gzip数据流解压
gzip数据流解压
package org.jzlib; /* * GZIP library for j2me applications. * * Copyright (c) 2004-2006 Carlos Araiz ([email protected]) * * This library is free software; you can redistribute it and/or modify it under * the terms of the GNU Lesser General Public License as published by the Free * Software Foundation; either version 2.1 of the License, or (at your option) * any later version. * * This library is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more * details. * * You should have received a copy of the GNU Lesser General Public License * along with this library; if not, write to the Free Software Foundation, Inc., * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ import java.io.IOException; /** * Clase que permite leer ficheros GZIP. * * @author Carlos Araiz * * @version 1.2.0 */ public class GzipUtil { // private static final int FTEXT_MASK = 1; // private static final int FHCRC_MASK = 2; // private static final int FEXTRA_MASK = 4; // private static final int FNAME_MASK = 8; // private static final int FCOMMENT_MASK = 16; // Tipos de bloques. private static final int BTYPE_NONE = 0; // private static final int BTYPE_FIXED = 1; private static final int BTYPE_DYNAMIC = 2; // private static final int BTYPE_RESERVED = 3; 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; // Datos prefijados (LENGTH: 257..287 / DISTANCE: 0..29 / // DYNAMIC_LENGTH_ORDER: 0..18). 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 }; /** ********************************************************************** */ // Variables para la lectura de datos comprimidos. private static int gzipIndex, gzipByte, gzipBit; /** ********************************************************************** */ /** ********************************************************************** */ /** * Descomprime un fichero GZIP. * * @param gzip * Array con los datos del fichero comprimido * * @return Array con los datos descomprimidos */ public static byte[] inflate(byte gzip[]) throws IOException { // Inicializa. gzipIndex = gzipByte = gzipBit = 0; // Cabecera. if (readBits(gzip, 16) != 0x8B1F || readBits(gzip, 8) != 8) throw new IOException("Invalid GZIP format"); // Flag. /*int flg = */readBits(gzip, 8); // Fecha(4) / XFL(1) / OS(1). gzipIndex += 6; // Comprueba los flags. // if ((flg & FEXTRA_MASK) != 0) // gzipIndex += readBits(gzip, 16); // if ((flg & FNAME_MASK) != 0) // while (gzip[gzipIndex++] != 0) // ; // if ((flg & FCOMMENT_MASK) != 0) // while (gzip[gzipIndex++] != 0) // ; // if ((flg & FHCRC_MASK) != 0) // gzipIndex += 2; // Tama�o de los datos descomprimidos. int index = gzipIndex; gzipIndex = gzip.length - 4; byte uncompressed[] = new byte[readBits(gzip, 16) | (readBits(gzip, 16) << 16)]; int uncompressedIndex = 0; gzipIndex = index; // Bloque con datos comprimidos. int bfinal = 0, btype = 0; do { // Lee la cabecera del bloque. bfinal = readBits(gzip, 1); btype = readBits(gzip, 2); // Comprueba el tipo de compresi�n. if (btype == BTYPE_NONE) { // Ignora los bits dentro del byte actual. gzipBit = 0; // LEN. int len = readBits(gzip, 16); // NLEN. /*int nlen = */readBits(gzip, 16); // Lee los datos. System.arraycopy(gzip, gzipIndex, uncompressed, uncompressedIndex, len); gzipIndex += len; // Actualiza el �ndice de los datos descomprimidos. uncompressedIndex += len; } else { int literalTree[], distanceTree[]; if (btype == BTYPE_DYNAMIC) { // N�mero de datos de cada tipo. int hlit = readBits(gzip, 5) + 257; int hdist = readBits(gzip, 5) + 1; int hclen = readBits(gzip, 4) + 4; // Lee el n�mero de bits para cada c�digo de longitud. byte lengthBits[] = new byte[MAX_CODE_LENGTHS + 1]; for (int i = 0; i < hclen; i++) lengthBits[DYNAMIC_LENGTH_ORDER[i]] = (byte) readBits( gzip, 3); // Crea los c�digos para la longitud. int lengthTree[] = createHuffmanTree(lengthBits, MAX_CODE_LENGTHS); // Genera los �rboles. literalTree = createHuffmanTree(decodeCodeLengths(gzip, lengthTree, hlit), hlit - 1); distanceTree = createHuffmanTree(decodeCodeLengths(gzip, lengthTree, hdist), hdist - 1); } else { byte literalBits[] = new