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// Copyright 2009 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 url parses URLs and implements query escaping.
// See RFC 3986.
package url
import (
"bytes"
"errors"
"sort"
"strconv"
"strings"
)
// Error reports an error and the operation and URL that caused it.
type Error struct {
Op string
URL string
Err error
}
func (e *Error) Error() string { return e.Op + " " + e.URL + ": " + e.Err.Error() }
func ishex(c byte) bool {
switch {
case '0' <= c && c <= '9':
return true
case 'a' <= c && c <= 'f':
return true
case 'A' <= c && c <= 'F':
return true
}
return false
}
func unhex(c byte) byte {
switch {
case '0' <= c && c <= '9':
return c - '0'
case 'a' <= c && c <= 'f':
return c - 'a' + 10
case 'A' <= c && c <= 'F':
return c - 'A' + 10
}
return 0
}
type encoding int
const (
encodePath encoding = 1 + iota
encodeUserPassword
encodeQueryComponent
encodeFragment
)
type EscapeError string
func (e EscapeError) Error() string {
return "invalid URL escape " + strconv.Quote(string(e))
}
// Return true if the specified character should be escaped when
// appearing in a URL string, according to RFC 3986.
func shouldEscape(c byte, mode encoding) bool {
// §2.3 Unreserved characters (alphanum)
if 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z' || '0' <= c && c <= '9' {
return false
}
switch c {
case '-', '_', '.', '~': // §2.3 Unreserved characters (mark)
return false
case '$', '&', '+', ',', '/', ':', ';', '=', '?', '@': // §2.2 Reserved characters (reserved)
// Different sections of the URL allow a few of
// the reserved characters to appear unescaped.
switch mode {
case encodePath: // §3.3
// The RFC allows : @ & = + $ but saves / ; , for assigning
// meaning to individual path segments. This package
// only manipulates the path as a whole, so we allow those
// last two as well. That leaves only ? to escape.
return c == '?'
case encodeUserPassword: // §3.2.1
// The RFC allows ';', ':', '&', '=', '+', '$', and ',' in
// userinfo, so we must escape only '@', '/', and '?'.
// The parsing of userinfo treats ':' as special so we must escape
// that too.
return c == '@' || c == '/' || c == '?' || c == ':'
case encodeQueryComponent: // §3.4
// The RFC reserves (so we must escape) everything.
return true
case encodeFragment: // §4.1
// The RFC text is silent but the grammar allows
// everything, so escape nothing.
return false
}
}
// Everything else must be escaped.
return true
}
// QueryUnescape does the inverse transformation of QueryEscape, converting
// %AB into the byte 0xAB and '+' into ' ' (space). It returns an error if
// any % is not followed by two hexadecimal digits.
func QueryUnescape(s string) (string, error) {
return unescape(s, encodeQueryComponent)
}
// unescape unescapes a string; the mode specifies
// which section of the URL string is being unescaped.
func unescape(s string, mode encoding) (string, error) {
// Count %, check that they're well-formed.
n := 0
hasPlus := false
for i := 0; i < len(s); {
switch s[i] {
case '%':
n++
if i+2 >= len(s) || !ishex(s[i+1]) || !ishex(s[i+2]) {
s = s[i:]
if len(s) > 3 {
s = s[0:3]
}
return "", EscapeError(s)
}
i += 3
case '+':
hasPlus = mode == encodeQueryComponent
i++
default:
i++
}
}
if n == 0 && !hasPlus {
return s, nil
}
t := make([]byte, len(s)-2*n)
j := 0
for i := 0; i < len(s); {
switch s[i] {
case '%':
t[j] = unhex(s[i+1])<<4 | unhex(s[i+2])
j++
i += 3
case '+':
if mode == encodeQueryComponent {
t[j] = ' '
} else {
t[j] = '+'
}
j++
i++
default:
t[j] = s[i]
j++
i++
}
}
return string(t), nil
}
// QueryEscape escapes the string so it can be safely placed
// inside a URL query.
func QueryEscape(s string) string {
return escape(s, encodeQueryComponent)
}
func escape(s string, mode encoding) string {
spaceCount, hexCount := 0, 0
for i := 0; i < len(s); i++ {
c := s[i]
if shouldEscape(c, mode) {
if c == ' ' && mode == encodeQueryComponent {
spaceCount++
} else {
hexCount++
}
}
}
if spaceCount == 0 && hexCount == 0 {
return s
}
t := make([]byte, len(s)+2*hexCount)
j := 0
for i := 0; i < len(s); i++ {
switch c := s[i]; {
case c == ' ' && mode == encodeQueryComponent:
t[j] = '+'
j++
case shouldEscape(c, mode):
t[j] = '%'
t[j+1] = "0123456789ABCDEF"[c>>4]
t[j+2] = "0123456789ABCDEF"[c&15]
j += 3
default:
t[j] = s[i]
j++
}
}
return string(t)
}
// A URL represents a parsed URL (technically, a URI reference).
