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/*
* #%L
* nom.tam FITS library
* %%
* Copyright (C) 2004 - 2024 nom-tam-fits
* %%
* This is free and unencumbered software released into the public domain.
*
* Anyone is free to copy, modify, publish, use, compile, sell, or
* distribute this software, either in source code form or as a compiled
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* In jurisdictions that recognize copyright laws, the author or authors
* of this software dedicate any and all copyright interest in the
* software to the public domain. We make this dedication for the benefit
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*/
package nom.tam.fits;
import nom.tam.fits.FitsFactory.FitsSettings;
import static nom.tam.fits.header.Standard.CONTINUE;
/**
* Converts {@link HeaderCard}s into one or more 80-character wide FITS header records. It is a replacement for
* {@link nom.tam.fits.utilities.FitsLineAppender}, which is still available for external use for backward
* compatibility, but is no longer used internally in this library itself.
*
* @author Attila Kovacs
*
* @since 1.16
*/
class HeaderCardFormatter {
/**
* The FITS settings to use, such as support for long strings, support for HIERARCH-style cards, or the use of 'D'
* for high-precision exponential values. These settings control when and how header cards are represented exactly
* in the FITS header.
*/
private FitsSettings settings;
/** The length of two single quotes. */
private static final int QUOTES_LENGTH = 2;
/**
* Character sequence that comes after a value field, and before the comment string in the header record. While only
* a '/' character is really required, we like to add spaces around it for a more pleasing visual of the resulting
* header record. The space before the '/' is strongly recommended by the FITS standard.
*/
private static final String COMMENT_PREFIX = " / ";
/**
* Long string comments should not add a space after the '/', because we want to preserve spaces in continued long
* string comments, hece we start the comment immediately after the '/' to ensure that internal spaces in wrapped
* comments remain intact and properly accounted for. The space before the '/' is strongly recommended by the FITS
* standard.
*/
private static final String LONG_COMMENT_PREFIX = " /";
/**
* In older FITS standards there was a requirement that a closing quote for string values may not come before byte
* 20 (counted from 1) in the header record. To ensure that, strings need to be padded with blank spaces to push the
* closing quote out to that position, if necessary. While it is no longer required by the current FITS standard, it
* is possible (or even likely) that some existing tools rely on the earlier requirement. Therefore, we will abide
* by the requirements of the older standard. (In the future, we may make this requirement optional, and
* controllable through the API).
*/
private static final int MIN_STRING_END = 19;
/** whatever fits after "CONTINUE '' /" */
private static final int MAX_LONG_END_COMMENT = 68 - LONG_COMMENT_PREFIX.length();
/**
* Instantiates a new header card formatter with the specified FITS settings.
*
* @param settings the local FITS settings to use by this card formatter.
*
* @see #HeaderCardFormatter()
*/
HeaderCardFormatter(FitsSettings settings) {
this.settings = settings;
}
/**
* Converts a {@link HeaderCard} to one or more 80-character wide FITS header records following the FITS rules, and
* the various conventions that are allowed by the FITS settings with which this card formatter instance was
* created.
*
* @param card the header card object
*
* @return the correspoinding FITS header snipplet, as one or more 80-character wide
* header 'records'.
*
* @throws HierarchNotEnabledException if the cards is a HIERARCH-style card, but support for HIERARCH keywords
* is not enabled in the FITS settings used by this formatter.
* @throws LongValueException if the (non-string) value stored in the card cannot fit in the header
* record.
* @throws LongStringsNotEnabledException if the card contains a string value that cannot fit into a single header
* record, and the use of long string is not enabled in the FITS settings
* used by this formatter.
*
* @see FitsFactory#setLongStringsEnabled(boolean)
*/
String toString(HeaderCard card)
throws HierarchNotEnabledException, LongValueException, LongStringsNotEnabledException {
StringBuffer buf = new StringBuffer(HeaderCard.FITS_HEADER_CARD_SIZE);
appendKey(buf, card);
int valueStart = appendValue(buf, card);
int valueEnd = buf.length();
appendComment(buf, card);
if (!card.isCommentStyleCard()) {
// Strings must be left aligned with opening quote in byte 11 (counted from 1)
realign(buf, card.isStringValue() ? valueEnd : valueStart, valueEnd);
}
pad(buf);
return HeaderCard.sanitize(new String(buf));
}
/**
* Adds the FITS keyword to the header record (normally at the beginning).
*
* @param buf The string buffer in which we are building the header record.
* @param card The header card to be formatted.
*
* @throws HierarchNotEnabledException if the card contains a HIERARCH-style long keyword, but support for these has
* not been enabled in the settings used by this formatter.
