sane_get_option_descriptor

This function is used to access option descriptors. The function returns the option descriptor for option number n of the device represented by handle h. Option number 0 is guaranteed to be a valid option. Its value is an integer that specifies the number of options that are available for device handle h (the count includes option 0). If $n$ is not a valid option index, the function returns NULL. The returned option descriptor is guaranteed to remain valid (and at the returned address) until the device is closed.

const SANE_Option_Descriptor *
    sane_get_option_descriptor (SANE_Handle h, SANE_Int n);