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474 lines
21 KiB
474 lines
21 KiB
#region Copyright notice and license
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// Protocol Buffers - Google's data interchange format
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// Copyright 2015 Google Inc. All rights reserved.
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// https://developers.google.com/protocol-buffers/
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//
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#endregion
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using Google.Protobuf.Compatibility;
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using Google.Protobuf.WellKnownTypes;
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using System;
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using System.Collections.Generic;
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namespace Google.Protobuf
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{
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/// <summary>
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/// Factory methods for <see cref="FieldCodec{T}"/>.
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/// </summary>
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public static class FieldCodec
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{
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// TODO: Avoid the "dual hit" of lambda expressions: create open delegates instead. (At least test...)
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/// <summary>
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/// Retrieves a codec suitable for a string field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<string> ForString(uint tag)
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{
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return new FieldCodec<string>(input => input.ReadString(), (output, value) => output.WriteString(value), CodedOutputStream.ComputeStringSize, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a bytes field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<ByteString> ForBytes(uint tag)
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{
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return new FieldCodec<ByteString>(input => input.ReadBytes(), (output, value) => output.WriteBytes(value), CodedOutputStream.ComputeBytesSize, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a bool field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<bool> ForBool(uint tag)
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{
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return new FieldCodec<bool>(input => input.ReadBool(), (output, value) => output.WriteBool(value), CodedOutputStream.ComputeBoolSize, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an int32 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<int> ForInt32(uint tag)
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{
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return new FieldCodec<int>(input => input.ReadInt32(), (output, value) => output.WriteInt32(value), CodedOutputStream.ComputeInt32Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an sint32 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<int> ForSInt32(uint tag)
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{
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return new FieldCodec<int>(input => input.ReadSInt32(), (output, value) => output.WriteSInt32(value), CodedOutputStream.ComputeSInt32Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a fixed32 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<uint> ForFixed32(uint tag)
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{
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return new FieldCodec<uint>(input => input.ReadFixed32(), (output, value) => output.WriteFixed32(value), 4, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an sfixed32 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<int> ForSFixed32(uint tag)
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{
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return new FieldCodec<int>(input => input.ReadSFixed32(), (output, value) => output.WriteSFixed32(value), 4, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a uint32 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<uint> ForUInt32(uint tag)
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{
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return new FieldCodec<uint>(input => input.ReadUInt32(), (output, value) => output.WriteUInt32(value), CodedOutputStream.ComputeUInt32Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an int64 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<long> ForInt64(uint tag)
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{
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return new FieldCodec<long>(input => input.ReadInt64(), (output, value) => output.WriteInt64(value), CodedOutputStream.ComputeInt64Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an sint64 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<long> ForSInt64(uint tag)
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{
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return new FieldCodec<long>(input => input.ReadSInt64(), (output, value) => output.WriteSInt64(value), CodedOutputStream.ComputeSInt64Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a fixed64 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<ulong> ForFixed64(uint tag)
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{
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return new FieldCodec<ulong>(input => input.ReadFixed64(), (output, value) => output.WriteFixed64(value), 8, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for an sfixed64 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<long> ForSFixed64(uint tag)
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{
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return new FieldCodec<long>(input => input.ReadSFixed64(), (output, value) => output.WriteSFixed64(value), 8, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a uint64 field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<ulong> ForUInt64(uint tag)
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{
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return new FieldCodec<ulong>(input => input.ReadUInt64(), (output, value) => output.WriteUInt64(value), CodedOutputStream.ComputeUInt64Size, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a float field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<float> ForFloat(uint tag)
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{
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return new FieldCodec<float>(input => input.ReadFloat(), (output, value) => output.WriteFloat(value), CodedOutputStream.ComputeFloatSize, tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a double field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<double> ForDouble(uint tag)
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{
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return new FieldCodec<double>(input => input.ReadDouble(), (output, value) => output.WriteDouble(value), CodedOutputStream.ComputeDoubleSize, tag);
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}
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// Enums are tricky. We can probably use expression trees to build these delegates automatically,
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// but it's easy to generate the code for it.
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/// <summary>
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/// Retrieves a codec suitable for an enum field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <param name="toInt32">A conversion function from <see cref="Int32"/> to the enum type.</param>
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/// <param name="fromInt32">A conversion function from the enum type to <see cref="Int32"/>.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<T> ForEnum<T>(uint tag, Func<T, int> toInt32, Func<int, T> fromInt32)
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{
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return new FieldCodec<T>(input => fromInt32(
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input.ReadEnum()),
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(output, value) => output.WriteEnum(toInt32(value)),
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value => CodedOutputStream.ComputeEnumSize(toInt32(value)), tag);
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}
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/// <summary>
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/// Retrieves a codec suitable for a message field with the given tag.
