Revert "Enable long path on Windows"

This reverts commit 08662f0575. Reason for revert: failure on pkg-win-release, https://dart-ci.appspot.com/log/pkg-win-release/unittest-asserts-release-win/12878/pkg/dartdev/test/commands/test_test Original change's description: > Enable long path on Windows > > File APIs on Windows can now handle files and directories identified by > long paths (greater than 260 characters). For directory, the limit is > 248. > > Some restrictions from Windows: > 1. The size limit for long path is 32,767 characters. > 2. Each component separated by backslashes should not be more than 255 > characters. > > Reference: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation. > > Note that `Directory.current` does not work with long path. > > Bug: https://github.com/dart-lang/sdk/issues/42416 > Change-Id: Ia1b4608d393fb36f1d843858c6f076f3c825dc83 > Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/152736 > Reviewed-by: Alexander Aprelev <aam@google.com> > Commit-Queue: Zichang Guo <zichangguo@google.com> TBR=aam@google.com,zra@google.com,zichangguo@google.com Change-Id: If6701c887e616cd62f20faac43f601cfb53ed349 No-Presubmit: true No-Tree-Checks: true No-Try: true Bug: https://github.com/dart-lang/sdk/issues/42416 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/162104 Reviewed-by: Zichang Guo <zichangguo@google.com> Commit-Queue: Zichang Guo <zichangguo@google.com>
2020-09-08 22:34:50 +00:00
parent b8fa8c9052
commit f8fbefd951
11 changed files with 65 additions and 777 deletions
@@ -130,14 +130,9 @@ applications (issue [flutter/flutter#63038][]).
 *   [Abstract Unix Domain Socket][] is supported on Linux/Android now. Using an
    `InternetAddress` with `address` starting with '@' and type being
    `InternetAddressType.Unix` will create an abstract Unix Domain Socket.
-*   On Windows, file APIs can now handle files and directories identified by
-    long paths (greater than 260 characters). It complies with all restrictions
-    from [Long Path on Windows][]. Note that `Directory.current` does not work
-    with long path.

 [#42006]: https://github.com/dart-lang/sdk/issues/42006
 [Abstract Unix Domain Socket]: http://man7.org/linux/man-pages/man7/unix.7.html
-[Long Path on Windows]: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation

 #### `dart:html`

@@ -45,7 +45,6 @@ builtin_impl_sources = [
  "file_macos.cc",
  "file_support.cc",
  "file_win.cc",
-  "file_win.h",
  "io_buffer.cc",
  "io_buffer.h",
  "isolate_data.cc",
@@ -13,7 +13,6 @@
 #include "bin/crypto.h"
 #include "bin/dartutils.h"
 #include "bin/file.h"
-#include "bin/file_win.h"
 #include "bin/namespace.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"
@@ -22,6 +21,8 @@

 #undef DeleteFile

+#define MAX_LONG_PATH 32767
+
 namespace dart {
 namespace bin {

@@ -277,12 +278,7 @@ static bool DeleteEntry(LPWIN32_FIND_DATAW find_file_data, PathBuffer* path) {
 }

 static bool DeleteRecursively(PathBuffer* path) {
-  PathBuffer prefixed_path;
-  if (!prefixed_path.Add(PrefixLongDirectoryPath(path->AsScopedString()))) {
-    return false;
-  }
-
-  DWORD attributes = GetFileAttributesW(prefixed_path.AsStringW());
+  DWORD attributes = GetFileAttributesW(path->AsStringW());
  if (attributes == INVALID_FILE_ATTRIBUTES) {
    return false;
  }
@@ -290,34 +286,33 @@ static bool DeleteRecursively(PathBuffer* path) {
  // filesystem that we do not want to recurse into.
  if ((attributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0) {
    // Just delete the junction itself.
-    return RemoveDirectoryW(prefixed_path.AsStringW()) != 0;
+    return RemoveDirectoryW(path->AsStringW()) != 0;
  }
  // If it's a file, remove it directly.
  if ((attributes & FILE_ATTRIBUTE_DIRECTORY) == 0) {
-    return DeleteFile(L"", &prefixed_path);
+    return DeleteFile(L"", path);
  }

-  if (!prefixed_path.AddW(L"\\*")) {
+  if (!path->AddW(L"\\*")) {
    return false;
  }

  WIN32_FIND_DATAW find_file_data;
-  HANDLE find_handle =
-      FindFirstFileW(prefixed_path.AsStringW(), &find_file_data);
+  HANDLE find_handle = FindFirstFileW(path->AsStringW(), &find_file_data);

  if (find_handle == INVALID_HANDLE_VALUE) {
    return false;
  }

  // Adjust the path by removing the '*' used for the search.
-  int path_length = prefixed_path.length() - 1;
-  prefixed_path.Reset(path_length);
+  int path_length = path->length() - 1;
+  path->Reset(path_length);

  do {
-    if (!DeleteEntry(&find_file_data, &prefixed_path)) {
+    if (!DeleteEntry(&find_file_data, path)) {
      break;
    }
-    prefixed_path.Reset(path_length);  // DeleteEntry adds to the path.
+    path->Reset(path_length);  // DeleteEntry adds to the path.
  } while (FindNextFileW(find_handle, &find_file_data) != 0);

  DWORD last_error = GetLastError();
@@ -329,9 +324,8 @@ static bool DeleteRecursively(PathBuffer* path) {
    return false;
  }
  // All content deleted succesfully, try to delete directory.
-  prefixed_path.Reset(path_length -
-                      1);  // Drop the "\" from the end of the path.
-  return RemoveDirectoryW(prefixed_path.AsStringW()) != 0;
+  path->Reset(path_length - 1);  // Drop the "\" from the end of the path.
+  return RemoveDirectoryW(path->AsStringW()) != 0;
 }

 static Directory::ExistsResult ExistsHelper(const wchar_t* dir_name) {
@@ -355,8 +349,7 @@ static Directory::ExistsResult ExistsHelper(const wchar_t* dir_name) {

