Miha-x64/Xml.java

## Xml.java

import java.io.IOException;
import java.io.UncheckedIOException;

/**
 * XML escaping utils.
 *
 * Source: https://gist.github.com/Miha-x64/4ed50f1d5593e45a452efbf456aa1db4
 */
public final class Xml {
    private Xml() {}

    private static final long TEXT_ESCAPE = 1L << '&' | 1L << '<';
    private static final long DOUBLE_QUOTED_ATTR_ESCAPE = TEXT_ESCAPE | 1L << '"';
    private static final long SINGLE_QUOTED_ATTR_ESCAPE = TEXT_ESCAPE | 1L << '\'';
    private static final long ESCAPES = DOUBLE_QUOTED_ATTR_ESCAPE | SINGLE_QUOTED_ATTR_ESCAPE;

    // 'quot' and 'apos' are 1 char longer than '#34' and '#39' which I've decided to use
    private static final String REPLACEMENTS = "&#34;&amp;&#39;&lt;";
    private static final int REPL_SLICES = /*  [0,   5,   10,  15, 19) */ 5<<5 | 10<<10 | 15<<15 | 19<<20;
    // These 5-bit numbers packed into a single int are indices within REPLACEMENTS which is a 'flat' String[]

    public static <A extends Appendable> A appendEscapedForTagBody(A appendable, CharSequence content) {
        appendEscaped(appendable, content, TEXT_ESCAPE);
        return appendable;
    }
    public static <A extends Appendable> A appendEscapedForDoubleQuotedAttrValue(A appendable, CharSequence content) {
        appendEscaped(appendable, content, DOUBLE_QUOTED_ATTR_ESCAPE);
        return appendable;
    }
    public static <A extends Appendable> A appendEscapedForSingleQuotedAttrValue(A appendable, CharSequence content) {
        appendEscaped(appendable, content, SINGLE_QUOTED_ATTR_ESCAPE);
        return appendable;
    }
    private static void appendEscaped(Appendable builder, CharSequence content, long escapes) {
        try {
            int startIdx = 0, len = content.length();
            for (int i = 0; i < len; i++) {
                char c = content.charAt(i);
                long one;
                if (((c & 63) == c) && ((one = 1L << c) & escapes) != 0) {
                // -^^^^^^^^^^^^^^^   -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                // |                  | take only dangerous characters
                // | java shifts longs by 6 least significant bits,
                // | e. g. << 0b110111111 is same as >> 0b111111. Filter out bigger characters

                    int index = Long.bitCount(ESCAPES & (one - 1));
                    builder
                            .append(content, startIdx, i /* exclusive */)
                            .append(REPLACEMENTS, REPL_SLICES >>> (5 * index) & 31, REPL_SLICES >>> (5 * (index + 1)) & 31);
                    startIdx = i + 1;
                }
            }
            builder.append(content, startIdx, len);
        } catch (IOException e) {
            // typically, our Appendable is StringBuilder which does not throw; also,
            // there's no way to declare 'if A#append() throws E, then appendEscaped() throws E, too'
            throw new UncheckedIOException(e);
        }
    }

    public static void main(String[] args) {
        StringBuilder sb =
            new StringBuilder("<!DOCTYPE html>\n<html lang=\"en\">\n<head><title>Test</title></head>\n<body>\n\n");
        appendEscapedForDoubleQuotedAttrValue(sb.append("<p title=\""), "<\"I'm double-quoted!\">").append("\">");
        appendEscapedForTagBody(sb, "<\"Hello!\">").append("</p>\n");
        appendEscapedForSingleQuotedAttrValue(sb.append("<p title='"), "<\"I'm single-quoted!\">").append("'>");
        appendEscapedForTagBody(sb, "<\"Goodbye!\">").append("</p>\n\n</body>\n</html>");
        String escaped = sb.toString();
        String expected = "<!DOCTYPE html>\n<html lang=\"en\">\n<head><title>Test</title></head>\n<body>\n\n" +
            "<p title=\"&lt;&#34;I'm double-quoted!&#34;>\">&lt;\"Hello!\"></p>\n" +
            "<p title='&lt;\"I&#39;m single-quoted!\">'>&lt;\"Goodbye!\"></p>\n" +
            "\n</body>\n</html>";
        if (!expected.equals(escaped))
            throw new AssertionError("expected:<" + expected + "> but was:<" + escaped + ">");
        System.out.println(escaped);
    }

