Gets the byte offset of the data area for a named tag in a PV‑WAVE structure variable.

long wsdh_offset(wsdh, tagname)

WSDH wsdh;

char *tagname;

INTEGER*4 LF_WSDH_OFFSET(l_wsdh, tagname)

INTEGER*4 l_wsdh

CHARACTER*31 tagname

INTEGER*8 LF_WSDH_OFFSET(l_wsdh, tagname)

INTEGER*8 l_wsdh

CHARACTER*31 tagname

wsdh—A Wave structure definition handle.

tagname—The name of the desired tag in the structure.

Returns the offset in bytes of the tag’s data area.

Returns –1 on failure, if the handle argument is not a valid Wave structure definition handle, or if the tag doesn’t exist in the structure.

If the given tagname exists in the structure definition, wsdh_offset returns an offset which can be used to find the data associated with this tagname. The unit of offset is number of bytes. Given that (char *)P holds a pointer to the data area of a PV‑WAVE variable of this structure type, (P+offset) points to the data corresponding to this tagname. Note that (P+offset) must be cast to the type of the associated tagname. The pointer to the data area of a PV‑WAVE variable can be retrieved from the wvh_dataptr function and the type of the associated tagname can be retrieved from the wsdh_element function.