43 lines
1.1 KiB
Nim
43 lines
1.1 KiB
Nim
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## Nim-Dagger
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## Copyright (c) 2021 Status Research & Development GmbH
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## Licensed under either of
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## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
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## * MIT license ([LICENSE-MIT](LICENSE-MIT))
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## at your option.
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## This file may not be copied, modified, or distributed except according to
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## those terms.
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import pkg/libp2p/crypto/crypto
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import pkg/bearssl
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type
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Rng* = ref BrHmacDrbgContext
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var rng {.threadvar.}: Rng
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proc instance*(t: type Rng): Rng =
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if rng.isNil:
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rng = newRng()
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rng
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# Random helpers: similar as in stdlib, but with BrHmacDrbgContext rng
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# TODO: Move these somewhere else?
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const randMax = 18_446_744_073_709_551_615'u64
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proc rand*(rng: Rng, max: Natural): int =
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if max == 0: return 0
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var x: uint64
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while true:
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brHmacDrbgGenerate(addr rng[], addr x, csize_t(sizeof(x)))
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if x < randMax - (randMax mod (uint64(max) + 1'u64)): # against modulo bias
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return int(x mod (uint64(max) + 1'u64))
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proc sample*[T](rng: Rng, a: openArray[T]): T =
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result = a[rng.rand(a.high)]
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proc shuffle*[T](rng: Rng, a: var openArray[T]) =
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for i in countdown(a.high, 1):
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let j = rng.rand(i)
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swap(a[i], a[j])
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