Question

I am using autohotkey to make mysql calls. The mysql interface was deciphered by referencing a visual basic api to mysql.

I am using the mysql connect calls referenced in this post: http://www.autohotkey.com/forum/viewtopic.php?t=12482

I would like to add a dllcall to replicate this perl call to mysql_options…

mysql_options(mysql, MYSQL_OPT_RECONNECT, &true);

It is my understanding that this call would enable my program to gracefully reconnect to mysql after the standard 8 hour mysql timeout. I want my application to remain up indefinitely.

Here is my code. A reference on googles source code libary suggests that the reconnect constant is 20. Everything works except the mysql_opt_reconnect call.

Can anyone help me determine the proper call to libmysql.dll to get my app to automatically reconnect after mysql timeout has occurred?

;============================================================
; mysql.ahk
;
;   Provides a set of functions to connect and query a mysql database
;============================================================

FileInstall, libmysql.dll, %A_AppData%\libmysql.dll, 1

;============================================================
; Connect to mysql database and return db handle
;
; host = DTWRO-WS0061   
; user = alan
; password = *******
; database = rush
;============================================================

dbConnect(host,user,password,database){   

   if (A_IsCompiled) {
      ExternDir := A_AppData
   } else {
      ExternDir := A_WorkingDir
   }

   hModule := DllCall("LoadLibrary", "Str", ExternDir "\libmySQL.dll")

   If (hModule = 0)
   {
      MsgBox 16, MySQL Error 233, Can't load libmySQL.dll from directory %ExternDir%
      ExitApp
   }

   db := DllCall("libmySQL.dll\mysql_init", "UInt", 0)

   If (db = 0)
   {
      MsgBox 16, MySQL Error 445, Not enough memory to connect to MySQL
      ExitApp
   }

    ; figure out how to turn on reconnect call!
    ; mysql_options(mysql, MYSQL_OPT_RECONNECT, &true);
    value := DllCall("libmySQL.dll\mysql_options"
             , "UInt", db
             , "UInt", 20    ; is this the correct constant which represents MYSQL_OPT_RECONNECT?... see below
             , "UInt", 1)   ; true

   connection := DllCall("libmySQL.dll\mysql_real_connect"
         , "UInt", db
         , "Str", host       ; host name
         , "Str", user       ; user name
         , "Str", password   ; password
         , "Str", database   ; database name
         , "UInt", 3306   ; port
         , "UInt", 0   ; unix_socket
         , "UInt", 0)   ; client_flag

   If (connection = 0)
   {
      HandleMySQLError(db, "Cannot connect to database")
      Return
   }

   serverVersion := DllCall("libmySQL.dll\mysql_get_server_info", "UInt", db, "Str")



   ;MsgBox % "Ping database: " . DllCall("libmySQL.dll\mysql_ping", "UInt", db) . "`nServer version: " . serverVersion

   return db

}

;============================================================
; mysql error handling
;============================================================

HandleMySQLError(db, message, query="") {        ; the equal sign means optional
   errorCode := DllCall("libmySQL.dll\mysql_errno", "UInt", db)
   errorStr := DllCall("libmySQL.dll\mysql_error", "UInt", db, "Str")
   MsgBox 16, MySQL Error: %message%, Error %errorCode%: %errorStr%`n`n%query%
   Return
}

;============================================================
; mysql get address
;============================================================

GetUIntAtAddress(_addr, _offset)
{
   local addr

   addr := _addr + _offset * 4

   Return *addr + (*(addr + 1) << 8) +  (*(addr + 2) << 16) + (*(addr + 3) << 24)
}

;============================================================
; process query
;============================================================

dbQuery(_db, _query)
{
    local resultString, result, requestResult, fieldCount
    local row, lengths, length, fieldPointer, field

    query4error := RegExReplace(_query , "\t", "   ")    ; convert tabs to spaces so error message formatting is legible
    result := DllCall("libmySQL.dll\mysql_query", "UInt", _db , "Str", _query)

    If (result != 0) {
        errorMsg = %_query%
        HandleMySQLError(_db, "dbQuery Fail", query4error)
        Return
    }

    requestResult := DllCall("libmySQL.dll\mysql_store_result", "UInt", _db)

    if (requestResult = 0) {    ; call must have been an insert or delete ... a select would return results to pass back
        return
    }

    fieldCount := DllCall("libmySQL.dll\mysql_num_fields", "UInt", requestResult)

    Loop
    {
        row := DllCall("libmySQL.dll\mysql_fetch_row", "UInt", requestResult)
        If (row = 0 || row == "")
            Break

        ; Get a pointer on a table of lengths (unsigned long)
        lengths := DllCall("libmySQL.dll\mysql_fetch_lengths" , "UInt", requestResult)

        Loop %fieldCount%
        {
            length := GetUIntAtAddress(lengths, A_Index - 1)
            fieldPointer := GetUIntAtAddress(row, A_Index - 1)
            VarSetCapacity(field, length)
            DllCall("lstrcpy", "Str", field, "UInt", fieldPointer)
            resultString := resultString . field
            If (A_Index < fieldCount)
                resultString := resultString . "|"     ; seperator for fields
        }

        resultString := resultString . "`n"          ; seperator for records 

    }

    ; remove last newline from resultString
    resultString := RegExReplace(resultString , "`n$", "")    

    Return resultString
}

Answer 1

Even better… I used an oop class to retain the mysql connection parameters, so that when the mysql connection timed out and a new mysql call is made, it can automatically reconnect.