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| Original file line number | Diff line number | Diff line change |
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| // Copyright (c) 2021, Emir Pasic. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
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| // Package circularbuffer implements the circular buffer. | ||
| // | ||
| // In computer science, a circular buffer, circular queue, cyclic buffer or ring buffer is a data structure that uses a single, fixed-size buffer as if it were connected end-to-end. This structure lends itself easily to buffering data streams. | ||
| // | ||
| // Structure is not thread safe. | ||
| // | ||
| // Reference: https://en.wikipedia.org/wiki/Circular_buffer | ||
| package circularbuffer | ||
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|
||
| import ( | ||
| "fmt" | ||
| "strings" | ||
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| "github.com/emirpasic/gods/queues" | ||
| ) | ||
|
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| // Assert Queue implementation | ||
| var _ queues.Queue = (*Queue)(nil) | ||
|
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| // Queue holds values in a slice. | ||
| type Queue struct { | ||
| values []interface{} | ||
| start int | ||
| end int | ||
| full bool | ||
| maxSize int | ||
| size int | ||
| } | ||
|
|
||
| // New instantiates a new empty queue with the specified size of maximum number of elements that it can hold. | ||
| // This max size of the buffer cannot be changed. | ||
| func New(maxSize int) *Queue { | ||
| if maxSize < 1 { | ||
| panic("Invalid maxSize, should be at least 1") | ||
| } | ||
| queue := &Queue{maxSize: maxSize} | ||
| queue.Clear() | ||
| return queue | ||
| } | ||
|
|
||
| // Enqueue adds a value to the end of the queue | ||
| func (queue *Queue) Enqueue(value interface{}) { | ||
| if queue.Full() { | ||
| queue.Dequeue() | ||
| } | ||
| queue.values[queue.end] = value | ||
| queue.end = queue.end + 1 | ||
| if queue.end >= queue.maxSize { | ||
| queue.end = 0 | ||
| } | ||
| if queue.end == queue.start { | ||
| queue.full = true | ||
| } | ||
|
|
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| queue.size = queue.calculateSize() | ||
| } | ||
|
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| // Dequeue removes first element of the queue and returns it, or nil if queue is empty. | ||
| // Second return parameter is true, unless the queue was empty and there was nothing to dequeue. | ||
| func (queue *Queue) Dequeue() (value interface{}, ok bool) { | ||
| if queue.Empty() { | ||
| return nil, false | ||
| } | ||
|
|
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| value, ok = queue.values[queue.start], true | ||
|
|
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| if value != nil { | ||
| queue.values[queue.start] = nil | ||
| queue.start = queue.start + 1 | ||
| if queue.start >= queue.maxSize { | ||
| queue.start = 0 | ||
| } | ||
| queue.full = false | ||
| } | ||
|
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| queue.size = queue.size - 1 | ||
|
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| return | ||
| } | ||
|
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| // Peek returns first element of the queue without removing it, or nil if queue is empty. | ||
| // Second return parameter is true, unless the queue was empty and there was nothing to peek. | ||
| func (queue *Queue) Peek() (value interface{}, ok bool) { | ||
| if queue.Empty() { | ||
| return nil, false | ||
| } | ||
| return queue.values[queue.start], true | ||
| } | ||
|
|
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| // Empty returns true if queue does not contain any elements. | ||
| func (queue *Queue) Empty() bool { | ||
| return queue.Size() == 0 | ||
| } | ||
|
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| // Full returns true if the queue is full, i.e. has reached the maximum number of elements that it can hold. | ||
| func (queue *Queue) Full() bool { | ||
| return queue.Size() == queue.maxSize | ||
| } | ||
|
|
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| // Size returns number of elements within the queue. | ||
| func (queue *Queue) Size() int { | ||
| return queue.size | ||
| } | ||
|
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| // Clear removes all elements from the queue. | ||
| func (queue *Queue) Clear() { | ||
| queue.values = make([]interface{}, queue.maxSize, queue.maxSize) | ||
| queue.start = 0 | ||
| queue.end = 0 | ||
| queue.full = false | ||
| queue.size = 0 | ||
| } | ||
|
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| // Values returns all elements in the queue (FIFO order). | ||
| func (queue *Queue) Values() []interface{} { | ||
| values := make([]interface{}, queue.Size(), queue.Size()) | ||
| for i := 0; i < queue.Size(); i++ { | ||
| values[i] = queue.values[(queue.start+i)%queue.maxSize] | ||
| } | ||
| return values | ||
| } | ||
|
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| // String returns a string representation of container | ||
| func (queue *Queue) String() string { | ||
| str := "CircularBuffer\n" | ||
| var values []string | ||
| for _, value := range queue.Values() { | ||
| values = append(values, fmt.Sprintf("%v", value)) | ||
| } | ||
| str += strings.Join(values, ", ") | ||
| return str | ||
| } | ||
|
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| // Check that the index is within bounds of the list | ||
| func (queue *Queue) withinRange(index int) bool { | ||
| return index >= 0 && index < queue.size | ||
| } | ||
|
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| func (queue *Queue) calculateSize() int { | ||
| if queue.end < queue.start { | ||
| return queue.maxSize - queue.start + queue.end | ||
| } else if queue.end == queue.start { | ||
| if queue.full { | ||
| return queue.maxSize | ||
| } | ||
| return 0 | ||
| } | ||
| return queue.end - queue.start | ||
| } |
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