I have an IOStream and I want to read a series of floats that are stored in big-endian order, while my computer is usually little-endian. So there are a few parts to my question:
If I know that the computer is little-endian, can I read the float like this?:
value = bswap(read(io,Float32))
My thinking is that read(io,Float32) will at least give me the correct set of bytes, and bswap() seems to preserve the type.
What I wrote above is fine for a small file, but I eventually want to read several GiB of data. Is there a way to read many floats and then convert them all to little-endian? I know you can read all the bytes with
bytes = read(io,sizeof(Float32)*ncells)
But I don’t know what to do with those bytes once I have them? How do I put them into an array of floats?
To make my code more portable, it would be nice if it could test endianness. How do I determine whether the computer I’m currently running on is little-endian or big-endian?
The cost wouldn’t be with bswap but with disk IO. I don’t want to read a large file 4 bytes at a time. But in any case, I think I found a solution to that part of my problem: It looks like you can pre-allocate an array and use read!() to populate that array:
data = zeros(Float32,ncells)
for j in 1:ncells
data[j] = bswap(data[j])
That seems to work. So the read!() function must be inferring a few things from the type and length of the data array.