diff --git a/csharp/src/Google.Protobuf.Test/CodedInputStreamTest.cs b/csharp/src/Google.Protobuf.Test/CodedInputStreamTest.cs
new file mode 100644
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+++ b/csharp/src/Google.Protobuf.Test/CodedInputStreamTest.cs
@@ -0,0 +1,530 @@
+#region Copyright notice and license
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+#endregion
+
+using System;
+using System.IO;
+using Google.Protobuf.TestProtos;
+using NUnit.Framework;
+
+namespace Google.Protobuf
+{
+    public class CodedInputStreamTest
+    {
+        /// <summary>
+        /// Helper to construct a byte array from a bunch of bytes.  The inputs are
+        /// actually ints so that I can use hex notation and not get stupid errors
+        /// about precision.
+        /// </summary>
+        private static byte[] Bytes(params int[] bytesAsInts)
+        {
+            byte[] bytes = new byte[bytesAsInts.Length];
+            for (int i = 0; i < bytesAsInts.Length; i++)
+            {
+                bytes[i] = (byte) bytesAsInts[i];
+            }
+            return bytes;
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawVarint32() and ReadRawVarint64()
+        /// </summary>
+        private static void AssertReadVarint(byte[] data, ulong value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual((uint) value, input.ReadRawVarint32());
+
+            input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawVarint64());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int bufferSize = 1; bufferSize <= 16; bufferSize *= 2)
+            {
+                input = new CodedInputStream(new SmallBlockInputStream(data, bufferSize));
+                Assert.AreEqual((uint) value, input.ReadRawVarint32());
+
+                input = new CodedInputStream(new SmallBlockInputStream(data, bufferSize));
+                Assert.AreEqual(value, input.ReadRawVarint64());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+
+            // Try reading directly from a MemoryStream. We want to verify that it
+            // doesn't read past the end of the input, so write an extra byte - this
+            // lets us test the position at the end.
+            MemoryStream memoryStream = new MemoryStream();
+            memoryStream.Write(data, 0, data.Length);
+            memoryStream.WriteByte(0);
+            memoryStream.Position = 0;
+            Assert.AreEqual((uint) value, CodedInputStream.ReadRawVarint32(memoryStream));
+            Assert.AreEqual(data.Length, memoryStream.Position);
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawVarint32() and ReadRawVarint64() and
+        /// expects them to fail with an InvalidProtocolBufferException whose
+        /// description matches the given one.
+        /// </summary>
+        private static void AssertReadVarintFailure(InvalidProtocolBufferException expected, byte[] data)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            var exception = Assert.Throws<InvalidProtocolBufferException>(() => input.ReadRawVarint32());
+            Assert.AreEqual(expected.Message, exception.Message);
+
+            input = new CodedInputStream(data);
+            exception = Assert.Throws<InvalidProtocolBufferException>(() => input.ReadRawVarint64());
+            Assert.AreEqual(expected.Message, exception.Message);
+
+            // Make sure we get the same error when reading directly from a Stream.