 Directory::ExistsResult Directory::Exists(Namespace* namespc,
                                          const char* dir_name) {
-  const char* prefixed_dir_name = PrefixLongDirectoryPath(dir_name);
-  Utf8ToWideScope system_name(prefixed_dir_name);
+  Utf8ToWideScope system_name(dir_name);
  return ExistsHelper(system_name.wide());
 }

@@ -376,8 +369,7 @@ char* Directory::CurrentNoScope() {
 }

 bool Directory::Create(Namespace* namespc, const char* dir_name) {
-  const char* prefixed_dir_name = PrefixLongDirectoryPath(dir_name);
-  Utf8ToWideScope system_name(prefixed_dir_name);
+  Utf8ToWideScope system_name(dir_name);
  int create_status = CreateDirectoryW(system_name.wide(), NULL);
  // If the directory already existed, treat it as a success.
  if ((create_status == 0) && (GetLastError() == ERROR_ALREADY_EXISTS) &&
@@ -483,11 +475,10 @@ const char* Directory::CreateTemp(Namespace* namespc, const char* prefix) {
 bool Directory::Delete(Namespace* namespc,
                       const char* dir_name,
                       bool recursive) {
-  const char* prefixed_dir_name = PrefixLongDirectoryPath(dir_name);
  bool result = false;
-  Utf8ToWideScope system_dir_name(prefixed_dir_name);
+  Utf8ToWideScope system_dir_name(dir_name);
  if (!recursive) {
-    if (File::GetType(namespc, prefixed_dir_name, true) == File::kIsDirectory) {
+    if (File::GetType(namespc, dir_name, true) == File::kIsDirectory) {
      result = (RemoveDirectoryW(system_dir_name.wide()) != 0);
    } else {
      SetLastError(ERROR_FILE_NOT_FOUND);
@@ -504,20 +495,18 @@ bool Directory::Delete(Namespace* namespc,
 bool Directory::Rename(Namespace* namespc,
                       const char* path,
                       const char* new_path) {
-  const char* prefixed_dir = PrefixLongDirectoryPath(path);
-  Utf8ToWideScope system_path(prefixed_dir);
+  Utf8ToWideScope system_path(path);
+  Utf8ToWideScope system_new_path(new_path);
  ExistsResult exists = ExistsHelper(system_path.wide());
  if (exists != EXISTS) {
    return false;
  }
-  const char* prefixed_new_dir = PrefixLongDirectoryPath(new_path);
-  Utf8ToWideScope system_new_path(prefixed_new_dir);
  ExistsResult new_exists = ExistsHelper(system_new_path.wide());
  // MoveFile does not allow replacing existing directories. Therefore,
  // if the new_path is currently a directory we need to delete it
  // first.
  if (new_exists == EXISTS) {
-    bool success = Delete(namespc, prefixed_new_dir, true);
+    bool success = Delete(namespc, new_path, true);
    if (!success) {
      return false;
    }
@@ -5,11 +5,13 @@
 #include "platform/globals.h"
 #if defined(HOST_OS_WINDOWS)

-#include <Shlwapi.h>  // NOLINT
+#include "bin/file.h"
+
 #include <WinIoCtl.h>  // NOLINT
 #include <fcntl.h>     // NOLINT
 #include <io.h>        // NOLINT
-#undef StrDup          // defined in Shlwapi.h as StrDupW
+#include <Shlwapi.h>   // NOLINT
+#undef StrDup  // defined in Shlwapi.h as StrDupW
 #include <stdio.h>     // NOLINT
 #include <string.h>    // NOLINT
 #include <sys/stat.h>  // NOLINT
@@ -18,8 +20,6 @@
 #include "bin/builtin.h"
 #include "bin/crypto.h"
 #include "bin/directory.h"
-#include "bin/file.h"
-#include "bin/file_win.h"
 #include "bin/namespace.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"
@@ -299,7 +299,7 @@ File* File::FileOpenW(const wchar_t* system_name, FileOpenMode mode) {
 }

 File* File::Open(Namespace* namespc, const char* path, FileOpenMode mode) {
-  Utf8ToWideScope system_name(PrefixLongFilePath(path));
+  Utf8ToWideScope system_name(path);
  File* file = FileOpenW(system_name.wide(), mode);
  return file;
 }
@@ -365,7 +365,7 @@ static bool StatHelper(wchar_t* path, struct __stat64* st) {

 bool File::Exists(Namespace* namespc, const char* name) {
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  return StatHelper(system_name.wide(), &st);
 }

@@ -379,7 +379,7 @@ bool File::ExistsUri(Namespace* namespc, const char* uri) {
 }

 bool File::Create(Namespace* namespc, const char* name) {
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  int fd = _wopen(system_name.wide(), O_RDONLY | O_CREAT, 0666);
  if (fd < 0) {
    return false;
@@ -426,8 +426,8 @@ static const int kMountPointHeaderSize = 4 * sizeof(USHORT);
 bool File::CreateLink(Namespace* namespc,
                      const char* utf8_name,
                      const char* utf8_target) {
-  Utf8ToWideScope name(PrefixLongFilePath(utf8_name));
-  Utf8ToWideScope target(PrefixLongFilePath(utf8_target));
+  Utf8ToWideScope name(utf8_name);
+  Utf8ToWideScope target(utf8_target);
  DWORD flags = SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;

