#!/usr/bin/env python

# Copyright (c) 2024
#      Daniel O'Connor <darius@dons.net.au>.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
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def sifmt(_v, dp = 3, unit = 'Hz', sp = ' '):
    '''Format a number using SI prefixes'''
    si_prefixes = ('T', 'G', 'M', 'k', '', 'm', 'µ', 'n', 'p', 'f', 'a')
    scale = 10 ** 12
    v = abs(_v)
    if v == 0:
        sip = ""
        scale = 0
    for i, sip in enumerate(si_prefixes):
        if v >= scale:
            break
        scale /= 1e3
    return ('%.' + str(dp) + 'f%s%s%s') % (_v / scale, sp, si_prefixes[i], unit)