Add File::Duplicate to duplicate a file handle.

base/files/file_unittest.cc

 // Copyright (c) 2012 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 "base/files/file.h"
 #include "base/files/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 425 matching lines @@
   ASSERT_TRUE(file.IsValid());
 
   const int64 kOffset = 10;
   EXPECT_EQ(kOffset, file.Seek(base::File::FROM_BEGIN, kOffset));
   EXPECT_EQ(2 * kOffset, file.Seek(base::File::FROM_CURRENT, kOffset));
   EXPECT_EQ(kOffset, file.Seek(base::File::FROM_CURRENT, -kOffset));
   EXPECT_TRUE(file.SetLength(kOffset * 2));
   EXPECT_EQ(kOffset, file.Seek(base::File::FROM_END, -kOffset));
 }
 
+TEST(FileTest, Duplicate) {
+  base::ScopedTempDir temp_dir;
+  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
+  FilePath file_path = temp_dir.path().AppendASCII("file");
+  File file(file_path,(base::File::FLAG_CREATE |
+                       base::File::FLAG_READ |
+                       base::File::FLAG_WRITE));
+  ASSERT_TRUE(file.IsValid());
+
+  File file2(file.Duplicate());
+  ASSERT_TRUE(file2.IsValid());
+
+  // Write through one handle, close it, read through the other.
+  static const char kData[] = "now is a good time.";
+  static const int kDataLen = sizeof(kData) - 1;
+
+  ASSERT_EQ(0, file.Seek(base::File::FROM_CURRENT, 0));
+  ASSERT_EQ(0, file2.Seek(base::File::FROM_CURRENT, 0));
+  ASSERT_EQ(kDataLen, file.WriteAtCurrentPos(kData, kDataLen));
+  ASSERT_EQ(kDataLen, file.Seek(base::File::FROM_CURRENT, 0));
+  ASSERT_EQ(kDataLen, file2.Seek(base::File::FROM_CURRENT, 0));
+  file.Close();
+  char buf[kDataLen];
+  ASSERT_EQ(kDataLen, file2.Read(0, &buf[0], kDataLen));
+  ASSERT_EQ(std::string(kData, kDataLen), std::string(&buf[0], kDataLen));
+}
+
+TEST(FileTest, DuplicateDeleteOnClose) {
+  base::ScopedTempDir temp_dir;
+  ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
+  FilePath file_path = temp_dir.path().AppendASCII("file");
+  File file(file_path,(base::File::FLAG_CREATE |
+                       base::File::FLAG_READ |
+                       base::File::FLAG_WRITE |
+                       base::File::FLAG_DELETE_ON_CLOSE));
+  ASSERT_TRUE(file.IsValid());
+  File file2(file.Duplicate());
+  ASSERT_TRUE(file2.IsValid());
+  file.Close();
+  file2.Close();
+  ASSERT_FALSE(base::PathExists(file_path));
+}
+
 #if defined(OS_WIN)
 TEST(FileTest, GetInfoForDirectory) {
   base::ScopedTempDir temp_dir;
   ASSERT_TRUE(temp_dir.CreateUniqueTempDir());
   FilePath empty_dir = temp_dir.path().Append(FILE_PATH_LITERAL("gpfi_test"));
   ASSERT_TRUE(CreateDirectory(empty_dir));
 
   base::File dir(
       ::CreateFile(empty_dir.value().c_str(),
                    FILE_ALL_ACCESS,
@@ skipping 72 matching lines @@
     EXPECT_DEATH(file.Seek(File::FROM_BEGIN, 0), "");
     EXPECT_DEATH(file.Read(0, NULL, 0), "");
     EXPECT_DEATH(file.ReadAtCurrentPos(NULL, 0), "");
     EXPECT_DEATH(file.Write(0, NULL, 0), "");
 
     ignore_result(file.file_.file_.release());
     file.file_.UpdateChecksum();
   }
 }
 #endif  // defined(OS_POSIX)