PowerShell: Converting a hex variable into a single (float32) big endian variable

# Input: a string representing a number or big-endian byte sequence
# in hexadecimal form.
$hex = '0x41fe89de'

# Convert the hex input string to a byte array.
$byteArray = [byte[]] ($hex -replace '^0x' -split '(..)' -ne '' -replace '^', '0x')

# Convert from big-endian to little-endian, if necessary, by
# reversing the order of the bytes to match the platform's.
if ([BitConverter]::IsLittleEndian) {
  [Array]::Reverse($byteArray)
}

# Convert to a platform-native [single] instance.
[BitConverter]::ToSingle($byteArray, 0)

The above yields 31.81732 (with the default output formatting).

• The technique used to convert the hex string to a byte array is explained in this answer.

• The conversion of the byte array to a platform-native [single] instance (System.Single) is performed via the System.BitConverter class.

  • Note that the number of bytes passed to ::ToSingle() must be an exact match for the number of bytes that make up the target type; in this case, 4 bytes are required, because [single] is a 32-bit type (4 bytes times 8 bits); if necessary and appropriate, provide an array that is padded with 0 bytes; use an expression such as [System.Runtime.InteropServices.Marshal]::SizeOf([single] 0) to determine the required byte count.