Package uk.ac.starlink.fits
Class FitsUtil
- java.lang.Object
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- uk.ac.starlink.fits.FitsUtil
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public class FitsUtil extends java.lang.Object
Utilities for working with FITS files.- Since:
- 4 Mar 2022
- Author:
- Mark Taylor
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Field Summary
Fields Modifier and Type Field Description static int
BLOCK_LENG
FITS block length in bytes (@value).static int
CARD_LENG
FITS header card length in bytes (@value).static int
CARDS_PER_BLOCK
Number of header cards per FITS block (@value).static java.lang.String
FLOAT_REGEX
Regex pattern matching floating point value, no grouping.static int
MAX_NCOLSTD
Maximum No.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static java.lang.Object
asNumericArray(java.lang.String txt)
Attempts to interpret a string as a formatted numeric array.static void
checkColumnCount(WideFits wide, int ncol)
Checks that a table with the given number of columns can be written.static boolean
isFitsCharacter(int ch)
Indicates whether a given character is a legal FITS header character (0x20..0x7e inclusive).static boolean
isMagic(byte[] buffer)
Indicates whether the supplied buffer is the start of a FITS file.static ParsedCard<?>
parseCard(byte[] buf80)
Turns an 80-byte array into a ParsedCard.static FitsHeader
readHeader(java.io.InputStream in)
Reads a FITS header from an input stream.static long
roundUp(long value, int blockSize)
Utility method to round an integer value up to a multiple of a given block size.static long
skipHDUs(java.io.InputStream in, int nskip)
Skips forward over a given number of HDUs in the supplied stream.static void
writeEmptyPrimary(java.io.OutputStream out)
Writes a data-less Primary HDU.static int
writeHeader(CardImage[] cards, java.io.OutputStream out)
Writes a FITS header whose content is supplied by an array of cards.
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Field Detail
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BLOCK_LENG
public static final int BLOCK_LENG
FITS block length in bytes (@value).- See Also:
- Constant Field Values
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CARD_LENG
public static final int CARD_LENG
FITS header card length in bytes (@value).- See Also:
- Constant Field Values
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CARDS_PER_BLOCK
public static final int CARDS_PER_BLOCK
Number of header cards per FITS block (@value).- See Also:
- Constant Field Values
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MAX_NCOLSTD
public static final int MAX_NCOLSTD
Maximum No. of columns in standard FITS BINTABLE extension (@value).- See Also:
- Constant Field Values
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FLOAT_REGEX
public static final java.lang.String FLOAT_REGEX
Regex pattern matching floating point value, no grouping.- See Also:
- Constant Field Values
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Method Detail
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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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isFitsCharacter
public static boolean isFitsCharacter(int ch)
Indicates whether a given character is a legal FITS header character (0x20..0x7e inclusive).- Parameters:
ch
- character to check- Returns:
- true iff ch is legal for inclusion in a FITS header
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readHeader
public static FitsHeader readHeader(java.io.InputStream in) throws java.io.IOException
Reads a FITS header from an input stream. The stream is read until the end of the last header block.- Parameters:
in
- input stream positioned at start of HDU- Returns:
- header
- Throws:
java.io.IOException
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parseCard
public static ParsedCard<?> parseCard(byte[] buf80)
Turns an 80-byte array into a ParsedCard. This will always succeed, but if the card doesn't look like a FITS header, the result will have CardType.UNKNOWN.- Parameters:
buf80
- 80-byte array giving card image
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skipHDUs
public static long skipHDUs(java.io.InputStream in, int nskip) throws java.io.IOException
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:
in
- the stream to skip through, positioned at start of HDUnskip
- the number of HDUs to skip- Returns:
- the number of bytes the stream was advanced
- Throws:
java.io.IOException
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roundUp
public static long roundUp(long value, int blockSize)
Utility method to round an integer value up to a multiple of a given block size.- Parameters:
value
- non-negative countblockSize
- non-negative size of block- Returns:
- smallest integer that is >=
count
and a multiple ofblockSize
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writeHeader
public static int writeHeader(CardImage[] cards, java.io.OutputStream out) throws java.io.IOException
Writes a FITS header whose content is supplied by an array of cards. No checks are performed on the card content. An END card must be included in the supplied array if required. Padding is written to advance to a whole number of FITS blocks.- Parameters:
cards
- cards forming content of headerout
- destination stream- Returns:
- number of bytes written, including padding
- Throws:
java.io.IOException
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writeEmptyPrimary
public static void writeEmptyPrimary(java.io.OutputStream out) throws java.io.IOException
Writes a data-less Primary HDU. It declares EXTEND = T, indicating that extension HDUs will follow.- Parameters:
out
- destination stream- Throws:
java.io.IOException
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checkColumnCount
public static void checkColumnCount(WideFits wide, int ncol) throws java.io.IOException
Checks that a table with the given number of columns can be written. If the column count is not exceeded, nothing happens, but if there are too many columns an informative IOException is thrown.- Parameters:
wide
- extended column convention - may be null for FITS standard behaviour onlyncol
- number of columns to write- Throws:
java.io.IOException
- if there are too many columns
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asNumericArray
public static java.lang.Object asNumericArray(java.lang.String txt)
Attempts to interpret a string as a formatted numeric array. The string has to be of the form "(x, x, ...)", where x has the same form as a floating point header value. Whitespace is permitted. The output will be an int[] array if the tokens all look like 32-bit integers, or a double[] array if the tokens all look like floating point numbers, or null otherwise.This is a bit hacky, it doesn't correspond to prescriptions in the FITS stanard, but it's useful for some purposes.
- Parameters:
txt
- string- Returns:
- int[] array or double[] array or null
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