FUNCTION FXMOVE, UNIT, N_EXT, SILENT = Silent ;+ ; NAME: ; FXMOVE ; PURPOSE: ; Skip a specified number of extensions in a FITS file ; ; CALLING SEQUENCE: ; STATUS=FXMOVE(UNIT, N_EXT, /Silent) ; ; INPUT PARAMETERS: ; UNIT = An open unit descriptor for a FITS data stream. ; N_EXT = Number of extensions to skip. ; ; OPTIONAL INPUT PARAMETER: ; /SILENT - If set, then any messages about invalid characters in the ; FITS file are suppressed. ; RETURNS: ; 0 if successful. ; -1 if an error is encountered. ; ; COMMON BLOCKS: ; None. ; SIDE EFFECTS: ; Repositions the file pointer. ; PROCEDURE: ; Each FITS header is read in and parsed, and the file pointer is moved ; to where the next FITS extension header until the desired ; extension is reached. ; PROCEDURE CALLS: ; FXPAR(), MRD_HREAD, MRD_SKIP ; MODIFICATION HISTORY: ; Extracted from FXPOSIT 8-March-2000 by T. McGlynn ; Added /SILENT keyword 14-Dec-2000 by W. Landsman ; Save time by not reading the full header W. Landsman Feb. 2003 ;- FOR EXT = 1, N_EXT DO BEGIN ; ; Read the next header, and get the number of bytes taken up by the data. ; IF EOF(UNIT) THEN RETURN, -1 ; Can't use FXHREAD to read from pipe, since it uses ; POINT_LUN. So we read this in ourselves using mrd_hread MRD_HREAD, UNIT, HEADER, STATUS, SILENT = Silent, /FIRSTBLOCK IF STATUS LT 0 THEN RETURN, -1 ; Get parameters that determine size of data ; region. BITPIX = FXPAR(HEADER,'BITPIX') NAXIS = FXPAR(HEADER,'NAXIS') GCOUNT = FXPAR(HEADER,'GCOUNT') IF GCOUNT EQ 0 THEN GCOUNT = 1 PCOUNT = FXPAR(HEADER,'PCOUNT') IF NAXIS GT 0 THEN BEGIN DIMS = FXPAR(HEADER,'NAXIS*') ;Read dimensions NDATA = DIMS IF NAXIS GT 1 THEN FOR I=2,NAXIS DO NDATA = NDATA*DIMS[I-1] ENDIF ELSE NDATA = 0 NBYTES = (ABS(BITPIX) / 8) * GCOUNT * (PCOUNT + NDATA) ; ; Move to the next extension header in the file. ; NREC = LONG((NBYTES + 2879) / 2880) MRD_SKIP, UNIT, NREC*2880L ENDFOR RETURN, 0 END
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|Last modified on 2nd Mar 2009 by Richard Massey.|