Introduce CodeBuffer as StringBuffer replacement in compiler.

lib/compiler/implementation/code_buffer.dart

Index: lib/compiler/implementation/code_buffer.dart
diff --git a/lib/compiler/implementation/code_buffer.dart b/lib/compiler/implementation/code_buffer.dart
new file mode 100644
index 0000000000000000000000000000000000000000..476c8b7fe2ac1840f5053b667c5623019ddaae3e
--- /dev/null
+++ b/lib/compiler/implementation/code_buffer.dart
@@ -0,0 +1,78 @@
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class CodeBuffer {
+  StringBuffer _buffer;

[floitsch, 2012/07/12 16:29:09]

Any reason those fields are marked as private?
Unless you think somebody could mistakenly use a field or a method we generally
keep members public.

This is, of course, not necessarily true, if the CodeBuffers are exposed through
the public API.

[podivilov, 2012/07/13 12:49:57]

No, they aren't exposed. Made the fields public.

+  List<_SourceLocation> _sourceLocations;
+  int _lastBufferOffset = 0;
+
+  CodeBuffer()
+      : _buffer = new StringBuffer(),
+        _sourceLocations = new List<_SourceLocation>();
+
+  int get length() {
+    return _buffer.length;
+  }
+
+  bool isEmpty() {
+    return _buffer.isEmpty();
+  }
+
+  void add(Object object) {

[floitsch, 2012/07/12 16:29:09]

Use "var" if you want to show that this function accepts more than one type, but
needs to dispatch.
Also add comment /** */ explaining what it takes.

[podivilov, 2012/07/13 12:49:57]

Done.

+    if (object is CodeBuffer) {
+      addBuffer(object);
+      return;
+    }
+    _buffer.add(object);
+  }
+
+  void addBuffer(CodeBuffer other) {
+    if (other._sourceLocations.length > 0) {
+      _SourceLocation firstMapping = other._sourceLocations[0];
+      int offsetDelta = _buffer.length + firstMapping.offsetDelta -

[floitsch, 2012/07/12 16:29:09]

minor nit. we generally prefer to indent as follows (if it fits):
int offsetDelta =
    _buffer.length + firstMapping.offsetDelta - _lastBufferOffset;

Maybe it's just me, but to me reading it as firstMapping.offsetDelta +
(_buffer.length - _lastBufferOffset) reads more naturally.

[podivilov, 2012/07/13 12:49:57]

Done.

+                        _lastBufferOffset;
+      _sourceLocations.add(new _SourceLocation(firstMapping.element,
+                                             firstMapping.token,

[floitsch, 2012/07/12 16:29:09]

indentation.

[podivilov, 2012/07/13 12:49:57]

Done.

+                                             offsetDelta));
+      for (int i = 1; i < other._sourceLocations.length; ++i) {
+        _sourceLocations.add(other._sourceLocations[i]);
+      }
+      _lastBufferOffset = _buffer.length + other._lastBufferOffset;
+    }
+    _buffer.add(other);

[floitsch, 2012/07/12 16:29:09]

I prefer _buffer.add(other.toString()) but not a strong preference. Just shows
that you want to copy over the string now.

[podivilov, 2012/07/13 12:49:57]

Done.

+  }
+
+  void clear() {
+    _buffer.clear();
+    _sourceLocations.clear();
+    _lastBufferOffset = 0;
+  }
+
+  String toString() {
+    return _buffer.toString();
+  }
+
+  void setSourceLocation(Element element, Token token) {
+    int offsetDelta = _buffer.length - _lastBufferOffset;
+    _sourceLocations.add(new _SourceLocation(element, token, offsetDelta));
+    _lastBufferOffset = _buffer.length;
+  }
+
+  void visitSourceLocations(void visitor(Element element,

[floitsch, 2012/07/12 16:29:09]

This is not a visitor, rather call it "forEach".
void forEachSourceLocation(void f(Element element ....)

[podivilov, 2012/07/13 12:49:57]

Done.

+                                         Token token,
+                                         int offset)) {
+    int offset = 0;
+    _sourceLocations.forEach((sourceLocation) {
+      offset += sourceLocation.offsetDelta;
+      visitor(sourceLocation.element, sourceLocation.token, offset);
+    });
+  }
+}
+
+class _SourceLocation {

[floitsch, 2012/07/12 16:29:09]

ditto. why make this class private?

[podivilov, 2012/07/13 12:49:57]

Done.

+  Element element;
+  Token token;
+  int offsetDelta;
+  _SourceLocation(this.element, this.token, this.offsetDelta);
+}