* @throws LongValueException if the HIERARCH keyword is itself too long to fit on the record without
* leaving a minimum amount of space for a value.
*
* @see FitsFactory#setUseHierarch(boolean)
*/
private void appendKey(StringBuffer buf, HeaderCard card) throws HierarchNotEnabledException, LongValueException {
String key = card.getKey();
if (card.hasHierarchKey()) {
if (!settings.isUseHierarch()) {
throw new HierarchNotEnabledException(key);
}
key = settings.getHierarchKeyFormatter().toHeaderString(key);
if (key.length() > HeaderCard.MAX_HIERARCH_KEYWORD_LENGTH) {
// Truncate HIERARCH keywords as necessary to fit.
// This is really just a second parachute here. Normally, HeaderCards
// won't allow creation or setting longer keywords...
throw new LongValueException(key, HeaderCard.MAX_HIERARCH_KEYWORD_LENGTH);
}
} else {
// Just to be certain, we'll make sure base keywords are upper-case, if they
// were not already.
key = key.toUpperCase();
}
buf.append(key);
padTo(buf, HeaderCard.MAX_KEYWORD_LENGTH);
}
/**
* Adds the FITS value to the header record (normally after the keyword), including the standard "= " assigment
* marker in front of it, or the non-standard "=" (without space after) if
* {@link FitsFactory#setSkipBlankAfterAssign(boolean)} is set true.
*
* @param buf The string buffer in which we are building the header record.
* @param card The header card to be formatted.
*
* @return the buffer position at which the appended value starts, or the last
* posirtion if a value was not added at all. (This is used for
* realigning later...)
*
* @throws LongValueException if the card contained a non-string value that is too long to fit in the
* space available in the current record.
* @throws LongStringsNotEnabledException if the card contains a string value that cannot fit into a single header
* record, and the use of long string is not enabled in the FITS settings
* used by this formatter.
*/
private int appendValue(StringBuffer buf, HeaderCard card) throws LongValueException, LongStringsNotEnabledException {
String value = card.getValue();
if (card.isCommentStyleCard()) {
// omment-style card. Nothing to do here...
return buf.length();
}
// Add assignment sequence "= "
buf.append(getAssignString());
if (value == null) {
// 'null' value, nothing more to append.
return buf.length();
}
int valueStart = buf.length();
if (card.isStringValue()) {
int from = appendQuotedValue(buf, card, 0);
while (from < value.length()) {
pad(buf);
buf.append(CONTINUE.key() + " ");
from += appendQuotedValue(buf, card, from);
}
// TODO We prevent the creation of cards with longer values, so the following check is dead code here.
// } else if (value.length() > available) {
// throw new LongValueException(available, card.getKey(), card.getValue());
} else {
append(buf, value, 0);
}
return valueStart;
}
/**
* Returns the minimum size of a truncated header comment. When truncating header comments we should preserve at
* least the first word of the comment string wholly...
*
* @param card The header card to be formatted.
*
* @return the length of the first word in the comment string
*/
private int getMinTruncatedCommentSize(HeaderCard card) {
String comment = card.getComment();
// TODO We check for null before calling, so this is dead code here...
// if (comment == null) {
// return 0;
// }
int firstWordLength = comment.indexOf(' ');
if (firstWordLength < 0) {
firstWordLength = comment.length();
}
return COMMENT_PREFIX.length() + firstWordLength;
}
/**
* Appends the comment to the header record, or as much of it as possible, but never less than the first word (at
* minimum).
*
* @param buf The string buffer in which we are building the header record.
* @param card The header card to be formatted.
*
* @return true if the comment was fully represented in the record, or false if it
* was truncated or fully ommitted.
*/
private boolean appendComment(StringBuffer buf, HeaderCard card) {
String comment = card.getComment();
if ((comment == null) || comment.isEmpty()) {
return true;
}
int available = getAvailable(buf);
boolean longCommentOK = FitsFactory.isLongStringsEnabled() && card.isStringValue();
if (!card.isCommentStyleCard() && longCommentOK) {
if (COMMENT_PREFIX.length() + card.getComment().length() > available) {
// No room for a complete regular comment, but we can do a long string comment...
appendLongStringComment(buf, card);
return true;
}
}
if (card.isCommentStyleCard()) {
// ' ' instead of '= '
available--;
} else {
// ' / '
available -= COMMENT_PREFIX.length();
if (getMinTruncatedCommentSize(card) > available) {
if (!longCommentOK) {
return false;
}
}
}
if (card.isCommentStyleCard()) {
buf.append(' ');
} else {
buf.append(COMMENT_PREFIX);
}
if (available >= comment.length()) {
buf.append(comment);
return true;
}
buf.append(comment.substring(0, available));
return false;
}
/**
* Realigns the header record (single records only!) for more pleasing visual appearance by adding padding after a
* string value, or before a non-string value, as necessary to push the comment field to the alignment position, if
* it's possible without truncating the existing record.
