mirror of https://github.com/gofiber/fiber.git
93 lines
2.3 KiB
Go
93 lines
2.3 KiB
Go
package cache
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import (
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"container/heap"
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)
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type heapEntry struct {
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key string
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exp uint64
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bytes uint
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idx int
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}
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// indexedHeap is a regular min-heap that allows finding
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// elements in constant time. It does so by handing out special indices
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// and tracking entry movement.
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//
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// indexdedHeap is used for quickly finding entries with the lowest
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// expiration timestamp and deleting arbitrary entries.
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type indexedHeap struct {
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// Slice the heap is built on
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entries []heapEntry
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// Mapping "index" to position in heap slice
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indices []int
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// Max index handed out
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maxidx int
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}
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func (h indexedHeap) Len() int {
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return len(h.entries)
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}
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func (h indexedHeap) Less(i, j int) bool {
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return h.entries[i].exp < h.entries[j].exp
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}
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func (h indexedHeap) Swap(i, j int) {
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h.entries[i], h.entries[j] = h.entries[j], h.entries[i]
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h.indices[h.entries[i].idx] = i
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h.indices[h.entries[j].idx] = j
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}
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func (h *indexedHeap) Push(x interface{}) {
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h.pushInternal(x.(heapEntry)) //nolint:forcetypeassert // Forced type assertion required to implement the heap.Interface interface
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}
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func (h *indexedHeap) Pop() interface{} {
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n := len(h.entries)
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h.entries = h.entries[0 : n-1]
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return h.entries[0:n][n-1]
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}
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func (h *indexedHeap) pushInternal(entry heapEntry) {
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h.indices[entry.idx] = len(h.entries)
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h.entries = append(h.entries, entry)
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}
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// Returns index to track entry
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func (h *indexedHeap) put(key string, exp uint64, bytes uint) int {
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idx := 0
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if len(h.entries) < h.maxidx {
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// Steal index from previously removed entry
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// capacity > size is guaranteed
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n := len(h.entries)
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idx = h.entries[:n+1][n].idx
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} else {
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idx = h.maxidx
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h.maxidx++
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h.indices = append(h.indices, idx)
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}
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// Push manually to avoid allocation
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h.pushInternal(heapEntry{
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key: key, exp: exp, idx: idx, bytes: bytes,
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})
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heap.Fix(h, h.Len()-1)
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return idx
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}
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func (h *indexedHeap) removeInternal(realIdx int) (string, uint) {
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x := heap.Remove(h, realIdx).(heapEntry) //nolint:forcetypeassert,errcheck // Forced type assertion required to implement the heap.Interface interface
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return x.key, x.bytes
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}
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// Remove entry by index
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func (h *indexedHeap) remove(idx int) (string, uint) {
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return h.removeInternal(h.indices[idx])
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}
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// Remove entry with lowest expiration time
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func (h *indexedHeap) removeFirst() (string, uint) {
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return h.removeInternal(0)
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}
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