Class DiskDatasetMetadataCache

Namespace

EncDotNet.S100.Core.Metadata

Assembly

EncDotNet.S100.Core.dll

Disk-backed IDatasetMetadataCache: persists each dataset's DatasetMetadata as a small sidecar file so a later session can recover it without re-parsing the dataset (issue #467 WS3).

public sealed class DiskDatasetMetadataCache : IDatasetMetadataCache

Inheritance

object

DiskDatasetMetadataCache

Implements

IDatasetMetadataCache

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

Each sidecar stores the source file's last-write time and length alongside the serialized metadata; a read is a hit only when both still match the current file, so editing or replacing the dataset silently invalidates the entry. Robustness mirrors DiskPortrayalInstructionCache: any IO error, truncated / corrupt file, envelope-version mismatch, or FormatVersion mismatch is treated as a miss; failures never propagate. Writes are atomic (temp file + move), the store is bounded by a total-bytes cap with least-recently-used eviction (see DiskCacheBudget), and all members are thread-safe; hits are served without a lock.

Constructors

DiskDatasetMetadataCache(string, long)

Creates a disk-backed metadata cache rooted at cacheDirectory.

public DiskDatasetMetadataCache(string cacheDirectory, long maxBytes)

Parameters

cacheDirectory string

Directory under which sidecar files are stored. Created on first write if absent. Assumed private to this cache (the LRU sweep enumerates every *.dmeta file in it).

maxBytes long

Soft upper bound, in bytes, on the total size of all persisted files. After a write that exceeds it, the least-recently-used files are evicted until the total is at or below this cap. Must be positive.

Exceptions

ArgumentException

cacheDirectory is null or empty.

ArgumentOutOfRangeException

maxBytes is not positive.

Properties

Hits

Number of reads served from a valid cached entry.

public long Hits { get; }

Property Value

long

Misses

Number of lookups (via either GetOrRead(string, Func<string, DatasetMetadata>) or TryGet(string, out DatasetMetadata)) not served from a valid cached entry. In GetOrRead(string, Func<string, DatasetMetadata>) such a miss is where the producer runs; in TryGet(string, out DatasetMetadata) it simply returns false.

public long Misses { get; }

Property Value

long

Methods

GetOrRead(string, Func<string, DatasetMetadata>)

Returns the cached metadata for sourcePath when a valid entry exists (source unchanged since it was written), otherwise invokes producer, persists its result, and returns it. A cache failure never propagates: the freshly produced value is still returned.

public DatasetMetadata GetOrRead(string sourcePath, Func<string, DatasetMetadata> producer)

Parameters

sourcePath string

Absolute path to the dataset file whose metadata is cached. Its last-write time and length form the validity key.

producer Func<string, DatasetMetadata>

Cold path invoked on a miss to parse the metadata from sourcePath. Receives the same path.

Returns

DatasetMetadata

The cached or freshly produced metadata.

TryGet(string, out DatasetMetadata)

Attempts to read a valid cached entry for sourcePath without producing on a miss. Useful for a pure "is it already known?" probe.

public bool TryGet(string sourcePath, out DatasetMetadata metadata)

Parameters

sourcePath string

Absolute path to the dataset file.

metadata DatasetMetadata

The cached metadata when the method returns true.

Returns

bool

true on a valid hit; otherwise false.