Copy irregexp related code from V8.

runtime/vm/unibrow-inl.h

+// Copyright (c) 2014, 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 VM_UNIBROW_INL_H_
+#define VM_UNIBROW_INL_H_
+
+#include "vm/unibrow.h"
+
+// SNIP
+
+namespace unibrow {
+
+// SNIP
+
+template <class T, int s> int Mapping<T, s>::get(uchar c, uchar n,
+    uchar* result) {
+  CacheEntry entry = entries_[c & kMask];
+  if (entry.code_point_ == c) {
+    if (entry.offset_ == 0) {
+      return 0;
+    } else {
+      result[0] = c + entry.offset_;
+      return 1;
+    }
+  } else {
+    return CalculateValue(c, n, result);
+  }
+}
+
+template <class T, int s> int Mapping<T, s>::CalculateValue(uchar c, uchar n,
+    uchar* result) {
+  bool allow_caching = true;
+  int length = T::Convert(c, n, result, &allow_caching);
+  if (allow_caching) {
+    if (length == 1) {
+      entries_[c & kMask] = CacheEntry(c, result[0] - c);
+      return 1;
+    } else {
+      entries_[c & kMask] = CacheEntry(c, 0);
+      return 0;
+    }
+  } else {
+    return length;
+  }
+}
+
+// SNIP
+
+}  // namespace unibrow
+
+#endif  // VM_UNIBROW_INL_H_