reading unsigned integer 64 bit from binary file

Question

I am struggling with importing data from a binary file into R. Among others, the data file contains a 64 bit unsigned integer value (little Endian) which I need to read out.

The value represents the number of seconds since 12:00 am, January 1, 1900 and is to be converted to a date and time value (e.g. YYMMDDhhmmss).

As a beginner I have read about some packages (bit64, int64) but it seems they don't support unsigned integers or aren't maintained any longer.

Can someone please help me?

Answer 1

Use readBin to read the file into a raw vector, then convert manually.

# sample data
zz <- file("myBinaryFile", "wb")
writeBin(32L, zz, size=8L, endian="little")
close(zz)

# now read the data
zz <- file("myBinaryFile", "rb")
# n can be a mild over-estimate
rawvec <- readBin(zz, raw(), n=10, endian="little")
close(zz)
# convert the value to a number
nsec <- sum(2^.subset(0:63, as.logical(rawToBits(rawvec))))
# convert the number to POSIXct
as.POSIXct(nsec, tz="UTC", origin=as.POSIXct("1900-01-01", tz="UTC"))

Note that nsec will be a numeric/double value, since R's integers are 32-bit and signed. That shouldn't be a problem unless you have some datetimes that are way out in the future.