Interface Backend

core/fstable/backend.go:54–85

Backend is the contract every filesystem implementation satisfies. Methods take a context so the engine's request deadlines and cancellation flow through to the SDK calls.

// Methods take a context so the engine's request deadlines and
// cancellation flow through to the SDK calls.
type Backend interface {
	// Name reports the backend kind ("local", "s3", "gcs"). Used in logs
	// and error messages — never as control-flow input by callers.
	Name() string

	// List enumerates entries under opts.Prefix, returning a page of
	// results and an opaque token for the next page. nextToken is
	// empty when the result set is fully drained.
	List(ctx context.Context, opts ListOpts) (entries []Entry, nextToken string, err error)

	// Stat returns metadata for a single key, or ErrNotFound if absent.
	// No body is fetched.
	Stat(ctx context.Context, key string) (Entry, error)

	// Get returns the body and metadata for a key. Callers MUST close
	// the returned reader. Returns ErrNotFound when the key is absent.
	Get(ctx context.Context, key string) (io.ReadCloser, Entry, error)

	// Put writes a value at key. The reader is consumed entirely; the
	// returned Entry has Size populated from the actual bytes written.
	Put(ctx context.Context, key string, body io.Reader, meta PutMeta) (Entry, error)

	// Delete removes a key. Idempotent: deleting a missing key is not
	// an error.
	Delete(ctx context.Context, key string) error

	// Presign returns a URL that grants the named operation on the key
	// for ttl. Backends that don't support presigning (e.g. local) MAY
	// return a non-presigned URL (file://) when op==PresignGet and
	// ErrUnsupported when op==PresignPut.
	Presign(ctx context.Context, key string, op PresignOp, ttl time.Duration) (string, error)
}

// Sentinel errors used uniformly by backends so the bridge can map
// them to GraphQL-friendly responses without sniffing strings.