FileDocCategorySizeDatePackage
ExtraFieldUtils.javaAPI DocApache Ant 1.706371Wed Dec 13 06:16:22 GMT 2006org.apache.tools.zip

ExtraFieldUtils

public class ExtraFieldUtils extends Object
ZipExtraField related methods

Fields Summary
private static Hashtable
implementations
Static registry of known extra fields.
Constructors Summary
Methods Summary
public static ZipExtraFieldcreateExtraField(ZipShort headerId)
Create an instance of the approriate ExtraField, falls back to {@link UnrecognizedExtraField UnrecognizedExtraField}.

param
headerId the header identifier
return
an instance of the appropiate ExtraField
exception
InstantiationException if unable to instantiate the class
exception
IllegalAccessException if not allowed to instatiate the class
since
1.1

        Class c = (Class) implementations.get(headerId);
        if (c != null) {
            return (ZipExtraField) c.newInstance();
        }
        UnrecognizedExtraField u = new UnrecognizedExtraField();
        u.setHeaderId(headerId);
        return u;
public static byte[]mergeCentralDirectoryData(ZipExtraField[] data)
Merges the central directory fields of the given ZipExtraFields.

param
data an array of ExtraFields
return
an array of bytes
since
1.1

        int sum = 4 * data.length;
        for (int i = 0; i < data.length; i++) {
            sum += data[i].getCentralDirectoryLength().getValue();
        }
        byte[] result = new byte[sum];
        int start = 0;
        for (int i = 0; i < data.length; i++) {
            System.arraycopy(data[i].getHeaderId().getBytes(),
                             0, result, start, 2);
            System.arraycopy(data[i].getCentralDirectoryLength().getBytes(),
                             0, result, start + 2, 2);
            byte[] local = data[i].getCentralDirectoryData();
            System.arraycopy(local, 0, result, start + 4, local.length);
            start += (local.length + 4);
        }
        return result;
public static byte[]mergeLocalFileDataData(ZipExtraField[] data)
Merges the local file data fields of the given ZipExtraFields.

param
data an array of ExtraFiles
return
an array of bytes
since
1.1

        int sum = 4 * data.length;
        for (int i = 0; i < data.length; i++) {
            sum += data[i].getLocalFileDataLength().getValue();
        }
        byte[] result = new byte[sum];
        int start = 0;
        for (int i = 0; i < data.length; i++) {
            System.arraycopy(data[i].getHeaderId().getBytes(),
                             0, result, start, 2);
            System.arraycopy(data[i].getLocalFileDataLength().getBytes(),
                             0, result, start + 2, 2);
            byte[] local = data[i].getLocalFileDataData();
            System.arraycopy(local, 0, result, start + 4, local.length);
            start += (local.length + 4);
        }
        return result;
public static ZipExtraField[]parse(byte[] data)
Split the array into ExtraFields and populate them with the give data.

param
data an array of bytes
return
an array of ExtraFields
since
1.1
throws
ZipException on error

        Vector v = new Vector();
        int start = 0;
        while (start <= data.length - 4) {
            ZipShort headerId = new ZipShort(data, start);
            int length = (new ZipShort(data, start + 2)).getValue();
            if (start + 4 + length > data.length) {
                throw new ZipException("data starting at " + start
                    + " is in unknown format");
            }
            try {
                ZipExtraField ze = createExtraField(headerId);
                ze.parseFromLocalFileData(data, start + 4, length);
                v.addElement(ze);
            } catch (InstantiationException ie) {
                throw new ZipException(ie.getMessage());
            } catch (IllegalAccessException iae) {
                throw new ZipException(iae.getMessage());
            }
            start += (length + 4);
        }
        if (start != data.length) { // array not exhausted
            throw new ZipException("data starting at " + start
                + " is in unknown format");
        }

        ZipExtraField[] result = new ZipExtraField[v.size()];
        v.copyInto(result);
        return result;
public static voidregister(java.lang.Class c)
Register a ZipExtraField implementation.

The given class must have a no-arg constructor and implement the {@link ZipExtraField ZipExtraField interface}.

param
c the class to register
since
1.1

        implementations = new Hashtable();
        register(AsiExtraField.class);
        register(JarMarker.class);
    
        try {
            ZipExtraField ze = (ZipExtraField) c.newInstance();
            implementations.put(ze.getHeaderId(), c);
        } catch (ClassCastException cc) {
            throw new RuntimeException(c + " doesn\'t implement ZipExtraField");
        } catch (InstantiationException ie) {
            throw new RuntimeException(c + " is not a concrete class");
        } catch (IllegalAccessException ie) {
            throw new RuntimeException(c + "\'s no-arg constructor is not public");
        }