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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| defmodule ExWebRTC.RTP.JitterBuffer.Heap do | ||
| @moduledoc false | ||
| # Implementation of a heap (min-heap by default) | ||
| # | ||
| # At the moment, this module uses a regular `Map` (with O(log n) access) to store the data. | ||
| # | ||
| # TODO: Run performance tests and determine if it would be better to use: | ||
| # - ETS | ||
| # - :array | ||
| # - some other data structure? | ||
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| @type comparator :: (term(), term() -> boolean()) | ||
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| @opaque t :: %__MODULE__{ | ||
| comparator: comparator(), | ||
| tree: %{non_neg_integer() => term()} | ||
| } | ||
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| defstruct [:comparator, :tree] | ||
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| defimpl Enumerable do | ||
| alias ExWebRTC.RTP.JitterBuffer.Heap | ||
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| def count(heap), do: {:ok, map_size(heap.tree)} | ||
| def member?(heap, elem), do: {:ok, heap.tree |> Map.values() |> Enum.member?(elem)} | ||
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| def reduce(_heap, {:halt, acc}, _fun), do: {:halted, acc} | ||
| def reduce(heap, {:suspend, acc}, fun), do: {:suspended, acc, &reduce(heap, &1, fun)} | ||
| def reduce(heap, {:cont, acc}, _fun) when map_size(heap.tree) == 0, do: {:done, acc} | ||
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| def reduce(heap, {:cont, acc}, fun) do | ||
| elem = Heap.root(heap) | ||
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| heap |> Heap.pop() |> reduce(fun.(elem, acc), fun) | ||
| end | ||
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| def slice(_heap), do: {:error, __MODULE__} | ||
| end | ||
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| @spec new(comparator()) :: t() | ||
| def new(comparator \\ &</2) do | ||
| %__MODULE__{ | ||
| comparator: comparator, | ||
| tree: %{} | ||
| } | ||
| end | ||
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| @spec root(t()) :: term() | ||
| def root(heap) do | ||
| heap.tree[0] | ||
| end | ||
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| @spec size(t()) :: non_neg_integer() | ||
| def size(heap) do | ||
| map_size(heap.tree) | ||
| end | ||
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| @spec push(t(), term()) :: t() | ||
| def push(heap, elem) do | ||
| idx = map_size(heap.tree) | ||
| tree = Map.put(heap.tree, idx, elem) | ||
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| restore_heap(%{heap | tree: tree}, idx) | ||
| end | ||
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| @spec pop(t()) :: t() | ||
| def pop(heap) | ||
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| def pop(heap) when map_size(heap.tree) < 2, do: %{heap | tree: %{}} | ||
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| def pop(heap) do | ||
| last_idx = map_size(heap.tree) - 1 | ||
| %{0 => _first, ^last_idx => last} = heap.tree | ||
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| tree = | ||
| heap.tree | ||
| |> Map.delete(last_idx) | ||
| |> Map.put(0, last) | ||
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| heapify(%{heap | tree: tree}, 0) | ||
| end | ||
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| defp restore_heap(heap, 0), do: heap | ||
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| defp restore_heap(heap, idx) do | ||
| p = parent(idx) | ||
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| heap | ||
| |> heapify(p) | ||
| |> restore_heap(p) | ||
| end | ||
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| defp heapify(heap, i) do | ||
| n = map_size(heap.tree) | ||
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| max_idx = | ||
| [i, left(i), right(i)] | ||
| |> Stream.filter(&(&1 < n)) | ||
| |> Enum.max_by(&heap.tree[&1], heap.comparator, fn -> nil end) | ||
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| if max_idx != i do | ||
| %{^i => t1, ^max_idx => t2} = heap.tree | ||
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| tree = | ||
| heap.tree | ||
| |> Map.put(i, t2) | ||
| |> Map.put(max_idx, t1) | ||
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| heapify(%{heap | tree: tree}, max_idx) | ||
| else | ||
| heap | ||
| end | ||
| end | ||
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| defp left(i), do: 2 * i + 1 | ||
| defp right(i), do: 2 * i + 2 | ||
| defp parent(i), do: div(i - 1, 2) | ||
| end |
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