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SessionCache.pas
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// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
unit
SessionCache;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
interface
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
uses
IPUtils,
MD5;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
type
TSessionCache = class
public
class procedure Initialize;
class procedure ReserveItem(ReferenceTime: TDateTime; OriginalSessionId: Word; var RemappedSessionId: Word);
class procedure InsertIPv4Item(ReferenceTime: TDateTime; OriginalSessionId: Word; RemappedSessionId: Word; RequestHash: TMD5Digest; ClientAddress: TIPv4Address; ClientPort: Word; IsSilentUpdate: Boolean; IsCacheException: Boolean);
class procedure InsertIPv6Item(ReferenceTime: TDateTime; OriginalSessionId: Word; RemappedSessionId: Word; RequestHash: TMD5Digest; ClientAddress: TIPv6Address; ClientPort: Word; IsSilentUpdate: Boolean; IsCacheException: Boolean);
class function ExtractIPv4Item(ReferenceTime: TDateTime; var OriginalSessionId: Word; RemappedSessionId: Word; var RequestHash: TMD5Digest; var ClientAddress: TIPv4Address; var ClientPort: Word; var IsSilentUpdate: Boolean; var IsCacheException: Boolean): Boolean;
class function ExtractIPv6Item(ReferenceTime: TDateTime; var OriginalSessionId: Word; RemappedSessionId: Word; var RequestHash: TMD5Digest; var ClientAddress: TIPv6Address; var ClientPort: Word; var IsSilentUpdate: Boolean; var IsCacheException: Boolean): Boolean;
class procedure DeleteItem(RemappedSessionId: Word);
class procedure Finalize;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
implementation
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
uses
SysUtils;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
const
SESSION_CACHE_EXPIRATION_TIME = 3.472222e-4; // 30 seconds
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
type
TSessionCacheItem = packed record
SessionId: Word;
IsAllocated: Boolean;
AllocationTime: TDateTime;
RequestHash: TMD5Digest;
ClientAddress: TDualIPAddress;
ClientPort: Word;
IsSilentUpdate: Boolean;
IsCacheException: Boolean;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
var
TSessionCache_List: array [0..65535] of TSessionCacheItem;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.Initialize;
begin
FillChar(TSessionCache_List, SizeOf(TSessionCache_List), 0);
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.ReserveItem(ReferenceTime: TDateTime; OriginalSessionId: Word; var RemappedSessionId: Word);
var
i: Integer;
begin
for i := 1 to 100 do begin
RemappedSessionId := Random(65536);
if not(TSessionCache_List[RemappedSessionId].IsAllocated) or ((ReferenceTime - TSessionCache_List[RemappedSessionId].AllocationTime) > SESSION_CACHE_EXPIRATION_TIME) then Exit;
end;
raise Exception.Create('TSessionCache.ReserveItem: All reservation retries for Session ID ' + FormatCurr('00000', OriginalSessionId) + ' have been exhausted.');
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.InsertIPv4Item(ReferenceTime: TDateTime; OriginalSessionId: Word; RemappedSessionId: Word; RequestHash: TMD5Digest; ClientAddress: TIPv4Address; ClientPort: Word; IsSilentUpdate: Boolean; IsCacheException: Boolean);
begin
TSessionCache_List[RemappedSessionId].IsAllocated := True;
TSessionCache_List[RemappedSessionId].AllocationTime := ReferenceTime;
TSessionCache_List[RemappedSessionId].SessionId := OriginalSessionId;
TSessionCache_List[RemappedSessionId].RequestHash := RequestHash;
TSessionCache_List[RemappedSessionId].ClientAddress := TDualIPAddressUtility.CreateFromIPv4Address(ClientAddress);
TSessionCache_List[RemappedSessionId].ClientPort := ClientPort;
TSessionCache_List[RemappedSessionId].IsSilentUpdate := IsSilentUpdate;
TSessionCache_List[RemappedSessionId].IsCacheException := IsCacheException;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.InsertIPv6Item(ReferenceTime: TDateTime; OriginalSessionId: Word; RemappedSessionId: Word; RequestHash: TMD5Digest; ClientAddress: TIPv6Address; ClientPort: Word; IsSilentUpdate: Boolean; IsCacheException: Boolean);
begin
TSessionCache_List[RemappedSessionId].IsAllocated := True;
TSessionCache_List[RemappedSessionId].AllocationTime := ReferenceTime;
TSessionCache_List[RemappedSessionId].SessionId := OriginalSessionId;
TSessionCache_List[RemappedSessionId].RequestHash := RequestHash;
TSessionCache_List[RemappedSessionId].ClientAddress := TDualIPAddressUtility.CreateFromIPv6Address(ClientAddress);
TSessionCache_List[RemappedSessionId].ClientPort := ClientPort;
TSessionCache_List[RemappedSessionId].IsSilentUpdate := IsSilentUpdate;
TSessionCache_List[RemappedSessionId].IsCacheException := IsCacheException;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class function TSessionCache.ExtractIPv4Item(ReferenceTime: TDateTime; var OriginalSessionId: Word; RemappedSessionId: Word; var RequestHash: TMD5Digest; var ClientAddress: TIPv4Address; var ClientPort: Word; var IsSilentUpdate: Boolean; var IsCacheException: Boolean): Boolean;
begin
if TSessionCache_List[RemappedSessionId].IsAllocated and not(TSessionCache_List[RemappedSessionId].ClientAddress.IsIPv6Address) then begin
OriginalSessionId := TSessionCache_List[RemappedSessionId].SessionId;
RequestHash := TSessionCache_List[RemappedSessionId].RequestHash;
ClientAddress := TSessionCache_List[RemappedSessionId].ClientAddress.IPv4Address;
ClientPort := TSessionCache_List[RemappedSessionId].ClientPort;
IsSilentUpdate := TSessionCache_List[RemappedSessionId].IsSilentUpdate;
IsCacheException := TSessionCache_List[RemappedSessionId].IsCacheException;
Result := True;
end else begin
Result := False;
end;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class function TSessionCache.ExtractIPv6Item(ReferenceTime: TDateTime; var OriginalSessionId: Word; RemappedSessionId: Word; var RequestHash: TMD5Digest; var ClientAddress: TIPv6Address; var ClientPort: Word; var IsSilentUpdate: Boolean; var IsCacheException: Boolean): Boolean;
begin
if TSessionCache_List[RemappedSessionId].IsAllocated and TSessionCache_List[RemappedSessionId].ClientAddress.IsIPv6Address then begin
OriginalSessionId := TSessionCache_List[RemappedSessionId].SessionId;
RequestHash := TSessionCache_List[RemappedSessionId].RequestHash;
ClientAddress := TSessionCache_List[RemappedSessionId].ClientAddress.IPv6Address;
ClientPort := TSessionCache_List[RemappedSessionId].ClientPort;
IsSilentUpdate := TSessionCache_List[RemappedSessionId].IsSilentUpdate;
IsCacheException := TSessionCache_List[RemappedSessionId].IsCacheException;
Result := True;
end else begin
Result := False;
end;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.DeleteItem(RemappedSessionId: Word);
begin
TSessionCache_List[RemappedSessionId].IsAllocated := False;
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
class procedure TSessionCache.Finalize;
begin
// Nothing to do.
end;
// --------------------------------------------------------------------------
//
// --------------------------------------------------------------------------
end.