  File::Type type = File::GetType(namespc, utf8_target, true);
@@ -449,13 +449,13 @@ bool File::CreateLink(Namespace* namespc,
 }

 bool File::Delete(Namespace* namespc, const char* name) {
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  int status = _wremove(system_name.wide());
  return status != -1;
 }

 bool File::DeleteLink(Namespace* namespc, const char* name) {
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  bool result = false;
  DWORD attributes = GetFileAttributesW(system_name.wide());
  if ((attributes == INVALID_FILE_ATTRIBUTES) ||
@@ -477,15 +477,13 @@ bool File::DeleteLink(Namespace* namespc, const char* name) {
 bool File::Rename(Namespace* namespc,
                  const char* old_path,
                  const char* new_path) {
-  const char* prefixed_old_path = PrefixLongFilePath(old_path);
-  File::Type type = GetType(namespc, prefixed_old_path, false);
+  File::Type type = GetType(namespc, old_path, false);
  if (type != kIsFile) {
    SetLastError(ERROR_FILE_NOT_FOUND);
    return false;
  }
-  const char* prefixed_new_path = PrefixLongFilePath(new_path);
-  Utf8ToWideScope system_old_path(prefixed_old_path);
-  Utf8ToWideScope system_new_path(prefixed_new_path);
+  Utf8ToWideScope system_old_path(old_path);
+  Utf8ToWideScope system_new_path(new_path);
  DWORD flags = MOVEFILE_WRITE_THROUGH | MOVEFILE_REPLACE_EXISTING;
  int move_status =
      MoveFileExW(system_old_path.wide(), system_new_path.wide(), flags);
@@ -495,25 +493,23 @@ bool File::Rename(Namespace* namespc,
 bool File::RenameLink(Namespace* namespc,
                      const char* old_path,
                      const char* new_path) {
-  const char* prefixed_old_path = PrefixLongFilePath(old_path);
-  File::Type type = GetType(namespc, prefixed_old_path, false);
+  File::Type type = GetType(namespc, old_path, false);
  if (type != kIsLink) {
    SetLastError(ERROR_FILE_NOT_FOUND);
    return false;
  }
-  Utf8ToWideScope system_old_path(prefixed_old_path);
-  const char* prefixed_new_path = PrefixLongFilePath(new_path);
-  Utf8ToWideScope system_new_path(prefixed_new_path);
+  Utf8ToWideScope system_old_path(old_path);
+  Utf8ToWideScope system_new_path(new_path);
  DWORD flags = MOVEFILE_WRITE_THROUGH | MOVEFILE_REPLACE_EXISTING;

  // Junction links on Windows appear as special directories. MoveFileExW's
  // MOVEFILE_REPLACE_EXISTING does not allow for replacement of directories,
  // so we need to remove it before renaming a link. This step is only
  // necessary for junctions created by the old Link.create implementation.
-  if ((Directory::Exists(namespc, prefixed_new_path) == Directory::EXISTS) &&
-      (GetType(namespc, prefixed_new_path, false) == kIsLink)) {
+  if ((Directory::Exists(namespc, new_path) == Directory::EXISTS) &&
+      (GetType(namespc, new_path, false) == kIsLink)) {
    // Bail out if the DeleteLink call fails.
-    if (!DeleteLink(namespc, prefixed_new_path)) {
+    if (!DeleteLink(namespc, new_path)) {
      return false;
    }
  }
@@ -619,26 +615,24 @@ static wchar_t* CopyIntoTempFile(const char* src, const char* dest) {
 bool File::Copy(Namespace* namespc,
                const char* old_path,
                const char* new_path) {
-  const char* prefixed_old_path = PrefixLongFilePath(old_path);
-  const char* prefixed_new_path = PrefixLongFilePath(new_path);
-  File::Type type = GetType(namespc, prefixed_old_path, false);
+  File::Type type = GetType(namespc, old_path, false);
  if (type != kIsFile) {
    SetLastError(ERROR_FILE_NOT_FOUND);
    return false;
  }

-  wchar_t* temp_file = CopyIntoTempFile(prefixed_old_path, prefixed_new_path);
+  wchar_t* temp_file = CopyIntoTempFile(old_path, new_path);
  if (temp_file == NULL) {
    // If temp file creation fails, fall back on doing a direct copy.
-    Utf8ToWideScope system_old_path(prefixed_old_path);
-    Utf8ToWideScope system_new_path(prefixed_new_path);
+    Utf8ToWideScope system_old_path(old_path);
+    Utf8ToWideScope system_new_path(new_path);
    return CopyFileExW(system_old_path.wide(), system_new_path.wide(), NULL,
                       NULL, NULL, 0) != 0;
  }
-  Utf8ToWideScope system_new_dest(prefixed_new_path);
+  Utf8ToWideScope system_new_dest(new_path);

  // Remove the existing file. Otherwise, renaming will fail.
-  if (Exists(namespc, prefixed_new_path)) {
+  if (Exists(namespc, new_path)) {
    DeleteFileW(system_new_dest.wide());
  }

@@ -653,7 +647,7 @@ bool File::Copy(Namespace* namespc,

 int64_t File::LengthFromPath(Namespace* namespc, const char* name) {
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  if (!StatHelper(system_name.wide(), &st)) {
    return -1;
  }
@@ -664,8 +658,7 @@ const char* File::LinkTarget(Namespace* namespc,
                             const char* pathname,
                             char* dest,
                             int dest_size) {
-  const wchar_t* name =
-      StringUtilsWin::Utf8ToWide(PrefixLongFilePath(pathname));
+  const wchar_t* name = StringUtilsWin::Utf8ToWide(pathname);
  HANDLE dir_handle = CreateFileW(
      name, GENERIC_READ,
      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
@@ -675,10 +668,8 @@ const char* File::LinkTarget(Namespace* namespc,
    return NULL;
  }

