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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
// 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.
-------------------------------------------------------------------------
*/
#if WHAT_DO_WE_DO_WITH_THIS
using System;
namespace NpgsqlTypes
{
/// <summary>
/// Large Object.
/// </summary>
public class LargeObject
{
/// <summary>
/// Indicates a seek from the begining of a file.
/// </summary>
public const Int32 SEEK_SET = 0;
/// <summary>
/// Indicates a seek from the current position.
/// </summary>
public const Int32 SEEK_CUR = 1;
/// <summary>
/// Indicates a seek from the end of a file.
/// </summary>
public const Int32 SEEK_END = 2;
private readonly Fastpath fp; // Fastpath API to use
private readonly Int32 oid; // OID of this object
private readonly Int32 fd; // the descriptor of the open large object
private Boolean closed = false; // true when we are closed
/// <summary>
/// This opens a large object.
/// </summary>
/// <param name="fp">FastPath API for the connection to use.</param>
/// <param name="oid">OID of the Large Object to open.</param>
/// <param name="mode">Mode of opening the large object</param>
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);
}
/// <summary>
/// OID getter.
/// </summary>
/// <returns>The OID of this LargeObject.</returns>
public Int32 GetOID()
{
return oid;
}
/// <summary>
/// OID.
/// </summary>
public Int32 OID
{
get { return oid; }
}
/// <summary>
/// This method closes the object. You must not call methods in this
/// object after this is called.
/// </summary>
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;
}
}
/// <summary>
/// Reads some data from the object, and return as a byte[] array.
/// </summary>
/// <param name="len">Number of bytes to read.</param>
/// <returns>Array containing data read.</returns>
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;
//}
}
/// <summary>
/// Reads some data from the object into an existing array.
/// </summary>
/// <param name="buf">Destination array.</param>
/// <param name="off">Offset within array.</param>
/// <param name="len">Maximum number of bytes to read.</param>
/// <returns>The number of bytes actually read.</returns>
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;
}
/// <summary>
/// Writes an array to the object.
/// </summary>
/// <param name="buf">Array to write.</param>
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);
}
/// <summary>
/// Writes some data from an array to the object.
/// </summary>
/// <param name="buf">Destination array.</param>
/// <param name="off">Offset within array.</param>
/// <param name="len">Number of bytes to write.</param>
public void Write(Byte[] buf, Int32 off, Int32 len)
{
Byte[] data = new Byte[len];
Array.Copy(buf, off, data, 0, len);
Write(data);
}
/// <summary>
/// Sets the current position within the object.
/// This is similar to the fseek() call in the standard C library. It
/// allows you to have random access to the large object.
/// </summary>
/// <param name="pos">Position within object.</param>
/// <param name="refi">Either SEEK_SET, SEEK_CUR or SEEK_END.</param>
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);
}
/// <summary>
/// Sets the current position within the object.
/// This is similar to the fseek() call in the standard C library. It
/// allows you to have random access to the large object.
/// </summary>
/// <param name="pos">Position within object from begining.</param>
public void Seek(Int32 pos)
{
Seek(pos, SEEK_SET);
}
/// <summary>
/// Report the current position within the object.
/// </summary>
/// <returns>The current position within the object.</returns>
public Int32 Tell()
{
FastpathArg[] args = new FastpathArg[1];
args[0] = new FastpathArg(fd);
return fp.GetInteger("lo_tell", args);
}
/// <summary>
/// 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.
/// A better method will be found in the future.
/// </summary>
/// <returns>The size of the large object.</returns>
public Int32 Size()
{
Int32 cp = Tell();
Seek(0, SEEK_END);
Int32 sz = Tell();
Seek(cp, SEEK_SET);
return sz;
}
}
}
#endif