mediaview: Recognize more MIME types.

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 <algorithm>
+#include <utility>
 
+#include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "net/base/escape.h"
+#include "net/base/mime_util.h"
 #include "storage/browser/fileapi/file_system_url.h"
 #include "url/gurl.h"
 
 namespace arc {
 
+namespace {
+
+struct MimeTypeToExtensions {
+  const char* mime_type;
+  const char* extensions;
+};
+
+// The mapping from MIME types to file name extensions, taken from Android N.
+// See: frameworks/base/media/java/android/media/MediaFile.java
+constexpr MimeTypeToExtensions kAndroidMimeTypeMappings[] = {
+    {"application/mspowerpoint", "ppt"},
+    {"application/msword", "doc"},
+    {"application/ogg", "ogg,oga"},
+    {"application/pdf", "pdf"},
+    {"application/vnd.apple.mpegurl", "m3u8"},
+    {"application/vnd.ms-excel", "xls"},
+    {"application/vnd.ms-wpl", "wpl"},
+    {"application/x-android-drm-fl", "fl"},
+    {"application/x-mpegurl", "m3u"},
+    {"application/zip", "zip"},
+    {"audio/aac", "aac"},
+    {"audio/aac-adts", "aac"},
+    {"audio/amr", "amr"},
+    {"audio/amr-wb", "awb"},
+    {"audio/flac", "flac"},
+    {"audio/imelody", "imy"},
+    {"audio/midi", "mid,midi,xmf,rtttl,rtx,ota,mxmf"},
+    {"audio/mp4", "m4a"},
+    {"audio/mpeg", "mp3,mpga"},
+    {"audio/mpegurl", "m3u8"},
+    {"audio/ogg", "ogg"},
+    {"audio/sp-midi", "smf"},
+    {"audio/x-matroska", "mka"},
+    {"audio/x-mpegurl", "m3u,m3u8"},
+    {"audio/x-ms-wma", "wma"},
+    {"audio/x-scpls", "pls"},
+    {"audio/x-wav", "wav"},
+    {"image/gif", "gif"},
+    {"image/jpeg", "jpg,jpeg"},
+    {"image/png", "png"},
+    {"image/vnd.wap.wbmp", "wbmp"},
+    {"image/webp", "webp"},
+    {"image/x-adobe-dng", "dng"},
+    {"image/x-canon-cr2", "cr2"},
+    {"image/x-fuji-raf", "raf"},
+    {"image/x-ms-bmp", "bmp"},
+    {"image/x-nikon-nef", "nef"},
+    {"image/x-nikon-nrw", "nrw"},
+    {"image/x-olympus-orf", "orf"},
+    {"image/x-panasonic-rw2", "rw2"},
+    {"image/x-pentax-pef", "pef"},
+    {"image/x-samsung-srw", "srw"},
+    {"image/x-sony-arw", "arw"},
+    {"text/html", "html,htm"},
+    {"text/plain", "txt"},
+    {"video/3gpp", "3gp,3gpp"},
+    {"video/3gpp2", "3g2,3gpp2"},
+    {"video/avi", "avi"},
+    {"video/mp2p", "mpg,mpeg"},
+    {"video/mp2ts", "ts"},
+    {"video/mp4", "mp4,m4v"},
+    {"video/mpeg", "mpg,mpeg"},
+    {"video/quicktime", "mov"},
+    {"video/webm", "webm"},
+    {"video/x-matroska", "mkv"},
+    {"video/x-ms-asf", "asf"},
+    {"video/x-ms-wmv", "wmv"},
+};
+
+constexpr char kApplicationOctetStreamMimeType[] = "application/octet-stream";
+
+}  // namespace
+
 // This is based on net/base/escape.cc: net::(anonymous namespace)::Escape.
 // TODO(nya): Consider consolidating this function with EscapeFileSystemId() in
 // chrome/browser/chromeos/file_system_provider/mount_path_util.cc.
 // This version differs from the other one in the point that dots are not always
 // escaped because authorities often contain harmless dots.
 std::string EscapePathComponent(const std::string& name) {
   std::string escaped;
   // Escape dots only when they forms a special file name.
   if (name == "." || name == "..") {
     base::ReplaceChars(name, ".", "%2E", &escaped);
@@ skipping 65 matching lines @@
 }
 
 GURL BuildDocumentUrl(const std::string& authority,
                       const std::string& document_id) {
   return GURL(base::StringPrintf(
       "content://%s/document/%s",
       net::EscapeQueryParamValue(authority, false /* use_plus */).c_str(),
       net::EscapeQueryParamValue(document_id, false /* use_plus */).c_str()));
 }
 
+std::vector<base::FilePath::StringType> GetExtensionsForArcMimeType(
+    const std::string& mime_type) {
+  // net::GetExtensionsForMimeType() returns unwanted extensions like
+  // "exe,com,bin" for application/octet-stream.
+  if (net::MatchesMimeType(kApplicationOctetStreamMimeType, mime_type))
+    return std::vector<base::FilePath::StringType>();

[hidehiko, 2017/01/27 09:39:00]

Optional:

return {};

may be simpler?
It looks allowed
https://google.github.io/styleguide/cppguide.html#Braced_Initializer_List
and actually several code in chromium uses.
(Though it's not much popular?). Totally up to you.

[Shuhei Takahashi, 2017/01/27 09:44:32]

I also thought I can do that, but it gives a compilation error in some setups.
This is an output from target_os="chromeos", is_debug=true configuration:

../../chrome/browser/chromeos/arc/fileapi/arc_documents_provider_util.cc:183:12:
error: chosen constructor is explicit in copy-initialization
    return {};
           ^~
../../build/linux/ubuntu_precise_amd64-sysroot/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../include/c++/4.6/debug/vector:77:7:
note: constructor declared here
      vector(const _Allocator& __a = _Allocator())
      ^

+
+  // Attempt net::GetExtensionsForMimeType().
+  {
+    std::vector<base::FilePath::StringType> extensions;
+    net::GetExtensionsForMimeType(mime_type, &extensions);
+    if (!extensions.empty()) {
+      base::FilePath::StringType preferred_extension;
+      if (net::GetPreferredExtensionForMimeType(mime_type,
+                                                &preferred_extension)) {
+        auto iter = std::find(extensions.begin(), extensions.end(),
+                              preferred_extension);
+        if (iter == extensions.end()) {
+          // This is unlikely to happen, but there is no guarantee.

[hidehiko, 2017/01/27 09:39:00]

Nice comment!

+          extensions.insert(extensions.begin(), preferred_extension);
+        } else {
+          std::swap(extensions.front(), *iter);
+        }
+      }
+      return extensions;
+    }
+  }
+
+  // Fallback to our hard-coded list.
+  for (const auto& entry : kAndroidMimeTypeMappings) {
+    if (net::MatchesMimeType(entry.mime_type, mime_type)) {
+      return base::SplitString(entry.extensions, ",", base::TRIM_WHITESPACE,

[hidehiko, 2017/01/27 09:39:00]

How about commenting;
// This module is only for ChromeOS where base::File::StringType is std::string.

[Shuhei Takahashi, 2017/01/27 09:44:32]

Sure, added a short comment.

+                               base::SPLIT_WANT_ALL);
+    }
+  }
+
+  return std::vector<base::FilePath::StringType>();
+}
+
 }  // namespace arc