eu.medsea.mimeutil.detector.MagicMimeEntryOperation Maven / Gradle / Ivy

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mime-util is a simple to use, small, light weight and fast open source java utility library that can detect MIME types from files, input streams, URL's and byte arrays. Due to the use of regular expressions and the java.nio packages it requires at least Java 1.4.

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package eu.medsea.mimeutil.detector;

import java.util.HashMap;
import java.util.Map;

/**
 * Quote from http://linux.die.net/man/5/magic:
 * 
 * Numeric values may be preceded by a character indicating the operation to be performed.
 * It may be =, to specify that the value from the file must equal the specified value, <,
 * to specify that the value from the file must be less than the specified value, >, to
 * specify that the value from the file must be greater than the specified value, &, to
 * specify that the value from the file must have set all of the bits that are set in the
 * specified value, ^, to specify that the value from the file must have clear any of the
 * bits that are set in the specified value, or ~, the value specified after is negated before
 * tested. x, to specify that any value will match. If the character is omitted, it is assumed
 * to be =. For all tests except string and regex, operation ! specifies that the line matches
 * if the test does not succeed.
 * 
 * 
 * For string values, the byte string from the file must match the specified byte string. The
 * operators =, < and > (but not &) can be applied to strings. The length used for
 * matching is that of the string argument in the magic file. This means that a line can match any
 * string, and then presumably print that string, by doing >\0 (because all strings are greater
 * than the null string).
 * 
 *
 * @author marco schulze - marco at nightlabs dot de
 */
final class MagicMimeEntryOperation
{
	private static final Map operationID2operation = new HashMap();

	public static final MagicMimeEntryOperation EQUALS = new MagicMimeEntryOperation('=');
	public static final MagicMimeEntryOperation LESS_THAN = new MagicMimeEntryOperation('<');
	public static final MagicMimeEntryOperation GREATER_THAN = new MagicMimeEntryOperation('>');
	public static final MagicMimeEntryOperation AND = new MagicMimeEntryOperation('&');
	public static final MagicMimeEntryOperation CLEAR = new MagicMimeEntryOperation('^');
	public static final MagicMimeEntryOperation NEGATED = new MagicMimeEntryOperation('~');
	public static final MagicMimeEntryOperation ANY = new MagicMimeEntryOperation('x');
	public static final MagicMimeEntryOperation NOT_EQUALS = new MagicMimeEntryOperation('!');

	public static MagicMimeEntryOperation getOperation(char operationID)
	{
		Character operationIDCharacter = new Character(operationID);
		return (MagicMimeEntryOperation) operationID2operation.get(operationIDCharacter);
	}

	public static MagicMimeEntryOperation getOperationForStringField(String content)
	{
		MagicMimeEntryOperation operation = getOperation(content);
		// String and regex do only support a subset of the operations => filter.
		if (EQUALS.equals(operation) || LESS_THAN.equals(operation) || GREATER_THAN.equals(operation))
			return operation;
		else
			return EQUALS;
	}

	public static MagicMimeEntryOperation getOperationForNumberField(String content)
	{
		return getOperation(content);
	}

	private static MagicMimeEntryOperation getOperation(String content)
	{
		if (content.length() == 0)
			return EQUALS;

		MagicMimeEntryOperation operation = getOperation(content.charAt(0));
		if (operation == null)
			return EQUALS;
		else
			return operation;
	}

	private static void registerOperation(MagicMimeEntryOperation operation) {
		Character operationIDCharacter = new Character(operation.getOperationID());
		if (operationID2operation.containsKey(operationIDCharacter))
			throw new IllegalStateException("Duplicate registration of operation " + operationIDCharacter);

		operationID2operation.put(operationIDCharacter, operation);
	}

	private final char operationID;

	MagicMimeEntryOperation(char operationID) {
		this.operationID = operationID;

		registerOperation(this);
	}

	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + operationID;
		return result;
	}

	public boolean equals(Object obj) {
		if (this == obj) return true;
		if (obj == null) return false;
		if (getClass() != obj.getClass()) return false;
		MagicMimeEntryOperation other = (MagicMimeEntryOperation) obj;
		return this.operationID == other.operationID;
	}

	public final char getOperationID() {
		return operationID;
	}

	public String toString() {
		return this.getClass().getName() + '[' + operationID + ']';
	}
}