-  // Allocate a buffer for regular paths (smaller than MAX_PATH). If buffer is
-  // too small for a long path, allocate a bigger buffer and try again.
  int buffer_size =
-      sizeof(REPARSE_DATA_BUFFER) + (MAX_PATH + 1) * sizeof(WCHAR);
+      sizeof(REPARSE_DATA_BUFFER) + 2 * (MAX_PATH + 1) * sizeof(WCHAR);
  REPARSE_DATA_BUFFER* buffer =
      reinterpret_cast<REPARSE_DATA_BUFFER*>(Dart_ScopeAllocate(buffer_size));
  DWORD received_bytes;  // Value is not used.
@@ -686,26 +677,9 @@ const char* File::LinkTarget(Namespace* namespc,
                               buffer, buffer_size, &received_bytes, NULL);
  if (result == 0) {
    DWORD error = GetLastError();
-    // If ERROR_MORE_DATA is thrown, the target path exceeds the size limit. A
-    // bigger buffer will be required.
-    if (error == ERROR_MORE_DATA) {
-      // Allocate a bigger buffer with MAX_LONG_PATH
-      buffer_size =
-          sizeof(REPARSE_DATA_BUFFER) + (MAX_LONG_PATH + 1) * sizeof(WCHAR);
-      buffer = reinterpret_cast<REPARSE_DATA_BUFFER*>(
-          Dart_ScopeAllocate(buffer_size));
-      result = DeviceIoControl(dir_handle, FSCTL_GET_REPARSE_POINT, NULL, 0,
-                               buffer, buffer_size, &received_bytes, NULL);
-      if (result == 0) {
-        // Overwrite the ERROR_MORE_DATA.
-        error = GetLastError();
-      }
-    }
-    if (result == 0) {
-      CloseHandle(dir_handle);
-      SetLastError(error);
-      return NULL;
-    }
+    CloseHandle(dir_handle);
+    SetLastError(error);
+    return NULL;
  }
  if (CloseHandle(dir_handle) == 0) {
    return NULL;
@@ -752,12 +726,11 @@ const char* File::LinkTarget(Namespace* namespc,
 }

 void File::Stat(Namespace* namespc, const char* name, int64_t* data) {
-  const char* prefixed_name = PrefixLongFilePath(name);
-  File::Type type = GetType(namespc, prefixed_name, false);
+  File::Type type = GetType(namespc, name, false);
  data[kType] = type;
  if (type != kDoesNotExist) {
    struct _stat64 st;
-    Utf8ToWideScope system_name(prefixed_name);
+    Utf8ToWideScope system_name(name);
    int stat_status = _wstat64(system_name.wide(), &st);
    if (stat_status == 0) {
      data[kCreatedTime] = st.st_ctime * 1000;
@@ -773,7 +746,7 @@ void File::Stat(Namespace* namespc, const char* name, int64_t* data) {

 time_t File::LastAccessed(Namespace* namespc, const char* name) {
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  if (!StatHelper(system_name.wide(), &st)) {
    return -1;
  }
@@ -782,7 +755,7 @@ time_t File::LastAccessed(Namespace* namespc, const char* name) {

 time_t File::LastModified(Namespace* namespc, const char* name) {
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  if (!StatHelper(system_name.wide(), &st)) {
    return -1;
  }
@@ -794,7 +767,7 @@ bool File::SetLastAccessed(Namespace* namespc,
                           int64_t millis) {
  // First get the current times.
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  if (!StatHelper(system_name.wide(), &st)) {
    return false;
  }
@@ -811,7 +784,7 @@ bool File::SetLastModified(Namespace* namespc,
                           int64_t millis) {
  // First get the current times.
  struct __stat64 st;
-  Utf8ToWideScope system_name(PrefixLongFilePath(name));
+  Utf8ToWideScope system_name(name);
  if (!StatHelper(system_name.wide(), &st)) {
    return false;
  }
@@ -828,6 +801,7 @@ bool File::SetLastModified(Namespace* namespc,
 bool File::IsAbsolutePath(const char* pathname) {
  if (pathname == NULL) return false;
  char first = pathname[0];
+  if (pathname == 0) return false;
  char second = pathname[1];
  if (first == '\\' && second == '\\') return true;
  if (second != ':') return false;
@@ -836,77 +810,11 @@ bool File::IsAbsolutePath(const char* pathname) {
  return (first >= 'a') && (first <= 'z') && (third == '\\' || third == '/');
 }

