CrcLookupTableCache Class

Definition

Namespace: Bodu.IO.Hashing.Checksums

Assembly: Bodu.IO.Hashing.dll

Package: Bodu.IO.Hashing 1.0.0

Source: CrcLookupTableCache.cs

Thread-safe cache of precomputed CRC lookup tables keyed by width, polynomial, and input reflection - amortizes the per-tuple build cost of BuildLookupTable(int, ulong, bool) across every Crc instance that uses the same CrcStandard.

public class CrcLookupTableCache

Inheritance: object

CrcLookupTableCache

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Extension Methods: ComparableExtensions.AtLeast<T>(T, T, IComparer<T>)

ComparableExtensions.AtMost<T>(T, T, IComparer<T>)

ComparableExtensions.IsEqualTo<T>(T, T, IComparer<T>)

ComparableExtensions.Max<T>(T, T, IComparer<T>)

ComparableExtensions.Min<T>(T, T, IComparer<T>)

Examples

using Bodu.IO.Hashing.Checksums;

// Most callers do not interact with the cache directly - Crc resolves it through Crc.GlobalCache.
var crc = new Crc(CrcStandard.CRC32_ISOHDLC);

// Use a scoped cache for an isolated test, then restore the default.
CrcLookupTableCache previous = Crc.GlobalCache;
try
{
    Crc.GlobalCache = new CrcLookupTableCache();
    // ... run isolated tests against a fresh cache ...
}
finally
{
    Crc.GlobalCache = previous;
}

Remarks

Building a CRC lookup table is cheap in absolute terms but not free, and the same table is needed every time a Crc instance is constructed for a given CrcStandard. CrcLookupTableCache memoizes tables under the unique key (width, polynomial, reflectIn): the first lookup for a tuple builds and stores the table; subsequent lookups return the same shared array.

Default and custom caches. A process-wide default lives at GlobalCache and is used implicitly by every Crc instance - most callers never need to construct a cache by hand. Reach for a custom CrcLookupTableCache only when you want a scoped cache (e.g. per AppDomain, per test fixture) that the global default should not see, or when running diagnostic code that needs deterministic cache state. Custom caches can be installed by assigning to GlobalCache.

Thread safety and aliasing. Internally backed by ConcurrentDictionary<TKey, TValue>; concurrent GetLookupTable(int, ulong, bool) calls are safe and the build delegate runs at most once per key. The returned array is shared across all callers with the same parameters and must be treated as read-only - mutating it would corrupt every Crc instance that uses the same standard.

Constructors