+            exception = Assert.Throws<InvalidProtocolBufferException>(() => CodedInputStream.ReadRawVarint32(new MemoryStream(data)));
+            Assert.AreEqual(expected.Message, exception.Message);
+        }
+
+        [Test]
+        public void ReadVarint()
+        {
+            AssertReadVarint(Bytes(0x00), 0);
+            AssertReadVarint(Bytes(0x01), 1);
+            AssertReadVarint(Bytes(0x7f), 127);
+            // 14882
+            AssertReadVarint(Bytes(0xa2, 0x74), (0x22 << 0) | (0x74 << 7));
+            // 2961488830
+            AssertReadVarint(Bytes(0xbe, 0xf7, 0x92, 0x84, 0x0b),
+                             (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                             (0x0bL << 28));
+
+            // 64-bit
+            // 7256456126
+            AssertReadVarint(Bytes(0xbe, 0xf7, 0x92, 0x84, 0x1b),
+                             (0x3e << 0) | (0x77 << 7) | (0x12 << 14) | (0x04 << 21) |
+                             (0x1bL << 28));
+            // 41256202580718336
+            AssertReadVarint(Bytes(0x80, 0xe6, 0xeb, 0x9c, 0xc3, 0xc9, 0xa4, 0x49),
+                             (0x00 << 0) | (0x66 << 7) | (0x6b << 14) | (0x1c << 21) |
+                             (0x43L << 28) | (0x49L << 35) | (0x24L << 42) | (0x49L << 49));
+            // 11964378330978735131
+            AssertReadVarint(Bytes(0x9b, 0xa8, 0xf9, 0xc2, 0xbb, 0xd6, 0x80, 0x85, 0xa6, 0x01),
+                             (0x1b << 0) | (0x28 << 7) | (0x79 << 14) | (0x42 << 21) |
+                             (0x3bUL << 28) | (0x56UL << 35) | (0x00UL << 42) |
+                             (0x05UL << 49) | (0x26UL << 56) | (0x01UL << 63));
+
+            // Failures
+            AssertReadVarintFailure(
+                InvalidProtocolBufferException.MalformedVarint(),
+                Bytes(0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
+                      0x00));
+            AssertReadVarintFailure(
+                InvalidProtocolBufferException.TruncatedMessage(),
+                Bytes(0x80));
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawLittleEndian32() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertReadLittleEndian32(byte[] data, uint value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawLittleEndian32());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize <= 16; blockSize *= 2)
+            {
+                input = new CodedInputStream(
+                    new SmallBlockInputStream(data, blockSize));
+                Assert.AreEqual(value, input.ReadRawLittleEndian32());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+        }
+
+        /// <summary>
+        /// Parses the given bytes using ReadRawLittleEndian64() and checks
+        /// that the result matches the given value.
+        /// </summary>
+        private static void AssertReadLittleEndian64(byte[] data, ulong value)
+        {
+            CodedInputStream input = new CodedInputStream(data);
+            Assert.AreEqual(value, input.ReadRawLittleEndian64());
+            Assert.IsTrue(input.IsAtEnd);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize <= 16; blockSize *= 2)
+            {
+                input = new CodedInputStream(
+                    new SmallBlockInputStream(data, blockSize));
+                Assert.AreEqual(value, input.ReadRawLittleEndian64());
+                Assert.IsTrue(input.IsAtEnd);
+            }
+        }
+
+        [Test]
+        public void ReadLittleEndian()
+        {
+            AssertReadLittleEndian32(Bytes(0x78, 0x56, 0x34, 0x12), 0x12345678);
+            AssertReadLittleEndian32(Bytes(0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef0);
+
+            AssertReadLittleEndian64(Bytes(0xf0, 0xde, 0xbc, 0x9a, 0x78, 0x56, 0x34, 0x12),
+                                     0x123456789abcdef0L);
+            AssertReadLittleEndian64(
+                Bytes(0x78, 0x56, 0x34, 0x12, 0xf0, 0xde, 0xbc, 0x9a), 0x9abcdef012345678UL);
+        }
+
+        [Test]
+        public void DecodeZigZag32()
+        {
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag32(0));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag32(1));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag32(2));
+            Assert.AreEqual(-2, CodedInputStream.DecodeZigZag32(3));
+            Assert.AreEqual(0x3FFFFFFF, CodedInputStream.DecodeZigZag32(0x7FFFFFFE));
+            Assert.AreEqual(unchecked((int) 0xC0000000), CodedInputStream.DecodeZigZag32(0x7FFFFFFF));
+            Assert.AreEqual(0x7FFFFFFF, CodedInputStream.DecodeZigZag32(0xFFFFFFFE));
+            Assert.AreEqual(unchecked((int) 0x80000000), CodedInputStream.DecodeZigZag32(0xFFFFFFFF));
+        }
+
+        [Test]
+        public void DecodeZigZag64()
+        {
