dart:io | Add Link.targetSync on all platforms.

runtime/bin/file_win.cc

Index: runtime/bin/file_win.cc
diff --git a/runtime/bin/file_win.cc b/runtime/bin/file_win.cc
index b23049dce5bfc7241347d89db5fae8060409d6d5..295835bfa5692067ff684374f8a5bb78423fb8ff 100644
--- a/runtime/bin/file_win.cc
+++ b/runtime/bin/file_win.cc
@@ -279,6 +279,52 @@ off_t File::LengthFromPath(const char* name) {
 }
 
 
+char* File::LinkTarget(const char* pathname) {
+  const wchar_t* name = StringUtils::Utf8ToWide(pathname);
+  HANDLE dir_handle = CreateFileW(
+      name,
+      GENERIC_READ,
+      FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+      NULL,
+      OPEN_EXISTING,
+      FILE_FLAG_BACKUP_SEMANTICS | FILE_FLAG_OPEN_REPARSE_POINT,
+      NULL);
+  free(const_cast<wchar_t*>(name));
+  if (dir_handle == INVALID_HANDLE_VALUE) {
+    return NULL;
+  }
+
+  int reparse_data_buffer_size =
+      sizeof REPARSE_DATA_BUFFER + 2 * (MAX_PATH + 1) * sizeof WCHAR;
+  REPARSE_DATA_BUFFER* reparse_data_buffer =
+      static_cast<REPARSE_DATA_BUFFER*>(calloc(reparse_data_buffer_size, 1));
+  DWORD received_bytes;
+  int result = DeviceIoControl(
+      dir_handle,
+      FSCTL_GET_REPARSE_POINT,
+      NULL,
+      0,
+      reparse_data_buffer,
+      reparse_data_buffer_size,
+      &received_bytes,
+      NULL);
+  if (CloseHandle(dir_handle) == 0) return NULL;
+  if (result == 0) return NULL;
+  if (reparse_data_buffer->ReparseTag != IO_REPARSE_TAG_MOUNT_POINT) {
+    return NULL;
+  }
+  wchar_t* target = reparse_data_buffer->MountPointReparseBuffer.PathBuffer +
+      reparse_data_buffer->MountPointReparseBuffer.SubstituteNameOffset;
+  size_t target_length =
+      reparse_data_buffer->MountPointReparseBuffer.SubstituteNameLength;
+  if (wcsncmp(L"\\??\\", target, 4) != 0) return NULL;
+  target += 4;

[Bill Hesse, 2013/03/18 09:05:54]

We really need to copy the data out here, because the string is not guaranteed
to be null-terminated, and the place we want to write the null is not guaranteed
to be in-bounds.

Will fix and upload new version, or let StringUtils::WideToUtf8 take a length.

+  char* target_string = StringUtils::WideToUtf8(target);
+  free(reparse_data_buffer);
+  return target_string;
+}
+
+
 time_t File::LastModified(const char* name) {
   struct _stat st;
   const wchar_t* system_name = StringUtils::Utf8ToWide(name);