jpx_layer_source::get_codestream_id

If which is 0, the function returns the identifier of the first codestream used by this compositing layer. If which is 1, the function returns the identifier of the second codestream used by the compositing layer, and so forth. If which is greater than or equal to the value returned by get_num_codestreams, the present function will return -1. Otherwise, the identifier returned by this function may be passed to jpx_source::access_codestream to gain access to the codestream itself.

Any codestream identified here can be opened immediately, even if the ultimate data source is a dynamic cache derived from kdu_cache. This is because a non-empty jpx_layer_source interface will never be returned by jpx_source::access_layer until every one of its codestreams has become available for opening. Moreover, as documented in connection with jpx_codestream_source::open_stream, for this to happen, the embedded code-stream's main header must at least be fully available from a local file or from the dynamic cache.

which [int]