") && !strings.HasSuffix(p, "/") {
  1277  		p += "/"
  1278  	}
  1279  	url := *u
  1280  	err := url.setPath(p)
  1281  	return &url, err
  1282  }
  1283  
  1284  // validUserinfo reports whether s is a valid userinfo string per RFC 3986
  1285  // Section 3.2.1:
  1286  //
  1287  //	userinfo    = *( unreserved / pct-encoded / sub-delims / ":" )
  1288  //	unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"
  1289  //	sub-delims  = "!" / "$" / "&" / "'" / "(" / ")"
  1290  //	              / "*" / "+" / "," / ";" / "="
  1291  //
  1292  // It doesn't validate pct-encoded. The caller does that via func unescape.
  1293  func validUserinfo(s string) bool {
  1294  	for _, r := range s {
  1295  		if 'A' <= r && r <= 'Z' {
  1296  			continue
  1297  		}
  1298  		if 'a' <= r && r <= 'z' {
  1299  			continue
  1300  		}
  1301  		if '0' <= r && r <= '9' {
  1302  			continue
  1303  		}
  1304  		switch r {
  1305  		case '-', '.', '_', ':', '~', '!', '$', '&', '\'',
  1306  			'(', ')', '*', '+', ',', ';', '=', '%':
  1307  			continue
  1308  		case '@':
  1309  			// `RFC 3986 section 3.2.1` does not allow '@' in userinfo.
  1310  			// It is a delimiter between userinfo and host.
  1311  			// However, URLs are diverse, and in some cases,
  1312  			// the userinfo may contain an '@' character,
  1313  			// for example, in "http://username:p@ssword@google.com",
  1314  			// the string "username:p@ssword" should be treated as valid userinfo.
  1315  			// Ref:
  1316  			//   https://go.dev/issue/3439
  1317  			//   https://go.dev/issue/22655
  1318  			continue
  1319  		default:
  1320  			return false
  1321  		}
  1322  	}
  1323  	return true
  1324  }
  1325  
  1326  // stringContainsCTLByte reports whether s contains any ASCII control character.
  1327  func stringContainsCTLByte(s string) bool {
  1328  	for i := 0; i < len(s); i++ {
  1329  		b := s[i]
  1330  		if b < ' ' || b == 0x7f {
  1331  			return true
  1332  		}
  1333  	}
  1334  	return false
  1335  }
  1336  
  1337  // JoinPath returns a [URL] string with the provided path elements joined to
  1338  // the existing path of base and the resulting path cleaned of any ./ or ../ elements.
  1339  // Path elements must already be in escaped form, as produced by [PathEscape].
  1340  func JoinPath(base string, elem ...string) (result string, err error) {
  1341  	url, err := Parse(base)
  1342  	if err != nil {
  1343  		return
  1344  	}
  1345  	res, err := url.joinPath(elem...)
  1346  	if err != nil {
  1347  		return "", err
  1348  	}
  1349  	return res.String(), nil
  1350  }
  1351  
  1352  // Clone creates a deep copy of the fields of the subject [URL].
  1353  func (u *URL) Clone() *URL {
  1354  	if u == nil {
  1355  		return nil
  1356  	}
  1357  
  1358  	uc := new(*u)
  1359  	if u.User != nil {
  1360  		uc.User = new(*u.User)
  1361  	}
  1362  	return uc
  1363  }
  1364  

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