Add mojo interface to load hyphenation dictionaries on Android

content/browser/hyphenation/hyphenation_impl.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 "content/browser/hyphenation/hyphenation_impl.h"
+
+#include <algorithm>
+#include <map>
+#include <utility>
+
+#include "base/files/file.h"
+#include "base/files/file_path.h"
+#include "base/strings/stringprintf.h"
+#include "mojo/public/cpp/system/platform_handle.h"
+
+#if defined(HYPHENATION_DIR_HOME_FOR_TEST)
+#include "base/base_paths.h"
+#include "base/path_service.h"
+#endif
+
+namespace {
+
+using DictionaryFileMap = std::unordered_map<std::string, base::File>;
+
+static bool IsValidLocale(const std::string& locale) {
+  return std::all_of(locale.cbegin(), locale.cend(),
+                     [](const char ch) { return isalpha(ch) || ch == '-'; });
+}
+
+static base::File& GetDictionaryFile(const std::string& locale) {
+  // Keep Files open in the cache for subsequent calls.
+  CR_DEFINE_STATIC_LOCAL(DictionaryFileMap, cache, ());
+
+  // TODO(kojii): Replace find+insert with emplace()+std::piecewise_construct
+  // when std::map::emplace() is fully supported on all configurations.
+  const auto& it = cache.find(locale);
+  if (it != cache.end())
+    return it->second;
+  base::File file_on_stack;
+  const auto& inserted = cache.insert(
+      std::make_pair(locale, std::move(file_on_stack)));
+  base::File& file = inserted.first->second;
+  DCHECK(!file.IsValid());
+
+  // Only ISO lang code is accepted.

[jam, 2016/07/12 14:51:12]

don't we want to check this and early exit before the map is updated?

+  if (!IsValidLocale(locale))
+    return file;
+
+#if defined(HYPHENATION_DIR_HOME_FOR_TEST)

[jam, 2016/07/12 14:51:12]

normally this is done by adding a command line flag instead of a build flag

[kojii, 2016/07/12 17:32:21]

This is really for dev/testing on other platforms since debug on Android isn't
easy. I think we don't want to put a code to read files on user's home directory
in the shipped code.

Removed this. With your comment, I found a local patch is more appropriate.
Thank you for that.

+  base::FilePath dir;
+  if (!base::PathService::Get(base::DIR_HOME, &dir))
+    return file;

[jam, 2016/07/12 14:51:12]

here as well, don't we only want to put valid paths in the map?

+#elif defined(OS_ANDROID)
+  base::FilePath dir("/system/usr/hyphen-data");
+#else
+#error "This configuration is not supported."
+#endif
+  std::string filename = base::StringPrintf("hyph-%s.hyb", locale.c_str());
+  base::FilePath path = dir.AppendASCII(filename);
+  file.Initialize(path, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  return file;
+}
+
+}  // namespace
+
+namespace hyphenation {
+
+HyphenationImpl::HyphenationImpl(blink::mojom::HyphenationRequest request)
+    : binding_(this, std::move(request)) {}
+
+HyphenationImpl::~HyphenationImpl() {}
+
+// static
+void HyphenationImpl::Create(blink::mojom::HyphenationRequest request) {
+  new HyphenationImpl(std::move(request));
+}
+
+void HyphenationImpl::OpenDictionary(const mojo::String& locale,
+                                     const OpenDictionaryCallback& callback) {
+  mojo::ScopedHandle handle;
+  base::File& file = GetDictionaryFile(locale);
+  if (file.IsValid())
+    handle = mojo::WrapPlatformFile(file.Duplicate().TakePlatformFile());
+  callback.Run(std::move(handle));
+}
+
+}  // namespace hyphenation