Consolidate strings in summary output.

pkg/analyzer/lib/src/summary/flat_buffers.dart

 // Copyright (c) 2016, 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.
 
 library analyzer.src.summary.flat_buffers;
 
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:math';
 import 'dart:typed_data';
@@ skipping 92 matching lines @@
   int _tail;
 
   /**
    * The location of the end of the current table, measured in bytes from the
    * end of [_buf], or `null` if a table is not currently being built.
    */
   int _currentTableEndTail;
 
   _VTable _currentVTable;
 
+  /**
+   * Map containing all strings that have been written so far.  This allows us
+   * to avoid duplicating strings.
+   */
+  Map<String, Offset<String>> _strings = <String, Offset<String>>{};
+
   Builder({this.initialSize: 1024}) {
     reset();
   }
 
   /**
    * Add the [field] with the given boolean [value].  The field is not added if
    * the [value] is equal to [def].  Booleans are stored as 8-bit fields with
    * `0` for `false` and `1` for `true`.
    */
   void addBool(int field, bool value, [bool def]) {
@@ skipping 257 matching lines @@
   /**
    * Write the given string [value] and return its [Offset], or `null` if
    * the [value] is equal to [def].
    */
   Offset<String> writeString(String value, [String def]) {
     if (_currentVTable != null) {
       throw new StateError(
           'Cannot write a non-scalar value while writing a table.');
     }
     if (value != def) {
-      // TODO(scheglov) optimize for ASCII strings
-      List<int> bytes = UTF8.encode(value);
-      int length = bytes.length;
-      _prepare(4, 1, additionalBytes: length);
-      Offset<String> result = new Offset(_tail);
-      _setUint32AtTail(_buf, _tail, length);
-      int offset = _buf.lengthInBytes - _tail + 4;
-      for (int i = 0; i < length; i++) {
-        _buf.setUint8(offset++, bytes[i]);
-      }
-      return result;
+      return _strings.putIfAbsent(value, () {
+        // TODO(scheglov) optimize for ASCII strings
+        List<int> bytes = UTF8.encode(value);
+        int length = bytes.length;
+        _prepare(4, 1, additionalBytes: length);
+        Offset<String> result = new Offset(_tail);
+        _setUint32AtTail(_buf, _tail, length);
+        int offset = _buf.lengthInBytes - _tail + 4;
+        for (int i = 0; i < length; i++) {
+          _buf.setUint8(offset++, bytes[i]);
+        }
+        return result;
+      });
     }
     return null;
   }
 
   /**
    * Prepare for writing the given [count] of scalars of the given [size].
    * Additionally allocate the specified [additionalBytes]. Update the current
    * tail pointer to point at the allocated space.
    */
   void _prepare(int size, int count, {int additionalBytes: 0}) {
@@ skipping 340 matching lines @@
     // Table size.
     buf.setUint16(bufOffset, tableSize, Endianness.LITTLE_ENDIAN);
     bufOffset += 2;
     // Field offsets.
     for (int fieldOffset in fieldOffsets) {
       buf.setUint16(bufOffset, fieldOffset, Endianness.LITTLE_ENDIAN);
       bufOffset += 2;
     }
   }
 }