ZipInputStream类
/*
* @(#)ZipInputStream.java 1.45 09/11/10
*
* Copyright 2009 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util.zip;
import java.io.InputStream;
import java.io.IOException;
import java.io.EOFException;
import java.io.UnsupportedEncodingException;
import java.io.PushbackInputStream;
import sun.security.action.GetPropertyAction;
import java.util.jar.JarInputStream;
/**
* This class implements an input stream filter for reading files in the
* ZIP file format. Includes support for both compressed and uncompressed
* entries.
*
* @author David Connelly
* @version 1.45, 11/10/09
*/
public
class ZipInputStream extends InflaterInputStream implements ZipConstants {
private ZipEntry entry;
private int flag;
private CRC32 crc = new CRC32();
private long remaining;
private byte[] tmpbuf = new byte[512];
private static final int STORED = ZipEntry.STORED;
private static final int DEFLATED = ZipEntry.DEFLATED;
private boolean closed = false;
// this flag is set to true after EOF has reached for
// one entry
private boolean entryEOF = false;
// Used to decide what encoding to use while reading zip entries
private static final String fileEncoding = java.security.AccessController
.doPrivileged(new GetPropertyAction("sun.zip.encoding"));
/**
* Check to make sure that this stream has not been closed
*/
private void ensureOpen() throws IOException {
if (closed) {
throw new IOException("Stream closed");
}
}
/**
* Creates a new ZIP input stream.
* @param in the actual input stream
*/
public ZipInputStream(InputStream in) {
super(new PushbackInputStream(in, 512), new Inflater(true), 512);
usesDefaultInflater = true;
if(in == null) {
throw new NullPointerException("in is null");
}
}
/**
* Reads the next ZIP file entry and positions the stream at the
* beginning of the entry data.
* @return the next ZIP file entry, or null if there are no more entries
* @exception ZipException if a ZIP file error has occurred
* @exception IOException if an I/O error has occurred
*/
public ZipEntry getNextEntry() throws IOException {
ensureOpen();
if (entry != null) {
closeEntry();
}
crc.reset();
inf.reset();
if ((entry = readLOC()) == null) {
return null;
}
if (entry.method == STORED) {
remaining = entry.size;
}
entryEOF = false;
return entry;
}
/**
* Closes the current ZIP entry and positions the stream for reading the
* next entry.
* @exception ZipException if a ZIP file error has occurred
* @exception IOException if an I/O error has occurred
*/
public void closeEntry() throws IOException {
ensureOpen();
while (read(tmpbuf, 0, tmpbuf.length) != -1) ;
entryEOF = true;
}
/**
* Returns 0 after EOF has reached for the current entry data,
* otherwise always return 1.
* <p>
* Programs should not count on this method to return the actual number
* of bytes that could be read without blocking.
*
* @return 1 before EOF and 0 after EOF has reached for current entry.
* @exception IOException if an I/O error occurs.
*
*/
public int available() throws IOException {
ensureOpen();
if (entryEOF) {
return 0;
} else {
return 1;
}
}
/**
* Reads from the current ZIP entry into an array of bytes.
* If <code>len</code> is not zero, the method
* blocks until some input is available; otherwise, no
* bytes are read and <code>0</code> is returned.
* @param b the buffer into which the data is read
* @param off the start offset in the destination array <code>b</code>
* @param len the maximum number of bytes read
* @return the actual number of bytes read, or -1 if the end of the
* entry is reached
* @exception NullPointerException If <code>b</code> is <code>null</code>.
* @exception IndexOutOfBoundsException If <code>off</code> is negative,
* <code>len</code> is negative, or <code>len</code> is greater than
* <code>b.length - off</code>
* @exception ZipException if a ZIP file error has occurred
* @exception IOException if an I/O error has occurred
*/
public int read(byte[] b, int off, int len) throws IOException {
ensureOpen();
if (off < 0 || len < 0 || off > b.length - len) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}
if (entry == null) {
return -1;
}
switch (entry.method) {
case DEFLATED:
len = super.read(b, off, len);
if (len == -1) {
readEnd(entry);
entryEOF = true;
entry = null;
} else {
crc.update(b, off, len);
}
return len;
case STORED:
if (remaining <= 0) {
entryEOF = true;
entry = null;
return -1;
}
if (len > remaining) {
len = (int)remaining;
}
len = in.read(b, off, len);
if (len == -1) {
throw new ZipException("unexpected EOF");
}
crc.update(b, off, len);
remaining -= len;
if (remaining == 0 && entry.crc != crc.getValue()) {
throw new ZipException(
"invalid entry CRC (expected 0x" + Long.toHexString(entry.crc) +
" but got 0x" + Long.toHexString(crc.getValue()) + ")");
}
return len;
default:
throw new ZipException("invalid compression method");
}
}
/**
* Skips specified number of bytes in the current ZIP entry.
