3.9 Large Time Values

The WFDB_Time type is defined as a signed integer type of at least 32 bits, which means that it can represent sample numbers up to 2,147,483,647. By default, WFDB_Time is defined as an alias for the standard C long int, and many existing applications have been written with the assumption that WFDB_Time and long int are interchangeable.

However, it is quite possible for a record to be longer than 2,147,483,647 samples (about 25 days of recording at 1 kHz) and it is useful to be able to process such records on machines where a long int is only 32 bits.

If you are using a modern C compiler, with WFDB library version 10.7.0 or later, it is possible to define WFDB_Time as long long int instead of long int. This lets your program work with sample numbers as large as 9,223,372,036,854,775,807, even on a 32-bit machine. To do this, add the following line at the very beginning of your source file, before including ‘<wfdb/wfdb.h>’:

#define WFDB_LARGETIME

If your program consists of multiple ‘*.c’ files, be sure to do the same for each file. Alternatively, you can define this macro on the C compiler command line (e.g., -DWFDB_LARGETIME if you are using gcc).

When doing this, you will also need to ensure that your program handles large time values consistently, by using the WFDB_Time data type rather than long or long long, using WFDB_TIME_MAX rather than LONG_MAX or LLONG_MAX, using WFDB_Pd_TIME rather than "ld" or "lld", and so forth.