Introduce ForwardsTextBuffer and BackwardsTextBuffer

third_party/WebKit/Source/core/editing/iterators/BackwardsTextBufferTest.cpp

Index: third_party/WebKit/Source/core/editing/iterators/BackwardsTextBufferTest.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/BackwardsTextBufferTest.cpp b/third_party/WebKit/Source/core/editing/iterators/BackwardsTextBufferTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..da5827e7cef99854a9e46c629a4672081ed3f4eb
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/iterators/BackwardsTextBufferTest.cpp
@@ -0,0 +1,67 @@
+// 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 "core/editing/iterators/BackwardsTextBuffer.h"
+
+#include "core/editing/EditingTestBase.h"
+
+namespace blink {
+
+class BackwardsTextBufferTest : public EditingTestBase {
+};
+
+TEST_F(BackwardsTextBufferTest, pushCharacters)
+{
+    BackwardsTextBuffer buffer;
+
+    // Basic tests.
+    buffer.pushCharacters('a', 1);
+    buffer.pushCharacters(1u, 0);
+    buffer.pushCharacters('#', 2);
+    buffer.pushCharacters('\0', 1);
+    EXPECT_EQ('\0', buffer[0]);
+    EXPECT_EQ('#', buffer[1]);
+    EXPECT_EQ('#', buffer[2]);
+    EXPECT_EQ('a', buffer[3]);
+
+    // Tests with buffer reallocation.
+    buffer.pushCharacters('A', 4096);
+    EXPECT_EQ('A', buffer[0]);
+    EXPECT_EQ('A', buffer[4095]);
+    EXPECT_EQ('\0', buffer[4096]);
+    EXPECT_EQ('#', buffer[4097]);
+    EXPECT_EQ('#', buffer[4098]);
+    EXPECT_EQ('a', buffer[4099]);
+}
+
+TEST_F(BackwardsTextBufferTest, pushRange)
+{
+    BackwardsTextBuffer buffer;
+
+    // Basic tests.
+    buffer.pushRange("ababc", 1);
+    buffer.pushRange((UChar*)nullptr, 0);
+    buffer.pushRange("#@", 2);
+    UChar ch = 'x';
+    buffer.pushRange(&ch, 1);
+    EXPECT_EQ('x', buffer[0]);
+    EXPECT_EQ('#', buffer[1]);
+    EXPECT_EQ('@', buffer[2]);
+    EXPECT_EQ('a', buffer[3]);
+
+    // Tests with buffer reallocation.
+    Vector<UChar> chunk(4096);
+    for (unsigned i = 0; i < chunk.size(); ++i)
+        chunk[i] = i % 256;
+    buffer.pushRange(chunk.data(), chunk.size());
+    EXPECT_EQ(0, buffer[0]);
+    EXPECT_EQ(1111 % 256, buffer[1111]);
+    EXPECT_EQ(255, buffer[4095]);
+    EXPECT_EQ('x', buffer[4096]);
+    EXPECT_EQ('#', buffer[4097]);
+    EXPECT_EQ('@', buffer[4098]);
+    EXPECT_EQ('a', buffer[4099]);
+}
+
+} // namespace blink