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INpgsqlTypeHandler.cs
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56 lines (52 loc) · 3.26 KB
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using System.Diagnostics.CodeAnalysis;
using System.Threading;
using System.Threading.Tasks;
using Npgsql.BackendMessages;
namespace Npgsql.Internal.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 = null);
/// <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 should 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([DisallowNull] T value, ref NpgsqlLengthCache? lengthCache, 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>
/// <param name="cancellationToken">
/// An optional token to cancel the asynchronous operation. The default value is <see cref="CancellationToken.None"/>.
/// </param>
Task Write([DisallowNull] T value, NpgsqlWriteBuffer buf, NpgsqlLengthCache? lengthCache, NpgsqlParameter? parameter, bool async, CancellationToken cancellationToken = default);
}