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/// </summary>
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/// <param name="tag">The tag.</param>
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/// <param name="parser">A parser to use for the message type.</param>
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/// <returns>A codec for the given tag.</returns>
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public static FieldCodec<T> ForMessage<T>(uint tag, MessageParser<T> parser) where T : IMessage<T>
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{
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return new FieldCodec<T>(input => { T message = parser.CreateTemplate(); input.ReadMessage(message); return message; },
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(output, value) => output.WriteMessage(value), message => CodedOutputStream.ComputeMessageSize(message), tag);
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}
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/// <summary>
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/// Creates a codec for a wrapper type of a class - which must be string or ByteString.
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/// </summary>
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public static FieldCodec<T> ForClassWrapper<T>(uint tag) where T : class
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{
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var nestedCodec = WrapperCodecs.GetCodec<T>();
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return new FieldCodec<T>(
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input => WrapperCodecs.Read<T>(input, nestedCodec),
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(output, value) => WrapperCodecs.Write<T>(output, value, nestedCodec),
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value => WrapperCodecs.CalculateSize<T>(value, nestedCodec),
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tag,
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null); // Default value for the wrapper
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}
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/// <summary>
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/// Creates a codec for a wrapper type of a struct - which must be Int32, Int64, UInt32, UInt64,
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/// Bool, Single or Double.
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/// </summary>
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public static FieldCodec<T?> ForStructWrapper<T>(uint tag) where T : struct
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{
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var nestedCodec = WrapperCodecs.GetCodec<T>();
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return new FieldCodec<T?>(
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input => WrapperCodecs.Read<T>(input, nestedCodec),
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(output, value) => WrapperCodecs.Write<T>(output, value.Value, nestedCodec),
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value => value == null ? 0 : WrapperCodecs.CalculateSize<T>(value.Value, nestedCodec),
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tag,
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null); // Default value for the wrapper
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}
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/// <summary>
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/// Helper code to create codecs for wrapper types.
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/// </summary>
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/// <remarks>
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/// Somewhat ugly with all the static methods, but the conversions involved to/from nullable types make it
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/// slightly tricky to improve. So long as we keep the public API (ForClassWrapper, ForStructWrapper) in place,
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/// we can refactor later if we come up with something cleaner.
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/// </remarks>
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private static class WrapperCodecs
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{
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private static readonly Dictionary<System.Type, object> Codecs = new Dictionary<System.Type, object>
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{
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{ typeof(bool), ForBool(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint)) },
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{ typeof(int), ForInt32(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint)) },
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{ typeof(long), ForInt64(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint)) },
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{ typeof(uint), ForUInt32(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint)) },
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{ typeof(ulong), ForUInt64(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Varint)) },
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{ typeof(float), ForFloat(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Fixed32)) },
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{ typeof(double), ForDouble(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.Fixed64)) },
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{ typeof(string), ForString(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.LengthDelimited)) },
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{ typeof(ByteString), ForBytes(WireFormat.MakeTag(WrappersReflection.WrapperValueFieldNumber, WireFormat.WireType.LengthDelimited)) }
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};
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/// <summary>
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/// Returns a field codec which effectively wraps a value of type T in a message.
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///
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/// </summary>
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internal static FieldCodec<T> GetCodec<T>()
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{
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object value;
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if (!Codecs.TryGetValue(typeof(T), out value))
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{
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throw new InvalidOperationException("Invalid type argument requested for wrapper codec: " + typeof(T));
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}
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return (FieldCodec<T>) value;
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}
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internal static T Read<T>(CodedInputStream input, FieldCodec<T> codec)
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{
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int length = input.ReadLength();
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int oldLimit = input.PushLimit(length);
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uint tag;
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T value = codec.DefaultValue;
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while ((tag = input.ReadTag()) != 0)
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{
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if (tag == codec.Tag)
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{
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value = codec.Read(input);
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}
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else
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{
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input.SkipLastField();
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}
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}
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input.CheckReadEndOfStreamTag();
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input.PopLimit(oldLimit);
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return value;
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}
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internal static void Write<T>(CodedOutputStream output, T value, FieldCodec<T> codec)
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{
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output.WriteLength(codec.CalculateSizeWithTag(value));
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codec.WriteTagAndValue(output, value);
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}
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internal static int CalculateSize<T>(T value, FieldCodec<T> codec)
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{
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int fieldLength = codec.CalculateSizeWithTag(value);
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return CodedOutputStream.ComputeLengthSize(fieldLength) + fieldLength;
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}
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}
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}
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/// <summary>
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/// <para>
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/// An encode/decode pair for a single field. This effectively encapsulates
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/// all the information needed to read or write the field value from/to a coded
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/// stream.