+            Assert.AreEqual(0, CodedInputStream.DecodeZigZag64(0));
+            Assert.AreEqual(-1, CodedInputStream.DecodeZigZag64(1));
+            Assert.AreEqual(1, CodedInputStream.DecodeZigZag64(2));
+            Assert.AreEqual(-2, CodedInputStream.DecodeZigZag64(3));
+            Assert.AreEqual(0x000000003FFFFFFFL, CodedInputStream.DecodeZigZag64(0x000000007FFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0xFFFFFFFFC0000000L), CodedInputStream.DecodeZigZag64(0x000000007FFFFFFFL));
+            Assert.AreEqual(0x000000007FFFFFFFL, CodedInputStream.DecodeZigZag64(0x00000000FFFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0xFFFFFFFF80000000L), CodedInputStream.DecodeZigZag64(0x00000000FFFFFFFFL));
+            Assert.AreEqual(0x7FFFFFFFFFFFFFFFL, CodedInputStream.DecodeZigZag64(0xFFFFFFFFFFFFFFFEL));
+            Assert.AreEqual(unchecked((long) 0x8000000000000000L), CodedInputStream.DecodeZigZag64(0xFFFFFFFFFFFFFFFFL));
+        }
+        
+        [Test]
+        public void ReadWholeMessage_VaryingBlockSizes()
+        {
+            TestAllTypes message = SampleMessages.CreateFullTestAllTypes();
+
+            byte[] rawBytes = message.ToByteArray();
+            Assert.AreEqual(rawBytes.Length, message.CalculateSize());
+            TestAllTypes message2 = TestAllTypes.Parser.ParseFrom(rawBytes);
+            Assert.AreEqual(message, message2);
+
+            // Try different block sizes.
+            for (int blockSize = 1; blockSize < 256; blockSize *= 2)
+            {
+                message2 = TestAllTypes.Parser.ParseFrom(new SmallBlockInputStream(rawBytes, blockSize));
+                Assert.AreEqual(message, message2);
+            }
+        }
+                
+        [Test]
+        public void ReadHugeBlob()
+        {
+            // Allocate and initialize a 1MB blob.
+            byte[] blob = new byte[1 << 20];
+            for (int i = 0; i < blob.Length; i++)
+            {
+                blob[i] = (byte) i;
+            }
+
+            // Make a message containing it.
+            var message = new TestAllTypes { SingleBytes = ByteString.CopyFrom(blob) };
+
+            // Serialize and parse it.  Make sure to parse from an InputStream, not
+            // directly from a ByteString, so that CodedInputStream uses buffered
+            // reading.
+            TestAllTypes message2 = TestAllTypes.Parser.ParseFrom(message.ToByteString());
+
+            Assert.AreEqual(message, message2);
+        }
+
+        [Test]
+        public void ReadMaliciouslyLargeBlob()
+        {
+            MemoryStream ms = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(ms);
+
+            uint tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(tag);
+            output.WriteRawVarint32(0x7FFFFFFF);
+            output.WriteRawBytes(new byte[32]); // Pad with a few random bytes.
+            output.Flush();
+            ms.Position = 0;
+
+            CodedInputStream input = new CodedInputStream(ms);
+            Assert.AreEqual(tag, input.ReadTag());
+
+            Assert.Throws<InvalidProtocolBufferException>(() => input.ReadBytes());
+        }
+
+        internal static TestRecursiveMessage MakeRecursiveMessage(int depth)
+        {
+            if (depth == 0)
+            {
+                return new TestRecursiveMessage { I = 5 };
+            }
+            else
+            {
+                return new TestRecursiveMessage { A = MakeRecursiveMessage(depth - 1) };
+            }
+        }
+
+        internal static void AssertMessageDepth(TestRecursiveMessage message, int depth)
+        {
+            if (depth == 0)
+            {
+                Assert.IsNull(message.A);
+                Assert.AreEqual(5, message.I);
+            }
+            else
+            {
+                Assert.IsNotNull(message.A);
+                AssertMessageDepth(message.A, depth - 1);
+            }
+        }
+
+        [Test]
+        public void MaliciousRecursion()
+        {
+            ByteString data64 = MakeRecursiveMessage(64).ToByteString();
+            ByteString data65 = MakeRecursiveMessage(65).ToByteString();
+
+            AssertMessageDepth(TestRecursiveMessage.Parser.ParseFrom(data64), 64);
+
+            Assert.Throws<InvalidProtocolBufferException>(() => TestRecursiveMessage.Parser.ParseFrom(data65));
+
+            CodedInputStream input = CodedInputStream.CreateWithLimits(new MemoryStream(data64.ToByteArray()), 1000000, 63);
+            Assert.Throws<InvalidProtocolBufferException>(() => TestRecursiveMessage.Parser.ParseFrom(input));
+        }
+
+        [Test]
+        public void SizeLimit()
+        {
+            // Have to use a Stream rather than ByteString.CreateCodedInput as SizeLimit doesn't
+            // apply to the latter case.