// The general form represented is:
//
// scheme://[userinfo@]host/path[?query][#fragment]
//
// URLs that do not start with a slash after the scheme are interpreted as:
//
// scheme:opaque[?query][#fragment]
//
// Note that the Path field is stored in decoded form: /%47%6f%2f becomes /Go/.
// A consequence is that it is impossible to tell which slashes in the Path were
// slashes in the raw URL and which were %2f. This distinction is rarely important,
// but when it is a client must use other routines to parse the raw URL or construct
// the parsed URL. For example, an HTTP server can consult req.RequestURI, and
// an HTTP client can use URL{Host: "example.com", Opaque: "//example.com/Go%2f"}
// instead of URL{Host: "example.com", Path: "/Go/"}.
type URL struct {
Scheme string
Opaque string // encoded opaque data
User *Userinfo // username and password information
Host string // host or host:port
Path string
RawQuery string // encoded query values, without '?'
Fragment string // fragment for references, without '#'
}
// User returns a Userinfo containing the provided username
// and no password set.
func User(username string) *Userinfo {
return &Userinfo{username, "", false}
}
// UserPassword returns a Userinfo containing the provided username
// and password.
// This functionality should only be used with legacy web sites.
// RFC 2396 warns that interpreting Userinfo this way
// ``is NOT RECOMMENDED, because the passing of authentication
// information in clear text (such as URI) has proven to be a
// security risk in almost every case where it has been used.''
func UserPassword(username, password string) *Userinfo {
return &Userinfo{username, password, true}
}
// The Userinfo type is an immutable encapsulation of username and
// password details for a URL. An existing Userinfo value is guaranteed
// to have a username set (potentially empty, as allowed by RFC 2396),
// and optionally a password.
type Userinfo struct {
username string
password string
passwordSet bool
}
// Username returns the username.
func (u *Userinfo) Username() string {
return u.username
}
// Password returns the password in case it is set, and whether it is set.
func (u *Userinfo) Password() (string, bool) {
if u.passwordSet {
return u.password, true
}
return "", false
}
// String returns the encoded userinfo information in the standard form
// of "username[:password]".
func (u *Userinfo) String() string {
s := escape(u.username, encodeUserPassword)
if u.passwordSet {
s += ":" + escape(u.password, encodeUserPassword)
}
return s
}
// Maybe rawurl is of the form scheme:path.
// (Scheme must be [a-zA-Z][a-zA-Z0-9+-.]*)
// If so, return scheme, path; else return "", rawurl.
func getscheme(rawurl string) (scheme, path string, err error) {
for i := 0; i < len(rawurl); i++ {
c := rawurl[i]
switch {
case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
// do nothing
case '0' <= c && c <= '9' || c == '+' || c == '-' || c == '.':
if i == 0 {
return "", rawurl, nil
}
case c == ':':
if i == 0 {
return "", "", errors.New("missing protocol scheme")
}
return rawurl[0:i], rawurl[i+1:], nil
default:
// we have encountered an invalid character,
// so there is no valid scheme
return "", rawurl, nil
}
}
return "", rawurl, nil
}
// Maybe s is of the form t c u.
// If so, return t, c u (or t, u if cutc == true).
// If not, return s, "".
func split(s string, c string, cutc bool) (string, string) {
i := strings.Index(s, c)
if i < 0 {
return s, ""
}
if cutc {
return s[0:i], s[i+len(c):]
}
return s[0:i], s[i:]
}
// Parse parses rawurl into a URL structure.
// The rawurl may be relative or absolute.
func Parse(rawurl string) (url *URL, err error) {
// Cut off #frag
u, frag := split(rawurl, "#", true)
if url, err = parse(u, false); err != nil {
return nil, err
}
if frag == "" {
return url, nil
}
if url.Fragment, err = unescape(frag, encodeFragment); err != nil {
return nil, &Error{"parse", rawurl, err}
}
return url, nil
}
// ParseRequestURI parses rawurl into a URL structure. It assumes that
// rawurl was received in an HTTP request, so the rawurl is interpreted
// only as an absolute URI or an absolute path.
// The string rawurl is assumed not to have a #fragment suffix.
// (Web browsers strip #fragment before sending the URL to a web server.)
func ParseRequestURI(rawurl string) (url *URL, err error) {
return parse(rawurl, true)
}
// parse parses a URL from a string in one of two contexts. If
// viaRequest is true, the URL is assumed to have arrived via an HTTP request,
// in which case only absolute URLs or path-absolute relative URLs are allowed.
