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vendor/k8s.io/utils/buffer/ring_growing.go

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+/*
+Copyright 2017 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package buffer
+
+// defaultRingSize defines the default ring size if not specified
+const defaultRingSize = 16
+
+// RingGrowingOptions sets parameters for [RingGrowing] and
+// [TypedRingGrowing].
+type RingGrowingOptions struct {
+	// InitialSize is the number of pre-allocated elements in the
+	// initial underlying storage buffer.
+	InitialSize int
+}
+
+// RingGrowing is a growing ring buffer.
+// Not thread safe.
+//
+// Deprecated: Use TypedRingGrowing[any] instead.
+type RingGrowing = TypedRingGrowing[any]
+
+// NewRingGrowing constructs a new RingGrowing instance with provided parameters.
+//
+// Deprecated: Use NewTypedRingGrowing[any] instead.
+func NewRingGrowing(initialSize int) *RingGrowing {
+	return NewTypedRingGrowing[any](RingGrowingOptions{InitialSize: initialSize})
+}
+
+// TypedRingGrowing is a growing ring buffer.
+// The zero value has an initial size of 0 and is ready to use.
+// Not thread safe.
+type TypedRingGrowing[T any] struct {
+	data     []T
+	n        int // Size of Data
+	beg      int // First available element
+	readable int // Number of data items available
+}
+
+// NewTypedRingGrowing constructs a new TypedRingGrowing instance with provided parameters.
+func NewTypedRingGrowing[T any](opts RingGrowingOptions) *TypedRingGrowing[T] {
+	return &TypedRingGrowing[T]{
+		data: make([]T, opts.InitialSize),
+		n:    opts.InitialSize,
+	}
+}
+
+// ReadOne reads (consumes) first item from the buffer if it is available, otherwise returns false.
+func (r *TypedRingGrowing[T]) ReadOne() (data T, ok bool) {
+	if r.readable == 0 {
+		return
+	}
+	r.readable--
+	element := r.data[r.beg]
+	var zero T
+	r.data[r.beg] = zero // Remove reference to the object to help GC
+	if r.beg == r.n-1 {
+		// Was the last element
+		r.beg = 0
+	} else {
+		r.beg++
+	}
+	return element, true
+}
+
+// WriteOne adds an item to the end of the buffer, growing it if it is full.
+func (r *TypedRingGrowing[T]) WriteOne(data T) {
+	if r.readable == r.n {
+		// Time to grow
+		newN := r.n * 2
+		if newN == 0 {
+			newN = defaultRingSize
+		}
+		newData := make([]T, newN)
+		to := r.beg + r.readable
+		if to <= r.n {
+			copy(newData, r.data[r.beg:to])
+		} else {
+			copied := copy(newData, r.data[r.beg:])
+			copy(newData[copied:], r.data[:(to%r.n)])
+		}
+		r.beg = 0
+		r.data = newData
+		r.n = newN
+	}
+	r.data[(r.readable+r.beg)%r.n] = data
+	r.readable++
+}
+
+// Len returns the number of items in the buffer.
+func (r *TypedRingGrowing[T]) Len() int {
+	return r.readable
+}
+
+// Cap returns the capacity of the buffer.
+func (r *TypedRingGrowing[T]) Cap() int {
+	return r.n
+}
+
+// RingOptions sets parameters for [Ring].
+type RingOptions struct {
+	// InitialSize is the number of pre-allocated elements in the
+	// initial underlying storage buffer.
+	InitialSize int
+	// NormalSize is the number of elements to allocate for new storage
+	// buffers once the Ring is consumed and
+	// can shrink again.
+	NormalSize int
+}
+
+// Ring is a dynamically-sized ring buffer which can grow and shrink as-needed.
+// The zero value has an initial size and normal size of 0 and is ready to use.
+// Not thread safe.
+type Ring[T any] struct {
+	growing    TypedRingGrowing[T]
+	normalSize int // Limits the size of the buffer that is kept for reuse. Read-only.
+}
+
+// NewRing constructs a new Ring instance with provided parameters.
+func NewRing[T any](opts RingOptions) *Ring[T] {
+	return &Ring[T]{
+		growing:    *NewTypedRingGrowing[T](RingGrowingOptions{InitialSize: opts.InitialSize}),
+		normalSize: opts.NormalSize,
+	}
+}
+
+// ReadOne reads (consumes) first item from the buffer if it is available,
+// otherwise returns false. When the buffer has been totally consumed and has
+// grown in size beyond its normal size, it shrinks down to its normal size again.
+func (r *Ring[T]) ReadOne() (data T, ok bool) {
+	element, ok := r.growing.ReadOne()
+
+	if r.growing.readable == 0 && r.growing.n > r.normalSize {
+		// The buffer is empty. Reallocate a new buffer so the old one can be
+		// garbage collected.
+		r.growing.data = make([]T, r.normalSize)
+		r.growing.n = r.normalSize
+		r.growing.beg = 0
+	}
+
+	return element, ok
+}
+
+// WriteOne adds an item to the end of the buffer, growing it if it is full.
+func (r *Ring[T]) WriteOne(data T) {
+	r.growing.WriteOne(data)
+}
+
+// Len returns the number of items in the buffer.
+func (r *Ring[T]) Len() int {
+	return r.growing.Len()
+}
+
+// Cap returns the capacity of the buffer.
+func (r *Ring[T]) Cap() int {
+	return r.growing.Cap()
+}