I have been writing a HST file reader, that I have confirmed to work with an older HST file ( originating from an older version of MT4 ). But since LiveUpdate updated my MT4 build to 225, I don't seem to be able to read the header properly, and not any of the RateInfo.

I have quoted the docs on this topic, but it doesn't seem to be describing this newer HST file. So, may I know what's the latest HST format ?

Historical File Format (HST Files)

The database header is the first

struct HistoryHeader
{
  int               version;            // database version
  char              copyright[64];      // copyright info
  char              symbol[12];         // symbol name
  int               period;             // symbol timeframe
  int               digits;             // the amount of digits after decimal point in the symbol
  time_t            timesign;           // timesign of the database creation
  time_t            last_sync;          // the last synchronization time
  int               unused[13];         // to be used in future
};

then goes the bars array (single-byte justification)

#pragma pack(push,1)
//---- standard representation of the quote in the database
struct RateInfo
{
  time_t            ctm;                // current time in seconds
  double            open;
  double            low;
  double            high;
  double            close;
  double            vol;
};
#pragma pack(pop)