Dear All,
I have recently written a small Web Server application using the THttpServer
component in ICS 5 with C++ Builder 5.
It serves GET requests perfectly, but when I added POST functionality,
(following the WebServ example) it has started generating EAccessViolations.
CodeGuard reports that these are due to my PostedDataBuffer having only a 1
byte heap length when I am writing the NULL string termination character in
the "HttpServerPostedData" event handler.
I have managed to improve the code reliability by not dynamically allocating
the PostedDataBuffer at all, (but this is not an acceptable solution). In
the code snippets below I pre-allocate once in the constructor but this
still generates AV's.
Can anyone shed some light on what might be happening here?
Regards,
Keith Willis.
<<< CODE SNIPPETS >>>
//--------------------------------------------------------------------------
-
class TMyHttpConnection : public THttpConnection
{
public:
char* Junk;
char *PostedDataBuffer; // Will hold dynamically allocated buffer
int PostedDataSize; // Databuffer size
int RcvdByteCount; // Keep track of received byte count.
public:
__fastcall TMyHttpConnection(Classes::TComponent* AOwner);
virtual __fastcall ~TMyHttpConnection();
};
//--------------------------------------------------------------------------
-
//--------------------------------------------------------------------------
-
__fastcall TMyHttpConnection::TMyHttpConnection(Classes::TComponent* AOwner)
: THttpConnection(AOwner)
{
try
{
Junk = new char(65536);
PostedDataBuffer = new char(65536); // Pre-allocate here in a desperate
attempt to avoid EAccessViolations
PostedDataSize = 65536;
}
catch(...) {}
}
//--------------------------------------------------------------------------
-
__fastcall TMyHttpConnection::~TMyHttpConnection()
{
try
{
delete [] Junk;
delete [] PostedDataBuffer;
PostedDataBuffer = NULL;
PostedDataSize = 0;
}
catch(...) {}
}
//--------------------------------------------------------------------------
-
//--------------------------------------------------------------------------
-
void __fastcall TAegisWebServerForm::HttpServerPostedData(TObject *Sender,
TObject *Client, WORD Error)
{
try
{
int Len, Remains;
TMyHttpConnection* Connection = (TMyHttpConnection*)Client;
Remains = Connection->RequestContentLength - Connection->RcvdByteCount;
if (Remains <= 0)
{
Len = Connection->Receive(Connection->Junk, sizeof(Connection->Junk)- 1);
if (Len >= 0) Connection->Junk[Len] = 0;
return;
}
// Len = Connection->Receive(Connection->PostedDataBuffer +
Connection->RcvdByteCount, Remains);
Len =
Connection->Receive(&(Connection->PostedDataBuffer[Connection->RcvdByteCount
]), Remains);
if (Len <= 0) return;
Connection->RcvdByteCount += Len;
if (Connection->RcvdByteCount > Connection->RequestContentLength)
Connection->RcvdByteCount = Connection->RequestContentLength;
if (Connection->RcvdByteCount == Connection->RequestContentLength)
{
Connection->PostedDataBuffer[Connection->RcvdByteCount] = 0; // <=
CRASHES HERE! CodeGuard reports that the Heap length of is only 1 byte at
this point???
if (CompareText(Connection->Path, "/content/home.html") == 0)
ProcessPostedData(Connection);
// else Connection->Answer404(); // I need to make Answer404 accessible
else
{
AnsiString Body = AnsiString("<HTML><HEAD><TITLE>404 Not
Found</TITLE></HEAD><BODY><H1>404 Not Found</H1>The requested URL ") +
TextToHtmlText(Connection->Path) + " was not found on this
server.<P></BODY></HTML>\r\n";
Connection->SendHeader(Connection->Version + " 404 Not
Found\r\nContent-Type: text/html\r\nContent-Length: " +
Utility->IntToStrEx(Body.Length()) + "\r\n\r\n");
Connection->SendStr(Body);
}
Connection->PostedDataReceived();
}
}
catch (Exception &E)
{HandleError("TAegisWebServerForm::HttpServerPostedData", E.Message);}
catch (const exception &e)
{HandleError("TAegisWebServerForm::HttpServerPostedData", e.what());}
catch (...) {HandleError("TAegisWebServerForm::HttpServerPostedData",
"Unknown Exception");}
}
//--------------------------------------------------------------------------
-
--
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