diff --git a/src/runtime/runtime-uri.cc b/src/runtime/runtime-uri.cc
new file mode 100644
index 0000000..477071a
--- /dev/null
+++ b/src/runtime/runtime-uri.cc
@@ -0,0 +1,288 @@
+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/v8.h"
+
+#include "src/arguments.h"
+#include "src/conversions.h"
+#include "src/runtime/runtime-utils.h"
+#include "src/string-search.h"
+#include "src/utils.h"
+
+
+namespace v8 {
+namespace internal {
+
+class URIUnescape : public AllStatic {
+ public:
+  template <typename Char>
+  MUST_USE_RESULT static MaybeHandle<String> Unescape(Isolate* isolate,
+                                                      Handle<String> source);
+
+ private:
+  static const signed char kHexValue['g'];
+
+  template <typename Char>
+  MUST_USE_RESULT static MaybeHandle<String> UnescapeSlow(Isolate* isolate,
+                                                          Handle<String> string,
+                                                          int start_index);
+
+  static INLINE(int TwoDigitHex(uint16_t character1, uint16_t character2));
+
+  template <typename Char>
+  static INLINE(int UnescapeChar(Vector<const Char> vector, int i, int length,
+                                 int* step));
+};
+
+
+const signed char URIUnescape::kHexValue[] = {
+    -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, -0, 1,  2,  3,  4,  5,
+    6,  7,  8,  9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -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, 10, 11, 12, 13, 14, 15};
+
+
+template <typename Char>
+MaybeHandle<String> URIUnescape::Unescape(Isolate* isolate,
+                                          Handle<String> source) {
+  int index;
+  {
+    DisallowHeapAllocation no_allocation;
+    StringSearch<uint8_t, Char> search(isolate, STATIC_CHAR_VECTOR("%"));
+    index = search.Search(source->GetCharVector<Char>(), 0);
+    if (index < 0) return source;
+  }
+  return UnescapeSlow<Char>(isolate, source, index);
+}
+
+
+template <typename Char>
+MaybeHandle<String> URIUnescape::UnescapeSlow(Isolate* isolate,
+                                              Handle<String> string,
+                                              int start_index) {
+  bool one_byte = true;
+  int length = string->length();
+
+  int unescaped_length = 0;
+  {
+    DisallowHeapAllocation no_allocation;
+    Vector<const Char> vector = string->GetCharVector<Char>();
+    for (int i = start_index; i < length; unescaped_length++) {
+      int step;
+      if (UnescapeChar(vector, i, length, &step) >
+          String::kMaxOneByteCharCode) {
+        one_byte = false;
+      }
+      i += step;
+    }
+  }
+
+  DCHECK(start_index < length);
+  Handle<String> first_part =
+      isolate->factory()->NewProperSubString(string, 0, start_index);
+
+  int dest_position = 0;
+  Handle<String> second_part;
+  DCHECK(unescaped_length <= String::kMaxLength);
+  if (one_byte) {
+    Handle<SeqOneByteString> dest = isolate->factory()
+                                        ->NewRawOneByteString(unescaped_length)
+                                        .ToHandleChecked();
+    DisallowHeapAllocation no_allocation;
+    Vector<const Char> vector = string->GetCharVector<Char>();
+    for (int i = start_index; i < length; dest_position++) {
+      int step;
+      dest->SeqOneByteStringSet(dest_position,
+                                UnescapeChar(vector, i, length, &step));
+      i += step;
+    }
+    second_part = dest;
+  } else {
+    Handle<SeqTwoByteString> dest = isolate->factory()
+                                        ->NewRawTwoByteString(unescaped_length)
+                                        .ToHandleChecked();
+    DisallowHeapAllocation no_allocation;
+    Vector<const Char> vector = string->GetCharVector<Char>();
+    for (int i = start_index; i < length; dest_position++) {
+      int step;
+      dest->SeqTwoByteStringSet(dest_position,
+                                UnescapeChar(vector, i, length, &step));
+      i += step;
+    }
+    second_part = dest;
+  }
+  return isolate->factory()->NewConsString(first_part, second_part);
+}
+
+
+int URIUnescape::TwoDigitHex(uint16_t character1, uint16_t character2) {
+  if (character1 > 'f') return -1;
+  int hi = kHexValue[character1];
+  if (hi == -1) return -1;
+  if (character2 > 'f') return -1;
+  int lo = kHexValue[character2];
+  if (lo == -1) return -1;
+  return (hi << 4) + lo;
+}
+
+
+template <typename Char>
+int URIUnescape::UnescapeChar(Vector<const Char> vector, int i, int length,
+                              int* step) {
+  uint16_t character = vector[i];
+  int32_t hi = 0;
+  int32_t lo = 0;
+  if (character == '%' && i <= length - 6 && vector[i + 1] == 'u' &&
