來自:http://www.cnjm.net/tech/article4729.html
超級短小精悍的ZIP解壓縮類，只有280行java代碼，混淆並壓縮後的class文件僅4K左右，特別適用於J2ME開發。
解壓縮算法來自網上那個著名的GZIP.java，我只添加了解析ZIP文件格式的部分。
list()方法：
列出zip包中所有的文件及目錄，列出的是包括路徑的全名，比如文件"dir1/dir2/file.txt"，或目錄"dir1/dir2/"，注意路徑分隔符是正斜槓'/'，目錄的最後一個字符一定是'/'。
get(String filename)方法：
從zip包中解壓縮給定名字的文件，返回字節數組。
ZipMe(InputStream is)：
從一個輸入流讀取zip文件，可以是jar包中的文件，也可以是通過FileConnection獲取的手機文件系統中的文件，或從網絡上下載的zip包。
下面的例子代碼訪問jar包中的zip文件並逐一解壓縮包中的所有文件：
InputStream is = "".getClass().getResourceAsStream("/res/test.zip");
ZipMe file = new ZipMe(is);
is.close();
Vector p = file.list();
for (int i = 0; i < p.size(); i++) {
String name = (String) p.get(i);
byte[] bb = file.get(name);
System.out.println("file: " + name + " / data_len: " + (bb != null ? bb.length : -1));
}
====================================================
package net.cnjm.j2me.utils;
import java.io.*;
import java.util.*;
public class ZipMe {
private static final int BTYPE_NONE = 0;
private static final int BTYPE_DYNAMIC = 2;
private static final int MAX_BITS = 16;
private static final int MAX_CODE_LITERALS = 287;
private static final int MAX_CODE_DISTANCES = 31;
private static final int MAX_CODE_LENGTHS = 18;
private static final int EOB_CODE = 256;
private static final int LENGTH_EXTRA_BITS[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1,
1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 99, 99 };
private static final int LENGTH_VALUES[] = { 3, 4, 5, 6, 7, 8, 9, 10, 11,
13, 15, 17, 19, 23, 27, 31, 35, 43, 51, 59, 67, 83, 99, 115, 131,
163, 195, 227, 258, 0, 0 };
private static final int DISTANCE_EXTRA_BITS[] = { 0, 0, 0, 0, 1, 1, 2, 2,
3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12,
13, 13 };
private static final int DISTANCE_VALUES[] = { 1, 2, 3, 4, 5, 7, 9, 13, 17,
25, 33, 49, 65, 97, 129, 193, 257, 385, 513, 769, 1025, 1537, 2049,
3073, 4097, 6145, 8193, 12289, 16385, 24577 };
private static final int DYNAMIC_LENGTH_ORDER[] = { 16, 17, 18, 0, 8, 7, 9,
6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
private int curIndex, curByte, curBit;
public final byte[] inflate(byte data[], int startIdx, int size) {
curIndex = startIdx;
byte ret[] = new byte[size];
int idx, bfinal, btype;
idx = bfinal = btype = curByte = curBit = 0;
do {
bfinal = readBits(data, 1);
btype = readBits(data, 2);
if (btype == BTYPE_NONE) {
curBit = 0;
// LEN.
int len = readBits(data, 16);
// NLEN.
readBits(data, 16);
System.arraycopy(data, curIndex, ret, idx, len);
curIndex += len;
idx += len;
} else {
int literalTree[], distanceTree[];
if (btype == BTYPE_DYNAMIC) {
int hlit = readBits(data, 5) + 257;
int hdist = readBits(data, 5) + 1;
int hclen = readBits(data, 4) + 4;
byte lengthBits[] = new byte[MAX_CODE_LENGTHS + 1];
for (int i = 0; i < hclen; i++)
lengthBits[DYNAMIC_LENGTH_ORDER[i]] = (byte) readBits(data, 3);
int lengthTree[] = huffmanTree(lengthBits, MAX_CODE_LENGTHS);
literalTree = huffmanTree(codeLengths(data,
lengthTree, hlit), hlit - 1);
distanceTree = huffmanTree(codeLengths(data,
lengthTree, hdist), hdist - 1);
} else {
byte literalBits[] = new byte[MAX_CODE_LITERALS + 1];
for (int i = 144; --i >= 0; literalBits[i] = 8);
for (int i = 256; --i >= 144; literalBits[i] = 9);
for (int i = 280; --i >= 256; literalBits[i] = 7);
for (int i = 288; --i >= 280; literalBits[i] = 8);
literalTree = huffmanTree(literalBits, MAX_CODE_LITERALS);
byte distanceBits[] = new byte[MAX_CODE_DISTANCES + 1];
for (int i = distanceBits.length; --i >= 0; distanceBits[i] = 5);
distanceTree = huffmanTree(distanceBits, MAX_CODE_DISTANCES);
}
int code = 0, leb = 0, deb = 0;
while ((code = readCode(data, literalTree)) != EOB_CODE) {
if (code > EOB_CODE) {
code -= 257;
int length = LENGTH_VALUES[code];
if ((leb = LENGTH_EXTRA_BITS[code]) > 0)
length += readBits(data, leb);
code = readCode(data, distanceTree);
int distance = DISTANCE_VALUES[code];
if ((deb = DISTANCE_EXTRA_BITS[code]) > 0)
distance += readBits(data, deb);
int offset = idx - distance;
while (distance < length) {
System.arraycopy(ret, offset, ret, idx, distance);
idx += distance;
length -= distance;
distance <<= 1;
}
System.arraycopy(ret, offset, ret, idx, length);
idx += length;
