ceremonyclient/pebble/merging_iter_heap.go
Cassandra Heart 2e2a1e4789
v1.2.0 (#31)
2024-01-03 01:31:42 -06:00

93 lines
1.7 KiB
Go

// Copyright 2018 The LevelDB-Go and Pebble Authors. All rights reserved. Use
// of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
package pebble
type mergingIterHeap struct {
cmp Compare
reverse bool
items []*mergingIterLevel
}
func (h *mergingIterHeap) len() int {
return len(h.items)
}
func (h *mergingIterHeap) clear() {
h.items = h.items[:0]
}
func (h *mergingIterHeap) less(i, j int) bool {
ikey, jkey := h.items[i].iterKey, h.items[j].iterKey
if c := h.cmp(ikey.UserKey, jkey.UserKey); c != 0 {
if h.reverse {
return c > 0
}
return c < 0
}
if h.reverse {
return ikey.Trailer < jkey.Trailer
}
return ikey.Trailer > jkey.Trailer
}
func (h *mergingIterHeap) swap(i, j int) {
h.items[i], h.items[j] = h.items[j], h.items[i]
}
// init, fix, up and down are copied from the go stdlib.
func (h *mergingIterHeap) init() {
// heapify
n := h.len()
for i := n/2 - 1; i >= 0; i-- {
h.down(i, n)
}
}
func (h *mergingIterHeap) fix(i int) {
if !h.down(i, h.len()) {
h.up(i)
}
}
func (h *mergingIterHeap) pop() *mergingIterLevel {
n := h.len() - 1
h.swap(0, n)
h.down(0, n)
item := h.items[n]
h.items = h.items[:n]
return item
}
func (h *mergingIterHeap) up(j int) {
for {
i := (j - 1) / 2 // parent
if i == j || !h.less(j, i) {
break
}
h.swap(i, j)
j = i
}
}
func (h *mergingIterHeap) down(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
}