src/mscorlib/shared/System/Buffers/Utilities.cs


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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.

using System.Diagnostics;
using System.Runtime.CompilerServices;

namespace System.Buffers
{
    internal static class Utilities
    {
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static int SelectBucketIndex(int bufferSize)
        {
            uint bitsRemaining = ((uint)bufferSize - 1) >> 4;

            int poolIndex = 0;
            if (bitsRemaining > 0xFFFF) { bitsRemaining >>= 16; poolIndex = 16; }
            if (bitsRemaining > 0xFF) { bitsRemaining >>= 8; poolIndex += 8; }
            if (bitsRemaining > 0xF) { bitsRemaining >>= 4; poolIndex += 4; }
            if (bitsRemaining > 0x3) { bitsRemaining >>= 2; poolIndex += 2; }
            if (bitsRemaining > 0x1) { bitsRemaining >>= 1; poolIndex += 1; }

            return poolIndex + (int)bitsRemaining;
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        internal static int GetMaxSizeForBucket(int binIndex)
        {
            int maxSize = 16 << binIndex;
            Debug.Assert(maxSize >= 0);
            return maxSize;
        }
    }
}