Add StringBuilder::erase(index)

third_party/WebKit/Source/platform/wtf/text/StringBuilder.cpp

 /*
  * Copyright (C) 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 212 matching lines @@
 
 void StringBuilder::AppendNumber(unsigned long long number) {
   AppendIntegerInternal(*this, number);
 }
 
 void StringBuilder::AppendNumber(double number, unsigned precision) {
   NumberToStringBuffer buffer;
   Append(NumberToFixedPrecisionString(number, precision, buffer));
 }
 
+void StringBuilder::erase(unsigned index) {
+  if (index >= length_)
+    return;
+  if (index == length_ - 1)
+    return Resize(index);
+
+  if (is8_bit_) {
+    EnsureBuffer8(0);

[haraken, 2017/06/23 13:16:49]

Do you need this?

[kojii, 2017/06/23 13:45:23]

Yes, since StringBuilder may have StringImpl but not buffer yet. This ensures
there's a buffer, and StringImpl is copied into it.

I can call it only when "!HasBuffer()", but that's all what "EnsureBuffer" does;
it calls CreateBuffer() if !HasBuffer.

+    buffer8_->erase(index);
+  } else {
+    EnsureBuffer16(0);

[haraken, 2017/06/23 13:16:49]

Ditto.

+    buffer16_->erase(index);
+  }
+  --length_;

[haraken, 2017/06/23 13:16:49]

Do you want to call Resize() in this case as well?

It looks inconsistent that you call Resize() only when index == length_ - 1.

[kojii, 2017/06/23 13:45:23]

I guess you misunderstood something, probably due to micro-optimization I put
in? Resize() does two things:
1. Change buffer8_/buffer16_.
2. Change length_.
Since this function changes buffer8_/buffer16_, we can't call Resize() here.

The Resize() call, as mentioned above, is a suspective micro-optimization for
when removing the last character, I guess I shouldn't put it in if it makes
readability worse. Should I?

[haraken, 2017/06/23 13:56:17]

Makes sense. Yeah, remove it or add a comment.

[kojii, 2017/06/23 14:04:21]

Thank you for prompt reply, removed.

+}
+
 }  // namespace WTF