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Making lazylru generic, deprecating the lazylru/generic package (#25)
This was supposed to happen last September. There is no need to support Go <=1.17 at this point, so the generic interface is sufficient for everyone. This will cause deprecation warnings for everyone using the `github.com/TriggerMail/lazylru/genric`, but switching to the `github.com/TriggerMail/lazylru` package should be seamless.
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,5 @@ | ||
| # Generic Heap | ||
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| This is a LITERAL COPY from the Go standard library because there is not yet a genric version of the `containers/heap` module in the Go 1.18 beta 1 release. I am sure this will come out in Go 1.18 or in a subsequent release shortly thereafter. This library is meant to be a bridge until that is done and nothing more. | ||
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| Please do not use this for anything outside the lazylru module because it _will_ be deleted as soon as a generic heap is available in the stardard library. |
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| @@ -0,0 +1,118 @@ | ||
| // Copyright 2009 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| // Package heap provides heap operations for any type that implements | ||
| // heap.Interface. A heap is a tree with the property that each node is the | ||
| // minimum-valued node in its subtree. | ||
| // | ||
| // The minimum element in the tree is the root, at index 0. | ||
| // | ||
| // A heap is a common way to implement a priority queue. To build a priority | ||
| // queue, implement the Heap interface with the (negative) priority as the | ||
| // ordering for the Less method, so Push adds items while Pop removes the | ||
| // highest-priority item from the queue. The Examples include such an | ||
| // implementation; the file example_pq_test.go has the complete source. | ||
| package heap | ||
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| import "sort" | ||
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| // The Interface type describes the requirements | ||
| // for a type using the routines in this package. | ||
| // Any type that implements it may be used as a | ||
| // min-heap with the following invariants (established after | ||
| // Init has been called or if the data is empty or sorted): | ||
| // | ||
| // !h.Less(j, i) for 0 <= i < h.Len() and 2*i+1 <= j <= 2*i+2 and j < h.Len() | ||
| // | ||
| // Note that Push and Pop in this interface are for package heap's | ||
| // implementation to call. To add and remove things from the heap, | ||
| // use heap.Push and heap.Pop. | ||
| type Interface[T any] interface { | ||
| sort.Interface | ||
| Push(x T) // add x as element Len() | ||
| Pop() T // remove and return element Len() - 1. | ||
| } | ||
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| // Init establishes the heap invariants required by the other routines in this package. | ||
| // Init is idempotent with respect to the heap invariants | ||
| // and may be called whenever the heap invariants may have been invalidated. | ||
| // The complexity is O(n) where n = h.Len(). | ||
| func Init[T any](h Interface[T]) { | ||
| // heapify | ||
| n := h.Len() | ||
| for i := n/2 - 1; i >= 0; i-- { | ||
| down(h, i, n) | ||
| } | ||
| } | ||
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| // Push pushes the element x onto the heap. | ||
| // The complexity is O(log n) where n = h.Len(). | ||
| func Push[T any](h Interface[T], x T) { | ||
| h.Push(x) | ||
| up(h, h.Len()-1) | ||
| } | ||
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| // Pop removes and returns the minimum element (according to Less) from the heap. | ||
| // The complexity is O(log n) where n = h.Len(). | ||
| // Pop is equivalent to Remove(h, 0). | ||
| func Pop[T any](h Interface[T]) T { | ||
| n := h.Len() - 1 | ||
| h.Swap(0, n) | ||
| down(h, 0, n) | ||
| return h.Pop() | ||
| } | ||
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| // Remove removes and returns the element at index i from the heap. | ||
| // The complexity is O(log n) where n = h.Len(). | ||
| func Remove[T any](h Interface[T], i int) T { | ||
| n := h.Len() - 1 | ||
| if n != i { | ||
| h.Swap(i, n) | ||
| if !down(h, i, n) { | ||
| up(h, i) | ||
| } | ||
| } | ||
| return h.Pop() | ||
| } | ||
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| // Fix re-establishes the heap ordering after the element at index i has changed its value. | ||
| // Changing the value of the element at index i and then calling Fix is equivalent to, | ||
| // but less expensive than, calling Remove(h, i) followed by a Push of the new value. | ||
| // The complexity is O(log n) where n = h.Len(). | ||
| func Fix[T any](h Interface[T], i int) { | ||
| if !down(h, i, h.Len()) { | ||
| up(h, i) | ||
| } | ||
| } | ||
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| func up[T any](h Interface[T], j int) { | ||
| for { | ||
| i := (j - 1) / 2 // parent | ||
| if i == j || !h.Less(j, i) { | ||
| break | ||
| } | ||
| h.Swap(i, j) | ||
| j = i | ||
| } | ||
| } | ||
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| func down[T any](h Interface[T], i0, n int) bool { | ||
| i := i0 | ||
| for { | ||
| j1 := 2*i + 1 | ||
| if j1 >= n || j1 < 0 { // j1 < 0 after int overflow | ||
| break | ||
| } | ||
| j := j1 // left child | ||
| if j2 := j1 + 1; j2 < n && h.Less(j2, j1) { | ||
| j = j2 // = 2*i + 2 // right child | ||
| } | ||
| if !h.Less(j, i) { | ||
| break | ||
| } | ||
| h.Swap(i, j) | ||
| i = j | ||
| } | ||
| return i > i0 | ||
| } |
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