+      (hi = TwoDigitHex(vector[i + 2], vector[i + 3])) != -1 &&
+      (lo = TwoDigitHex(vector[i + 4], vector[i + 5])) != -1) {
+    *step = 6;
+    return (hi << 8) + lo;
+  } else if (character == '%' && i <= length - 3 &&
+             (lo = TwoDigitHex(vector[i + 1], vector[i + 2])) != -1) {
+    *step = 3;
+    return lo;
+  } else {
+    *step = 1;
+    return character;
+  }
+}
+
+
+class URIEscape : public AllStatic {
+ public:
+  template <typename Char>
+  MUST_USE_RESULT static MaybeHandle<String> Escape(Isolate* isolate,
+                                                    Handle<String> string);
+
+ private:
+  static const char kHexChars[17];
+  static const char kNotEscaped[256];
+
+  static bool IsNotEscaped(uint16_t c) { return kNotEscaped[c] != 0; }
+};
+
+
+const char URIEscape::kHexChars[] = "0123456789ABCDEF";
+
+
+// kNotEscaped is generated by the following:
+//
+// #!/bin/perl
+// for (my $i = 0; $i < 256; $i++) {
+//   print "\n" if $i % 16 == 0;
+//   my $c = chr($i);
+//   my $escaped = 1;
+//   $escaped = 0 if $c =~ m#[A-Za-z0-9@*_+./-]#;
+//   print $escaped ? "0, " : "1, ";
+// }
+
+const char URIEscape::kNotEscaped[] = {
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 1,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 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, 0, 0, 0, 0, 1,
+    0, 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, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+
+template <typename Char>
+MaybeHandle<String> URIEscape::Escape(Isolate* isolate, Handle<String> string) {
+  DCHECK(string->IsFlat());
+  int escaped_length = 0;
+  int length = string->length();
+
+  {
+    DisallowHeapAllocation no_allocation;
+    Vector<const Char> vector = string->GetCharVector<Char>();
+    for (int i = 0; i < length; i++) {
+      uint16_t c = vector[i];
+      if (c >= 256) {
+        escaped_length += 6;
+      } else if (IsNotEscaped(c)) {
+        escaped_length++;
+      } else {
+        escaped_length += 3;
+      }
+
+      // We don't allow strings that are longer than a maximal length.
+      DCHECK(String::kMaxLength < 0x7fffffff - 6);     // Cannot overflow.
+      if (escaped_length > String::kMaxLength) break;  // Provoke exception.
+    }
+  }
+
+  // No length change implies no change.  Return original string if no change.
+  if (escaped_length == length) return string;
+
+  Handle<SeqOneByteString> dest;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, dest, isolate->factory()->NewRawOneByteString(escaped_length),
+      String);
+  int dest_position = 0;
+
+  {
+    DisallowHeapAllocation no_allocation;
+    Vector<const Char> vector = string->GetCharVector<Char>();
+    for (int i = 0; i < length; i++) {
+      uint16_t c = vector[i];
+      if (c >= 256) {
+        dest->SeqOneByteStringSet(dest_position, '%');
+        dest->SeqOneByteStringSet(dest_position + 1, 'u');
+        dest->SeqOneByteStringSet(dest_position + 2, kHexChars[c >> 12]);
+        dest->SeqOneByteStringSet(dest_position + 3, kHexChars[(c >> 8) & 0xf]);
+        dest->SeqOneByteStringSet(dest_position + 4, kHexChars[(c >> 4) & 0xf]);
+        dest->SeqOneByteStringSet(dest_position + 5, kHexChars[c & 0xf]);
+        dest_position += 6;
+      } else if (IsNotEscaped(c)) {
+        dest->SeqOneByteStringSet(dest_position, c);
+        dest_position++;
+      } else {
+        dest->SeqOneByteStringSet(dest_position, '%');
+        dest->SeqOneByteStringSet(dest_position + 1, kHexChars[c >> 4]);
+        dest->SeqOneByteStringSet(dest_position + 2, kHexChars[c & 0xf]);
+        dest_position += 3;
+      }
+    }
+  }
+
+  return dest;
+}
+
+
+RUNTIME_FUNCTION(Runtime_URIEscape) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
+  Handle<String> string = String::Flatten(source);
+  DCHECK(string->IsFlat());
+  Handle<String> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, string->IsOneByteRepresentationUnderneath()
+                           ? URIEscape::Escape<uint8_t>(isolate, source)
+                           : URIEscape::Escape<uc16>(isolate, source));
+  return *result;
+}
+
+
+RUNTIME_FUNCTION(Runtime_URIUnescape) {
+  HandleScope scope(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_HANDLE_CHECKED(String, source, 0);
+  Handle<String> string = String::Flatten(source);
+  DCHECK(string->IsFlat());
+  Handle<String> result;
+  ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
+      isolate, result, string->IsOneByteRepresentationUnderneath()
+                           ? URIUnescape::Unescape<uint8_t>(isolate, source)
+                           : URIUnescape::Unescape<uc16>(isolate, source));
+  return *result;
+}
+}
+}  // namespace v8::internal