float_to_hex.py

#!/usr/bin/env python

# Useful for calculating depth values for helixmod.blogspot.com.au to fix
# objects/UI being rendered at the wrong depth in 3D Vision.

# Helixmod author recommends http://gregstoll.dyndns.org/~gregstoll/floattohex/
# to do these conversions, but I found that using a web interface was too
# clunky and would rather just call a program from the command line to do it.
# It is somewhat amusing to me that the author of that page created it because
# he was originally using a java applet and found that to be too heavy-weight.

# His module also seemed to be overkill to me, given that the struct module can
# do exactly the same thing in one line of python, so I wrote my own.

from __future__ import print_function

import struct

def float_to_hex(val):
	return '0x%.8x' % struct.unpack('I', struct.pack('f', val))[0]

def double_to_hex(val):
	return '0x%.16x' % struct.unpack('Q', struct.pack('d', val))[0]

def _hex_to_float(val):
	return struct.unpack('f', struct.pack('I', val))[0]

def _hex_to_double(val):
	return struct.unpack('d', struct.pack('Q', val))[0]

def hex_to_float(val):
	return _hex_to_float(int(val, 16))

def hex_to_double(val):
	return _hex_to_double(int(val, 16))

def process_vals(vals):
	yield ('from', 'float', 'double')
	yield ('----', '-----', '------')
	for val_str in vals:
		if val_str.startswith('0x'):
			val = int(val_str, 16)
			f = 'N/A'
			if (val & 0xffffffff) == val:
				f = str(_hex_to_float(val))
			yield (val_str, f, str(_hex_to_double(val)))
		else:
			val = float(val_str)
			yield (val_str, float_to_hex(val), double_to_hex(val))

def align_output(input):
	lengths = [ map(len, x) for x in input ]
	lengths = map(max, zip(*lengths))
	format = '   '.join([ '%%%is' % l for l in lengths ])
	return '\n'.join([format % line for line in input])

def main():
	import sys
	if len(sys.argv) == 1:
		print('usage: %s {float | hex}...' % sys.argv[0])
		sys.exit(1)

	print(align_output(list(process_vals(sys.argv[1:]))))

if __name__ == '__main__':
	main()