SourceStructure

struct SourceStructure

Declared in Sources/PrismCore/Probe/SourceStructure.swift · PrismCore 3.5.4

What a probe can say about a container's layout and index — the half of an open that SourceInfo has never described.

SourceInfo answers "what streams are in here"; this answers "where does the header end, where does the media start, and is there an index". A server that has already analysed a file can hand these two scalars to a client about to read the same bytes over a network, which turns the client's first open-ended request into a bounded one.

Every field is optional or has an unknown case, and nothing here is ever inferred. A value that was not measured is absent; a question that was not asked is unknown. The cost of a wrong scalar is paid by the host that trusts it, at a distance, on a file this process will never see again — so the export refuses to guess in the one direction that would be convenient.

Initializers

init(headerBytes:firstClusterOffset:indexLocation:index:byteSize:)source

init(headerBytes: Int?, firstClusterOffset: Int64?, indexLocation: IndexLocation, index: IndexSummary?, byteSize: Int64?)

No documentation comment in the source.

Instance properties

headerBytes source

let headerBytes: Int?

The length of the initial metadata region, from byte 0 of the source.

A sizing hint and nothing more: a consumer reads these bytes and parses them exactly as it does today, so a wrong value costs an extra read, never a wrong parse.

firstClusterOffset source

let firstClusterOffset: Int64?

The offset of the first top-level media element — for Matroska the first byte of the first Cluster element's ID, for ISO-BMFF the first byte of the mdat box. Same coordinates as headerBytes.

indexLocation source

let indexLocation: IndexLocation

No documentation comment in the source.

index source

let index: IndexSummary?

The index, when one was actually read. nil when no index load was requested, or when it was requested and did not fit its budget.

byteSize source

let byteSize: Int64?

The source's own length as the transport reports it, when it knows. Here because every offset above is only interpretable against it, and a consumer's bounds check (offset < byteSize) should not have to ask a second layer for the denominator.

Type properties

unknown source

static let unknown: SourceStructure

Nothing measured. The resting state of a probe that was not asked for a structure export, and the only shape that costs no I/O at all.

maxExportedKeyframes source

static let maxExportedKeyframes: Int

The ceiling on how many timestamps an export will carry.

The consumer of this export is a helper with a 1 MiB output limit, and a timestamp costs roughly eight bytes as JSON text. Twenty thousand entries is a three-hour film at a half-second keyframe cadence — well past any real VOD encode — and still leaves the rest of the document room. Past the cap entryCount and completeness are still reported: a poorer document, on time, rather than a complete one that overruns.

Generated from the public symbols of PrismCore 3.5.4. All types