FileReadInteger
FileReadInteger
The function reads int, short or char value from the current position of the file pointer depending on the length specified in bytes.
int FileReadInteger(
int file_handle, // File handle
int size=INT_VALUE // Size of an integer in bytes
);Parameters
- file_handle
[in] File descriptor returned by FileOpen().
- size=INT_VALUE
[in] Number of bytes (up to 4 inclusive) that should be read. The corresponding constants are provided: CHAR_VALUE = 1, SHORT_VALUE = 2 and INT_VALUE (LONG_VALUE) = 4, so the function can read the whole value of char, short, int or long type.
Return Value
A value of the int type. The result of this function must be explicitly cast to a target type, i.e. to the type of data that you need to read. Since a value of the int type is returned, it can be easily converted to any integer value. The file pointer is shifted by the number of bytes read.
Note
When reading less than 4 bytes, the received result is always positive. If one or two bytes are read, the sign of the number can be determined by explicit casting to type char (1 byte) or short (2 bytes). Getting the sign for a three-byte number is not trivial, since there is no corresponding underlying type.
Example (the file obtained after executing the example for FileWriteInteger() function is used here)
//+------------------------------------------------------------------+
//| Demo_FileReadInteger.mq4 |
//| Copyright 2014, MetaQuotes Software Corp. |
//| https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2014, MetaQuotes Software Corp."
#property link "https://www.mql5.com"
#property version "1.00"
#property strict
#property indicator_chart_window
#property indicator_buffers 1
//---- plot Label1
#property indicator_label1 "Trends"
#property indicator_type1 DRAW_SECTION
#property indicator_color1 clrRed
#property indicator_style1 STYLE_SOLID
#property indicator_width1 2
//--- parameters for data reading
input string InpFileName="Trend.bin"; // File name
input string InpDirectoryName="Data"; // Folder name
//--- global variables
int ind=0;
int size=0;
datetime time_buff[];
//--- indicator buffers
double buff[];
//+------------------------------------------------------------------+
//| Custom indicator initialization function |
//+------------------------------------------------------------------+
int OnInit()
{
int def_size=100;
//--- allocate memory for the array
ArrayResize(time_buff,def_size);
//--- open the file
ResetLastError();
int file_handle=FileOpen(InpDirectoryName+"//"+InpFileName,FILE_READ|FILE_BIN);
if(file_handle!=INVALID_HANDLE)
{
PrintFormat("%s file is available for reading",InpFileName);
PrintFormat("File path: %s\\Files\\",TerminalInfoString(TERMINAL_DATA_PATH));
//--- additional variables
int arr_size;
uchar arr[];
//--- read data from the file
while(!FileIsEnding(file_handle))
{
//--- find out how many bytes are used for writing the time
arr_size=FileReadInteger(file_handle,INT_VALUE);
ArrayResize(arr,arr_size);
for(int i=0;i<arr_size;i++)
arr[i]=(char)FileReadInteger(file_handle,CHAR_VALUE);
//--- store the time value
time_buff[size]=StringToTime(CharArrayToString(arr));
size++;
//--- increase the sizes of the arrays if they are filled
if(size==def_size)
{
def_size+=100;
ArrayResize(time_buff,def_size);
}
}
//--- close the file
FileClose(file_handle);
PrintFormat("Data is read, %s file is closed",InpFileName);
}
else
{
PrintFormat("Failed to open %s file, Error code = %d",InpFileName,GetLastError());
return(INIT_FAILED);
}
//--- bind the array to the indicator buffer
SetIndexBuffer(0,buff,INDICATOR_DATA);
//---- set the indicator values that will not be visible on the chart
SetIndexEmptyValue(0,0.0);
//--- set indexing as timeseries
ArraySetAsSeries(time_buff,true);
//---
return(INIT_SUCCEEDED);
}
//+------------------------------------------------------------------+
//| Custom indicator iteration function |
//+------------------------------------------------------------------+
int OnCalculate(const int rates_total,
const int prev_calculated,
const datetime &time[],
const double &open[],
const double &high[],
const double &low[],
const double &close[],
const long &tick_volume[],
const long &volume[],
const int &spread[])
{
ArraySetAsSeries(time,true);
ArraySetAsSeries(close,true);
//--- the loop for the bars that have not been handled yet
for(int i=prev_calculated;i<rates_total;i++)
{
//--- 0 by default
buff[i]=0;
for(int j=0;j<size;j++)
{
//--- if dates coincide, set as close price
if(time[i]==time_buff[j])
{
//--- set as close price
buff[i]=close[i];
}
}
}
//---
return(rates_total);
}See also
IntegerToString(), StringToInteger(), Integer types, FileWriteInteger()