* @param n the number of bytes to skip
* @return the actual number of bytes skipped
* @exception ZipException if a ZIP file error has occurred
* @exception IOException if an I/O error has occurred
* @exception IllegalArgumentException if n < 0
*/
public long skip(long n) throws IOException {
if (n < 0) {
throw new IllegalArgumentException("negative skip length");
}
ensureOpen();
int max = (int)Math.min(n, Integer.MAX_VALUE);
int total = 0;
while (total < max) {
int len = max - total;
if (len > tmpbuf.length) {
len = tmpbuf.length;
}
len = read(tmpbuf, 0, len);
if (len == -1) {
entryEOF = true;
break;
}
total += len;
}
return total;
}
/**
* Closes this input stream and releases any system resources associated
* with the stream.
* @exception IOException if an I/O error has occurred
*/
public void close() throws IOException {
if (!closed) {
super.close();
closed = true;
}
}
private byte[] b = new byte[256];
/*
* Reads local file (LOC) header for next entry.
*/
private ZipEntry readLOC() throws IOException {
try {
readFully(tmpbuf, 0, LOCHDR);
} catch (EOFException e) {
return null;
}
if (get32(tmpbuf, 0) != LOCSIG) {
return null;
}
// get the entry name and create the ZipEntry first
int len = get16(tmpbuf, LOCNAM);
int blen = b.length;
if (len > blen) {
do
blen = blen * 2;
while (len > blen);
b = new byte[blen];
}
readFully(b, 0, len);
String name = getFileName(b, len);
ZipEntry e = createZipEntry(name);
// now get the remaining fields for the entry
flag = get16(tmpbuf, LOCFLG);
if ((flag & 1) == 1) {
throw new ZipException("encrypted ZIP entry not supported");
}
e.method = get16(tmpbuf, LOCHOW);
e.time = get32(tmpbuf, LOCTIM);
if ((flag & 8) == 8) {
/* "Data Descriptor" present */
if (e.method != DEFLATED) {
throw new ZipException(
"only DEFLATED entries can have EXT descriptor");
}
} else {
e.crc = get32(tmpbuf, LOCCRC);
e.csize = get32(tmpbuf, LOCSIZ);
e.size = get32(tmpbuf, LOCLEN);
}
len = get16(tmpbuf, LOCEXT);
if (len > 0) {
byte[] bb = new byte[len];
readFully(bb, 0, len);
e.setExtra(bb);
}
return e;
}
/*
* Fetches a UTF8-encoded String from the specified byte array.
*/
private static String getUTF8String(byte[] b, int off, int len) {
// First, count the number of characters in the sequence
int count = 0;
int max = off + len;
int i = off;
while (i < max) {
int c = b[i++] & 0xff;
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
// 0xxxxxxx
count++;
break;
case 12: case 13:
// 110xxxxx 10xxxxxx
if ((int)(b[i++] & 0xc0) != 0x80) {
throw new IllegalArgumentException();
}
count++;
break;
case 14:
// 1110xxxx 10xxxxxx 10xxxxxx
if (((int)(b[i++] & 0xc0) != 0x80) ||
((int)(b[i++] & 0xc0) != 0x80)) {
throw new IllegalArgumentException();
}
count++;
break;
default:
// 10xxxxxx, 1111xxxx
throw new IllegalArgumentException();
}
}
if (i != max) {
throw new IllegalArgumentException();
}
// Now decode the characters...
char[] cs = new char[count];
i = 0;
while (off < max) {
int c = b[off++] & 0xff;
switch (c >> 4) {
case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
// 0xxxxxxx
cs[i++] = (char)c;
break;
case 12: case 13:
// 110xxxxx 10xxxxxx
cs[i++] = (char)(((c & 0x1f) << 6) | (b[off++] & 0x3f));
break;
case 14:
// 1110xxxx 10xxxxxx 10xxxxxx
int t = (b[off++] & 0x3f) << 6;
cs[i++] = (char)(((c & 0x0f) << 12) | t | (b[off++] & 0x3f));
break;
default:
// 10xxxxxx, 1111xxxx
throw new IllegalArgumentException();
}
}
return new String(cs, 0, count);
}
/**
* Creates a new <code>ZipEntry</code> object for the specified
* entry name.
