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MathGroup Archive 2012

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Reading Single and Double reals in Little-endian and Big-endian

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125003] Reading Single and Double reals in Little-endian and Big-endian
  • From: ezh <dgolber at aol.com>
  • Date: Fri, 17 Feb 2012 06:25:18 -0500 (EST)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com

I am running Mathematica 4 on a PC.

I am reading a file (an STL file), which has 32-bit integers and 32-
bit reals in little-endian format.  I can read in the integers
correctly, using

numTriangles = ReadBinary[strm, Int32, ByteOrder ->
LeastSignificantByteFirst];

However, the documentation states (and is correct) that ByteOrder ->
LeastSignificantByteFirst only affects reading integers.  So far, I
have not figured out how to read 32-bit reals ("Single") correctly.

I could read in the 32-bits as bytes, and reverse the order, and build
a 32-bit integer with the correct bits in it to be the desired 32-bit
real.  But how do I get Mathematica to regard those 32-bits as an IEEE
real number?

I'd hate to have to read up on the IEEE format and build the value
myself.

I can't be the first person in theworld to hit this problem!

And why (futile question) doesn't mathematica know about big- and
little-endian for _reals_ as well as for _integers_?

Thanks
Dave Golber




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