mediaview: Introduce ArcDocumentsProviderRoot.

chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.h"
+
+#include <vector>
+
+#include "base/strings/string_util.h"
+#include "storage/browser/fileapi/file_system_url.h"
+
+namespace arc {
+
+namespace {
+
+constexpr base::FilePath::CharType kSpecialDirectory[] =
+    FILE_PATH_LITERAL("special");
+
+}  // namespace
+
+const char kDocumentsProviderMountPointName[] = "arc-documents-provider";
+const base::FilePath::CharType kDocumentsProviderMountPointPath[] =
+    "/special/arc-documents-provider";
+
+bool ParseDocumentsProviderUrl(const storage::FileSystemURL& url,
+                               std::string* authority,
+                               std::string* root_document_id,
+                               base::FilePath* path) {
+  if (url.type() != storage::kFileSystemTypeArcDocumentsProvider)
+    return false;
+
+  // Filesystem URL format for documents provider is:
+  // /special/arc-documents-provider/<authority>/<root_doc_id>/<relative_path>
+  std::vector<base::FilePath::StringType> components;
+  url.path().GetComponents(&components);
+  if (components.size() < 5 || components[0] != FILE_PATH_LITERAL("/") ||
+      components[1] != kSpecialDirectory ||
+      components[2] != kDocumentsProviderMountPointName) {

[hashimoto, 2016/12/16 09:03:52]

How about using base::FilePath::IsParent() instead of checking components[0..2]?

[Shuhei Takahashi, 2016/12/16 09:42:13]

That sounds better!

+    return false;
+  }
+
+  *authority = components[3];
+  *root_document_id = components[4];
+
+  base::FilePath url_path_stripped = url.path().StripTrailingSeparators();
+  base::FilePath root_path = base::FilePath(kDocumentsProviderMountPointPath)
+                                 .Append(*authority)
+                                 .Append(*root_document_id);
+  // Special case: AppendRelativePath() fails for identical paths.
+  if (url_path_stripped == root_path) {
+    path->clear();
+  } else {
+    bool success = root_path.AppendRelativePath(url_path_stripped, path);
+    DCHECK(success);
+  }
+  return true;
+}
+
+}  // namespace arc