// If viaRequest is false, all forms of relative URLs are allowed.
func parse(rawurl string, viaRequest bool) (url *URL, err error) {
var rest string
if rawurl == "" && viaRequest {
err = errors.New("empty url")
goto Error
}
url = new(URL)
if rawurl == "*" {
url.Path = "*"
return
}
// Split off possible leading "http:", "mailto:", etc.
// Cannot contain escaped characters.
if url.Scheme, rest, err = getscheme(rawurl); err != nil {
goto Error
}
url.Scheme = strings.ToLower(url.Scheme)
rest, url.RawQuery = split(rest, "?", true)
if !strings.HasPrefix(rest, "/") {
if url.Scheme != "" {
// We consider rootless paths per RFC 3986 as opaque.
url.Opaque = rest
return url, nil
}
if viaRequest {
err = errors.New("invalid URI for request")
goto Error
}
}
if (url.Scheme != "" || !viaRequest && !strings.HasPrefix(rest, "///")) && strings.HasPrefix(rest, "//") {
var authority string
authority, rest = split(rest[2:], "/", false)
url.User, url.Host, err = parseAuthority(authority)
if err != nil {
goto Error
}
if strings.Contains(url.Host, "%") {
err = errors.New("hexadecimal escape in host")
goto Error
}
}
if url.Path, err = unescape(rest, encodePath); err != nil {
goto Error
}
return url, nil
Error:
return nil, &Error{"parse", rawurl, err}
}
func parseAuthority(authority string) (user *Userinfo, host string, err error) {
i := strings.LastIndex(authority, "@")
if i < 0 {
host = authority
return
}
userinfo, host := authority[:i], authority[i+1:]
if strings.Index(userinfo, ":") < 0 {
if userinfo, err = unescape(userinfo, encodeUserPassword); err != nil {
return
}
user = User(userinfo)
} else {
username, password := split(userinfo, ":", true)
if username, err = unescape(username, encodeUserPassword); err != nil {
return
}
if password, err = unescape(password, encodeUserPassword); err != nil {
return
}
user = UserPassword(username, password)
}
return
}
// String reassembles the URL into a valid URL string.
// The general form of the result is one of:
//
// scheme:opaque
// scheme://userinfo@host/path?query#fragment
//
// If u.Opaque is non-empty, String uses the first form;
// otherwise it uses the second form.
//
// In the second form, the following rules apply:
// - if u.Scheme is empty, scheme: is omitted.
// - if u.User is nil, userinfo@ is omitted.
// - if u.Host is empty, host/ is omitted.
// - if u.Scheme and u.Host are empty and u.User is nil,
// the entire scheme://userinfo@host/ is omitted.
// - if u.Host is non-empty and u.Path begins with a /,
// the form host/path does not add its own /.
// - if u.RawQuery is empty, ?query is omitted.
// - if u.Fragment is empty, #fragment is omitted.
func (u *URL) String() string {
var buf bytes.Buffer
if u.Scheme != "" {
buf.WriteString(u.Scheme)
buf.WriteByte(':')
}
if u.Opaque != "" {
buf.WriteString(u.Opaque)
} else {
if u.Scheme != "" || u.Host != "" || u.User != nil {
buf.WriteString("//")
if ui := u.User; ui != nil {
buf.WriteString(ui.String())
buf.WriteByte('@')
}
if h := u.Host; h != "" {
buf.WriteString(h)
}
}
if u.Path != "" && u.Path[0] != '/' && u.Host != "" {
buf.WriteByte('/')
}
buf.WriteString(escape(u.Path, encodePath))
}
if u.RawQuery != "" {
buf.WriteByte('?')
buf.WriteString(u.RawQuery)
}
if u.Fragment != "" {
buf.WriteByte('#')
buf.WriteString(escape(u.Fragment, encodeFragment))
}
return buf.String()
}
// Values maps a string key to a list of values.
// It is typically used for query parameters and form values.
// Unlike in the http.Header map, the keys in a Values map
// are case-sensitive.
type Values map[string][]string
// Get gets the first value associated with the given key.
// If there are no values associated with the key, Get returns
// the empty string. To access multiple values, use the map
// directly.
func (v Values) Get(key string) string {
if v == nil {
return ""
}
vs, ok := v[key]
if !ok || len(vs) == 0 {
return ""
}
return vs[0]
}
// Set sets the key to value. It replaces any existing
// values.
func (v Values) Set(key, value string) {
v[key] = []string{value}
}
// Add adds the value to key. It appends to any existing
// values associated with key.
func (v Values) Add(key, value string) {
v[key] = append(v[key], value)
}
// Del deletes the values associated with key.
func (v Values) Del(key string) {
delete(v, key)
}
// ParseQuery parses the URL-encoded query string and returns
// a map listing the values specified for each key.
