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 = ArrayPoolUtilities.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);
}
}
internal AOTCompatibleArrayPool(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 = ArrayPoolUtilities.SelectBucketIndex(maxArrayLength);
var buckets = new Bucket[maxBuckets + 1];
for (int i = 0; i < buckets.Length; i++)
{
buckets[i] = new Bucket(ArrayPoolUtilities.GetMaxSizeForBucket(i), maxArraysPerBucket, poolId);
}
_buckets = buckets;
}
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(Array.Empty <T>());
}
T[] buffer;
int index = ArrayPoolUtilities.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);
}