} else {
ret[idx++] = (byte) code;
}
}
}
} while (bfinal == 0);
return ret;
}
private final int readBits(byte bb[], int n) {
int data = (curBit == 0 ? (curByte = (bb[curIndex++] & 0xFF))
: (curByte >> curBit));
for (int i = (8 - curBit); i < n; i += 8) {
curByte = (bb[curIndex++] & 0xFF);
data |= (curByte << i);
}
curBit = (curBit + n) & 7;
return (data & ((1 << n) - 1));
}
private final int readCode(byte bb[], int tree[]) {
int node = tree[0];
while (node >= 0) {
if (curBit == 0) curByte = (bb[curIndex++] & 0xFF);
node = (((curByte & (1 << curBit)) == 0) ? tree[node >> 16]
: tree[node & 0xFFFF]);
curBit = (curBit + 1) & 7;
}
return (node & 0xFFFF);
}
private final byte[] codeLengths(byte bb[], int lentree[], int count) {
byte bits[] = new byte[count];
for (int i = 0, code = 0, last = 0; i < count;) {
code = readCode(bb, lentree);
if (code >= 16) {
int repeat = 0;
if (code == 16) {
repeat = 3 + readBits(bb, 2);
code = last;
} else {
if (code == 17)
repeat = 3 + readBits(bb, 3);
else
repeat = 11 + readBits(bb, 7);
code = 0;
}
while (repeat-- > 0)
bits[i++] = (byte) code;
} else {
bits[i++] = (byte) code;
}
last = code;
}
return bits;
}
private final static int[] huffmanTree(byte bits[], int maxCode) {
int bl_count[] = new int[MAX_BITS + 1];
for (int i = 0, n = bits.length; i < n; i++)
bl_count[bits[i]]++;
int code = 0;
bl_count[0] = 0;
int next_code[] = new int[MAX_BITS + 1];
for (int i = 1; i <= MAX_BITS; i++)
next_code[i] = code = (code + bl_count[i - 1]) << 1;
int tree[] = new int[(maxCode << 1) + MAX_BITS];
int treeInsert = 1;
for (int i = 0; i <= maxCode; i++) {
int len = bits[i];
if (len != 0) {
code = next_code[len]++;
int node = 0;
for (int bit = len - 1; bit >= 0; bit--) {
int value = code & (1 << bit);
if (value == 0) {
int left = tree[node] >> 16;
if (left == 0) {
tree[node] |= (treeInsert << 16);
node = treeInsert++;
} else
node = left;
} else {
int right = tree[node] & 0xFFFF;
if (right == 0) {
tree[node] |= treeInsert;
node = treeInsert++;
} else
node = right;
}
}
tree[node] = 0x80000000 | i;
}
}
return tree;
}
private byte[] data;
private Hashtable htToc;
public ZipMe(byte[] data) {
reset(data);
}
public ZipMe(InputStream is) throws IOException {
byte[] bb = inputStreamToBytes(is);
reset(bb);
}
public final ZipMe reset(byte[] data) {
this.data = data;
htToc = null;
return this;
}
public final Vector list() {
Hashtable toc;
if ((toc = htToc) == null) {
toc = htToc = new Hashtable();
int offset, i;
offset = i = 0;
for (;;) {
int n = read(data, offset, 4);
if (n != 0x04034B50) break; // end of data section
offset += 8; // header,pkware_ver,global_flag
int method = read(data, offset, 2);
offset += 10; // method,date,time,crc
int size = read(data, offset, 4);
offset += 4; // compressed_size
int orisize = read(data, offset, 4);
offset += 4; // original_size
int filenamelen = read(data, offset, 2);
offset += 2;
int extlen = read(data, offset, 2);
offset += 2;
String filename = new String(data, offset, filenamelen);
offset += filenamelen + extlen;
toc.put(filename, new int[] { offset, size, orisize, method, i++ } );
offset += size;
}
}
Vector ret = new Vector(toc.size());
for (Enumeration e = toc.keys(); e.hasMoreElements();) {
String filename = (String) e.nextElement();
ret.add(filename);
}
return ret;
}
public final byte[] get(String name) {
if (htToc == null) list();
int[] info = (int[]) htToc.get(name);
if (info == null) return null;
if (info[1] == 0) return new byte[0];
if (info[3] == 0) { // store
byte[] ret = new byte[info[2]];
System.arraycopy(data, info[0], ret, 0, info[2]);
return ret;
} else if (info[3] == 8) { // deflate
byte[] ret = inflate(data, info[0], info[2]);
return ret;
}
return null;
}
private static final int read(byte[] data, int offset, int len) {
int ret = 0;
for (int i = offset, j = 0, n = offset + len; i < n; i++, j += 8) {
ret |= ((data[i] & 0xff) << j);
}
return ret;
}
private static final byte[] inputStreamToBytes(InputStream is) throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] bb = new byte[10000];
for (int len = is.read(bb); len > 0; len = is.read(bb)) {
bos.write(bb, 0, len);
}
return bos.toByteArray();
}
}