Improve WriteUtf8 and WriteAscii.

test/cctest/test-api.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 5425 matching lines @@
   }
 }
 
 
 THREADED_TEST(StringWrite) {
   LocalContext context;
   v8::HandleScope scope;
   v8::Handle<String> str = v8_str("abcde");
   // abc<Icelandic eth><Unicode snowman>.
   v8::Handle<String> str2 = v8_str("abc\303\260\342\230\203");
+  v8::Handle<String> str3 = v8::String::New("abc\0def", 7);
   const int kStride = 4;  // Must match stride in for loops in JS below.
   CompileRun(
       "var left = '';"
       "for (var i = 0; i < 0xd800; i += 4) {"
       "  left = left + String.fromCharCode(i);"
       "}");
   CompileRun(
       "var right = '';"
       "for (var i = 0; i < 0xd800; i += 4) {"
       "  right = String.fromCharCode(i) + right;"
@@ skipping 190 matching lines @@
   utf8buf[8] = 'X';
   len = str2->WriteUtf8(utf8buf, sizeof(utf8buf), &charlen,
                         String::NO_NULL_TERMINATION);
   CHECK_EQ(8, len);
   CHECK_EQ('X', utf8buf[8]);
   CHECK_EQ(5, charlen);
   CHECK_EQ(0, strncmp(utf8buf, "abc\303\260\342\230\203", 8));
   CHECK_NE(0, strcmp(utf8buf, "abc\303\260\342\230\203"));
   utf8buf[8] = '\0';
   CHECK_EQ(0, strcmp(utf8buf, "abc\303\260\342\230\203"));
+
+  memset(utf8buf, 0x1, sizeof(utf8buf));
+  utf8buf[6] = 'X';
+  len = str->WriteUtf8(utf8buf, sizeof(utf8buf), &charlen,
+                        String::NO_NULL_TERMINATION);
+  CHECK_EQ(5, len);
+  CHECK_EQ('X', utf8buf[6]);
+  CHECK_EQ(5, charlen);
+  CHECK_EQ(0, strncmp(utf8buf, "abcde", 5));
+  CHECK_NE(0, strcmp(utf8buf, "abcde"));
+  utf8buf[5] = '\0';
+  CHECK_EQ(0, strcmp(utf8buf, "abcde"));
+
+  memset(buf, 0x1, sizeof(buf));
+  len = str3->WriteAscii(buf);
+  CHECK_EQ(7, len);
+  CHECK_EQ(0, strcmp("abc def", buf));
 }
 
 
 THREADED_TEST(ToArrayIndex) {
   v8::HandleScope scope;
   LocalContext context;
 
   v8::Handle<String> str = v8_str("42");
   v8::Handle<v8::Uint32> index = str->ToArrayIndex();
   CHECK(!index.IsEmpty());
@@ skipping 9821 matching lines @@
   CHECK(i->Equals(CompileRun("'abcbd'.replace(/b/g,func)[3]")));
 
   // TODO(1547): Make the following also return "i".
   // Calling with environment record as base.
   TestReceiver(o, context->Global(), "func()");
   // Calling with no base.
   TestReceiver(o, context->Global(), "(1,func)()");
 
   foreign_context.Dispose();
 }