Windows, JNI: implement native isJunction method.

WindowsFileSystem.java does not yet use it.

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MOS_MIGRATED_REVID=132043739

1 files changed, 73 insertions, 0 deletions

diff --git a/src/main/native/windows_file_operations.cc b/src/main/native/windows_file_operations.cc
new file mode 100644
index 0000000000..cbec4715c0
--- /dev/null
+++ b/src/main/native/windows_file_operations.cc
@@ -0,0 +1,73 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <jni.h>
+#include <windows.h>
+
+#include <string>
+
+#include "src/main/native/windows_error_handling.h"
+
+// Keep in sync with j.c.g.devtools.build.lib.windows.WindowsFileOperations
+enum {
+  IS_JUNCTION_YES = 0,
+  IS_JUNCTION_NO = 1,
+  IS_JUNCTION_ERROR = 2,
+};
+
+// Determines whether `path` is a junction point or directory symlink.
+//
+// To read about differences between junction points and directory symlinks,
+// see http://superuser.com/a/343079.
+//
+// Returns:
+// - IS_JUNCTION_YES, if `path` exists and is either a directory junction or a
+//   directory symlink
+// - IS_JUNCTION_NO, if `path` exists but is neither a directory junction nor a
+//   directory symlink; also when `path` is a symlink to a directory but it was
+//   created using "mklink" instead of "mklink /d", as such symlinks don't
+//   behave the same way as directories (e.g. they can't be listed)
+// - IS_JUNCTION_ERROR, if `path` doesn't exist or some error occurred
+int IsJunctionOrDirectorySymlink(const char* path) {
+  DWORD attrs = GetFileAttributesA(path);
+  if (attrs == INVALID_FILE_ATTRIBUTES) {
+    return IS_JUNCTION_ERROR;
+  } else {
+    if ((attrs & FILE_ATTRIBUTE_DIRECTORY) &&
+        (attrs & FILE_ATTRIBUTE_REPARSE_POINT)) {
+      return IS_JUNCTION_YES;
+    } else {
+      return IS_JUNCTION_NO;
+    }
+  }
+}
+
+extern "C" JNIEXPORT jint JNICALL
+Java_com_google_devtools_build_lib_windows_WindowsFileOperations_nativeIsJunction(
+    JNIEnv* env, jclass clazz, jstring path, jobjectArray error_msg_holder) {
+  const char* path_cstr = env->GetStringUTFChars(path, NULL);
+  bool report_error =
+      error_msg_holder != NULL && env->GetArrayLength(error_msg_holder) > 0;
+  int result = IsJunctionOrDirectorySymlink(path_cstr);
+  if (result == IS_JUNCTION_ERROR && report_error) {
+    std::string error_str =
+        GetLastErrorString(std::string("GetFileAttributesA(") +
+                           std::string(path_cstr) + std::string(")"));
+    jstring error_msg = env->NewStringUTF(error_str.c_str());
+    env->SetObjectArrayElement(error_msg_holder, 0, error_msg);
+  }
+
+  env->ReleaseStringUTFChars(path, path_cstr);
+  return result;
+}