-const char* PrefixLongFilePath(const char* path) {
-  return PrefixLongPathIfExceedLimit(path, true);
-}
-
-const char* PrefixLongDirectoryPath(const char* path) {
-  return PrefixLongPathIfExceedLimit(path, false);
-}
-
-const char* PrefixLongPathIfExceedLimit(const char* path, bool file_name) {
-  const char* prefix = "\\\\?\\";
-  // File name and Directory name has a different size limit.
-  // Reference: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation
-  int limit = file_name ? MAX_PATH : MAX_DIRECTORY_SIZE;
-  int length;
-  if (!File::IsAbsolutePath(path)) {
-    // Convert relative paths to absolute paths because relative paths don't
-    // work when they represent long(>MAX_PATH) absolute paths.
-    wchar_t* buffer =
-        reinterpret_cast<wchar_t*>(malloc(sizeof(wchar_t) * (limit + 1)));
-    Utf8ToWideScope dir(path);
-    LPWSTR* file = NULL;
-    int size = GetFullPathNameW(dir.wide(), limit + 1, buffer, file);
-    free(buffer);
-    if (size == 0) {
-      return path;
-    }
-    if (size > limit) {
-      // The absolute path is a long path. Assign a buffer with right size and
-      // try again.
-      // Note that in this case, size represents the size of the path plus the
-      // null terminator.
-      wchar_t* buf =
-          reinterpret_cast<wchar_t*>(malloc(sizeof(wchar_t) * (size)));
-      size = GetFullPathNameW(dir.wide(), size, buf, file);
-      if (size == 0) {
-        return path;
-      }
-      path = StringUtilsWin::WideToUtf8(buf);
-      free(buf);
-    }
-    // length doesn't include null terminator on success return.
-    length = size;
-  } else {
-    length = strlen(path);
-  }
-  if (length <= limit) {
-    return path;
-  }
-  int length_prefix = strlen(prefix);
-  // If a path is already prefixed, return it.
-  if ((length > length_prefix && strncmp(path, prefix, length_prefix) == 0)) {
-    return path;
-  }
-  // Replace forward slashes with backward slashes.
-  char* result = reinterpret_cast<char*>(
-      Dart_ScopeAllocate((length_prefix + 1 + length) * sizeof(char)));
-
-  strncpy(result, prefix, length_prefix);
-
-  for (int i = 0; i < length; i++) {
-    result[length_prefix + i] = path[i] == '/' ? '\\' : path[i];
-  }
-  result[length + length_prefix] = '\0';
-  return result;
-}
-
 const char* File::GetCanonicalPath(Namespace* namespc,
                                   const char* pathname,
                                   char* dest,
                                   int dest_size) {
-  Utf8ToWideScope system_name(PrefixLongFilePath(pathname));
+  Utf8ToWideScope system_name(pathname);
  HANDLE file_handle =
      CreateFileW(system_name.wide(), 0, FILE_SHARE_READ, NULL, OPEN_EXISTING,
                  FILE_FLAG_BACKUP_SEMANTICS, NULL);
@@ -930,8 +838,9 @@ const char* File::GetCanonicalPath(Namespace* namespc,

  // Remove leading \\?\ if possible, unless input used it.
  int offset = 0;
-  if ((result_size > 4) && (wcsncmp(path.get(), L"\\\\?\\", 4) == 0) &&
-      (strncmp(pathname, "\\\\?\\", 4) != 0)) {
+  if ((result_size < MAX_PATH - 1 + 4) && (result_size > 4) &&
+      (wcsncmp(path.get(), L"\\\\?\\", 4) == 0) &&
+      (wcsncmp(system_name.wide(), L"\\\\?\\", 4) != 0)) {
    offset = 4;
  }
  int utf8_size = WideCharToMultiByte(CP_UTF8, 0, path.get() + offset, -1,
@@ -970,7 +879,7 @@ File::Type File::GetType(Namespace* namespc,
                         const char* pathname,
                         bool follow_links) {
  // Convert to wchar_t string.
-  Utf8ToWideScope name(PrefixLongFilePath(pathname));
+  Utf8ToWideScope name(pathname);
  DWORD attributes = GetFileAttributesW(name.wide());
  File::Type result = kIsFile;
  if (attributes == INVALID_FILE_ATTRIBUTES) {
@@ -1010,8 +919,7 @@ File::Identical File::AreIdentical(Namespace* namespc_1,
  USE(namespc_1);
  USE(namespc_2);
  BY_HANDLE_FILE_INFORMATION file_info[2];
-  const char* file_names[2] = {PrefixLongFilePath(file_1),
-                               PrefixLongFilePath(file_2)};
+  const char* file_names[2] = {file_1, file_2};
  for (int i = 0; i < 2; ++i) {
    Utf8ToWideScope wide_name(file_names[i]);
    HANDLE file_handle = CreateFileW(
@@ -1,24 +0,0 @@
-// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-#ifndef RUNTIME_BIN_FILE_WIN_H_
-#define RUNTIME_BIN_FILE_WIN_H_
-
-#include "file.h"
-
-// The limit for a regular directory is 248.
-// Reference: https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#maximum-path-length-limitation
-#define MAX_DIRECTORY_SIZE (MAX_PATH - 12)
-
-namespace dart {
-namespace bin {
-
-const char* PrefixLongFilePath(const char* path);
-const char* PrefixLongDirectoryPath(const char* path);
-const char* PrefixLongPathIfExceedLimit(const char* path, bool file_name);
-
-}  // namespace bin
-}  // namespace dart
-
-#endif  // RUNTIME_BIN_FILE_WIN_H_
@@ -10,8 +10,6 @@
 #include <errno.h>
 #include <sys/stat.h>

-#include "bin/file.h"
-#include "bin/file_win.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"

@@ -48,9 +46,6 @@ const char* Namespace::GetCurrent(Namespace* namespc) {
 }

 bool Namespace::SetCurrent(Namespace* namespc, const char* path) {
-  // TODO(zichangguo): "\\?\" prepended long path doesn't work.
-  // https://github.com/dart-lang/sdk/issues/42416
-  path = PrefixLongDirectoryPath(path);
  Utf8ToWideScope system_path(path);
  bool result = SetCurrentDirectoryW(system_path.wide()) != 0;
  return result;
@@ -9,8 +9,6 @@

 #include "platform/utils.h"

