gio:resource-info (resource path &optional lookup)

resource -- a g:resource instance
path -- a string for a pathname inside the resource
lookup -- an optional g:resource-lookup-flags value, the default value is :none
size -- an integer for the length of the contents of the file
flags -- an unsigned integer for the flags about the file

Looks for a file at the specified path in the resource and if found returns information about it. The lookup argument controls the behaviour of the lookup.