Copy irregexp related code from V8.

runtime/vm/unibrow.h

Index: runtime/vm/unibrow.h
diff --git a/runtime/vm/unibrow.h b/runtime/vm/unibrow.h
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+// 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_H_
+#define VM_UNIBROW_H_
+
+#include <sys/types.h>
+
+// SNIP
+
+/**
+ * \file
+ * Definitions and convenience functions for working with unicode.
+ */
+
+namespace unibrow {
+
+// SNIP
+
+// A cache used in case conversion.  It caches the value for characters
+// that either have no mapping or map to a single character independent
+// of context.  Characters that map to more than one character or that
+// map differently depending on context are always looked up.
+template <class T, int size = 256>
+class Mapping {
+ public:
+  inline Mapping() { }
+  inline int get(uchar c, uchar n, uchar* result);
+ private:
+  friend class Test;
+  int CalculateValue(uchar c, uchar n, uchar* result);
+  struct CacheEntry {
+    inline CacheEntry() : code_point_(kNoChar), offset_(0) { }
+    inline CacheEntry(uchar code_point, signed offset)
+      : code_point_(code_point),
+        offset_(offset) { }
+    uchar code_point_;
+    signed offset_;
+    static const int kNoChar = (1 << 21) - 1;
+  };
+  static const int kSize = size;
+  static const int kMask = kSize - 1;
+  CacheEntry entries_[kSize];
+};
+
+// SNIP
+
+struct Letter {
+  static bool Is(uchar c);
+};
+struct Ecma262Canonicalize {
+  static const int kMaxWidth = 1;
+  static int Convert(uchar c,
+                     uchar n,
+                     uchar* result,
+                     bool* allow_caching_ptr);
+};
+struct Ecma262UnCanonicalize {
+  static const int kMaxWidth = 4;
+  static int Convert(uchar c,
+                     uchar n,
+                     uchar* result,
+                     bool* allow_caching_ptr);
+};
+struct CanonicalizationRange {
+  static const int kMaxWidth = 1;
+  static int Convert(uchar c,
+                     uchar n,
+                     uchar* result,
+                     bool* allow_caching_ptr);
+};
+
+}  // namespace unibrow
+
+#endif  // VM_UNIBROW_H_