99 lines
2.6 KiB
Nim
99 lines
2.6 KiB
Nim
# Nim-LibP2P
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# Copyright (c) 2023 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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{.push raises: [].}
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import std/[tables]
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import chronos/timer, stew/results
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const Timeout* = 10.seconds # default timeout in ms
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type
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TimedEntry*[K] = ref object of RootObj
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key: K
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addedAt: Moment
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expiresAt: Moment
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next, prev: TimedEntry[K]
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TimedCache*[K] = object of RootObj
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head, tail: TimedEntry[K] # nim linked list doesn't allow inserting at pos
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entries: Table[K, TimedEntry[K]]
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timeout: Duration
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func expire*(t: var TimedCache, now: Moment = Moment.now()) =
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while t.head != nil and t.head.expiresAt < now:
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t.entries.del(t.head.key)
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t.head.prev = nil
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t.head = t.head.next
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if t.head == nil: t.tail = nil
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func del*[K](t: var TimedCache[K], key: K): Opt[TimedEntry[K]] =
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# Removes existing key from cache, returning the previous value if present
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var item: TimedEntry[K]
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if t.entries.pop(key, item):
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if t.head == item: t.head = item.next
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if t.tail == item: t.tail = item.prev
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if item.next != nil: item.next.prev = item.prev
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if item.prev != nil: item.prev.next = item.next
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Opt.some(item)
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else:
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Opt.none(TimedEntry[K])
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func put*[K](t: var TimedCache[K], k: K, now = Moment.now()): bool =
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# Puts k in cache, returning true if the item was already present and false
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# otherwise. If the item was already present, its expiry timer will be
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# refreshed.
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t.expire(now)
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var previous = t.del(k) # Refresh existing item
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let addedAt =
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if previous.isSome: previous.get().addedAt
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else: now
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let node = TimedEntry[K](key: k, addedAt: addedAt, expiresAt: now + t.timeout)
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if t.head == nil:
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t.tail = node
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t.head = t.tail
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else:
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# search from tail because typically that's where we add when now grows
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var cur = t.tail
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while cur != nil and node.expiresAt < cur.expiresAt:
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cur = cur.prev
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if cur == nil:
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node.next = t.head
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t.head.prev = node
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t.head = node
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else:
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node.prev = cur
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node.next = cur.next
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cur.next = node
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if cur == t.tail:
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t.tail = node
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t.entries[k] = node
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previous.isSome()
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func contains*[K](t: TimedCache[K], k: K): bool =
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k in t.entries
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func addedAt*[K](t: TimedCache[K], k: K): Moment =
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t.entries.getOrDefault(k).addedAt
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func init*[K](T: type TimedCache[K], timeout: Duration = Timeout): T =
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T(
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timeout: timeout
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)
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