Use zone allocated C-strings instead of String heap objects to construct signature symbols

runtime/vm/symbols.cc

 // 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.
 
 #include "vm/symbols.h"
 
 #include "vm/handles.h"
 #include "vm/handles_impl.h"
 #include "vm/hash_table.h"
 #include "vm/isolate.h"
@@ skipping 375 matching lines @@
   if (str1.Length() == 0) {
     return New(str2);
   } else if (str2.Length() == 0) {
     return New(str1);
   } else {
     return NewSymbol(ConcatString(str1, str2));
   }
 }
 
 
+// TODO(srdjan): If this becomes performance critical code, consider looking
+// up symbol from pieces instead of concatenating them first into a big string.
+RawString* Symbols::FromConcatAll(const GrowableArray<const String*>& strs) {
+  GrowableArray<const char*> cchars(strs.length());
+  GrowableArray<intptr_t> lengths(strs.length());
+  intptr_t len_sum = 0;
+  for (intptr_t i = 0; i < strs.length(); i++) {
+    const char* to_cstr = strs[i]->ToCString();
+    intptr_t len = strlen(to_cstr);
+    cchars.Add(to_cstr);
+    lengths.Add(len);
+    len_sum += len;
+  }
+
+  Zone* zone = Thread::Current()->zone();
+  char* buffer = zone->Alloc<char>(len_sum);
+  const char* const orig_buffer = buffer;
+  for (intptr_t i = 0; i < cchars.length(); i++) {
+    intptr_t len = lengths[i];
+    strncpy(buffer, cchars[i], len);
+    buffer += len;
+  }
+  ASSERT(len_sum == buffer - orig_buffer);
+  return Symbols::New(orig_buffer, len_sum);
+}
+
+
 // StringType can be StringSlice, ConcatString, or {Latin1,UTF16,UTF32}Array.
 template<typename StringType>
 RawString* Symbols::NewSymbol(const StringType& str) {
   Thread* thread = Thread::Current();
   Isolate* isolate = thread->isolate();
   Zone* zone = thread->zone();
   String& symbol = String::Handle(zone);
   {
     Isolate* vm_isolate = Dart::vm_isolate();
     SymbolTable table(zone, vm_isolate->object_store()->symbol_table());
@@ skipping 63 matching lines @@
 RawObject* Symbols::GetVMSymbol(intptr_t object_id) {
   ASSERT(IsVMSymbolId(object_id));
   intptr_t i = (object_id - kMaxPredefinedObjectIds);
   if ((i > kIllegal) && (i < Symbols::kMaxPredefinedId)) {
     return symbol_handles_[i]->raw();
   }
   return Object::null();
 }
 
 }  // namespace dart