-#define MAX_LONG_PATH 32767
-
 namespace dart {
 namespace bin {

@@ -1,247 +0,0 @@
-// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-//
-// This test is Windows-only.
-
-import 'dart:io';
-
-import "package:expect/expect.dart";
-
-const maxPath = 260;
-const maxDirectoryPath = maxPath - 12;
-String longName = '${'x' * 248}';
-
-Directory createLongPathDir(Directory tmp) {
-  if (tmp.path.length <= maxDirectoryPath) {
-    var path = tmp.path;
-    path += '\\${'t' * 248}';
-    var dir = Directory(path);
-    dir.createSync(recursive: true);
-    // Test the rename() of directory
-    dir = dir.renameSync(tmp.path + '\\$longName');
-    Expect.isTrue(dir.existsSync());
-    Expect.isFalse(Directory(path).existsSync());
-    return dir;
-  } else {
-    return tmp;
-  }
-}
-
-void testCreate(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  Expect.isTrue(file.existsSync());
-  file.deleteSync();
-}
-
-void testCopy(String dir) {
-  final src = '${dir}\\a_long_path_filename_1';
-  final dest = '${dir}\\a_long_path_filename_2';
-  Expect.isTrue(src.length > maxPath);
-  final file1 = File(src);
-  file1.createSync();
-
-  final file2 = file1.copySync(dest);
-  Expect.isTrue(file2.existsSync());
-  file1.deleteSync();
-  file2.deleteSync();
-}
-
-void testRename(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  Expect.isTrue(file.existsSync());
-
-  final renamedFile = file.renameSync('${path}_copy');
-
-  Expect.isFalse(file.existsSync());
-  Expect.isTrue(renamedFile.existsSync());
-  renamedFile.deleteSync();
-}
-
-void testReadWrite(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-
-  final content = "testReadWrite";
-  file.writeAsStringSync(content);
-  Expect.isTrue(file.existsSync());
-
-  int length = file.lengthSync();
-  Expect.equals(content.length, length);
-
-  final string = file.readAsStringSync();
-  Expect.equals(content, string);
-  file.deleteSync();
-}
-
-void testOpen(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  final access = file.openSync();
-  access.closeSync();
-}
-
-void testFileStat(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  final stat = FileStat.statSync(file.path);
-
-  final dateTime = DateTime.utc(2020);
-
-  file.setLastModifiedSync(dateTime);
-  Expect.notEquals(
-      stat.modified.toString(), file.lastModifiedSync().toString());
-
-  file.setLastAccessedSync(dateTime);
-  Expect.notEquals(
-      stat.accessed.toString(), file.lastAccessedSync().toString());
-}
-
-void testCreateLinkToDir(String dir) {
-  final path = '${dir}\\a_long_path_linkname';
-  Expect.isTrue(path.length > maxPath);
-  var target = '$dir\\a_long_path_target';
-  final link = Link(path)..createSync(target);
-
-  final dest = Directory(target)..createSync();
-  Expect.isTrue(dest.existsSync());
-
-  Expect.isTrue(link.existsSync());
-  Expect.isTrue(link.targetSync().contains('a_long_path_target'));
-
-  // Rename link
-  var renamedLink = link.renameSync('${dir}\\a_renamed_long_path_link');
-  Expect.isTrue(renamedLink.existsSync());
-  Expect.isFalse(link.existsSync());
-  Expect.isTrue(renamedLink.targetSync().contains('a_long_path_target'));
-
-  // Update link target
-  target = '$dir\\an_updated_target';
-  final renamedDest = Directory(target)..createSync();
-  renamedLink.updateSync(target);
-  Expect.isTrue(renamedLink.targetSync().contains('an_updated_target'));
-
-  dest.deleteSync();
-  renamedDest.deleteSync();
-  renamedLink.deleteSync();
-}
-
-void testCreateLinkToFile(String dir) {
-  final path = '${dir}\\a_long_path_linkname';
-  Expect.isTrue(path.length > maxPath);
-  var target = '$dir\\a_long_path_target';
-  final link = Link(path)..createSync(target);
-
-  final dest = File(target)..createSync();
-  Expect.isTrue(dest.existsSync());
-
-  Expect.isTrue(link.existsSync());
-  Expect.isTrue(link.targetSync().contains('a_long_path_target'));
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('a_long_path_target'));
-
-  // Rename link
-  var renamedLink = link.renameSync('${dir}\\a_renamed_long_path_link');
-  Expect.isTrue(renamedLink.existsSync());
-  Expect.isFalse(link.existsSync());
-  Expect.isTrue(renamedLink.targetSync().contains('a_long_path_target'));
-
-  // Update link target
-  target = '$dir\\an_updated_target';
-  final renamedDest = File(target)..createSync();
-  renamedLink.updateSync(target);
-  Expect.isTrue(renamedLink.targetSync().contains('an_updated_target'));
-
-  dest.deleteSync();
-  renamedDest.deleteSync();
-  renamedLink.deleteSync();
-}
-
-testNormalLinkToLongPath(String short, String long) {
-  var target = File('$long\\file_target')..createSync();
-  final link = Link('$short\\link')..createSync(target.path);
-  Expect.isTrue(target.path.length > maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().length > maxPath);
-  Expect.isTrue(link.path.length < maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('file_target'));
-
-  Expect.isTrue(link.existsSync());
-  Expect.equals(target.path, link.targetSync());
-
-  var targetDir = Directory('$long\\dir_target')..createSync();
-  link.updateSync(targetDir.path);
-  Expect.equals(targetDir.path, link.targetSync());
-
-  link.deleteSync();
-  target.deleteSync();
-  targetDir.deleteSync();
-}
-
-testLongPathLinkToNormal(String short, String long) {
-  var target = File('$short\\file_target')..createSync();
-  final link = Link('$long\\link')..createSync(target.path);
-
-  Expect.isTrue(target.path.length < maxPath);