*
* @param buf The string buffer in which we are building the header record.
* @param at The position at which to insert padding
* @param from The position in the record that is to be pushed to the alignment position.
*
* @return true if the card was successfully realigned. Otherwise false.
*/
private boolean realign(StringBuffer buf, int at, int from) {
if ((buf.length() >= HeaderCard.FITS_HEADER_CARD_SIZE) || (from >= Header.getCommentAlignPosition())) {
// We are beyond the alignment point already...
return false;
}
return realign(buf, at, from, Header.getCommentAlignPosition());
}
/**
* Realigns the header record (single records only!) for more pleasing visual appearance by adding padding after a
* string value, or before a non-string value, as necessary to push the comment field to the specified alignment
* position, if it's possible without truncating the existing record
*
* @param buf The string buffer in which we are building the header record.
* @param at The position at which to insert padding
* @param from The position in the record that is to be pushed to the alignment position.
* @param to The new alignment position.
*
* @return true if the card was successfully realigned. Otherwise false.
*/
private boolean realign(StringBuffer buf, int at, int from, int to) {
int spaces = to - from;
if (spaces > getAvailable(buf)) {
// No space left in card to align the the specified position.
return false;
}
StringBuffer sBuf = new StringBuffer(spaces);
while (--spaces >= 0) {
sBuf.append(' ');
}
buf.insert(at, sBuf.toString());
return true;
}
/**
* Adds a long string comment. When long strings are enabled, it is possible to fully preserve a comment of any
* length after a string value, by wrapping into multiple records with CONTINUE keywords. Crucially, we will want to
* do this in a way as to preserve internal spaces within the comment, when wrapped into multiple records.
*
* @param buf The string buffer in which we are building the header record.
* @param card The header card to be formatted.
*/
private void appendLongStringComment(StringBuffer buf, HeaderCard card) {
// We can wrap the comment to our delight, with CONTINUE!
int iLast = buf.length() - 1;
String comment = card.getComment();
// We need to amend the last string to end with '&'
if (getAvailable(buf) >= LONG_COMMENT_PREFIX.length() + comment.length()) {
// We can append the entire comment, easy...
buf.append(LONG_COMMENT_PREFIX);
append(buf, comment, 0);
return;
}
// Add '&' to the end of the string value.
// appendQuotedValue() must always leave space for it!
buf.setCharAt(iLast, '&');
buf.append("'");
int from = 0;
int available = getAvailable(buf);
// If there is room for a standard inline comment, then go for it
if (available < COMMENT_PREFIX.length()) {
// Add a CONTINUE card with an empty string and try again...
pad(buf);
buf.append(CONTINUE.key() + " ''");
appendComment(buf, card);
return;
}
buf.append(COMMENT_PREFIX);
from = append(buf, comment, 0);
// Now add records as needed to write the comment fully...
while (from < comment.length()) {
pad(buf);
buf.append(CONTINUE.key() + " ");
buf.append((comment.length() >= from + MAX_LONG_END_COMMENT) ? "'&'" : "''");
buf.append(LONG_COMMENT_PREFIX);
from += append(buf, comment, from);
}
}
/**
* Appends as many characters as possible from a string, starting at the specified string position, into the header
* record.
*
* @param buf The string buffer in which we are building the header record.
* @param text The string from which to append characters up to the end of the record.
* @param from The starting position in the string
*
* @return the number of characters deposited into the header record from the string after the starting
* position.
*/
private int append(StringBuffer buf, String text, int from) {
int available = getAvailable(buf);
int n = Math.min(available, text.length() - from);
if (n < 1) {
return 0;
}
for (int i = 0; i < n; i++) {
buf.append(text.charAt(from + i));
}
return n;
}
/**
* Appends quoted text from the specified string position, until the end of the string is reached, or until the
* 80-character header record is full. It replaces quotes in the string with doubled quotes, while making sure that
* not unclosed quotes are left and there is space for an '&' character for
*
* @param buf The string buffer in which we are building the header record.
* @param card The header card whose value to quote in the header record.
* @param from The starting position in the string.
*
* @return the number of characters consumed from the string, which may be different from the number of
* characters deposited as each single quote in the input string is represented as 2 single quotes
* in the record.
