VM: Speed up output of UTF8 for 1-byte strings.

runtime/vm/unicode_test.cc

 // Copyright (c) 2011, 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/unicode.h"
 #include "vm/globals.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
+TEST_CASE(Utf8Encode) {
+  const intptr_t kInputLen = 3;
+  const uint16_t kInput[kInputLen] = {0xe6, 0xe7, 0xe8};  // æøå
+  const String& input = String::Handle(String::FromUTF16(kInput, kInputLen));
+  static const uintptr_t kBufferLength = 10;
+  unsigned char buffer[kBufferLength];
+  for (uintptr_t i = 0; i < kBufferLength; i++) {
+    buffer[i] = 42;
+  }
+  Utf8::Encode(input, reinterpret_cast<char*>(&buffer[0]), 10);
+  uintptr_t i;
+  for (i = 0; i < static_cast<uintptr_t>(Utf8::Length(input)); i++) {
+    EXPECT(buffer[i] > 127);
+  }
+  for (; i < kBufferLength; i++) {
+    EXPECT(buffer[i] == 42);
+  }
+}
+
 TEST_CASE(Utf8Decode) {
   // Examples from the Unicode specification, chapter 3
   {
     const char* src = "\x41\xC3\xB1\x42";
     int32_t expected[] = {0x41, 0xF1, 0x42};
     int32_t dst[ARRAY_SIZE(expected)];
     memset(dst, 0, sizeof(dst));
     bool is_valid = Utf8::DecodeCStringToUTF32(src, dst, ARRAY_SIZE(dst));
     EXPECT(is_valid);
     EXPECT(!memcmp(expected, dst, sizeof(expected)));
@@ skipping 1010 matching lines @@
     int32_t expected[] = {0xFFFF};
     int32_t dst[ARRAY_SIZE(expected)];
     memset(dst, 0, sizeof(dst));
     bool is_valid = Utf8::DecodeCStringToUTF32(src, dst, ARRAY_SIZE(dst));
     EXPECT(is_valid);
     EXPECT(!memcmp(expected, dst, sizeof(expected)));
   }
 }
 
 }  // namespace dart