#region Copyright notice and license
// Protocol Buffers - Google's data interchange format
// Copyright 2015 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.Collections.Generic;
namespace Google.Protobuf
{
/// <summary>
/// Factory methods for <see cref="FieldCodec{T}"/>.
/// </summary>
public static class FieldCodec
{
// TODO: Avoid the "dual hit" of lambda expressions: create open delegates instead. (At least test...)
/// <summary>
/// Retrieves a codec suitable for a string field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<string> ForString(uint tag)
{
return new FieldCodec<string>(input => input.ReadString(), (output, value) => output.WriteString(value), CodedOutputStream.ComputeStringSize, tag);
}
/// <summary>
/// Retrieves a codec suitable for a bytes field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<ByteString> ForBytes(uint tag)
{
return new FieldCodec<ByteString>(input => input.ReadBytes(), (output, value) => output.WriteBytes(value), CodedOutputStream.ComputeBytesSize, tag);
}
/// <summary>
/// Retrieves a codec suitable for a bool field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<bool> ForBool(uint tag)
{
return new FieldCodec<bool>(input => input.ReadBool(), (output, value) => output.WriteBool(value), CodedOutputStream.ComputeBoolSize, tag);
}
/// <summary>
/// Retrieves a codec suitable for an int32 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<int> ForInt32(uint tag)
{
return new FieldCodec<int>(input => input.ReadInt32(), (output, value) => output.WriteInt32(value), CodedOutputStream.ComputeInt32Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for an sint32 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<int> ForSInt32(uint tag)
{
return new FieldCodec<int>(input => input.ReadSInt32(), (output, value) => output.WriteSInt32(value), CodedOutputStream.ComputeSInt32Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for a fixed32 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<uint> ForFixed32(uint tag)
{
return new FieldCodec<uint>(input => input.ReadFixed32(), (output, value) => output.WriteFixed32(value), 4, tag);
}
/// <summary>
/// Retrieves a codec suitable for an sfixed32 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<int> ForSFixed32(uint tag)
{
return new FieldCodec<int>(input => input.ReadSFixed32(), (output, value) => output.WriteSFixed32(value), 4, tag);
}
/// <summary>
/// Retrieves a codec suitable for a uint32 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<uint> ForUInt32(uint tag)
{
return new FieldCodec<uint>(input => input.ReadUInt32(), (output, value) => output.WriteUInt32(value), CodedOutputStream.ComputeUInt32Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for an int64 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<long> ForInt64(uint tag)
{
return new FieldCodec<long>(input => input.ReadInt64(), (output, value) => output.WriteInt64(value), CodedOutputStream.ComputeInt64Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for an sint64 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<long> ForSInt64(uint tag)
{
return new FieldCodec<long>(input => input.ReadSInt64(), (output, value) => output.WriteSInt64(value), CodedOutputStream.ComputeSInt64Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for a fixed64 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<ulong> ForFixed64(uint tag)
{
return new FieldCodec<ulong>(input => input.ReadFixed64(), (output, value) => output.WriteFixed64(value), 8, tag);
}
/// <summary>
/// Retrieves a codec suitable for an sfixed64 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<long> ForSFixed64(uint tag)
{
return new FieldCodec<long>(input => input.ReadSFixed64(), (output, value) => output.WriteSFixed64(value), 8, tag);
}
/// <summary>
/// Retrieves a codec suitable for a uint64 field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<ulong> ForUInt64(uint tag)
{
return new FieldCodec<ulong>(input => input.ReadUInt64(), (output, value) => output.WriteUInt64(value), CodedOutputStream.ComputeUInt64Size, tag);
}
/// <summary>
/// Retrieves a codec suitable for a float field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<float> ForFloat(uint tag)
{
return new FieldCodec<float>(input => input.ReadFloat(), (output, value) => output.WriteFloat(value), CodedOutputStream.ComputeFloatSize, tag);
}
/// <summary>
/// Retrieves a codec suitable for a double field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<double> ForDouble(uint tag)
{
return new FieldCodec<double>(input => input.ReadDouble(), (output, value) => output.WriteDouble(value), CodedOutputStream.ComputeDoubleSize, tag);
}
// Enums are tricky. We can probably use expression trees to build these delegates automatically,
// but it's easy to generate the code for it.
/// <summary>
/// Retrieves a codec suitable for an enum field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <param name="toInt32">A conversion function from <see cref="Int32"/> to the enum type.</param>
/// <param name="fromInt32">A conversion function from the enum type to <see cref="Int32"/>.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<T> ForEnum<T>(uint tag, Func<T, int> toInt32, Func<int, T> fromInt32)
{
return new FieldCodec<T>(input => fromInt32(
input.ReadEnum()),
(output, value) => output.WriteEnum(toInt32(value)),
value => CodedOutputStream.ComputeEnumSize(toInt32(value)), tag);
}
/// <summary>
/// Retrieves a codec suitable for a message field with the given tag.