*/
private int appendQuotedValue(StringBuffer buf, HeaderCard card, int from) {
// Always leave room for an extra & character at the end...
int available = getAvailable(buf) - QUOTES_LENGTH;
// If long strings are enabled leave space for '&' at the end.
if (FitsFactory.isLongStringsEnabled() && card.getComment() != null) {
if (card.getComment().length() > 0) {
available--;
}
}
String text = card.getValue();
// TODO We check for null before calling, so this is dead code here...
// if (text == null) {
// return 0;
// }
// The the remaining part of the string fits in the space with the
// quoted quotes, then it's easy...
if (available >= text.length() - from) {
String escaped = text.substring(from).replace("'", "''");
if (escaped.length() <= available) {
buf.append('\'');
buf.append(escaped);
// Earlier versions of the FITS standard required that the closing quote
// does not come before byte 20. It's no longer required but older tools
// may still expect it, so let's conform. This only affects single
// record card, but not continued long strings...
if (buf.length() < MIN_STRING_END) {
padTo(buf, MIN_STRING_END);
}
buf.append('\'');
return text.length() - from;
}
}
if (!FitsFactory.isLongStringsEnabled()) {
throw new LongStringsNotEnabledException(card.getKey() + "= " + card.getValue());
}
// Now, we definitely need space for '&' at the end...
available = getAvailable(buf) - QUOTES_LENGTH - 1;
// We need room for an '&' character at the end also...
// TODO Again we prevent this ever occuring before we reach this point, so it is dead code...
// if (available < 1) {
// return 0;
// }
// Opening quote
buf.append("'");
// For counting the characters consumed from the input
int consumed = 0;
for (int i = 0; i < available; i++, consumed++) {
// TODO We already know we cannot show the whole string on one line, so this is dead code...
// if (from + i >= text.length()) {
// // Reached end of string;
// break;
// }
char c = text.charAt(from + consumed);
if (c == '\'') {
// Quoted quotes take up 2 spaces...
i++;
if (i + 1 >= available) {
// Otherwise leave the value quote unconsumed.
break;
}
// Only append the quoted quote if there is room for both.
buf.append("''");
} else {
// Append a non-quote character.
buf.append(c);
}
}
// & and Closing quote
buf.append("&'");
return consumed;
}
/**
* Adds a specific amount of padding (empty spaces) in the header record.
*
* @param buf The string buffer in which we are building the header record.
* @param n the number of empty spaces to add.
*/
private void pad(StringBuffer buf, int n) {
for (int i = n; --i >= 0;) {
buf.append(' ');
}
}
/**
* Pads the current header record with empty spaces to up to the end of the 80-character record.
*
* @param buf The string buffer in which we are building the header record.
*/
private void pad(StringBuffer buf) {
pad(buf, getAvailable(buf));
}
/**
* Adds padding (empty spaces) in the header record, up to the specified position within the record.
*
* @param buf The string buffer in which we are building the header record.
* @param to The position in the record to which to pad with spaces.
*/
private void padTo(StringBuffer buf, int to) {
for (int pos = buf.length() % HeaderCard.FITS_HEADER_CARD_SIZE; pos < to; pos++) {
buf.append(' ');
}
}
/**
* Returns the number of characters available for remaining fields in the current record. Empty records will return
* 0.
*
* @param buf The string buffer in which we are building the header record.
*
* @return the number of characters still available in the currently started 80-character header record. Empty
* records will return 0.
*/
private int getAvailable(StringBuffer buf) {
return (HeaderCard.FITS_HEADER_CARD_SIZE - buf.length() % HeaderCard.FITS_HEADER_CARD_SIZE)
% HeaderCard.FITS_HEADER_CARD_SIZE;
}
/**
* Returns the assignment string to use between the keyword and the value. The FITS standard requires the
* 2-character sequence "= ", but for some reason we allow to skip the required space after the '=' if
* {@link FitsFactory#setSkipBlankAfterAssign(boolean)} is set to true...
*
* @return The character sequence to insert between the keyword and the value.
*
* @see #getAssignLength()
*/
@SuppressWarnings("deprecation")
static String getAssignString() {
return FitsFactory.isSkipBlankAfterAssign() ? "=" : "= ";
}
/**
* Returns the number of characters we use for assignment. Normally, it should be 2 as per FITS standard, but if
* {@link FitsFactory#setSkipBlankAfterAssign(boolean)} is set to true, it may be only 1.
*
* @return The number of characters that should be between the keyword and the value indicating assignment.
*
* @see #getAssignString()
*/
@SuppressWarnings("deprecation")
static int getAssignLength() {
int n = 1;
if (!FitsFactory.isSkipBlankAfterAssign()) {
n++;
}
return n;
}
}
