I using the following class for UnZip password-protected file but unzipping to too much slow to fast it or any improvement in such class or method. Thanks in advance.
Class for Unzip Password Protect Zip file.
public class ZipDecryptInputStream extends InputStream {
private static final int[] CRC_TABLE = new int[256];
private static final int DECRYPT_HEADER_SIZE = 12;
private static final int[] LFH_SIGNATURE = {0x50, 0x4b, 0x03, 0x04};
static {
for (int i = 0; i < 256; i++) {
int r = i;
for (int j = 0; j < 8; j++) {
if ((r & 1) == 1) {
r = (r >>> 1) ^ 0xedb88320;
} else {
r >>>= 1;
}
}
CRC_TABLE[i] = r;
}
}
private final InputStream delegate;
private final String password;
private final int[] keys = new int[3];
private State state = State.SIGNATURE;
private int skipBytes;
private int compressedSize;
private int value;
private int valuePos;
private int valueInc;
public ZipDecryptInputStream(InputStream stream, String password) {
this.delegate = stream;
this.password = password;
}
@Override
public int read() throws IOException {
int result = delegate.read();
if (skipBytes == 0) {
switch (state) {
case SIGNATURE:
if (result != LFH_SIGNATURE[valuePos]) {
state = State.TAIL;
} else {
valuePos++;
if (valuePos >= LFH_SIGNATURE.length) {
skipBytes = 2;
state = State.FLAGS;
}
}
break;
case FLAGS:
if ((result & 1) == 0) {
throw new IllegalStateException("ZIP not password protected.");
}
if ((result & 64) == 64) {
throw new IllegalStateException("Strong encryption used.");
}
if ((result & 8) == 8) {
throw new IllegalStateException("Unsupported ZIP format.");
}
result -= 1;
compressedSize = 0;
valuePos = 0;
valueInc = DECRYPT_HEADER_SIZE;
state = State.COMPRESSED_SIZE;
skipBytes = 11;
break;
case COMPRESSED_SIZE:
compressedSize += result << (8 * valuePos);
result -= valueInc;
if (result < 0) {
valueInc = 1;
result += 256;
} else {
valueInc = 0;
}
valuePos++;
if (valuePos > 3) {
valuePos = 0;
value = 0;
state = State.FN_LENGTH;
skipBytes = 4;
}
break;
case FN_LENGTH:
case EF_LENGTH:
value += result << 8 * valuePos;
if (valuePos == 1) {
valuePos = 0;
if (state == State.FN_LENGTH) {
state = State.EF_LENGTH;
} else {
state = State.HEADER;
skipBytes = value;
}
} else {
valuePos = 1;
}
break;
case HEADER:
initKeys(password);
for (int i = 0; i < DECRYPT_HEADER_SIZE; i++) {
updateKeys((byte) (result ^ decryptByte()));
result = delegate.read();
}
compressedSize -= DECRYPT_HEADER_SIZE;
state = State.DATA;
// intentionally no break
case DATA:
result = (result ^ decryptByte()) & 0xff;
updateKeys((byte) result);
compressedSize--;
if (compressedSize == 0) {
valuePos = 0;
state = State.SIGNATURE;
}
break;
case TAIL:
// do nothing
}
} else {
skipBytes--;
}
return result;
}
@Override
public void close() throws IOException {
delegate.close();
super.close();
}
private void initKeys(String password) {
keys[0] = 305419896;
keys[1] = 591751049;
keys[2] = 878082192;
for (int i = 0; i < password.length(); i++) {
updateKeys((byte) (password.charAt(i) & 0xff));
}
}
private void updateKeys(byte charAt) {
keys[0] = crc32(keys[0], charAt);
keys[1] += keys[0] & 0xff;
keys[1] = keys[1] * 134775813 + 1;
keys[2] = crc32(keys[2], (byte) (keys[1] >> 24));
}
private byte decryptByte() {
int temp = keys[2] | 2;
return (byte) ((temp * (temp ^ 1)) >>> 8);
}
private int crc32(int oldCrc, byte charAt) {
return ((oldCrc >>> 8) ^ CRC_TABLE[(oldCrc ^ charAt) & 0xff]);
}
private enum State {
SIGNATURE, FLAGS, COMPRESSED_SIZE, FN_LENGTH, EF_LENGTH, HEADER, DATA, TAIL
}
}
Usage
InputStream zin = new FileInputStream(new File(zipFilePath));
ZipDecryptInputStream inputStream = new ZipDecryptInputStream(zin, "myPassWord");
ZipInputStream zis = new ZipInputStream(inputStream);
ZipEntry ze ;
while ((ze = zis.getNextEntry()) != null) {
FileOutputStream fos = new FileOutputStream(unzipAtLocation + File.separator + ze.getName());
int BUFFER = 2048;
byte[] data = new byte[BUFFER];
int count;
while ((count = zis.read(data, 0, BUFFER)) != -1) {
fos.write(data, 0, count);
}
}
zis.close();
