Added new ReadFileToString API with a max_size argument

base/file_util_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 "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #include <shellapi.h>
 #include <shlobj.h>
@@ skipping 1906 matching lines @@
   EXPECT_EQ(-1, file_util::AppendToFile(foobar, data.c_str(), data.length()));
   EXPECT_EQ(static_cast<int>(data.length()),
             file_util::WriteFile(foobar, data.c_str(), data.length()));
   EXPECT_EQ(static_cast<int>(data.length()),
             file_util::AppendToFile(foobar, data.c_str(), data.length()));
 
   const std::wstring read_content = ReadTextFile(foobar);
   EXPECT_EQ(L"hellohello", read_content);
 }
 
+TEST_F(FileUtilTest, ReadFileToString) {
+  const char kTestData[] = "0123";
+  std::string data;
+
+  FilePath file_path =
+      temp_dir_.path().Append(FILE_PATH_LITERAL("ReadFileToStringTest"));
+
+  ASSERT_EQ(4, file_util::WriteFile(file_path, kTestData, 4));
+
+  EXPECT_TRUE(ReadFileToString(file_path, &data));
+  EXPECT_EQ(kTestData, data);
+
+  data = "temp";
+  EXPECT_FALSE(ReadFileToString(file_path, &data, 0));
+  EXPECT_EQ(data.length(), 0u);
+
+  data = "temp";
+  EXPECT_FALSE(ReadFileToString(file_path, &data, 2));
+  EXPECT_EQ("01", data);
+
+  data.clear();
+  EXPECT_FALSE(ReadFileToString(file_path, &data, 3));
+  EXPECT_EQ("012", data);
+
+  data.clear();
+  EXPECT_TRUE(ReadFileToString(file_path, &data, 4));
+  EXPECT_EQ("0123", data);
+
+  data.clear();
+  EXPECT_TRUE(ReadFileToString(file_path, &data, 6));
+  EXPECT_EQ("0123", data);
+
+  EXPECT_TRUE(ReadFileToString(file_path, NULL, 6));
+
+  EXPECT_TRUE(ReadFileToString(file_path, NULL));
+
+  EXPECT_TRUE(base::DeleteFile(file_path, false));
+
+  EXPECT_FALSE(ReadFileToString(file_path, &data));

[bartfab (slow), 2014/02/18 14:56:51]

Nit: You could add a data = "temp" statement before this to verify that it
clears |data|.

+  EXPECT_EQ(data.length(), 0u);
+
+  EXPECT_FALSE(ReadFileToString(file_path, &data, 6));

[bartfab (slow), 2014/02/18 14:56:51]

Nit: You could add a data = "temp" statement before this to verify that it
clears |data|.

+  EXPECT_EQ(data.length(), 0u);
+}
+
 TEST_F(FileUtilTest, TouchFile) {
   FilePath data_dir =
       temp_dir_.path().Append(FILE_PATH_LITERAL("FilePathTest"));
 
   // Create a fresh, empty copy of this directory.
   if (PathExists(data_dir)) {
     ASSERT_TRUE(DeleteFile(data_dir, true));
   }
   ASSERT_TRUE(CreateDirectory(data_dir));
 
@@ skipping 449 matching lines @@
   int fd = OpenContentUriForRead(path);
   EXPECT_EQ(-1, fd);
 }
 #endif
 
 #endif  // defined(OS_POSIX)
 
 }  // namespace
 
 }  // namespace base