123 lines
3.6 KiB
Nim
123 lines
3.6 KiB
Nim
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# Nimbus
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# Copyright (c) 2018 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) or
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# http://www.apache.org/licenses/LICENSE-2.0)
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# * MIT license ([LICENSE-MIT](LICENSE-MIT) or
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# http://opensource.org/licenses/MIT)
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# at your option. This file may not be copied, modified, or distributed except
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# according to those terms.
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## LRU Cache for Epoch Indexed Hashimoto Cache
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## ============================================
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##
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## This module uses the eth-block number (mapped to epoch) to hold and re-use
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## the cache needed for running the `hasimotoLight()` proof-of-work function.
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import
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eth/common,
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ethash,
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nimcrypto,
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stew/keyed_queue
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{.push raises: [Defect].}
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type
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PowCacheItemRef* = ref object
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size*: uint64
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data*: seq[MDigest[512]]
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PowCacheStats* = tuple
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maxItems: int
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size: int
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PowCache* = object
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cacheMax: int
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cache: KeyedQueue[uint64,PowCacheItemRef]
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PowCacheRef* = ref PowCache
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const
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nItemsMax = 10
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nItemsInit = 2
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# ------------------------------------------------------------------------------
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# Private helpers
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# ------------------------------------------------------------------------------
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proc toKey(bn: BlockNumber): uint64 =
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bn.truncate(uint64) div EPOCH_LENGTH
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# ------------------------------------------------------------------------------
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# Public functions, constructor
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# ------------------------------------------------------------------------------
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proc init*(pc: var PowCache; maxItems = nItemsMax) =
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## Constructor for PoW cache
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pc.cacheMax = maxItems
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pc.cache.init(nItemsInit)
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proc init*(T: type PowCache; maxItems = nItemsMax): T =
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## Constructor variant
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result.init(maxItems)
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proc new*(T: type PowCacheRef; maxItems = nItemsMax): T =
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## Constructor variant
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new result
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result[].init(maxItems)
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# ------------------------------------------------------------------------------
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# Public functions, constructor
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# ------------------------------------------------------------------------------
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proc get*(pc: var PowCache; bn: BlockNumber): PowCacheItemRef
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{.gcsafe,raises: [Defect,CatchableError].} =
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## Return a cache derived from argument `blockNumber` ready to be used
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## for the `hashimotoLight()` method.
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let
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key = bn.toKey
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rc = pc.cache.lruFetch(key)
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if rc.isOK:
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return rc.value
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let
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# note that `getDataSize()` and `getCacheSize()` depend on
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# `key * EPOCH_LENGTH` rather than the original block number.
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top = key * EPOCH_LENGTH
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pair = PowCacheItemRef(
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size: top.getDataSize,
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data: top.getCacheSize.mkcache(top.getSeedhash))
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pc.cache.lruAppend(key, pair, pc.cacheMax)
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proc get*(pcr: PowCacheRef; bn: BlockNumber): PowCacheItemRef
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{.gcsafe,raises: [Defect,CatchableError].} =
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## Variant of `getCache()`
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pcr[].get(bn)
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proc hasItem*(pc: var PowCache; bn: BlockNumber): bool
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{.gcsafe,raises: [Defect,CatchableError].} =
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## Returns true if there is a cache entry for argument `bn`.
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pc.cache.hasKey(bn.toKey)
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proc hasItem*(pcr: PowCacheRef; bn: BlockNumber): bool
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{.gcsafe,raises: [Defect,CatchableError].} =
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## Variant of `hasItem()`
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pcr[].hasItem(bn)
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# -------------------------
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proc stats*(pc: var PowCache): PowCacheStats =
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## Return current cache sizes
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result = (maxItems: pc.cacheMax, size: pc.cache.len)
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proc stats*(pcr: PowCacheRef): PowCacheStats =
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## Variant of `stats()`
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pcr[].stats
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# ------------------------------------------------------------------------------
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# End
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# ------------------------------------------------------------------------------
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