Hard C++ to Delphi Conversion

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Views: 1161 | Replies: 10

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Join Date: May 2008

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rayman341

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Hard C++ to Delphi Conversion

May 15th, 2008

I am working on porting C++ code to Delphi and I am only having a problem with the correct conversion of memmove() statements in the C++ code.

If you or any one you know could help me to convert this C++ code to Delphi I would be thankful.

// Move TCP packet body by sizeof(VPNSEC_HEADER) bytes
memmove(((unsigned char*)pTcpHdr) + sizeof (VPNSEC_HEADER), pTcpHdr, PacketBuffer.m_Length - (sizeof(ether_header) + sizeof(DWORD)*pIpHeader->ip_hl));

// Initialize the injected header
pVpnHdr = (PVPNSEC_HEADER)pTcpHdr;
pVpnHdr->m_Length = (unsigned short)(PacketBuffer.m_Length - (sizeof(ether_header) + sizeof(DWORD)*pIpHeader->ip_hl));
memcpy (pVpnHdr->m_Key, EncKey, 8);

// Calculate padding
padding = 8 - (pVpnHdr->m_Length%8);

// Zero initialize padding
memset (((unsigned char*)(pVpnHdr + 1)) + pVpnHdr->m_Length, 0, padding);

Ray

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Micheus

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Re: Hard C++ to Delphi Conversion

May 15th, 2008

I think that you can use this procedures (bellow) from System unit:
memmove or memcpy: procedure Move(const Source; var Dest; Count: Integer);

memset: procedure FillChar(var X; Count: Integer; value: Byte);

Bye

"It always has, at least, two ways to make one same thing. Exactly that they are certain and wrong"(Micheus)

Brazil - Blumenau

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rayman341

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Re: Hard C++ to Delphi Conversion

May 15th, 2008

Thank you, but how do I handle the offset:

memmove(((unsigned char*)pTcpHdr) + sizeof (VPNSEC_HEADER), pTcpHdr, PacketBuffer.m_Length - (sizeof(ether_header) + sizeof(DWORD)*pIpHeader->ip_hl));

Ray

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Micheus

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Re: Hard C++ to Delphi Conversion

May 15th, 2008

I'm not sure about Delphi I, but maybe you can do something like this:

 Help with Code Tags 
 delphi Syntax (Toggle Plain Text) 
var
  PtrSource :^Byte;
begin
  PtrSource := pTcpHdr;
  Inc(PtrSource, sizeof (VPNSEC_HEADER));
  Move(pTcpHdr^, PtrSource^, PacketBuffer.m_Length - (sizeof(ether_header) + sizeof(DWORD)*pIpHeader^.ip_hl))
end;
var
  PtrSource :^Byte;
begin
  PtrSource := pTcpHdr;
  Inc(PtrSource, sizeof (VPNSEC_HEADER));
  Move(pTcpHdr^, PtrSource^, PacketBuffer.m_Length - (sizeof(ether_header) + sizeof(DWORD)*pIpHeader^.ip_hl))
end;

notice that parameters positions change between the two compilers:
void * memmove ( void * destination, const void * source, size_t num );
procedure Move(const Source; var Dest; Count: Integer);

You must try.

"It always has, at least, two ways to make one same thing. Exactly that they are certain and wrong"(Micheus)

Brazil - Blumenau

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rayman341

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Re: Hard C++ to Delphi Conversion

May 15th, 2008

//
// Custom VPN information header
//
type
TVPNSecHeaderPtr = ^TVPNSecHeader;
TVPNSecHeader = packed record
h_KeyId: array [1..8] of Byte;
h_Length: Word;
h_IpProto: Byte;
end;

//
// IP header
//
type
TIPHeaderPtr = ^TIPHeader;
TIPHeader = packed record
VerLen: Byte;
TOS: Byte;
TotalLen: Word;
Identifer: Word;
FragOffsets: Word;
TTL: Byte;
Protocol: Byte;
CheckSum: Word;
SourceIp: DWORD;
DestIp: DWORD;
Options: DWORD;
end;

//
// TCP header
//
TTCPHeaderPtr = ^TTCPHeader;
TTCPHeader = packed record
SourcePort:Word;
DestPort:Word;
SequenceNumber

Word;
AcknowledgementNumber

Word;
Offset:Byte; //only left 4 bits. Header length in 32-bit segments
Flags:Byte;
Window:Word;
Checksum:Word; //includes speudo header instead of TCP header.
UrgentPointer:Word;
end;

pIPHeader: TIPHeaderPtr;
pTcpHdr: TTCPHeaderPtr;

Are you sure PtrSource should be a Byte?

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Duoas

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Re: Hard C++ to Delphi Conversion

May 15th, 2008

Yes, it should be cast to a BytePtr. If you don't then anything you add to it is multiplied by the size of the object's elements.

 Help with Code Tags 
 Delphi Syntax (Toggle Plain Text) 
type 
  pPoint = ^tPoint;
  tPoint: record x, y: integer end;
 
function get_point( points: pPoint; index: integer ): tPoint;
  begin
  inc( points, index );  // same as in C (points += index)
  result := points^
  end;
 
function get_point( points: pPoint; index: integer ): tPoint;
  var p: BytePtr;
  begin
  p := pointer( points );
  inc( p, index *sizeof( tPoint ) );
  points := pointer( p );
  result := points^
  end;
type 
  pPoint = ^tPoint;
  tPoint: record x, y: integer end;

function get_point( points: pPoint; index: integer ): tPoint;
  begin
  inc( points, index );  // same as in C (points += index)
  result := points^
  end;

function get_point( points: pPoint; index: integer ): tPoint;
  var p: BytePtr;
  begin
  p := pointer( points );
  inc( p, index *sizeof( tPoint ) );
  points := pointer( p );
  result := points^
  end;

The first version works the same as in C and C++. If the size of the pointer's target is known, it is automatically multiplied into the index:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int *a;
a[ 5 ] == (a +5)
int *a;
a[ 5 ] == (a +5)

If, however, the offset calculation is in bytes you must first cast it to a byte pointer:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
int *a;
a[ 5 ] == ((unsigned char*)a +(5 *sizeof( a[ 0 ] )))
int *a;
a[ 5 ] == ((unsigned char*)a +(5 *sizeof( a[ 0 ] )))

Hope this helps.

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rayman341

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Re: Hard C++ to Delphi Conversion

May 16th, 2008

So what is:
memset (((unsigned char*)(pVpnHdr + 1)) + pVpnHdr->m_Length, 0, padding);

converted to Delphi?

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Duoas

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Re: Hard C++ to Delphi Conversion

May 16th, 2008

Messy.

 Help with Code Tags 
 Delphi Syntax (Toggle Plain Text) 
var
  bp: PByte;
begin
  bp := pVpnHdr;
  inc( bp, sizeof( pVpnHdr ) +pVpnHdr^.m_Length );
  fillchar( bp^, padding, 0 )
end;
var
  bp: PByte;
begin
  bp := pVpnHdr;
  inc( bp, sizeof( pVpnHdr ) +pVpnHdr^.m_Length );
  fillchar( bp^, padding, 0 )
end;