51 lines
1.7 KiB
Go
51 lines
1.7 KiB
Go
package cuckoo
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import "fmt"
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// DefaultCapacity is the initial capacity of a [HashTable]. It is inspired from
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// Java's [HashMap] implementation, which also uses 16.
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//
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// [HashMap]: https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html#HashMap--
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const DefaultCapacity uint64 = 16
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// DefaultGrowthFactor is the standard resize multiplier for a [HashTable]. Most
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// implementations use 2.
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const DefaultGrowthFactor uint64 = 2
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// defaultMinimumLoad is the default lowest acceptable occupancy of a [HashTable].
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// The higher the minimum load, the more likely that a [HashTable.Put] will not
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// succeed. The value of 5% is taken from [libcuckoo].
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//
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// [libcuckoo]: https://github.com/efficient/libcuckoo/blob/656714705a055df2b7a605eb3c71586d9da1e119/libcuckoo/cuckoohash_config.hh#L21
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const defaultMinimumLoad float64 = 0.05
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type settings struct {
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growthFactor uint64
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minLoadFactor float64
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bucketSize uint64
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}
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// An Option modifies the settings of a [HashTable]. It is used in its constructors
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// like [New], for example.
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type Option func(*settings)
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// Capacity modifies the starting capacity of each bucket of the [HashTable]. The
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// value must be non-negative.
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func Capacity(value int) Option {
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if value < 0 {
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panic(fmt.Sprintf("go-cuckoo: Capacity must be non-negative, got %d", value))
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}
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return func(s *settings) { s.bucketSize = uint64(value) }
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}
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// GrowthFactor controls how much the capacity of the [HashTable] multiplies when
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// it must resize. The value must be greater than 1.
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func GrowthFactor(value int) Option {
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if value < 2 {
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panic(fmt.Sprintf("go-cuckoo: GrowthFactor must be greater than 1, got %d", value))
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}
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return func(s *settings) { s.growthFactor = uint64(value) }
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}
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