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d42f0b6a21
I need a ringbuffer in the more traditional sense, one that has a notion of item removal as well as tail loss on overrun. This implementation is really a clearable log window, and is used as such where it is used. Updates #cleanup Updates tailscale/corp#31762 Signed-off-by: James Tucker <james@tailscale.com>
79 lines
1.6 KiB
Go
79 lines
1.6 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package ringlog contains a limited-size concurrency-safe generic ring log.
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package ringlog
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import "sync"
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// New creates a new [RingLog] containing at most max items.
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func New[T any](max int) *RingLog[T] {
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return &RingLog[T]{
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max: max,
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}
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}
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// RingLog is a concurrency-safe fixed size log window containing entries of [T].
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type RingLog[T any] struct {
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mu sync.Mutex
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pos int
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buf []T
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max int
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}
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// Add appends a new item to the [RingLog], possibly overwriting the oldest
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// item in the log if it is already full.
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//
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// It does nothing if rb is nil.
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func (rb *RingLog[T]) Add(t T) {
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if rb == nil {
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return
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}
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rb.mu.Lock()
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defer rb.mu.Unlock()
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if len(rb.buf) < rb.max {
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rb.buf = append(rb.buf, t)
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} else {
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rb.buf[rb.pos] = t
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rb.pos = (rb.pos + 1) % rb.max
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}
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}
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// GetAll returns a copy of all the entries in the ring log in the order they
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// were added.
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//
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// It returns nil if rb is nil.
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func (rb *RingLog[T]) GetAll() []T {
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if rb == nil {
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return nil
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}
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rb.mu.Lock()
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defer rb.mu.Unlock()
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out := make([]T, len(rb.buf))
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for i := range len(rb.buf) {
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x := (rb.pos + i) % rb.max
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out[i] = rb.buf[x]
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}
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return out
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}
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// Len returns the number of elements in the ring log. Note that this value
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// could change immediately after being returned if a concurrent caller
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// modifies the log.
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func (rb *RingLog[T]) Len() int {
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if rb == nil {
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return 0
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}
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rb.mu.Lock()
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defer rb.mu.Unlock()
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return len(rb.buf)
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}
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// Clear will empty the ring log.
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func (rb *RingLog[T]) Clear() {
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rb.mu.Lock()
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defer rb.mu.Unlock()
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rb.pos = 0
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rb.buf = nil
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}
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