/// </summary>
/// <param name="tag">The tag.</param>
/// <param name="parser">A parser to use for the message type.</param>
/// <returns>A codec for the given tag.</returns>
public static FieldCodec<T> ForMessage<T>(uint tag, MessageParser<T> parser) where T : IMessage
{
return new FieldCodec<T>(input => { T message = parser.CreateTemplate(); input.ReadMessage(message); return message; },
(output, value) => output.WriteMessage(value), message => CodedOutputStream.ComputeMessageSize(message), tag);
}
}
/// <summary>
/// <para>
/// An encode/decode pair for a single field. This effectively encapsulates
/// all the information needed to read or write the field value from/to a coded
/// stream.
/// </para>
/// <para>
/// This class is public and has to be as it is used by generated code, but its public
/// API is very limited - just what the generated code needs to call directly.
/// </para>
/// </summary>
/// <remarks>
/// This never writes default values to the stream, and does not address "packedness"
/// in repeated fields itself, other than to know whether or not the field *should* be packed.
/// </remarks>
public sealed class FieldCodec<T>
{
private static readonly T DefaultDefault;
// Only non-nullable value types support packing. This is the simplest way of detecting that.
private static readonly bool TypeSupportsPacking = default(T) != null;
static FieldCodec()
{
if (typeof(T) == typeof(string))
{
DefaultDefault = (T)(object)"";
}
else if (typeof(T) == typeof(ByteString))
{
DefaultDefault = (T)(object)ByteString.Empty;
}
// Otherwise it's the default value of the CLR type
}
internal static bool IsPackedRepeatedField(uint tag)
{
return TypeSupportsPacking && WireFormat.GetTagWireType(tag) == WireFormat.WireType.LengthDelimited;
}
internal readonly bool PackedRepeatedField;
/// <summary>
/// Returns a delegate to write a value (unconditionally) to a coded output stream.
/// </summary>
internal readonly Action<CodedOutputStream, T> ValueWriter;
/// <summary>
/// Returns the size calculator for just a value.
/// </summary>
internal readonly Func<T, int> ValueSizeCalculator;
/// <summary>
/// Returns a delegate to read a value from a coded input stream. It is assumed that
/// the stream is already positioned on the appropriate tag.
/// </summary>
internal readonly Func<CodedInputStream, T> ValueReader;
/// <summary>
/// Returns the fixed size for an entry, or 0 if sizes vary.
/// </summary>
internal readonly int FixedSize;
/// <summary>
/// Gets the tag of the codec.
/// </summary>
/// <value>
/// The tag of the codec.
/// </value>
internal readonly uint Tag;
/// <summary>
/// Default value for this codec. Usually the same for every instance of the same type, but
/// for string/ByteString wrapper fields the codec's default value is null, whereas for
/// other string/ByteString fields it's "" or ByteString.Empty.
/// </summary>
/// <value>
/// The default value of the codec's type.
/// </value>
internal readonly T DefaultValue;
private readonly int tagSize;
internal FieldCodec(
Func<CodedInputStream, T> reader,
Action<CodedOutputStream, T> writer,
int fixedSize,
uint tag) : this(reader, writer, _ => fixedSize, tag)
{
FixedSize = fixedSize;
}
internal FieldCodec(
Func<CodedInputStream, T> reader,
Action<CodedOutputStream, T> writer,
Func<T, int> sizeCalculator,
uint tag) : this(reader, writer, sizeCalculator, tag, DefaultDefault)
{
}
internal FieldCodec(
Func<CodedInputStream, T> reader,
Action<CodedOutputStream, T> writer,
Func<T, int> sizeCalculator,
uint tag,
T defaultValue)
{
ValueReader = reader;
ValueWriter = writer;
ValueSizeCalculator = sizeCalculator;
FixedSize = 0;
Tag = tag;
DefaultValue = defaultValue;
tagSize = CodedOutputStream.ComputeRawVarint32Size(tag);
// Detect packed-ness once, so we can check for it within RepeatedField<T>.
PackedRepeatedField = IsPackedRepeatedField(tag);
}
/// <summary>
/// Write a tag and the given value, *if* the value is not the default.
/// </summary>
public void WriteTagAndValue(CodedOutputStream output, T value)
{
if (!IsDefault(value))
{
output.WriteTag(Tag);
ValueWriter(output, value);
}
}
/// <summary>
/// Reads a value of the codec type from the given <see cref="CodedInputStream"/>.
/// </summary>
/// <param name="input">The input stream to read from.</param>
/// <returns>The value read from the stream.</returns>
public T Read(CodedInputStream input)
{
return ValueReader(input);
}
/// <summary>
/// Calculates the size required to write the given value, with a tag,
/// if the value is not the default.
/// </summary>
public int CalculateSizeWithTag(T value)
{
return IsDefault(value) ? 0 : ValueSizeCalculator(value) + tagSize;
}
private bool IsDefault(T value)
{
return EqualityComparer<T>.Default.Equals(value, DefaultValue);
}
}
}