Have media gallery (through native media file util) use MIME sniffer

webkit/fileapi/media/native_media_file_util.cc

Index: webkit/fileapi/media/native_media_file_util.cc
diff --git a/webkit/fileapi/media/native_media_file_util.cc b/webkit/fileapi/media/native_media_file_util.cc
index 115278c5b7c617b72ef58d9751b86eb7ed17dfde..66320dbd62a320fd77c05f812d81aba02586105f 100644
--- a/webkit/fileapi/media/native_media_file_util.cc
+++ b/webkit/fileapi/media/native_media_file_util.cc
@@ -4,7 +4,12 @@
 
 #include "webkit/fileapi/media/native_media_file_util.h"
 
+#include "base/string_util.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/mime_sniffer.h"
+#include "webkit/fileapi/file_system_context.h"
 #include "webkit/fileapi/file_system_operation_context.h"
+#include "webkit/fileapi/file_system_task_runners.h"
 #include "webkit/fileapi/media/media_path_filter.h"
 #include "webkit/fileapi/media/filtering_file_enumerator.h"
 #include "webkit/fileapi/native_file_util.h"
@@ -13,6 +18,27 @@ using base::PlatformFile;
 using base::PlatformFileError;
 using base::PlatformFileInfo;
 
+namespace {
+
+// Modelled after ScopedFILEClose.
+class ScopedPlatformFileClose {
+ public:
+  void operator()(base::PlatformFile* ppf) const {
+    base::ClosePlatformFile(*ppf);
+  }
+};
+
+typedef scoped_ptr<base::PlatformFile,
+                   ScopedPlatformFileClose> ScopedPlatformFile;
+
+// Returns true if the current thread is capable of doing IO.
+bool IsOnTaskRunnerThread(fileapi::FileSystemOperationContext* context) {
+  return context->file_system_context()->task_runners()->
+      media_task_runner()->RunsTasksOnCurrentThread();
+}
+
+}
+
 namespace fileapi {
 
 NativeMediaFileUtil::NativeMediaFileUtil() {
@@ -214,4 +240,51 @@ NativeMediaFileUtil::GetFilteredLocalFilePathForExistingFileOrDirectory(
   return base::PLATFORM_FILE_OK;
 }
 
+base::PlatformFileError NativeMediaFileUtil::CreateSnapshotFile(
+    FileSystemOperationContext* context,
+    const FileSystemURL& url,
+    base::PlatformFileInfo* file_info,
+    base::FilePath* platform_path,
+    SnapshotFilePolicy* policy) {
+  DCHECK(IsOnTaskRunnerThread(context));
+  base::PlatformFileError error = IsolatedFileUtil::CreateSnapshotFile(
+      context, url, file_info, platform_path, policy);
+  if (error != base::PLATFORM_FILE_OK)
+    return error;
+  return IsMediaFile(*platform_path);
+}
+
+base::PlatformFileError NativeMediaFileUtil::IsMediaFile(
+    const base::FilePath& path) {
+  base::PlatformFile file_handle;
+  bool created;
+  base::PlatformFileError error;
+  error = NativeFileUtil::CreateOrOpen(path,
+      base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ, &file_handle,
+      &created);
+  if (error != base::PLATFORM_FILE_OK)
+    return error;
+  ScopedPlatformFile scoped_platform_file(new base::PlatformFile(file_handle));
+  char buffer[net::kMaxBytesToSniff];
+  int64 len;
+  // Read as much as SniffMimeType() will bother looking at.
+  len = base::ReadPlatformFile(file_handle, 0, buffer, net::kMaxBytesToSniff);
+  if (len < 0)
+    return base::PLATFORM_FILE_ERROR_FAILED;
+  if (len == 0)
+    return base::PLATFORM_FILE_ERROR_SECURITY;
+  std::string mime_type;
+  if (!net::SniffMimeType(buffer, len, GURL("file://" + path.value()),
+                          "no/idea", &mime_type)) {
+    return base::PLATFORM_FILE_ERROR_SECURITY;
+  }
+  if (StartsWithASCII(mime_type, "image/", true) ||
+      StartsWithASCII(mime_type, "audio/", true) ||
+      StartsWithASCII(mime_type, "video/", true)) {
+    return base::PLATFORM_FILE_OK;
+  } else {
+    return base::PLATFORM_FILE_ERROR_SECURITY;
+  }
+}
+
 }  // namespace fileapi