*
* @param name the ZIP file entry name
* @return the ZipEntry just created
*/
protected ZipEntry createZipEntry(String name) {
return new ZipEntry(name);
}
/*
* Reads end of deflated entry as well as EXT descriptor if present.
*/
private void readEnd(ZipEntry e) throws IOException {
int n = inf.getRemaining();
if (n > 0) {
((PushbackInputStream)in).unread(buf, len - n, n);
}
if ((flag & 8) == 8) {
/* "Data Descriptor" present */
readFully(tmpbuf, 0, EXTHDR);
long sig = get32(tmpbuf, 0);
if (sig != EXTSIG) { // no EXTSIG present
e.crc = sig;
e.csize = get32(tmpbuf, EXTSIZ - EXTCRC);
e.size = get32(tmpbuf, EXTLEN - EXTCRC);
((PushbackInputStream)in).unread(
tmpbuf, EXTHDR - EXTCRC - 1, EXTCRC);
} else {
e.crc = get32(tmpbuf, EXTCRC);
e.csize = get32(tmpbuf, EXTSIZ);
e.size = get32(tmpbuf, EXTLEN);
}
}
if (e.size != inf.getBytesWritten()) {
throw new ZipException(
"invalid entry size (expected " + e.size +
" but got " + inf.getBytesWritten() + " bytes)");
}
if (e.csize != inf.getBytesRead()) {
throw new ZipException(
"invalid entry compressed size (expected " + e.csize +
" but got " + inf.getBytesRead() + " bytes)");
}
if (e.crc != crc.getValue()) {
throw new ZipException(
"invalid entry CRC (expected 0x" + Long.toHexString(e.crc) +
" but got 0x" + Long.toHexString(crc.getValue()) + ")");
}
}
/*
* Reads bytes, blocking until all bytes are read.
*/
private void readFully(byte[] b, int off, int len) throws IOException {
while (len > 0) {
int n = in.read(b, off, len);
if (n == -1) {
throw new EOFException();
}
off += n;
len -= n;
}
}
/*
* Fetches unsigned 16-bit value from byte array at specified offset.
* The bytes are assumed to be in Intel (little-endian) byte order.
*/
private static final int get16(byte b[], int off) {
return (b[off] & 0xff) | ((b[off+1] & 0xff) << 8);
}
/*
* Fetches unsigned 32-bit value from byte array at specified offset.
* The bytes are assumed to be in Intel (little-endian) byte order.
*/
private static final long get32(byte b[], int off) {
return get16(b, off) | ((long)get16(b, off+2) << 16);
}
private String getFileName(byte[] b, int len) throws IOException {
String name;
try {
if (fileEncoding == null || fileEncoding.equals("") || this instanceof JarInputStream) {
name = getUTF8String(b, 0, len);
} else {
if (fileEncoding.equalsIgnoreCase("default")) {
// use platforms's default encoding
name = new String(b, 0, len);
} else {
try {
name = new String(b, 0, len, fileEncoding);
} catch (UnsupportedEncodingException UEE) {
throw new ZipException("Unable to encode entry " +
"name (sun.zip.encoding is " + fileEncoding + ")");
}
}
}
} catch (IllegalArgumentException e) {
// Alt encoding that can be used if
// the initial decoding attempt fails.
String altEncoding = java.security.AccessController
.doPrivileged(new GetPropertyAction("sun.zip.altEncoding"));
if (altEncoding == null || altEncoding.equals("") ||
this instanceof JarInputStream) {
throw e;
}
if (altEncoding.equalsIgnoreCase("default")) {
// use platform's default encoding
name = new String(b, 0, len);
} else {
try {
// use the specified encoding
name = new String(b, 0, len, altEncoding);
} catch (UnsupportedEncodingException UEE) {
throw new ZipException("Unable to encode entry " +
"name (sun.zip.altEncoding is " + altEncoding + ")");
}
}
}
return name;
}
}
这个是JAVA语言中SDK中的一个类的源代码，这个类中的private static String getUTF8String(byte[] b, int off, int len)方法声明中为什么有抛出异常自己为什么不处理或往上抛了呢。