56 lines
1.3 KiB
Go
56 lines
1.3 KiB
Go
package dht
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import (
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"math/big"
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)
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// TODO: The bitcounting is a relic of the old and incorrect distance
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// calculation. It is still useful in some tests but should eventually be
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// replaced with actual distances.
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// How many bits?
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func bitCount(n big.Int) int {
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var count int = 0
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for _, b := range n.Bytes() {
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count += int(bitCounts[b])
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}
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return count
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}
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// The bit counts for each byte value (0 - 255).
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var bitCounts = []int8{
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// Generated by Java BitCount of all values from 0 to 255
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0, 1, 1, 2, 1, 2, 2, 3,
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1, 2, 2, 3, 2, 3, 3, 4,
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1, 2, 2, 3, 2, 3, 3, 4,
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2, 3, 3, 4, 3, 4, 4, 5,
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1, 2, 2, 3, 2, 3, 3, 4,
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2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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1, 2, 2, 3, 2, 3, 3, 4,
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2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6,
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4, 5, 5, 6, 5, 6, 6, 7,
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1, 2, 2, 3, 2, 3, 3, 4,
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2, 3, 3, 4, 3, 4, 4, 5,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6,
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4, 5, 5, 6, 5, 6, 6, 7,
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2, 3, 3, 4, 3, 4, 4, 5,
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3, 4, 4, 5, 4, 5, 5, 6,
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3, 4, 4, 5, 4, 5, 5, 6,
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4, 5, 5, 6, 5, 6, 6, 7,
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3, 4, 4, 5, 4, 5, 5, 6,
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4, 5, 5, 6, 5, 6, 6, 7,
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4, 5, 5, 6, 5, 6, 6, 7,
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5, 6, 6, 7, 6, 7, 7, 8,
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}
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