using Npgsql.FrontendMessages;
using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Text;
using AsyncRewriter;
namespace Npgsql
{
///
/// Large object manager. This class can be used to store very large files in a PostgreSQL database.
///
public partial class NpgsqlLargeObjectManager
{
const int INV_WRITE = 0x00020000;
const int INV_READ = 0x00040000;
internal readonly NpgsqlConnection _connection;
///
/// The largest chunk size (in bytes) read and write operations will read/write each roundtrip to the network. Default 4 MB.
///
public int MaxTransferBlockSize { get; set; }
///
/// Creates an NpgsqlLargeObjectManager for this connection. The connection must be opened to perform remote operations.
///
///
public NpgsqlLargeObjectManager(NpgsqlConnection connection)
{
_connection = connection;
MaxTransferBlockSize = 4 * 1024 * 1024; // 4MB
}
///
/// Execute a function
///
///
///
///
[RewriteAsync]
internal T ExecuteFunction(string function, params object[] arguments)
{
using (var command = new NpgsqlCommand(function, _connection))
{
command.CommandType = CommandType.StoredProcedure;
command.CommandText = function;
foreach (var argument in arguments)
{
command.Parameters.Add(new NpgsqlParameter() { Value = argument });
}
return (T)command.ExecuteScalar();
}
}
///
/// Execute a function that returns a byte array
///
///
[RewriteAsync]
internal int ExecuteFunctionGetBytes(string function, byte[] buffer, int offset, int len, params object[] arguments)
{
using (var command = new NpgsqlCommand(function, _connection))
{
command.CommandType = CommandType.StoredProcedure;
foreach (var argument in arguments)
{
command.Parameters.Add(new NpgsqlParameter() { Value = argument });
}
using (var reader = command.ExecuteReader(System.Data.CommandBehavior.SequentialAccess))
{
reader.Read();
return (int)reader.GetBytes(0, 0, buffer, offset, len);
}
}
}
///
/// Create an empty large object in the database. If an oid is specified but is already in use, an NpgsqlException will be thrown.
///
/// A preferred oid, or specify 0 if one should be automatically assigned
/// The oid for the large object created
/// If an oid is already in use
[RewriteAsync]
[CLSCompliant(false)]
public uint Create(uint preferredOid = 0)
{
return ExecuteFunction("lo_create", (int)preferredOid);
}
///
/// Opens a large object on the backend, returning a stream controlling this remote object.
/// A transaction snapshot is taken by the backend when the object is opened with only read permissions.
/// When reading from this object, the contents reflects the time when the snapshot was taken.
/// Note that this method, as well as operations on the stream must be wrapped inside a transaction.
///
/// Oid of the object
/// An NpgsqlLargeObjectStream
[RewriteAsync]
public NpgsqlLargeObjectStream OpenRead(uint oid)
{
var fd = ExecuteFunction("lo_open", (int)oid, INV_READ);
return new NpgsqlLargeObjectStream(this, oid, fd, false);
}
///
/// Opens a large object on the backend, returning a stream controlling this remote object.
/// Note that this method, as well as operations on the stream must be wrapped inside a transaction.
///
/// Oid of the object
/// An NpgsqlLargeObjectStream
[RewriteAsync]
public NpgsqlLargeObjectStream OpenReadWrite(uint oid)
{
var fd = ExecuteFunction("lo_open", (int)oid, INV_READ | INV_WRITE);
return new NpgsqlLargeObjectStream(this, oid, fd, true);
}
///
/// Deletes a large object on the backend.
///
/// Oid of the object to delete
[RewriteAsync]
public void Unlink(uint oid)
{
ExecuteFunction