[#803]: feat(plugins): move plugins to a separate repositoryv2.5.0-alpha.2

[#803]: feat(plugins): move plugins to a separate repository

1 files changed, 125 insertions, 0 deletions

diff --git a/priority_queue/binary_heap.go b/priority_queue/binary_heap.go
new file mode 100644
index 00000000..fc043927
--- /dev/null
+++ b/priority_queue/binary_heap.go
@@ -0,0 +1,125 @@
+/*
+binary heap (min-heap) algorithm used as a core for the priority queue
+*/
+
+package priorityqueue
+
+import (
+	"sync"
+	"sync/atomic"
+)
+
+type BinHeap struct {
+	items []Item
+	// find a way to use pointer to the raw data
+	len    uint64
+	maxLen uint64
+	cond   sync.Cond
+}
+
+func NewBinHeap(maxLen uint64) *BinHeap {
+	return &BinHeap{
+		items:  make([]Item, 0, 1000),
+		len:    0,
+		maxLen: maxLen,
+		cond:   sync.Cond{L: &sync.Mutex{}},
+	}
+}
+
+func (bh *BinHeap) fixUp() {
+	k := bh.len - 1
+	p := (k - 1) >> 1 // k-1 / 2
+
+	for k > 0 {
+		cur, par := (bh.items)[k], (bh.items)[p]
+
+		if cur.Priority() < par.Priority() {
+			bh.swap(k, p)
+			k = p
+			p = (k - 1) >> 1
+		} else {
+			return
+		}
+	}
+}
+
+func (bh *BinHeap) swap(i, j uint64) {
+	(bh.items)[i], (bh.items)[j] = (bh.items)[j], (bh.items)[i]
+}
+
+func (bh *BinHeap) fixDown(curr, end int) {
+	cOneIdx := (curr << 1) + 1
+	for cOneIdx <= end {
+		cTwoIdx := -1
+		if (curr<<1)+2 <= end {
+			cTwoIdx = (curr << 1) + 2
+		}
+
+		idxToSwap := cOneIdx
+		if cTwoIdx > -1 && (bh.items)[cTwoIdx].Priority() < (bh.items)[cOneIdx].Priority() {
+			idxToSwap = cTwoIdx
+		}
+		if (bh.items)[idxToSwap].Priority() < (bh.items)[curr].Priority() {
+			bh.swap(uint64(curr), uint64(idxToSwap))
+			curr = idxToSwap
+			cOneIdx = (curr << 1) + 1
+		} else {
+			return
+		}
+	}
+}
+
+func (bh *BinHeap) Len() uint64 {
+	return atomic.LoadUint64(&bh.len)
+}
+
+func (bh *BinHeap) Insert(item Item) {
+	bh.cond.L.Lock()
+
+	// check the binary heap len before insertion
+	if bh.Len() > bh.maxLen {
+		// unlock the mutex to proceed to get-max
+		bh.cond.L.Unlock()
+
+		// signal waiting goroutines
+		for bh.Len() > 0 {
+			// signal waiting goroutines
+			bh.cond.Signal()
+		}
+		// lock mutex to proceed inserting into the empty slice
+		bh.cond.L.Lock()
+	}
+
+	bh.items = append(bh.items, item)
+
+	// add len to the slice
+	atomic.AddUint64(&bh.len, 1)
+
+	// fix binary heap up
+	bh.fixUp()
+	bh.cond.L.Unlock()
+
+	// signal the goroutine on wait
+	bh.cond.Signal()
+}
+
+func (bh *BinHeap) ExtractMin() Item {
+	bh.cond.L.Lock()
+
+	// if len == 0, wait for the signal
+	for bh.Len() == 0 {
+		bh.cond.Wait()
+	}
+
+	bh.swap(0, bh.len-1)
+
+	item := (bh.items)[int(bh.len)-1]
+	bh.items = (bh).items[0 : int(bh.len)-1]
+	bh.fixDown(0, int(bh.len-2))
+
+	// reduce len
+	atomic.AddUint64(&bh.len, ^uint64(0))
+
+	bh.cond.L.Unlock()
+	return item
+}