-  Expect.isTrue(link.path.length > maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('file_target'));
-
-  Expect.isTrue(link.existsSync());
-  Expect.equals(target.path, link.targetSync());
-
-  var targetDir = Directory('$short\\dir_target')..createSync();
-  link.updateSync(targetDir.path);
-  Expect.equals(targetDir.path, link.targetSync());
-
-  link.deleteSync();
-  target.deleteSync();
-  targetDir.deleteSync();
-}
-
-testDirectorySetCurrent(String dir) {
-  // This tests setting a long path directory to current directory.
-  // This will fail.
-  Expect.isTrue(dir.length > maxPath);
-  Expect.throws<FileSystemException>(() {
-    Directory.current = dir;
-  }, (e) => e.toString().contains('extension is too long'));
-}
-
-void main() {
-  if (!Platform.isWindows) {
-    return;
-  }
-  final tmp = Directory.systemTemp.createTempSync('dart-file-long-path');
-  final oldCurrent = Directory.current;
-  Directory.current = tmp;
-  try {
-    String dir = createLongPathDir(tmp).path;
-    testDirectorySetCurrent(dir);
-    for (final path in [dir, ".\\$longName", ".\\$longName\\..\\$longName"]) {
-      testCreate(path);
-      testCopy(path);
-      testRename(path);
-      testReadWrite(path);
-      testOpen(path);
-      testFileStat(path);
-      testCreateLinkToDir(path);
-      testCreateLinkToFile(path);
-    }
-
-    testNormalLinkToLongPath(tmp.path, dir);
-    testLongPathLinkToNormal(tmp.path, dir);
-  } finally {
-    // Reset the current Directory.
-    Directory.current = oldCurrent;
-    tmp.deleteSync(recursive: true);
-  }
-}
@@ -1,39 +0,0 @@
-// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-//
-// This test is Windows-only. It tests a short (shorter than 260) relative path
-// representing a long absolute path cannot be used by Windows API. Running this
-// test without proper support on long path will get an error.
-
-import 'dart:io';
-
-const maxPath = 260;
-
-void main(args) {
-  if (!Platform.isWindows) {
-    return;
-  }
-  final dir = Directory.systemTemp.createTempSync('test');
-
-  if (dir.path.length >= maxPath) {
-    return;
-  }
-
-  // Make sure oldpath is shorter than MAX_PATH (260).
-  int length = (maxPath - dir.path.length) ~/ 2;
-  final oldpath = Directory('${dir.path}\\${'x' * length}}');
-  oldpath.createSync(recursive: true);
-  final temp = Directory.current;
-
-  Directory.current = oldpath.path;
-
-  // The length of relative path is always shorter than maxPath, but it
-  // represents a path exceeding the maxPath.
-  final newpath = Directory('.\\${'y' * 2 * length}');
-  newpath.createSync();
-
-  // Reset current directory before deletion.
-  Directory.current = temp.path;
-  dir.deleteSync(recursive: true);
-}
@@ -1,247 +0,0 @@
-// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-//
-// This test is Windows-only.
-
-import 'dart:io';
-
-import "package:expect/expect.dart";
-
-const maxPath = 260;
-const maxDirectoryPath = maxPath - 12;
-String longName = '${'x' * 248}';
-
-Directory createLongPathDir(Directory tmp) {
-  if (tmp.path.length <= maxDirectoryPath) {
-    var path = tmp.path;
-    path += '\\${'t' * 248}';
-    var dir = Directory(path);
-    dir.createSync(recursive: true);
-    // Test the rename() of directory
-    dir = dir.renameSync(tmp.path + '\\$longName');
-    Expect.isTrue(dir.existsSync());
-    Expect.isFalse(Directory(path).existsSync());
-    return dir;
-  } else {
-    return tmp;
-  }
-}
-
-void testCreate(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  Expect.isTrue(file.existsSync());
-  file.deleteSync();
-}
-
-void testCopy(String dir) {
-  final src = '${dir}\\a_long_path_filename_1';
-  final dest = '${dir}\\a_long_path_filename_2';
-  Expect.isTrue(src.length > maxPath);
-  final file1 = File(src);
-  file1.createSync();
-
-  final file2 = file1.copySync(dest);
-  Expect.isTrue(file2.existsSync());
-  file1.deleteSync();
-  file2.deleteSync();
-}
-
-void testRename(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  Expect.isTrue(file.existsSync());
-
-  final renamedFile = file.renameSync('${path}_copy');
-
-  Expect.isFalse(file.existsSync());
-  Expect.isTrue(renamedFile.existsSync());
-  renamedFile.deleteSync();
-}
-
-void testReadWrite(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-
-  final content = "testReadWrite";
-  file.writeAsStringSync(content);
-  Expect.isTrue(file.existsSync());
-
-  int length = file.lengthSync();
-  Expect.equals(content.length, length);
-
-  final string = file.readAsStringSync();
-  Expect.equals(content, string);
-  file.deleteSync();
-}
-
-void testOpen(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  final access = file.openSync();
-  access.closeSync();
-}
-
-void testFileStat(String dir) {
-  final path = '${dir}\\a_long_path_filename';
-  Expect.isTrue(path.length > maxPath);
-  final file = File(path);
-  file.createSync();
-  final stat = FileStat.statSync(file.path);
-
-  final dateTime = DateTime.utc(2020);
-
-  file.setLastModifiedSync(dateTime);
-  Expect.notEquals(
-      stat.modified.toString(), file.lastModifiedSync().toString());
-
-  file.setLastAccessedSync(dateTime);
-  Expect.notEquals(
-      stat.accessed.toString(), file.lastAccessedSync().toString());
-}
-
-void testCreateLinkToDir(String dir) {
-  final path = '${dir}\\a_long_path_linkname';
-  Expect.isTrue(path.length > maxPath);
-  var target = '$dir\\a_long_path_target';
-  final link = Link(path)..createSync(target);
-
-  final dest = Directory(target)..createSync();
