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29 lines
1.1 KiB
Lua
29 lines
1.1 KiB
Lua
--[[
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Inheritable abstraction for cache items
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--]]
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local CacheItem = {
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size = 128, -- some reasonable default for a small table.
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}
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--- NOTE: As far as size estimations go, the assumption is that a key, value pair should roughly take two words,
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--- and the most common items we cache are Geom-like tables (i.e., 4 key-value pairs).
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--- That's generally a low estimation, especially for larger tables, where memory allocation trickery may be happening.
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function CacheItem:extend(o)
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o = o or {}
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setmetatable(o, self)
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self.__index = self
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return o
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end
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-- NOTE: There's no object-specific initialization, the entirety of the new data *is* the table we pass to new.
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-- We only keep the distinction as a matter of semantics, to differentiate class declarations from object instantiations.
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CacheItem.new = CacheItem.extend
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-- Called on eviction.
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-- We generally use it to free C/FFI resources *immediately* (as opposed to relying on our Userdata/FFI finalizers to do it "later" on GC).
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-- c.f., TileCacheItem
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function CacheItem:onFree()
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end
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return CacheItem
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