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- // Licensed to the .NET Foundation under one or more agreements.
- // The .NET Foundation licenses this file to you under the MIT license.
- // See the LICENSE file in the project root for more information.
- #if NETCORE
- using System;
- namespace SharpCompress.Buffers
- {
- internal sealed partial class DefaultArrayPool<T> : ArrayPool<T>
- {
- /// <summary>The default maximum length of each array in the pool (2^20).</summary>
- private const int DefaultMaxArrayLength = 1024 * 1024;
- /// <summary>The default maximum number of arrays per bucket that are available for rent.</summary>
- private const int DefaultMaxNumberOfArraysPerBucket = 50;
- /// <summary>Lazily-allocated empty array used when arrays of length 0 are requested.</summary>
- private static T[] s_emptyArray; // we support contracts earlier than those with Array.Empty<T>()
- private readonly Bucket[] _buckets;
- internal DefaultArrayPool() : this(DefaultMaxArrayLength, DefaultMaxNumberOfArraysPerBucket)
- {
- }
- internal DefaultArrayPool(int maxArrayLength, int maxArraysPerBucket)
- {
- if (maxArrayLength <= 0)
- {
- throw new ArgumentOutOfRangeException(nameof(maxArrayLength));
- }
- if (maxArraysPerBucket <= 0)
- {
- throw new ArgumentOutOfRangeException(nameof(maxArraysPerBucket));
- }
- // Our bucketing algorithm has a min length of 2^4 and a max length of 2^30.
- // Constrain the actual max used to those values.
- const int MinimumArrayLength = 0x10, MaximumArrayLength = 0x40000000;
- if (maxArrayLength > MaximumArrayLength)
- {
- maxArrayLength = MaximumArrayLength;
- }
- else if (maxArrayLength < MinimumArrayLength)
- {
- maxArrayLength = MinimumArrayLength;
- }
- // Create the buckets.
- int poolId = Id;
- int maxBuckets = Utilities.SelectBucketIndex(maxArrayLength);
- var buckets = new Bucket[maxBuckets + 1];
- for (int i = 0; i < buckets.Length; i++)
- {
- buckets[i] = new Bucket(Utilities.GetMaxSizeForBucket(i), maxArraysPerBucket, poolId);
- }
- _buckets = buckets;
- }
- /// <summary>Gets an ID for the pool to use with events.</summary>
- private int Id => GetHashCode();
- public override T[] Rent(int minimumLength)
- {
- // Arrays can't be smaller than zero. We allow requesting zero-length arrays (even though
- // pooling such an array isn't valuable) as it's a valid length array, and we want the pool
- // to be usable in general instead of using `new`, even for computed lengths.
- if (minimumLength < 0)
- {
- throw new ArgumentOutOfRangeException(nameof(minimumLength));
- }
- else if (minimumLength == 0)
- {
- // No need for events with the empty array. Our pool is effectively infinite
- // and we'll never allocate for rents and never store for returns.
- return s_emptyArray ?? (s_emptyArray = new T[0]);
- }
- T[] buffer = null;
- int index = Utilities.SelectBucketIndex(minimumLength);
- if (index < _buckets.Length)
- {
- // Search for an array starting at the 'index' bucket. If the bucket is empty, bump up to the
- // next higher bucket and try that one, but only try at most a few buckets.
- const int MaxBucketsToTry = 2;
- int i = index;
- do
- {
- // Attempt to rent from the bucket. If we get a buffer from it, return it.
- buffer = _buckets[i].Rent();
- if (buffer != null)
- {
- return buffer;
- }
- }
- while (++i < _buckets.Length && i != index + MaxBucketsToTry);
- // The pool was exhausted for this buffer size. Allocate a new buffer with a size corresponding
- // to the appropriate bucket.
- buffer = new T[_buckets[index]._bufferLength];
- }
- else
- {
- // The request was for a size too large for the pool. Allocate an array of exactly the requested length.
- // When it's returned to the pool, we'll simply throw it away.
- buffer = new T[minimumLength];
- }
- return buffer;
- }
- public override void Return(T[] array, bool clearArray = false)
- {
- if (array == null)
- {
- throw new ArgumentNullException(nameof(array));
- }
- else if (array.Length == 0)
- {
- // Ignore empty arrays. When a zero-length array is rented, we return a singleton
- // rather than actually taking a buffer out of the lowest bucket.
- return;
- }
- // Determine with what bucket this array length is associated
- int bucket = Utilities.SelectBucketIndex(array.Length);
- // If we can tell that the buffer was allocated, drop it. Otherwise, check if we have space in the pool
- if (bucket < _buckets.Length)
- {
- // Clear the array if the user requests
- if (clearArray)
- {
- Array.Clear(array, 0, array.Length);
- }
- // Return the buffer to its bucket. In the future, we might consider having Return return false
- // instead of dropping a bucket, in which case we could try to return to a lower-sized bucket,
- // just as how in Rent we allow renting from a higher-sized bucket.
- _buckets[bucket].Return(array);
- }
- }
- }
- }
- #endif
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