-  Expect.isTrue(dest.existsSync());
-
-  Expect.isTrue(link.existsSync());
-  Expect.isTrue(link.targetSync().contains('a_long_path_target'));
-
-  // Rename link
-  var renamedLink = link.renameSync('${dir}\\a_renamed_long_path_link');
-  Expect.isTrue(renamedLink.existsSync());
-  Expect.isFalse(link.existsSync());
-  Expect.isTrue(renamedLink.targetSync().contains('a_long_path_target'));
-
-  // Update link target
-  target = '$dir\\an_updated_target';
-  final renamedDest = Directory(target)..createSync();
-  renamedLink.updateSync(target);
-  Expect.isTrue(renamedLink.targetSync().contains('an_updated_target'));
-
-  dest.deleteSync();
-  renamedDest.deleteSync();
-  renamedLink.deleteSync();
-}
-
-void testCreateLinkToFile(String dir) {
-  final path = '${dir}\\a_long_path_linkname';
-  Expect.isTrue(path.length > maxPath);
-  var target = '$dir\\a_long_path_target';
-  final link = Link(path)..createSync(target);
-
-  final dest = File(target)..createSync();
-  Expect.isTrue(dest.existsSync());
-
-  Expect.isTrue(link.existsSync());
-  Expect.isTrue(link.targetSync().contains('a_long_path_target'));
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('a_long_path_target'));
-
-  // Rename link
-  var renamedLink = link.renameSync('${dir}\\a_renamed_long_path_link');
-  Expect.isTrue(renamedLink.existsSync());
-  Expect.isFalse(link.existsSync());
-  Expect.isTrue(renamedLink.targetSync().contains('a_long_path_target'));
-
-  // Update link target
-  target = '$dir\\an_updated_target';
-  final renamedDest = File(target)..createSync();
-  renamedLink.updateSync(target);
-  Expect.isTrue(renamedLink.targetSync().contains('an_updated_target'));
-
-  dest.deleteSync();
-  renamedDest.deleteSync();
-  renamedLink.deleteSync();
-}
-
-testNormalLinkToLongPath(String short, String long) {
-  var target = File('$long\\file_target')..createSync();
-  final link = Link('$short\\link')..createSync(target.path);
-  Expect.isTrue(target.path.length > maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().length > maxPath);
-  Expect.isTrue(link.path.length < maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('file_target'));
-
-  Expect.isTrue(link.existsSync());
-  Expect.equals(target.path, link.targetSync());
-
-  var targetDir = Directory('$long\\dir_target')..createSync();
-  link.updateSync(targetDir.path);
-  Expect.equals(targetDir.path, link.targetSync());
-
-  link.deleteSync();
-  target.deleteSync();
-  targetDir.deleteSync();
-}
-
-testLongPathLinkToNormal(String short, String long) {
-  var target = File('$short\\file_target')..createSync();
-  final link = Link('$long\\link')..createSync(target.path);
-
-  Expect.isTrue(target.path.length < maxPath);
-  Expect.isTrue(link.path.length > maxPath);
-  Expect.isTrue(link.resolveSymbolicLinksSync().contains('file_target'));
-
-  Expect.isTrue(link.existsSync());
-  Expect.equals(target.path, link.targetSync());
-
-  var targetDir = Directory('$short\\dir_target')..createSync();
-  link.updateSync(targetDir.path);
-  Expect.equals(targetDir.path, link.targetSync());
-
-  link.deleteSync();
-  target.deleteSync();
-  targetDir.deleteSync();
-}
-
-testDirectorySetCurrent(String dir) {
-  // This tests setting a long path directory to current directory.
-  // This will fail.
-  Expect.isTrue(dir.length > maxPath);
-  Expect.throws<FileSystemException>(() {
-    Directory.current = dir;
-  }, (e) => e.toString().contains('extension is too long'));
-}
-
-void main() {
-  if (!Platform.isWindows) {
-    return;
-  }
-  final tmp = Directory.systemTemp.createTempSync('dart-file-long-path');
-  final oldCurrent = Directory.current;
-  Directory.current = tmp;
-  try {
-    String dir = createLongPathDir(tmp).path;
-    testDirectorySetCurrent(dir);
-    for (final path in [dir, ".\\$longName", ".\\$longName\\..\\$longName"]) {
-      testCreate(path);
-      testCopy(path);
-      testRename(path);
-      testReadWrite(path);
-      testOpen(path);
-      testFileStat(path);
-      testCreateLinkToDir(path);
-      testCreateLinkToFile(path);
-    }
-
-    testNormalLinkToLongPath(tmp.path, dir);
-    testLongPathLinkToNormal(tmp.path, dir);
-  } finally {
-    // Reset the current Directory.
-    Directory.current = oldCurrent;
-    tmp.deleteSync(recursive: true);
-  }
-}
@@ -1,39 +0,0 @@
-// Copyright (c) 2020, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-//
-// This test is Windows-only. It tests a short (shorter than 260) relative path
-// representing a long absolute path cannot be used by Windows API. Running this
-// test without proper support on long path will get an error.
-
-import 'dart:io';
-
-const maxPath = 260;
-
-void main(args) {
-  if (!Platform.isWindows) {
-    return;
-  }
-  final dir = Directory.systemTemp.createTempSync('test');
-
-  if (dir.path.length >= maxPath) {
-    return;
-  }
-
-  // Make sure oldpath is shorter than MAX_PATH (260).
-  int length = (maxPath - dir.path.length) ~/ 2;
-  final oldpath = Directory('${dir.path}\\${'x' * length}}');
-  oldpath.createSync(recursive: true);
-  final temp = Directory.current;
-
-  Directory.current = oldpath.path;
-
-  // The length of relative path is always shorter than maxPath, but it
-  // represents a path exceeding the maxPath.
-  final newpath = Directory('.\\${'y' * 2 * length}');
-  newpath.createSync();
-
-  // Reset current directory before deletion.
-  Directory.current = temp.path;
-  dir.deleteSync(recursive: true);
-}