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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <string_view>
#include "base/check.h"
#include "url/third_party/mozilla/url_parse.h"
#include "url/url_file.h"
#include "url/url_parse_internal.h"
// Interesting IE file:isms...
// ========================= ==============================
// file:/foo/bar file:///foo/bar
// The result here seems totally invalid!?!? This isn't UNC.
// file:/
// file:// or any other number of slashes
// IE6 doesn't do anything at all if you click on this link. No error:
// nothing. IE6's history system seems to always color this link, so I'm
// guessing that it maps internally to the empty URL.
// C:\ file:///C:/
// When on a file: URL source page, this link will work. When over HTTP,
// the file: URL will appear in the status bar but the link will not work
// (security restriction for all file URLs).
// file:foo/ file:foo/ (invalid?!?!?)
// file:/foo/ file:///foo/ (invalid?!?!?)
// file://foo/ file://foo/ (UNC to server "foo")
// file:///foo/ file:///foo/ (invalid, seems to be a file)
// file:////foo/ file://foo/ (UNC to server "foo")
// Any more than four slashes is also treated as UNC.
// file:C:/ file://C:/
// file:/C:/ file://C:/
// The number of slashes after "file:" don't matter if the thing following
// it looks like an absolute drive path. Also, slashes and backslashes are
// equally valid here.
namespace url {
namespace {
// Returns the index of the next slash in the input after the given index, or
// `spec.size()` if the end of the input is reached.
template <typename CharT>
size_t FindNextSlash(std::basic_string_view<CharT> spec, size_t begin_index) {
size_t idx = begin_index;
while (idx < spec.size() && !IsSlashOrBackslash(spec[idx])) {
return idx;
// A subcomponent of DoParseFileURL, the input of this function should be a UNC
// path name, with the index of the first character after the slashes following
// the scheme given in `after_slashes`. This will initialize the host, path,
// query, and ref, and leave the other output components untouched
// (DoParseFileURL handles these for us).
template <typename CharT>
void DoParseUNC(std::basic_string_view<CharT> url,
size_t after_slashes,
Parsed* parsed) {
int url_len = base::checked_cast<int>(url.size());
// The cast is safe because `FindNextSlash` will never return anything longer
// than `url_len`.
int next_slash = static_cast<int>(FindNextSlash(url, after_slashes));
// Everything up until that first slash we found (or end of string) is the
// host name, which will end up being the UNC host. For example,
// "file://foo/bar.txt" will get a server name of "foo" and a path of "/bar".
// Later, on Windows, this should be treated as the filename "\\foo\bar.txt"
// in proper UNC notation.
if (after_slashes < static_cast<size_t>(next_slash)) {
parsed->host = MakeRange(after_slashes, next_slash);
} else {
if (next_slash < url_len) {
ParsePathInternal(, MakeRange(next_slash, url_len), &parsed->path,
&parsed->query, &parsed->ref);
} else {
// A subcomponent of DoParseFileURL, the input should be a local file, with the
// beginning of the path indicated by the index in `path_begin`. This will
// initialize the host, path, query, and ref, and leave the other output
// components untouched (DoParseFileURL handles these for us).
template <typename CharT>
void DoParseLocalFile(std::basic_string_view<CharT> url,
int path_begin,
Parsed* parsed) {
MakeRange(path_begin, base::checked_cast<int>(url.size())),
&parsed->path, &parsed->query, &parsed->ref);
// Backend for the external functions that operates on either char type.
// Handles cases where there is a scheme, but also when handed the first
// character following the "file:" at the beginning of the spec. If so,
// this is usually a slash, but needn't be; we allow paths like "file:c:\foo".
template <typename CharT>
Parsed DoParseFileURL(std::basic_string_view<CharT> url) {
// Strip leading & trailing spaces and control characters.
int begin = 0;
int url_len = base::checked_cast<int>(url.size());
TrimURL(, &begin, &url_len);
// Find the scheme, if any.
int num_slashes = CountConsecutiveSlashes(, begin, url_len);
int after_scheme;
size_t after_slashes;
Parsed parsed;
#ifdef WIN32
// See how many slashes there are. We want to handle cases like UNC but also
// "/c:/foo". This is when there is no scheme, so we can allow pages to do
// links like "c:/foo/bar" or "//foo/bar". This is also called by the
// relative URL resolver when it determines there is an absolute URL, which
// may give us input like "/c:/foo".
after_slashes = begin + num_slashes;
if (DoesBeginWindowsDriveSpec(, after_slashes, url_len)) {
// Windows path, don't try to extract the scheme (for example, "c:\foo").
after_scheme = after_slashes;
} else if (DoesBeginUNCPath(, begin, url_len, false)) {
// Windows UNC path: don't try to extract the scheme, but keep the slashes.
after_scheme = begin;
} else
// ExtractScheme doesn't understand the possibility of filenames with
// colons in them, in which case it returns the entire spec up to the
// colon as the scheme. So handle /foo.c:5 as a file but foo.c:5 as
// the foo.c: scheme.
if (!num_slashes &&
ExtractScheme(&url[begin], url_len - begin, &parsed.scheme)) {
// Offset the results since we gave ExtractScheme a substring.
parsed.scheme.begin += begin;
after_scheme = parsed.scheme.end() + 1;
} else {
// No scheme found, remember that.
after_scheme = begin;
// Handle empty specs ones that contain only whitespace or control chars,
// or that are just the scheme (for example "file:").
if (after_scheme == url_len) {
return parsed;
num_slashes = CountConsecutiveSlashes(, after_scheme, url_len);
after_slashes = after_scheme + num_slashes;
#ifdef WIN32
// Check whether the input is a drive again. We checked above for windows
// drive specs, but that's only at the very beginning to see if we have a
// scheme at all. This test will be duplicated in that case, but will
// additionally handle all cases with a real scheme such as "file:///C:/".
if (!DoesBeginWindowsDriveSpec(, after_slashes, url_len) &&
num_slashes != 3) {
// Anything not beginning with a drive spec ("c:\") on Windows is treated
// as UNC, with the exception of three slashes which always means a file.
// Even IE7 treats file:///foo/bar as "/foo/bar", which then fails.
DoParseUNC(url.substr(0, url_len), after_slashes, &parsed);
return parsed;
// file: URL with exactly 2 slashes is considered to have a host component.
if (num_slashes == 2) {
DoParseUNC(url.substr(0, url_len), after_slashes, &parsed);
return parsed;
#endif // WIN32
// Easy and common case, the full path immediately follows the scheme
// (modulo slashes), as in "file://c:/foo". Just treat everything from
// there to the end as the path. Empty hosts have 0 length instead of -1.
// We include the last slash as part of the path if there is one.
url.substr(0, url_len),
num_slashes > 0 ? after_scheme + num_slashes - 1 : after_scheme, &parsed);
return parsed;
} // namespace
Parsed ParseFileURL(std::string_view url) {
return DoParseFileURL(url);
Parsed ParseFileURL(std::u16string_view url) {
return DoParseFileURL(url);
} // namespace url