How to read a static array of a composite type

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I am trying to read arrays of composite types from some binary files using static arrays. I get into some issues reading the data because the sizeof the composite type is not equal to the sizeof the fields summed. Here is an small example.

using StaticArrays

struct LongCdsTime
    day::UInt16
    millisecond::UInt32
    microsecond::UInt16
end

Base.read(io::IO, T::Type{LongCdsTime}) = T((read(io, t) for t in fieldtypes(T))...)

# test array
T = SMatrix{20,30,LongCdsTime}

# test data
test_file, fp = mktemp()
write(fp, rand(UInt8, 8*length(T)))

seekstart(fp)
a1 = read(fp, T) ## EOFError: read end of file

seekstart(fp)
a2 = T([ read(fp,eltype(T)) for i = 1:length(T)]) ## works fine

sizeof(LongCdsTime) ## 12 bytes 
sum(sizeof.(fieldtypes(LongCdsTime))) ## 8 bytes

Question, What is the best way to read SMatrix{20,30,LongCdsTime} when each element is stored as 8 bytes in a file?