byte[MAX_CODE_LITERALS + 1]; for (int i = 0; i < 144; i++) literalBits[i] = 8; for (int i = 144; i < 256; i++) literalBits[i] = 9; for (int i = 256; i < 280; i++) literalBits[i] = 7; for (int i = 280; i < 288; i++) literalBits[i] = 8; literalTree = createHuffmanTree(literalBits, MAX_CODE_LITERALS); // byte distanceBits[] = new byte[MAX_CODE_DISTANCES + 1]; for (int i = 0; i < distanceBits.length; i++) distanceBits[i] = 5; distanceTree = createHuffmanTree(distanceBits, MAX_CODE_DISTANCES); } // Descomprime el bloque. int code = 0, leb = 0, deb = 0; while ((code = readCode(gzip, literalTree)) != EOB_CODE) { if (code > EOB_CODE) { code -= 257; int length = LENGTH_VALUES[code]; if ((leb = LENGTH_EXTRA_BITS[code]) > 0) length += readBits(gzip, leb); code = readCode(gzip, distanceTree); int distance = DISTANCE_VALUES[code]; if ((deb = DISTANCE_EXTRA_BITS[code]) > 0) distance += readBits(gzip, deb); // Repite la informaci�n. int offset = uncompressedIndex - distance; while (distance < length) { System.arraycopy(uncompressed, offset, uncompressed, uncompressedIndex, distance); uncompressedIndex += distance; length -= distance; distance <<= 1; } System.arraycopy(uncompressed, offset, uncompressed, uncompressedIndex, length); uncompressedIndex += length; } else uncompressed[uncompressedIndex++] = (byte) code; } } } while (bfinal == 0); // return uncompressed; } /** * Lee un n�mero de bits * * @param n * N�mero de bits [0..16] */ private static int readBits(byte gzip[], int n) { // Asegura que tenemos un byte. int data = (gzipBit == 0 ? (gzipByte = (gzip[gzipIndex++] & 0xFF)) : (gzipByte >> gzipBit)); // Lee hasta completar los bits. for (int i = (8 - gzipBit); i < n; i += 8) { gzipByte = (gzip[gzipIndex++] & 0xFF); data |= (gzipByte << i); } // Ajusta la posici�n actual. gzipBit = (gzipBit + n) & 7; // Devuelve el dato. return (data & ((1 << n) - 1)); } /** * Lee un c�digo. */ private static int readCode(byte gzip[], int tree[]) { int node = tree[0]; while (node >= 0) { // Lee un byte si es necesario. if (gzipBit == 0) gzipByte = (gzip[gzipIndex++] & 0xFF); // Accede al nodo correspondiente. node = (((gzipByte & (1 << gzipBit)) == 0) ? tree[node >> 16] : tree[node & 0xFFFF]); // Ajusta la posici�n actual. gzipBit = (gzipBit + 1) & 7; } return (node & 0xFFFF); } /** * Decodifica la longitud de c�digos (usado en bloques comprimidos con * c�digos din�micos). */ private static byte[] decodeCodeLengths(byte gzip[], int lengthTree[], int count) { byte bits[] = new byte[count]; for (int i = 0, code = 0, last = 0; i < count;) { code = readCode(gzip, lengthTree); if (code >= 16) { int repeat = 0; if (code == 16) { repeat = 3 + readBits(gzip, 2); code = last; } else { if (code == 17) repeat = 3 + readBits(gzip, 3); else repeat = 11 + readBits(gzip, 7); code = 0; } while (repeat-- > 0) bits[i++] = (byte) code; } else bits[i++] = (byte) code; // last = code; } return bits; } /** * Crea el �rbol para los c�digos Huffman. */ private static int[] createHuffmanTree(byte bits[], int maxCode) { // N�mero de c�digos por cada longitud de c�digo. int bl_count[] = new int[MAX_BITS + 1]; for (int i = 0; i < bits.length; i++) bl_count[bits[i]]++; // M�nimo valor num�rico del c�digo para cada longitud de c�digo. 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; // Genera el �rbol. // Bit 31 => Nodo (0) o c�digo (1). // (Nodo) bit 16..30 => �ndice del nodo de la izquierda (0 si no tiene). // (Nodo) bit 0..15 => �ndice del nodo de la derecha (0 si no tiene). // (C�digo) bit 0..15 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]++; // Lo mete en en �rbol. int node = 0; for (int bit = len - 1; bit >= 0; bit--) { int value = code & (1 << bit); // Inserta a la izquierda. if (value == 0) { int left = tree[node] >> 16; if (left == 0) { tree[node] |= (treeInsert << 16); node = treeInsert++; } else node = left; } // Inserta a la derecha. else { int right = tree[node] & 0xFFFF; if (right == 0) { tree[node] |= treeInsert; node = treeInsert++; } else node = right; } } // Inserta el c�digo. tree[node] = 0x80000000 | i; } } return tree; } }