21 lines
458 B
Plaintext
21 lines
458 B
Plaintext
fn entropy(s: &[u8]) -> f32 {
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let mut histogram = [0u64; 256];
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for &b in s {
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histogram[b as usize] += 1;
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}
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histogram
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.iter()
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.cloned()
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.filter(|&h| h != 0)
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.map(|h| h as f32 / s.len() as f32)
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.map(|ratio| -ratio * ratio.log2())
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.sum()
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}
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fn main() {
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let arg = std::env::args().nth(1).expect("Need a string.");
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println!("Entropy of {} is {}.", arg, entropy(arg.as_bytes()));
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}
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