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INpgsqlTypeHandler.cs
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#region License
// The PostgreSQL License
//
// Copyright (C) 2017 The Npgsql Development Team
//
// Permission to use, copy, modify, and distribute this software and its
// documentation for any purpose, without fee, and without a written
// agreement is hereby granted, provided that the above copyright notice
// and this paragraph and the following two paragraphs appear in all copies.
//
// IN NO EVENT SHALL THE NPGSQL DEVELOPMENT TEAM BE LIABLE TO ANY PARTY
// FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES,
// INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS
// DOCUMENTATION, EVEN IF THE NPGSQL DEVELOPMENT TEAM HAS BEEN ADVISED OF
// THE POSSIBILITY OF SUCH DAMAGE.
//
// THE NPGSQL DEVELOPMENT TEAM SPECIFICALLY DISCLAIMS ANY WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
// ON AN "AS IS" BASIS, AND THE NPGSQL DEVELOPMENT TEAM HAS NO OBLIGATIONS
// TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
#endregion
using System.Threading.Tasks;
using JetBrains.Annotations;
using Npgsql.BackendMessages;
namespace Npgsql.TypeHandling
{
/// <summary>
/// Type handlers that wish to support reading other types in additional to the main one can
/// implement this interface for all those types.
/// </summary>
public interface INpgsqlTypeHandler<T>
{
/// <summary>
/// Reads a value of type <typeparamref name="T"/> with the given length from the provided buffer,
/// using either sync or async I/O.
/// </summary>
/// <param name="buf">The buffer from which to read.</param>
/// <param name="len">The byte length of the value. The buffer might not contain the full length, requiring I/O to be performed.</param>
/// <param name="async">If I/O is required to read the full length of the value, whether it should be performed synchronously or asynchronously.</param>
/// <param name="fieldDescription">Additional PostgreSQL information about the type, such as the length in varchar(30).</param>
/// <returns>The fully-read value.</returns>
ValueTask<T> Read(NpgsqlReadBuffer buf, int len, bool async, FieldDescription fieldDescription);
/// <summary>
/// Responsible for validating that a value represents a value of the correct and which can be
/// written for PostgreSQL - if the value cannot be written for any reason, an exception shold be thrown.
/// Also returns the byte length needed to write the value.
/// </summary>
/// <param name="value">The value to be written to PostgreSQL</param>
/// <param name="lengthCache">A cache where the length calculated during the validation phase can be stored for use at the writing phase.</param>
/// <param name="parameter">
/// The <see cref="NpgsqlParameter"/> instance where this value resides. Can be used to access additional
/// information relevant to the write process (e.g. <see cref="NpgsqlParameter.Size"/>).
/// </param>
/// <returns>The number of bytes required to write the value.</returns>
int ValidateAndGetLength(T value, ref NpgsqlLengthCache lengthCache, [CanBeNull] NpgsqlParameter parameter);
/// <summary>
/// Writes a value to the provided buffer.
/// </summary>
/// <param name="value">The value to write.</param>
/// <param name="buf">The buffer to which to write.</param>
/// <param name="lengthCache">A cache where the length calculated during the validation phase can be stored for use at the writing phase.</param>
/// <param name="parameter">
/// The <see cref="NpgsqlParameter"/> instance where this value resides. Can be used to access additional
/// information relevant to the write process (e.g. <see cref="NpgsqlParameter.Size"/>).
/// </param>
/// <param name="async">
/// If I/O will be necessary (i.e. the buffer is full), determines whether it will be done synchronously or asynchronously.
/// </param>
Task Write(T value, NpgsqlWriteBuffer buf, NpgsqlLengthCache lengthCache, [CanBeNull] NpgsqlParameter parameter, bool async);
}
}