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/// </para>
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/// <para>
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/// This class is public and has to be as it is used by generated code, but its public
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/// API is very limited - just what the generated code needs to call directly.
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/// </para>
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/// </summary>
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/// <remarks>
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/// This never writes default values to the stream, and does not address "packedness"
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/// in repeated fields itself, other than to know whether or not the field *should* be packed.
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/// </remarks>
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public sealed class FieldCodec<T>
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{
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private static readonly T DefaultDefault;
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// Only non-nullable value types support packing. This is the simplest way of detecting that.
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private static readonly bool TypeSupportsPacking = default(T) != null;
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static FieldCodec()
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{
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if (typeof(T) == typeof(string))
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{
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DefaultDefault = (T)(object)"";
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}
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else if (typeof(T) == typeof(ByteString))
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{
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DefaultDefault = (T)(object)ByteString.Empty;
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}
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// Otherwise it's the default value of the CLR type
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}
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internal static bool IsPackedRepeatedField(uint tag) =>
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TypeSupportsPacking && WireFormat.GetTagWireType(tag) == WireFormat.WireType.LengthDelimited;
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internal bool PackedRepeatedField { get; }
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/// <summary>
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/// Returns a delegate to write a value (unconditionally) to a coded output stream.
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/// </summary>
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internal Action<CodedOutputStream, T> ValueWriter { get; }
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/// <summary>
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/// Returns the size calculator for just a value.
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/// </summary>
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internal Func<T, int> ValueSizeCalculator { get; }
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/// <summary>
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/// Returns a delegate to read a value from a coded input stream. It is assumed that
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/// the stream is already positioned on the appropriate tag.
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/// </summary>
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internal Func<CodedInputStream, T> ValueReader { get; }
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/// <summary>
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/// Returns the fixed size for an entry, or 0 if sizes vary.
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/// </summary>
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internal int FixedSize { get; }
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/// <summary>
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/// Gets the tag of the codec.
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/// </summary>
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/// <value>
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/// The tag of the codec.
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/// </value>
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internal uint Tag { get; }
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/// <summary>
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/// Default value for this codec. Usually the same for every instance of the same type, but
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/// for string/ByteString wrapper fields the codec's default value is null, whereas for
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/// other string/ByteString fields it's "" or ByteString.Empty.
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/// </summary>
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/// <value>
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/// The default value of the codec's type.
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/// </value>
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internal T DefaultValue { get; }
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private readonly int tagSize;
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internal FieldCodec(
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Func<CodedInputStream, T> reader,
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Action<CodedOutputStream, T> writer,
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int fixedSize,
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uint tag) : this(reader, writer, _ => fixedSize, tag)
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{
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FixedSize = fixedSize;
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}
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internal FieldCodec(
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Func<CodedInputStream, T> reader,
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Action<CodedOutputStream, T> writer,
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Func<T, int> sizeCalculator,
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uint tag) : this(reader, writer, sizeCalculator, tag, DefaultDefault)
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{
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}
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internal FieldCodec(
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Func<CodedInputStream, T> reader,
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Action<CodedOutputStream, T> writer,
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Func<T, int> sizeCalculator,
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uint tag,
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T defaultValue)
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{
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ValueReader = reader;
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ValueWriter = writer;
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ValueSizeCalculator = sizeCalculator;
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FixedSize = 0;
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Tag = tag;
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DefaultValue = defaultValue;
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tagSize = CodedOutputStream.ComputeRawVarint32Size(tag);
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// Detect packed-ness once, so we can check for it within RepeatedField<T>.
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PackedRepeatedField = IsPackedRepeatedField(tag);
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}
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/// <summary>
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/// Write a tag and the given value, *if* the value is not the default.
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/// </summary>
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public void WriteTagAndValue(CodedOutputStream output, T value)
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{
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if (!IsDefault(value))
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{
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output.WriteTag(Tag);
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ValueWriter(output, value);
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}
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}
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/// <summary>
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/// Reads a value of the codec type from the given <see cref="CodedInputStream"/>.
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/// </summary>
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/// <param name="input">The input stream to read from.</param>
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/// <returns>The value read from the stream.</returns>
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public T Read(CodedInputStream input) => ValueReader(input);
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/// <summary>
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/// Calculates the size required to write the given value, with a tag,
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/// if the value is not the default.
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/// </summary>
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public int CalculateSizeWithTag(T value) => IsDefault(value) ? 0 : ValueSizeCalculator(value) + tagSize;
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private bool IsDefault(T value) => EqualityComparer<T>.Default.Equals(value, DefaultValue);
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}
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}
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