Restructure the Kernel string table.

runtime/vm/kernel_binary_flowgraph.h

 // Copyright (c) 2017, 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.
 
 #ifndef RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_
 #define RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_
 
 #if !defined(DART_PRECOMPILED_RUNTIME)
 
 #include <map>
@@ skipping 33 matching lines @@
   StreamingFlowGraphBuilder* builder_;
   Isolate* isolate_;
   Zone* zone_;
   TranslationHelper& translation_helper_;
   //  DartTypeTranslator& type_translator_;
 
   Script& script_;
   Instance& result_;
 };
 
+
 class StreamingFlowGraphBuilder {
  public:
   StreamingFlowGraphBuilder(FlowGraphBuilder* flow_graph_builder,
                             const uint8_t* buffer,
                             intptr_t buffer_length)
       : flow_graph_builder_(flow_graph_builder),
         translation_helper_(flow_graph_builder->translation_helper_),
         zone_(flow_graph_builder->zone_),
         reader_(new kernel::Reader(buffer, buffer_length)),
         constant_evaluator_(this,
                             flow_graph_builder->zone_,
                             &flow_graph_builder->translation_helper_,
                             &flow_graph_builder->type_translator_),
-        string_table_offsets_(NULL),
-        string_table_size_(-1),
-        string_table_entries_read_(0),
+        string_offset_count_(0),
+        string_offsets_(NULL),
         canonical_names_(NULL),
         canonical_names_size_(-1),
         canonical_names_entries_read_(0),
         canonical_names_next_offset_(-1) {}
 
   virtual ~StreamingFlowGraphBuilder() {
     delete reader_;
-    if (string_table_offsets_ != NULL) {
-      delete[] string_table_offsets_;
-    }
-    if (canonical_names_ != NULL) {
-      // At least for now we'll leak whatever's inside
-      delete[] canonical_names_;
-    }
+    delete[] string_offsets_;
+    // The canonical names themselves are not (yet) deallocated.
+    delete[] canonical_names_;
   }
 
   Fragment BuildAt(intptr_t kernel_offset);
 
  private:
-  intptr_t GetStringTableOffset(intptr_t index);
+  intptr_t GetStringOffset(intptr_t index);
   CanonicalName* GetCanonicalName(intptr_t index);
 
   intptr_t ReaderOffset();
   void SetOffset(intptr_t offset);
   void SkipBytes(intptr_t skip);
   uint32_t ReadUInt();
   intptr_t ReadListLength();
   TokenPosition ReadPosition(bool record = true);
   Tag ReadTag(uint8_t* payload = NULL);
 
@@ skipping 28 matching lines @@
   Fragment BuildIntLiteral(bool is_negative);
   Fragment BuildDoubleLiteral();
   Fragment BuildBoolLiteral(bool value);
   Fragment BuildNullLiteral();
 
   FlowGraphBuilder* flow_graph_builder_;
   TranslationHelper& translation_helper_;
   Zone* zone_;
   kernel::Reader* reader_;
   StreamingConstantEvaluator constant_evaluator_;
-  intptr_t* string_table_offsets_;
-  intptr_t string_table_size_;
-  intptr_t string_table_entries_read_;
+
+  // We build a table that gives us the start and end offsets of all the strings
+  // in the binary.
+  //
+  // The number of string offsets.  Note that this is one more than the number
+  // of strings in the binary.
+  intptr_t string_offset_count_;
+
+  // An array of offsets of size string_table_size_ + 1, in order to include the
+  // end offset of the last string.  The string with index N consists of the
+  // UTF-8 encoded bytes stretching from string_table_offsets_[N] (enclusive) to
+  // string_table_offsets_[N+1] (exclusive).
+  intptr_t* string_offsets_;
+
   CanonicalName** canonical_names_;
   intptr_t canonical_names_size_;
   intptr_t canonical_names_entries_read_;
   intptr_t canonical_names_next_offset_;
 
   friend class StreamingConstantEvaluator;
 };
 
+
 }  // namespace kernel
 }  // namespace dart
 
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 #endif  // RUNTIME_VM_KERNEL_BINARY_FLOWGRAPH_H_