questions about FileWriteInteger() and FileReadInteger()

New comment
  
// test_file_funcs.mq4 : indicator
#property indicator_chart_window

int init()
  {
//----   
//----
   return(0);
  }

int deinit()
  {
//----   
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int start()
  {


            static bool once = false;  // true only run one time 
            if(once) return(0);
//----
           int i,handle;       
     
            //  write 5 numbers to file : file_write.dat 
           handle  = FileOpen("file_write.dat",FILE_BIN|FILE_WRITE);  
              
               if(handle>0)
               {    
                     for(i=0;i<5;i++)
                     FileWriteInteger(handle,i+1,LONG_VALUE); // 5 numbers:1,2,3,4,5
               }
               
           FileClose(handle); 
         
         
         //  read these 5 numbers to an array : data[]
          handle  = FileOpen("file_write.dat",FILE_BIN|FILE_READ);        
         if(handle>0)
         {  
                  int cnt=0;  // count the times of run FileReadInteger()
                  int dat,size,data[1];
                  
                  Print("FileSize(handle) = ",FileSize(handle));   
                  
                  while(FileIsEnding(handle)==false)
                      {
                       
                        dat = FileReadInteger(handle,LONG_VALUE);
                        size = ArraySize(data);
                        if(size>0)
                           {
                              data[size-1]=dat;
                              ArrayResize(data,size+1);//
                              cnt++;  // cnt = 6 ? why not 5 ?
                            } 
                       }                 
         }
          FileClose(handle);   
          
           
        
               size = ArraySize(data);
               Print("size = ",size, " cnt = ",cnt);// size = 7 ,cnt = 6 ? why are they not 5 ?     
               for(i=0;i<size;i++) Print(data[i]);                            
          
           
         
//----        
          once = true; // only run one time 
   
//----
   return(0);
  }
//+------------------------------------------------------------------+
 

my questions :

why size is 7 ?

why cnt is 6?

 

anyone please help to give some idea ?

 
sergery:

anyone please help to give some idea ?


This is the way the variables change, sequence is from top to bottom . . .

2012.10.15 08:36:15 sergery USDCHF,H1: loaded successfully

2012.10.15 08:36:17 sergery USDCHF,H1: initialized

2012.10.15 08:36:17 sergery USDCHF,H1: FileSize(handle) = 20

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 1

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 2

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 1

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 2

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 3

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 2

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 3

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 4

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 3

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 4

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 5

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 4

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 5

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 6

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 5

2012.10.15 08:36:17 sergery USDCHF,H1: size = ArraySize(data) - size = 6

2012.10.15 08:36:17 sergery USDCHF,H1: ArrayResize(data,size+1) - size + 1 = 7

2012.10.15 08:36:17 sergery USDCHF,H1: cnt++ - cnt = 6

2012.10.15 08:36:17 sergery USDCHF,H1: size = 7 cnt = 6

2012.10.15 08:36:17 sergery USDCHF,H1: 1

2012.10.15 08:36:17 sergery USDCHF,H1: 2

2012.10.15 08:36:17 sergery USDCHF,H1: 3

2012.10.15 08:36:17 sergery USDCHF,H1: 4

2012.10.15 08:36:17 sergery USDCHF,H1: 5

2012.10.15 08:36:17 sergery USDCHF,H1: 0

2012.10.15 08:36:17 sergery USDCHF,H1: 0

cnt is 6 and not 5 because you increment it during the final run of the loop, but anyway . . . cnt should be 4 not 5 as it starts at 0.

To see the EOF marker you have to read the next element . . then you see you are at the EOF. When you do this it is already too late and your loop has run 2 more times than it needed . . .

It's a little hard for me to explain . . . take a look at this modification to your code . . .

                  Print("FileSize(handle) = ",FileSize(handle));   
                  
                  dat = FileReadInteger(handle,LONG_VALUE);    //  read the first entry in the file
                  while(FileIsEnding(handle)==false)
                      {
                        size = ArraySize(data);
                        Print("size = ArraySize(data) - size = ", size);
                        
                        if(size>0)
                           {
                              data[size-1]=dat;             //  write the entry from the file into the array
                              
                              dat = FileReadInteger(handle,LONG_VALUE);   // read the next entry in the file
                              if(FileIsEnding(handle)) break;   //  if we have just read past the last element to the EOF quit the while loop
                              
                              ArrayResize(data,size+1);//
                              Print("ArrayResize(data,size+1) - size + 1 = ", size + 1);
                              
                              cnt++;  // cnt = 6 ? why not 5 ?
                              Print("cnt++ - cnt = ", cnt);
                              
                            } 
                       }                
 

The end result . . .

2012.10.15 09:11:46 sergery USDCHF,H1: size = 5 cnt = 4

2012.10.15 09:11:46 sergery USDCHF,H1: 1

2012.10.15 09:11:46 sergery USDCHF,H1: 2

2012.10.15 09:11:46 sergery USDCHF,H1: 3

2012.10.15 09:11:46 sergery USDCHF,H1: 4

2012.10.15 09:11:46 sergery USDCHF,H1: 5

 
RaptorUK:

The end result . . .

2012.10.15 09:11:46 sergery USDCHF,H1: size = 5 cnt = 4

2012.10.15 09:11:46 sergery USDCHF,H1: 1

2012.10.15 09:11:46 sergery USDCHF,H1: 2

2012.10.15 09:11:46 sergery USDCHF,H1: 3

2012.10.15 09:11:46 sergery USDCHF,H1: 4

2012.10.15 09:11:46 sergery USDCHF,H1: 5

Thank you very much !

// test_file_funcs.mq4 : indicator
#property indicator_chart_window

int init()
  {
//----   
//----
   return(0);
  }

int deinit()
  {
//----   
//----
   return(0);
  }
//+------------------------------------------------------------------+
//| Custom indicator iteration function                              |
//+------------------------------------------------------------------+
int start()
  {
        


            static bool once = false;  // true only run one time 
            if(once) return(0);
//----
            

           int i,handle;       
     
            //  write 5 numbers to file : file_write.dat 
           handle  = FileOpen("file_write.dat",FILE_BIN|FILE_WRITE);  
              
               if(handle>0)
               {    
                     for(i=0;i<5;i++)
                     FileWriteInteger(handle,i+1,LONG_VALUE); // 5 numbers:1,2,3,4,5
               }
               
           FileClose(handle); 
         
         
         //  read these 5 numbers to an array : data[]
          handle  = FileOpen("file_write.dat",FILE_BIN|FILE_READ);        
         if(handle>0)
         {  
                  int cnt=0;  //
                  int dat,size,data[1];
                  dat = FileReadInteger(handle,LONG_VALUE); //  read the first entry in the file 
                  while(FileIsEnding(handle)==false)
                      {
                        size = ArraySize(data);                                           
                        if(size>0)
                           {
                              data[size-1]=dat;             //  write the entry from the file into the array                              
                              dat = FileReadInteger(handle,LONG_VALUE);   // read the next entry in the file
                              if(FileIsEnding(handle)) break;  //  if we have just read past the last element to the EOF quit the while loop                  
                              ArrayResize(data,size+1);//
                              cnt++;  //
                            } 
                       }  
         }
          FileClose(handle);   
        
               size = ArraySize(data);
               Print("size = ",size, " cnt = ",cnt);// size = 5 ,cnt = 4 
               for(i=0;i<size;i++) Print(data[i]);  

//----        
          once = true; // only run one time 
          
        
     
   
//----
   return(0);
  }
//+------------------------------------------------------------------+
New comment