37 lines
1.1 KiB
Go
37 lines
1.1 KiB
Go
package npc
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import (
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"crypto/sha1"
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"math/big"
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)
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const (
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// This array:
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// * Must include only printable UTF8 characters that are represented with a single byte
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// * Must be at least of length 85 (`len("weave-") + l(2^160)/l(85)` equals 31, the maximum ipset name length)
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// * Must not include commas as those are treated specially by `ipset add` when adding a named set to a list:set
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// * Should not include space for readability
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// * Should not include single quote or backslash to be nice to shell users
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ShortNameSymbols = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789(){}[]<>_$%^&*|/?.;:@#~"
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)
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// sha1 hash an arbitrary string and represent it using the full range of
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// printable ascii characters
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func shortName(arbitrary string) string {
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symbols := []byte(ShortNameSymbols)
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sum := sha1.Sum([]byte(arbitrary))
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i := big.NewInt(0).SetBytes(sum[:])
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base := big.NewInt(int64(len(symbols)))
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zero := big.NewInt(0)
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result := make([]byte, 0)
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for i.Cmp(zero) > 0 {
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remainder := new(big.Int).Mod(i, base)
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i.Sub(i, remainder)
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i.Div(i, base)
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result = append(result, symbols[remainder.Int64()])
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}
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return string(result)
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}
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