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/*-------------------------------------------------------------------------
LargeObject.cs
This class is a port of the class LargeObject.java implemented by
PostgreSQL Global Development Group
Copyright (c) 2004, Emiliano Necciari
Original Code: Copyright (c) 2003, PostgreSQL Global Development Group
Note: (Francisco Figueiredo Jr.)
Changed case of method names to conform to .Net names standard.
Also changed type names to their true names. i.e. int -> Int32
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-------------------------------------------------------------------------
*/
using System;
using System.IO;
using Npgsql;
namespace NpgsqlTypes
{
public class LargeObject
{
/*
* Indicates a seek from the begining of a file
*/
public const Int32 SEEK_SET = 0;
/*
* Indicates a seek from the current position
*/
public const Int32 SEEK_CUR = 1;
/*
* Indicates a seek from the end of a file
*/
public const Int32 SEEK_END = 2;
private Fastpath fp; // Fastpath API to use
private Int32 oid; // OID of this object
private Int32 fd; // the descriptor of the open large object
private Boolean closed = false; // true when we are closed
/*
* This opens a large object.
*
* <p>If the object does not exist, then an NpgsqlException is thrown.
*
* @param fp FastPath API for the connection to use
* @param oid of the Large Object to open
* @param mode Mode of opening the large object
* (defined in LargeObjectManager)
* @exception NpgsqlException if a database-access error occurs.
* @see org.postgresql.largeobject.LargeObjectManager
*/
public LargeObject(Fastpath fp, Int32 oid, Int32 mode)
{
this.fp = fp;
this.oid = oid;
FastpathArg[] args = new FastpathArg[2];
args[0] = new FastpathArg(oid);
args[1] = new FastpathArg(mode);
this.fd = fp.GetInteger("lo_open", args);
}
/*
* @return the OID of this LargeObject
*/
public Int32 GetOID()
{
return oid;
}
/*
* This method closes the object. You must not call methods in this
* object after this is called.
* @exception NpgsqlException if a database-access error occurs.
*/
public void Close()
{
if (!closed)
{
// finally close
FastpathArg[] args = new FastpathArg[1];
args[0] = new FastpathArg(fd);
fp.FastpathCall("lo_close", false, args); // true here as we dont care!!
closed = true;
}
}
/*
* Reads some data from the object, and return as a byte[] array
*
* @param len number of bytes to read
* @return byte[] array containing data read
* @exception NpgsqlException if a database-access error occurs.
*/
public Byte[] Read(Int32 len)
{
// This is the original method, where the entire block (len bytes)
// is retrieved in one go.
FastpathArg[] args = new FastpathArg[2];
args[0] = new FastpathArg(fd);
args[1] = new FastpathArg(len);
return fp.GetData("loread", args);
// This version allows us to break this down Int32o 4k blocks
//if (len<=4048) {
//// handle as before, return the whole block in one go
//FastpathArg args[] = new FastpathArg[2];
//args[0] = new FastpathArg(fd);
//args[1] = new FastpathArg(len);
//return fp.getData("loread",args);
//} else {
//// return in 4k blocks
//byte[] buf=new byte[len];
//int off=0;
//while (len>0) {
//int bs=4048;
//len-=bs;
//if (len<0) {
//bs+=len;
//len=0;
//}
//read(buf,off,bs);
//off+=bs;
//}
//return buf;
//}
}
/*
* Reads some data from the object into an existing array
*
* @param buf destination array
* @param off offset within array
* @param len number of bytes to read
* @return the number of bytes actually read
* @exception NpgsqlException if a database-access error occurs.
*/
public Int32 Read(Byte[] buf, Int32 off, Int32 len)
{
Byte[] b = Read(len);
if (b.Length < len)
len = b.Length;
Array.Copy(b,0,buf,off,len);
return len;
}
/*
* Writes an array to the object
*
* @param buf array to write
* @exception NpgsqlException if a database-access error occurs.
*/
public void Write(Byte[] buf)
{
FastpathArg[] args = new FastpathArg[2];
args[0] = new FastpathArg(fd);
args[1] = new FastpathArg(buf);
fp.FastpathCall("lowrite", false, args);
}
/*
* Writes some data from an array to the object
*
* @param buf destination array
* @param off offset within array
* @param len number of bytes to write
* @exception NpgsqlException if a database-access error occurs.
*/
public void Write(Byte[] buf, Int32 off, Int32 len)
{
Byte[] data = new Byte[len];
System.Array.Copy(buf, off, data, 0, len);
Write(data);
}
/*
* Sets the current position within the object.
*
* <p>This is similar to the fseek() call in the standard C library. It
* allows you to have random access to the large object.
*
* @param pos position within object
* @param ref Either SEEK_SET, SEEK_CUR or SEEK_END
* @exception NpgsqlException if a database-access error occurs.
*/
public void Seek(Int32 pos, Int32 refi)
{
FastpathArg[] args = new FastpathArg[3];
args[0] = new FastpathArg(fd);
args[1] = new FastpathArg(pos);
args[2] = new FastpathArg(refi);
fp.FastpathCall("lo_lseek", false, args);
}
/*
* Sets the current position within the object.
*
* <p>This is similar to the fseek() call in the standard C library. It
* allows you to have random access to the large object.
*
* @param pos position within object from begining
* @exception NpgsqlException if a database-access error occurs.
*/
public void Seek(Int32 pos)
{
Seek(pos, SEEK_SET);
}
/*
* @return the current position within the object
* @exception NpgsqlException if a database-access error occurs.
*/
public Int32 Tell()
{
FastpathArg[] args = new FastpathArg[1];
args[0] = new FastpathArg(fd);
return fp.GetInteger("lo_tell", args);
}
/*
* This method is inefficient, as the only way to find out the size of
* the object is to seek to the end, record the current position, then
* return to the original position.
*
* <p>A better method will be found in the future.
*
* @return the size of the large object
* @exception NpgsqlException if a database-access error occurs.
*/
public Int32 Size()
{
Int32 cp = Tell();
Seek(0, SEEK_END);
Int32 sz = Tell();
Seek(cp, SEEK_SET);
return sz;
}
}
}
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