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diff --git a/utf/unilib.h b/utf/unilib.h
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+/**
+ * Copyright 2010 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Routines to do manipulation of Unicode characters or text
+//
+// The StructurallyValid routines accept buffers of arbitrary bytes.
+// For CoerceToStructurallyValid(), the input buffer and output buffers may
+// point to exactly the same memory.
+//
+// In all other cases, the UTF-8 string must be structurally valid and
+// have all codepoints in the range  U+0000 to U+D7FF or U+E000 to U+10FFFF.
+// Debug builds take a fatal error for invalid UTF-8 input.
+// The input and output buffers may not overlap at all.
+//
+// The char32 routines are here only for convenience; they convert to UTF-8
+// internally and use the UTF-8 routines.
+
+#ifndef UTIL_UTF8_UNILIB_H__
+#define UTIL_UTF8_UNILIB_H__
+
+#include <string>
+#include "base/basictypes.h"
+
+namespace UniLib {
+
+// Returns true unless a surrogate code point
+inline bool IsValidCodepoint(char32 c) {
+  // In the range [0, 0xD800) or [0xE000, 0x10FFFF]
+  return (static_cast<uint32>(c) < 0xD800)
+    || (c >= 0xE000 && c <= 0x10FFFF);
+}
+
+// Table of UTF-8 character lengths, based on first byte
+static const unsigned char kUTF8LenTbl[256] = {
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1, 1,1,1,1,1,1,1,1,
+  2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,
+  3,3,3,3,3,3,3,3, 3,3,3,3,3,3,3,3, 4,4,4,4,4,4,4,4, 4,4,4,4,4,4,4,4
+};
+
+// Return length of a single UTF-8 source character
+inline int OneCharLen(const char* src) {
+  return kUTF8LenTbl[*reinterpret_cast<const uint8*>(src)];
+}
+
+// Return length of a single UTF-8 source character
+inline int OneCharLen(const uint8* src) {
+  return kUTF8LenTbl[*src];
+}
+
+// Return true if this byte is a trailing UTF-8 byte (10xx xxxx)
+inline bool IsTrailByte(char x) {
+  // return (x & 0xC0) == 0x80;
+  // Since trail bytes are always in [0x80, 0xBF], we can optimize:
+  return static_cast<signed char>(x) < -0x40;
+}
+
+// Returns the length in bytes of the prefix of src that is all
+//  interchange valid UTF-8
+int SpanInterchangeValid(const char* src, int byte_length);
+inline int SpanInterchangeValid(const std::string& src) {
+  return SpanInterchangeValid(src.data(), src.size());
+}
+
+// Returns true if the source is all interchange valid UTF-8
+// "Interchange valid" is a stronger than structurally valid --
+// no C0 or C1 control codes (other than CR LF HT FF) and no non-characters.
+inline bool IsInterchangeValid(const char* src, int byte_length) {
+  return (byte_length == SpanInterchangeValid(src, byte_length));
+}
+inline bool IsInterchangeValid(const std::string& src) {
+  return IsInterchangeValid(src.data(), src.size());
+}
+
+}  // namespace UniLib
+
+#endif  // UTIL_UTF8_PUBLIC_UNILIB_H_