}

	import java.io.IOException;
	import java.io.UncheckedIOException;

	/**
	* XML escaping utils.
	*
	* Source: https://gist.github.com/Miha-x64/4ed50f1d5593e45a452efbf456aa1db4
	*/
	public final class Xml {
	private Xml() {}

	private static final long TEXT_ESCAPE = 1L << '&' \| 1L << '<';
	private static final long DOUBLE_QUOTED_ATTR_ESCAPE = TEXT_ESCAPE \| 1L << '"';
	private static final long SINGLE_QUOTED_ATTR_ESCAPE = TEXT_ESCAPE \| 1L << '\'';
	private static final long ESCAPES = DOUBLE_QUOTED_ATTR_ESCAPE \| SINGLE_QUOTED_ATTR_ESCAPE;

	// 'quot' and 'apos' are 1 char longer than '#34' and '#39' which I've decided to use
	private static final String REPLACEMENTS = ""&'<";
	private static final int REPL_SLICES = /* [0, 5, 10, 15, 19) */ 5<<5 \| 10<<10 \| 15<<15 \| 19<<20;
	// These 5-bit numbers packed into a single int are indices within REPLACEMENTS which is a 'flat' String[]

	public static <A extends Appendable> A appendEscapedForTagBody(A appendable, CharSequence content) {
	appendEscaped(appendable, content, TEXT_ESCAPE);
	return appendable;
	}
	public static <A extends Appendable> A appendEscapedForDoubleQuotedAttrValue(A appendable, CharSequence content) {
	appendEscaped(appendable, content, DOUBLE_QUOTED_ATTR_ESCAPE);
	return appendable;
	}
	public static <A extends Appendable> A appendEscapedForSingleQuotedAttrValue(A appendable, CharSequence content) {
	appendEscaped(appendable, content, SINGLE_QUOTED_ATTR_ESCAPE);
	return appendable;
	}
	private static void appendEscaped(Appendable builder, CharSequence content, long escapes) {
	try {
	int startIdx = 0, len = content.length();
	for (int i = 0; i < len; i++) {
	char c = content.charAt(i);
	long one;
	if (((c & 63) == c) && ((one = 1L << c) & escapes) != 0) {
	// -^^^^^^^^^^^^^^^ -^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	// \| \| take only dangerous characters
	// \| java shifts longs by 6 least significant bits,
	// \| e. g. << 0b110111111 is same as >> 0b111111. Filter out bigger characters

	int index = Long.bitCount(ESCAPES & (one - 1));
	builder
	.append(content, startIdx, i /* exclusive */)
	.append(REPLACEMENTS, REPL_SLICES >>> (5 * index) & 31, REPL_SLICES >>> (5 * (index + 1)) & 31);
	startIdx = i + 1;
	}
	}
	builder.append(content, startIdx, len);
	} catch (IOException e) {
	// typically, our Appendable is StringBuilder which does not throw; also,
	// there's no way to declare 'if A#append() throws E, then appendEscaped() throws E, too'
	throw new UncheckedIOException(e);
	}
	}

	public static void main(String[] args) {
	StringBuilder sb =
	new StringBuilder("<!DOCTYPE html>\n<html lang=\"en\">\n<head><title>Test</title></head>\n<body>\n\n");
	appendEscapedForDoubleQuotedAttrValue(sb.append("<p title=\""), "<\"I'm double-quoted!\">").append("\">");
	appendEscapedForTagBody(sb, "<\"Hello!\">").append("</p>\n");
	appendEscapedForSingleQuotedAttrValue(sb.append("<p title='"), "<\"I'm single-quoted!\">").append("'>");
	appendEscapedForTagBody(sb, "<\"Goodbye!\">").append("</p>\n\n</body>\n</html>");
	String escaped = sb.toString();
	String expected = "<!DOCTYPE html>\n<html lang=\"en\">\n<head><title>Test</title></head>\n<body>\n\n" +
	"<p title=\"<"I'm double-quoted!">\"><\"Hello!\"></p>\n" +
	"<p title='<\"I'm single-quoted!\">'><\"Goodbye!\"></p>\n" +
	"\n</body>\n</html>";
	if (!expected.equals(escaped))
	throw new AssertionError("expected:<" + expected + "> but was:<" + escaped + ">");
	System.out.println(escaped);
	}

	}