Package uk.ac.starlink.oldfits
Class FitsConstants
java.lang.Object
uk.ac.starlink.oldfits.FitsConstants
Utility class providing some constants and static methods related to
FITS file format and starlink classes.
- Author:
- Mark Taylor (Starlink)
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final nom.tam.fits.HeaderCard
Image of end-of-header card.static final int
Standard size of a FITS block in bytes.static final int
Maximum number of columns in standard FITS BINTABLE extension.static final String
FITS header card for indicating NDArray origin values.static final String
Prefix for NDArray-related FITS header cards.static final String
Prefix for NDX-related FITS header cards.static final String
FITS header card for location (relative URL) of XML representation.static boolean
Whether HIERARCH convention is used; true by default.static final String
Default encoding used for writing WCS into FITS headers. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionstatic void
addStringValue
(nom.tam.fits.Header hdr, String key, String value, String comment) Attempts to add a string-valued card to the header.static void
addTrimmedValue
(nom.tam.fits.Header hdr, String key, String value, String comment) Adds a string-valued card to the header.static nom.tam.fits.HeaderCard
createHeaderCard
(String cardImage) Create a HeaderCard from a FITS card image.static nom.tam.fits.HeaderCard
createRawHeaderCard
(String keyname, String rawvalue, String comment) Create a header card given the final representation of the card value.static nom.tam.fits.Header
Creates a Header instance which does not perform any unsolicited reordering of the header cards.Gets the default permitted list of extensions which identify a FITS resource in the path part of a URL.static long
getDataSize
(nom.tam.fits.Header hdr) Utility function to find the number of bytes in the data segment of an HDU.static nom.tam.util.ArrayDataInput
getInputStreamStart
(uk.ac.starlink.util.DataSource datsrc) Returns an input stream which can be used with the various FITS classes based on a given DataSource object, positioned at the start of the stream.static Iterable
<nom.tam.fits.HeaderCard> headerIterable
(nom.tam.fits.Header hdr) Returns an iterable over HeaderCards for a given Header.static boolean
isMagic
(byte[] buffer) Indicates whether the supplied buffer is the start of a FITS file.static int
readHeader
(nom.tam.fits.Header hdr, nom.tam.util.ArrayDataInput strm) Populates a header from an input stream, reporting its length in bytes.static long
skipHDUs
(nom.tam.util.ArrayDataInput stream, int nskip) Skips forward over a given number of HDUs in the supplied stream.static void
writeEmptyPrimary
(DataOutput strm) Writes a null header representing an empty primary HDU to a stream.static void
writeHeader
(DataOutput strm, nom.tam.fits.Header hdr) Writes a header object to a DataOutput.
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Field Details
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NDARRAY_PREFIX
Prefix for NDArray-related FITS header cards.- See Also:
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END_CARD
public static final nom.tam.fits.HeaderCard END_CARDImage of end-of-header card. -
NDARRAY_ORIGIN
FITS header card for indicating NDArray origin values. An integer (1, 2, ... ) is appended to this value for the different axes like for NAXIS.- See Also:
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NDX_PREFIX
Prefix for NDX-related FITS header cards.- See Also:
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NDX_XML
FITS header card for location (relative URL) of XML representation.- See Also:
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WCS_ENCODING
Default encoding used for writing WCS into FITS headers.- See Also:
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FITS_BLOCK
public static final int FITS_BLOCKStandard size of a FITS block in bytes.- See Also:
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MAX_NCOLSTD
public static final int MAX_NCOLSTDMaximum number of columns in standard FITS BINTABLE extension.- See Also:
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REQUIRE_HIERARCH
public static boolean REQUIRE_HIERARCHWhether HIERARCH convention is used; true by default.
