Add string pools to save storage.

core/fxcrt/cfx_string_pool_template_unittest.cpp

+// Copyright 2016 PDFium 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 "core/fxcrt/include/cfx_string_pool_template.h"
+#include "core/fxcrt/include/fx_string.h"
+#include "testing/fx_string_testhelpers.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(fxcrt, ByteStringPool) {
+  CFX_ByteStringPool pool;
+
+  CFX_ByteString null1;
+  CFX_ByteString null2;
+  CFX_ByteString goats1("goats");
+  CFX_ByteString goats2("goats");
+
+  // Underlying storage, if non-null, is not shared.

[dsinclair, 2016/09/15 20:23:26]

Doesn't this check that the underlying storage is null?

[Tom Sepez, 2016/09/15 20:51:24]

Yes, I think that's inline with the comment, for all vars, assert either null or
shared.

+  EXPECT_EQ(nullptr, null1.m_pData.Get());
+  EXPECT_EQ(nullptr, null2.m_pData.Get());
+  EXPECT_NE(goats1.m_pData, goats2.m_pData);

[Tom Sepez, 2016/09/15 20:52:37]

Note that we don't get here because operator== on shared ptrs.

+
+  CFX_ByteString interned_null1 = pool.Intern(null1);
+  CFX_ByteString interned_null2 = pool.Intern(null2);
+  CFX_ByteString interned_goats1 = pool.Intern(goats1);
+  CFX_ByteString interned_goats2 = pool.Intern(goats2);
+
+  // Strings are logically equal after being interned.
+  EXPECT_EQ(null1, interned_null1);
+  EXPECT_EQ(null2, interned_null2);
+  EXPECT_EQ(goats1, interned_goats1);
+  EXPECT_EQ(goats2, interned_goats2);
+

[dsinclair, 2016/09/15 20:23:26]

Should EXPECT_EQ(interned_goats1, interned_goats2) be true as well?

[Tom Sepez, 2016/09/15 20:51:24]

Yes, but that should be covered by the basic string tests.  Also transitivity
...

+  // Interned underlying storage, if non-null, belongs to first seen.
+  EXPECT_EQ(nullptr, interned_null1.m_pData.Get());
+  EXPECT_EQ(nullptr, interned_null2.m_pData.Get());
+  EXPECT_EQ(goats1.m_pData, interned_goats1.m_pData);
+  EXPECT_EQ(goats1.m_pData, interned_goats2.m_pData);
+
+  pool.Clear();
+  CFX_ByteString reinterned_null2 = pool.Intern(null2);
+  CFX_ByteString reinterned_null1 = pool.Intern(null2);

[dsinclair, 2016/09/15 20:23:26]

Is it intentional that the null1 and goats1 are pointed at the 2 versions? 
(Maybe add a comment to say so)

[Tom Sepez, 2016/09/15 20:51:24]

Yes, otherwise they're not equal. 

+  CFX_ByteString reinterned_goats2 = pool.Intern(goats2);
+  CFX_ByteString reinterned_goats1 = pool.Intern(goats2);
+
+  // After clearing pool, storage was re-interned using second strings.
+  EXPECT_EQ(nullptr, interned_null1.m_pData.Get());
+  EXPECT_EQ(nullptr, interned_null2.m_pData.Get());
+  EXPECT_EQ(goats2.m_pData, reinterned_goats1.m_pData);
+  EXPECT_EQ(goats2.m_pData, reinterned_goats2.m_pData);
+}
+
+TEST(fxcrt, WideStringPool) {
+  CFX_WideStringPool pool;
+
+  CFX_WideString null1;
+  CFX_WideString null2;
+  CFX_WideString goats1(L"goats");
+  CFX_WideString goats2(L"goats");
+
+  // Underlying storage, if non-null, is not shared.
+  EXPECT_EQ(nullptr, null1.m_pData.Get());
+  EXPECT_EQ(nullptr, null2.m_pData.Get());
+  EXPECT_NE(goats1.m_pData, goats2.m_pData);
+
+  CFX_WideString interned_null1 = pool.Intern(null1);
+  CFX_WideString interned_null2 = pool.Intern(null2);
+  CFX_WideString interned_goats1 = pool.Intern(goats1);
+  CFX_WideString interned_goats2 = pool.Intern(goats2);
+
+  // Strings are logically equal after being interned.
+  EXPECT_EQ(null1, interned_null1);
+  EXPECT_EQ(null2, interned_null2);
+  EXPECT_EQ(goats1, interned_goats1);
+  EXPECT_EQ(goats2, interned_goats2);
+
+  // Interned underlying storage, if non-null, belongs to first seen.
+  EXPECT_EQ(nullptr, interned_null1.m_pData.Get());
+  EXPECT_EQ(nullptr, interned_null2.m_pData.Get());
+  EXPECT_EQ(goats1.m_pData, interned_goats1.m_pData);
+  EXPECT_EQ(goats1.m_pData, interned_goats2.m_pData);
+
+  pool.Clear();
+  CFX_WideString reinterned_null2 = pool.Intern(null2);
+  CFX_WideString reinterned_null1 = pool.Intern(null2);
+  CFX_WideString reinterned_goats2 = pool.Intern(goats2);
+  CFX_WideString reinterned_goats1 = pool.Intern(goats2);
+
+  // After clearing pool, storage was re-interned using second strings.
+  EXPECT_EQ(nullptr, interned_null1.m_pData.Get());
+  EXPECT_EQ(nullptr, interned_null2.m_pData.Get());
+  EXPECT_EQ(goats2.m_pData, reinterned_goats1.m_pData);
+  EXPECT_EQ(goats2.m_pData, reinterned_goats2.m_pData);
+}