de.undercouch.citeproc.bibtex.PageParser Maven / Gradle / Ivy
package de.undercouch.citeproc.bibtex;
import de.undercouch.citeproc.bibtex.internal.InternalPageLexer;
import de.undercouch.citeproc.bibtex.internal.InternalPageParser;
import de.undercouch.citeproc.bibtex.internal.InternalPageParser.PagesContext;
import org.antlr.v4.runtime.CharStream;
import org.antlr.v4.runtime.CharStreams;
import org.antlr.v4.runtime.CommonTokenStream;
/**
* Parses pages
* @author Michel Kraemer
*/
public class PageParser {
/**
* Parses a given page or range of pages. If the given string cannot
* be parsed, the method will return a single page range with a literal string.
* @param pages the page or range of pages
* @return the parsed page or page ranges (never {@code null} and never empty)
*/
public static PageRanges parse(String pages) {
CharStream cs = CharStreams.fromString(pages);
InternalPageLexer lexer = new InternalPageLexer(cs);
lexer.removeErrorListeners(); // do not output errors to console
CommonTokenStream tokens = new CommonTokenStream(lexer);
InternalPageParser parser = new InternalPageParser(tokens);
parser.removeErrorListeners(); // do not output errors to console
PagesContext ctx;
try {
ctx = parser.pages();
} catch (NumberFormatException e) {
ctx = null;
}
if (ctx == null || ctx.ranges == null || ctx.ranges.isEmpty() ||
ctx.exception != null || parser.getNumberOfSyntaxErrors() > 0) {
// unparsable fall back to literal string
return new PageRanges(new PageRange(pages, null, null, null, false));
}
return ctx.ranges;
}
}