Implement StringImpl sharing for StringView::toString().

third_party/WebKit/Source/wtf/text/StringBuilderTest.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 77 matching lines @@
     builder.append(builder1.characters8(), builder1.length());
     expectBuilderContent("0123456789abcdefg#0123456789abcdefg#XYZ", builder);
 
     StringBuilder builder2;
     builder2.reserveCapacity(100);
     builder2.append("xyz");
     const LChar* characters = builder2.characters8();
     builder2.append("0123456789");
     EXPECT_EQ(characters, builder2.characters8());
 
+    StringBuilder builder3;
+    builder3.append("xyz", 1, 2);
+    expectBuilderContent("yz", builder3);
+
+    StringBuilder builder4;
+    builder4.append("abc", 5, 3);
+    expectEmpty(builder4);
+
+    StringBuilder builder5;
+    builder5.append(StringView(StringView("def"), 1, 1));
+    expectBuilderContent("e", builder5);
+
+    // append() has special code paths for String backed StringView instead of
+    // just char* backed ones.
+    StringBuilder builder6;
+    builder6.append(String("ghi"), 1, 2);
+    expectBuilderContent("hi", builder6);
+
     // Test appending UChar32 characters to StringBuilder.
     StringBuilder builderForUChar32Append;
     UChar32 frakturAChar = 0x1D504;
     builderForUChar32Append.append(frakturAChar); // The fraktur A is not in the BMP, so it's two UTF-16 code units long.
     EXPECT_EQ(2U, builderForUChar32Append.length());
     builderForUChar32Append.append(static_cast<UChar32>('A'));
     EXPECT_EQ(3U, builderForUChar32Append.length());
     const UChar resultArray[] = { U16_LEAD(frakturAChar), U16_TRAIL(frakturAChar), 'A' };
     expectBuilderContent(String(resultArray, WTF_ARRAY_LENGTH(resultArray)), builderForUChar32Append);
 }
 
+TEST(StringBuilderTest, AppendSharingImpl)
+{
+    String string("abc");
+    StringBuilder builder1;
+    builder1.append(string);
+    EXPECT_EQ(string.impl(), builder1.toString().impl());
+    EXPECT_EQ(string.impl(), builder1.toAtomicString().impl());
+
+    StringBuilder builder2;
+    builder2.append(string, 0, string.length());
+    EXPECT_EQ(string.impl(), builder2.toString().impl());
+    EXPECT_EQ(string.impl(), builder2.toAtomicString().impl());
+}
+
 TEST(StringBuilderTest, ToString)
 {
     StringBuilder builder;
     builder.append("0123456789");
     String string = builder.toString();
     EXPECT_EQ(String("0123456789"), string);
     EXPECT_EQ(string.impl(), builder.toString().impl());
 
     // Changing the StringBuilder should not affect the original result of toString().
     builder.append("abcdefghijklmnopqrstuvwxyz");
@@ skipping 198 matching lines @@
     StringBuilder reference;
     reference.append(replacementCharacter); // Make it UTF-16.
     reference.append(String::number(someNumber));
     StringBuilder test;
     test.append(replacementCharacter);
     test.appendNumber(someNumber);
     EXPECT_EQ(reference, test);
 }
 
 } // namespace WTF