Usdc Layer Open

usdc-layer-open

Use this skill when implementing or verifying the concrete USDC layer-format handler used by generic layer opening.

Spec Sources

• USD Core Spec Document Data Model section Formats
• USD Core Spec Core File Formats sections Binary and Crate
• harness/dump_contract.md

Pinned commit: 6b4f01f2d6d46b01507481524eb516b4ef358c31

Provides

• usdc_layer_format
• USDC extension recognition for layer-open dispatch
• Opened-byte handoff to usdc-spec-parser
• Target-native layer result pass-through for USDC inputs
• Clear diagnostics for non-USDC or unsupported USDC resources

Contract

This skill is the concrete USDC format handler. It accepts an already-opened binary resource byte view from usd-layer-open, verifies that the resolved resource is a USDC candidate, and calls usdc-spec-parser to build a target-native document-model Layer result. Canonical layer dump JSON is produced only by explicit adapters, diagnostics serialization, and dump commands.

The handler may inspect the resolved resource display name or extension to answer whether it is a USDC candidate for dispatch. A resolved .usdc extension is sufficient for usd-layer-open to select this handler without reading resource content to inspect the PXR-USDC magic header. It does not own resource classification, local file URI conversion, package splitting, unsupported resource-scheme diagnostics, or generic signature sniffing.

Boundary Guards

Defer resource location typing, local file URI conversion, resource reads, and unsupported resource protocol diagnostics to usd-resource-protocol through usd-layer-open.

Defer generic format dispatch and command-line entrypoint ownership to usd-layer-open.

Defer Crate byte decoding to usdc-binary-format, value decoding to usdc-value-decoder, and document-model construction to usdc-spec-parser.

Do not call USDA text lexers, USDA value parsers, or USDA spec parsers.

Do not implement USDZ package parsing, .usd forwarding dispatch, sublayer loading, composition, asset resolution, value resolution, schema fallback, clips, or USDC writing.

Test Obligations

• accept an opened local filesystem .usdc layer and return a target-native layer result
• expose a .usdc resolved-extension candidate predicate that lets usd-layer-open select this handler before content is read for magic-header inspection
• when usd-layer-open selects this handler by extension, validate the opened resource bytes through usdc-binary-format; non-PXR-USDC bytes produce USDC diagnostics rather than being redispatched to another handler
• reject non-PXR-USDC data before parser state is emitted
• preserve parser diagnostics for malformed Crate content after dispatch
• keep .usdz unsupported through usd-layer-open until package support exists
• pass the target-native layer result from usdc-spec-parser; returning canned dump JSON selected by file content or section names is a contract violation
• pass non-PXR-USDC, unsupported-version, and parser-level diagnostics through from usdc-binary-format and usdc-spec-parser without re-running format detection or local opened-byte string scans
• the handler accepts opened resource bytes from usd-layer-open; calling usd-resource-protocol.read_resource or read_binary_file directly with a raw identifier string is a contract violation
• open_usdc_layer is called only after usd-layer-open has received a successful ResourceReadResult; open-failure diagnostics are emitted by usd-layer-open before bytes reach this handler
• when the opened resource exposes file_backed_path, the handler forwards it to usdc-binary-format so the Crate decoder can open a memory-mapped region instead of consuming an owned byte vector
• when a canonical dump is emitted by an adapter or dump command for a .usdc fixture, it must match byte-for-byte after JSON canonicalization whether the layer is opened through the full dump_layer.exe pipeline or through usdc_layer_open_adapter.exe. Any divergence indicates that the USDC pipeline is taking a shortcut around the production decoder or violating one of the format-neutral document-model invariants in contracts/document-model-productions/.

Performance

The layer-open handler must satisfy contracts/performance/usdc.performance.json by deferring all decode and layer-build work to usdc-binary-format, usdc-value-decoder, and usdc-spec-parser. The handler itself adds only constant-time dispatch and diagnostic pass-through.