// ParseQuery always returns a non-nil map containing all the
// valid query parameters found; err describes the first decoding error
// encountered, if any.
func ParseQuery(query string) (m Values, err error) {
m = make(Values)
err = parseQuery(m, query)
return
}
func parseQuery(m Values, query string) (err error) {
for query != "" {
key := query
if i := strings.IndexAny(key, "&;"); i >= 0 {
key, query = key[:i], key[i+1:]
} else {
query = ""
}
if key == "" {
continue
}
value := ""
if i := strings.Index(key, "="); i >= 0 {
key, value = key[:i], key[i+1:]
}
key, err1 := QueryUnescape(key)
if err1 != nil {
if err == nil {
err = err1
}
continue
}
value, err1 = QueryUnescape(value)
if err1 != nil {
if err == nil {
err = err1
}
continue
}
m[key] = append(m[key], value)
}
return err
}
// Encode encodes the values into ``URL encoded'' form
// ("bar=baz&foo=quux") sorted by key.
func (v Values) Encode() string {
if v == nil {
return ""
}
var buf bytes.Buffer
keys := make([]string, 0, len(v))
for k := range v {
keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
vs := v[k]
prefix := QueryEscape(k) + "="
for _, v := range vs {
if buf.Len() > 0 {
buf.WriteByte('&')
}
buf.WriteString(prefix)
buf.WriteString(QueryEscape(v))
}
}
return buf.String()
}
// resolvePath applies special path segments from refs and applies
// them to base, per RFC 3986.
func resolvePath(base, ref string) string {
var full string
if ref == "" {
full = base
} else if ref[0] != '/' {
i := strings.LastIndex(base, "/")
full = base[:i+1] + ref
} else {
full = ref
}
if full == "" {
return ""
}
var dst []string
src := strings.Split(full, "/")
for _, elem := range src {
switch elem {
case ".":
// drop
case "..":
if len(dst) > 0 {
dst = dst[:len(dst)-1]
}
default:
dst = append(dst, elem)
}
}
if last := src[len(src)-1]; last == "." || last == ".." {
// Add final slash to the joined path.
dst = append(dst, "")
}
return "/" + strings.TrimLeft(strings.Join(dst, "/"), "/")
}
// IsAbs returns true if the URL is absolute.
func (u *URL) IsAbs() bool {
return u.Scheme != ""
}
// Parse parses a URL in the context of the receiver. The provided URL
// may be relative or absolute. Parse returns nil, err on parse
// failure, otherwise its return value is the same as ResolveReference.
func (u *URL) Parse(ref string) (*URL, error) {
refurl, err := Parse(ref)
if err != nil {
return nil, err
}
return u.ResolveReference(refurl), nil
}
// ResolveReference resolves a URI reference to an absolute URI from
// an absolute base URI, per RFC 3986 Section 5.2. The URI reference
// may be relative or absolute. ResolveReference always returns a new
// URL instance, even if the returned URL is identical to either the
// base or reference. If ref is an absolute URL, then ResolveReference
// ignores base and returns a copy of ref.
func (u *URL) ResolveReference(ref *URL) *URL {
url := *ref
if ref.Scheme == "" {
url.Scheme = u.Scheme
}
if ref.Scheme != "" || ref.Host != "" || ref.User != nil {
// The "absoluteURI" or "net_path" cases.
url.Path = resolvePath(ref.Path, "")
return &url
}
if ref.Opaque != "" {
url.User = nil
url.Host = ""
url.Path = ""
return &url
}
if ref.Path == "" {
if ref.RawQuery == "" {
url.RawQuery = u.RawQuery
if ref.Fragment == "" {
url.Fragment = u.Fragment
}
}
}
// The "abs_path" or "rel_path" cases.
url.Host = u.Host
url.User = u.User
url.Path = resolvePath(u.Path, ref.Path)
return &url
}
// Query parses RawQuery and returns the corresponding values.
func (u *URL) Query() Values {
v, _ := ParseQuery(u.RawQuery)
return v
}
// RequestURI returns the encoded path?query or opaque?query
// string that would be used in an HTTP request for u.
func (u *URL) RequestURI() string {
result := u.Opaque
if result == "" {
result = escape(u.Path, encodePath)
if result == "" {
result = "/"
}
} else {
if strings.HasPrefix(result, "//") {
result = u.Scheme + ":" + result
}
}
if u.RawQuery != "" {
result += "?" + u.RawQuery
}
return result
}