+            MemoryStream ms = new MemoryStream(SampleMessages.CreateFullTestAllTypes().ToByteArray());
+            CodedInputStream input = CodedInputStream.CreateWithLimits(ms, 16, 100);
+            Assert.Throws<InvalidProtocolBufferException>(() => TestAllTypes.Parser.ParseFrom(input));
+        }
+
+        /// <summary>
+        /// Tests that if we read an string that contains invalid UTF-8, no exception
+        /// is thrown.  Instead, the invalid bytes are replaced with the Unicode
+        /// "replacement character" U+FFFD.
+        /// </summary>
+        [Test]
+        public void ReadInvalidUtf8()
+        {
+            MemoryStream ms = new MemoryStream();
+            CodedOutputStream output = new CodedOutputStream(ms);
+
+            uint tag = WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteRawVarint32(tag);
+            output.WriteRawVarint32(1);
+            output.WriteRawBytes(new byte[] {0x80});
+            output.Flush();
+            ms.Position = 0;
+
+            CodedInputStream input = new CodedInputStream(ms);
+
+            Assert.AreEqual(tag, input.ReadTag());
+            string text = input.ReadString();
+            Assert.AreEqual('\ufffd', text[0]);
+        }
+
+        /// <summary>
+        /// A stream which limits the number of bytes it reads at a time.
+        /// We use this to make sure that CodedInputStream doesn't screw up when
+        /// reading in small blocks.
+        /// </summary>
+        private sealed class SmallBlockInputStream : MemoryStream
+        {
+            private readonly int blockSize;
+
+            public SmallBlockInputStream(byte[] data, int blockSize)
+                : base(data)
+            {
+                this.blockSize = blockSize;
+            }
+
+            public override int Read(byte[] buffer, int offset, int count)
+            {
+                return base.Read(buffer, offset, Math.Min(count, blockSize));
+            }
+        }
+
+        [Test]
+        public void TestNegativeEnum()
+        {
+            byte[] bytes = { 0xFE, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x01 };
+            CodedInputStream input = new CodedInputStream(bytes);
+            Assert.AreEqual((int)SampleEnum.NegativeValue, input.ReadEnum());
+            Assert.IsTrue(input.IsAtEnd);
+        }
+
+        //Issue 71:	CodedInputStream.ReadBytes go to slow path unnecessarily
+        [Test]
+        public void TestSlowPathAvoidance()
+        {
+            using (var ms = new MemoryStream())
+            {
+                CodedOutputStream output = new CodedOutputStream(ms);
+                output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+                output.WriteBytes(ByteString.CopyFrom(new byte[100]));
+                output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+                output.WriteBytes(ByteString.CopyFrom(new byte[100]));
+                output.Flush();
+
+                ms.Position = 0;
+                CodedInputStream input = new CodedInputStream(ms, new byte[ms.Length / 2], 0, 0);
+
+                uint tag = input.ReadTag();
+                Assert.AreEqual(1, WireFormat.GetTagFieldNumber(tag));
+                Assert.AreEqual(100, input.ReadBytes().Length);
+
+                tag = input.ReadTag();
+                Assert.AreEqual(2, WireFormat.GetTagFieldNumber(tag));
+                Assert.AreEqual(100, input.ReadBytes().Length);
+            }
+        }
+
+        [Test]
+        public void Tag0Throws()
+        {
+            var input = new CodedInputStream(new byte[] { 0 });
+            Assert.Throws<InvalidProtocolBufferException>(() => input.ReadTag());
+        }
+
+        [Test]
+        public void SkipGroup()
+        {
+            // Create an output stream with a group in:
+            // Field 1: string "field 1"
+            // Field 2: group containing:
+            //   Field 1: fixed int32 value 100
+            //   Field 2: string "ignore me"
+            //   Field 3: nested group containing
+            //      Field 1: fixed int64 value 1000
+            // Field 3: string "field 3"
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.LengthDelimited);
+            output.WriteString("field 1");
+            
+            // The outer group...