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Constructor Details
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FitsConstants
public FitsConstants()
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Method Details
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defaultFitsExtensions
Gets the default permitted list of extensions which identify a FITS resource in the path part of a URL.- Returns:
- unmodifiable list of default FITS extensions - ".fits", ".fit" etc
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createUnsortedHeader
public static nom.tam.fits.Header createUnsortedHeader()Creates a Header instance which does not perform any unsolicited reordering of the header cards. Some versions of nom.tam.fits force the EXTEND keyword to go directly after the NAXISn keywords. That screws up specification of the FITS-plus magic number, which is expected to have VOTMETA directly after NAXISn. Headers created using this method will leave header cards in the order they are added.- Returns:
- new empty header
- See Also:
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createHeaderCard
Create a HeaderCard from a FITS card image.- Parameters:
cardImage
- the 80 character card image- Returns:
- card object
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createRawHeaderCard
public static nom.tam.fits.HeaderCard createRawHeaderCard(String keyname, String rawvalue, String comment) throws nom.tam.fits.HeaderCardException Create a header card given the final representation of the card value. No additional manipulation will be done on the value; for instance it will not be wrapped in quotes. Use this method with caution, since the arguments may not be checked as rigorously as during normal header creation, though steps will be taken to ensure that the header does not overflow the 80 character limit.- Parameters:
keyname
- header card namerawvalue
- raw header card valuecomment
- comment text (ignored if too long)- Returns:
- new header card
- Throws:
nom.tam.fits.HeaderCardException
- if card would be too long
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headerIterable
Returns an iterable over HeaderCards for a given Header.- Parameters:
hdr
- header- Returns:
- iterable over hdr's cards
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skipHDUs
Skips forward over a given number of HDUs in the supplied stream. If it reaches the end of the stream, it throws an IOException with a Cause of a TruncatedFileException.- Parameters:
stream
- the stream to skip throughnskip
- the number of HDUs to skip- Returns:
- the number of bytes the stream was advanced
- Throws:
IOException
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isMagic
public static boolean isMagic(byte[] buffer) Indicates whether the supplied buffer is the start of a FITS file. Its contents is checked against the FITS 'magic number', which is the ASCII string "SIMPLE =".- Parameters:
buffer
- a byte buffer containing the start of a file to test- Returns:
- true iff the bytes in buffer look like the start of a FITS file
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getInputStreamStart
public static nom.tam.util.ArrayDataInput getInputStreamStart(uk.ac.starlink.util.DataSource datsrc) throws IOException Returns an input stream which can be used with the various FITS classes based on a given DataSource object, positioned at the start of the stream.- Parameters:
datsrc
- the DataSource pointing to the file/HDU required- Returns:
- an ArrayDataInput acquired from datsrc,
- Throws:
IOException
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readHeader
public static int readHeader(nom.tam.fits.Header hdr, nom.tam.util.ArrayDataInput strm) throws nom.tam.fits.TruncatedFileException, IOException Populates a header from an input stream, reporting its length in bytes. This does the same asHeader.read(nom.tam.util.ArrayDataInput)
, but it returns the number of bytes read from the input stream in order to populate the header (including any padding bytes). There is no way to retrieve this information from the Header class in general; thoughHeader.getSize()
will sometimes give you the right answer, in the case of duplicated header keywords it can give an underestimate. This could be seen as a bug in nom.tam.fits classes, but there may be code somewhere which relies on that behaviour.You can make a Header from scratch by doing
Header hdr = new Header(); int headsize = read( hdr, strm );
This method also differs from the Header implementation in that it does not print warnings to standard output about duplicate keywords.- Parameters:
hdr
- the header to populatestrm
- the input stream supplying the data- Returns:
- the number of bytes in the FITS blocks which comprise the header content
- Throws:
nom.tam.fits.TruncatedFileException
IOException
- See Also:
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writeHeader
Writes a header object to a DataOutput.- Parameters:
strm
- destination streamhdr
- the header to write- Throws:
IOException
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writeEmptyPrimary
Writes a null header representing an empty primary HDU to a stream.- Parameters:
strm
- stream to write to- Throws:
IOException
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getDataSize
public static long getDataSize(nom.tam.fits.Header hdr) Utility function to find the number of bytes in the data segment of an HDU. As far as I can see, Header.getDataSize() ought to do this, but it doesn't seem to.- Parameters:
hdr
- the Header- Returns:
- the number of bytes in the data segment associated with hdr
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addTrimmedValue
public static void addTrimmedValue(nom.tam.fits.Header hdr, String key, String value, String comment) throws nom.tam.fits.HeaderCardException Adds a string-valued card to the header. If the value is too long, it is truncated appropriately, and a warning is emitted through the logging system.- Parameters:
hdr
- headerkey
- card keyvalue
- card valuecomment
- card comment- Throws:
nom.tam.fits.HeaderCardException
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addStringValue
public static void addStringValue(nom.tam.fits.Header hdr, String key, String value, String comment) Attempts to add a string-valued card to the header. If the value is too long, no header is added, and a message is emitted through the logging system.- Parameters:
hdr
- headerkey
- card keyvalue
- card valuecomment
- card comment
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