+            output.WriteTag(2, WireFormat.WireType.StartGroup);
+            output.WriteTag(1, WireFormat.WireType.Fixed32);
+            output.WriteFixed32(100);
+            output.WriteTag(2, WireFormat.WireType.LengthDelimited);
+            output.WriteString("ignore me");
+            // The nested group...
+            output.WriteTag(3, WireFormat.WireType.StartGroup);
+            output.WriteTag(1, WireFormat.WireType.Fixed64);
+            output.WriteFixed64(1000);
+            // Note: Not sure the field number is relevant for end group...
+            output.WriteTag(3, WireFormat.WireType.EndGroup);
+
+            // End the outer group
+            output.WriteTag(2, WireFormat.WireType.EndGroup);
+
+            output.WriteTag(3, WireFormat.WireType.LengthDelimited);
+            output.WriteString("field 3");
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.LengthDelimited), input.ReadTag());
+            Assert.AreEqual("field 1", input.ReadString());
+            Assert.AreEqual(WireFormat.MakeTag(2, WireFormat.WireType.StartGroup), input.ReadTag());
+            input.SkipLastField(); // Should consume the whole group, including the nested one.
+            Assert.AreEqual(WireFormat.MakeTag(3, WireFormat.WireType.LengthDelimited), input.ReadTag());
+            Assert.AreEqual("field 3", input.ReadString());
+        }
+
+        [Test]
+        public void EndOfStreamReachedWhileSkippingGroup()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            output.WriteTag(1, WireFormat.WireType.StartGroup);
+            output.WriteTag(2, WireFormat.WireType.StartGroup);
+            output.WriteTag(2, WireFormat.WireType.EndGroup);
+
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            input.ReadTag();
+            Assert.Throws<InvalidProtocolBufferException>(() => input.SkipLastField());
+        }
+
+        [Test]
+        public void RecursionLimitAppliedWhileSkippingGroup()
+        {
+            var stream = new MemoryStream();
+            var output = new CodedOutputStream(stream);
+            for (int i = 0; i < CodedInputStream.DefaultRecursionLimit + 1; i++)
+            {
+                output.WriteTag(1, WireFormat.WireType.StartGroup);
+            }
+            for (int i = 0; i < CodedInputStream.DefaultRecursionLimit + 1; i++)
+            {
+                output.WriteTag(1, WireFormat.WireType.EndGroup);
+            }
+            output.Flush();
+            stream.Position = 0;
+
+            // Now act like a generated client
+            var input = new CodedInputStream(stream);
+            Assert.AreEqual(WireFormat.MakeTag(1, WireFormat.WireType.StartGroup), input.ReadTag());
+            Assert.Throws<InvalidProtocolBufferException>(() => input.SkipLastField());
+        }
+
+        [Test]
+        public void Construction_Invalid()
+        {
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream((byte[]) null));
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream(null, 0, 0));
+            Assert.Throws<ArgumentNullException>(() => new CodedInputStream((Stream) null));
+            Assert.Throws<ArgumentOutOfRangeException>(() => new CodedInputStream(new byte[10], 100, 0));
+            Assert.Throws<ArgumentOutOfRangeException>(() => new CodedInputStream(new byte[10], 5, 10));
+        }
+
+        [Test]
+        public void CreateWithLimits_InvalidLimits()
+        {
+            var stream = new MemoryStream();
+            Assert.Throws<ArgumentOutOfRangeException>(() => CodedInputStream.CreateWithLimits(stream, 0, 1));
+            Assert.Throws<ArgumentOutOfRangeException>(() => CodedInputStream.CreateWithLimits(stream, 1, 0));
+        }
+    }
+}
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