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(doc) Added support for gzip extra subfields. (#604)
Co-authored-by: Danny Deschenes <[email protected]>
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src/main/java/org/apache/commons/compress/compressors/gzip/Extra.java
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, | ||
| * software distributed under the License is distributed on an | ||
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| * KIND, either express or implied. See the License for the | ||
| * specific language governing permissions and limitations | ||
| * under the License. | ||
| */ | ||
|
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| package org.apache.commons.compress.compressors.gzip; | ||
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| import java.io.IOException; | ||
| import java.util.ArrayList; | ||
| import java.util.Collections; | ||
| import java.util.List; | ||
| import java.util.stream.Collectors; | ||
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| /** | ||
| * Container for subfields. | ||
| * | ||
| * This class does not expose the internal subfields list to prevent adding | ||
| * subfields without total extra length validation. However a copy of the list | ||
| * is available. | ||
| * | ||
| * @since 1.28.0 | ||
| */ | ||
| public class Extra { | ||
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| static final int MAX_SIZE = 0xFFFF; | ||
| static final byte[] ZERO_BYTES = new byte[0]; | ||
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| static Extra fromBytes(byte[] ba) throws IOException { | ||
| if (ba == null) { | ||
| return null; | ||
| } | ||
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| Extra e = new Extra(); | ||
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| int pos = 0; | ||
| while (pos <= (ba.length - 4)) { | ||
| SubField f = new SubField(); | ||
| f.si1 = ba[pos++]; | ||
| f.si2 = ba[pos++]; | ||
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| int sublen = (ba[pos++] & 0xff) | ((ba[pos++] & 0xff) << 8); | ||
| if (sublen > (ba.length - pos)) { | ||
| throw new IOException("Extra subfield lenght exceeds remaining bytes in extra: " + sublen + " > " + (ba.length - pos)); | ||
| } | ||
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| f.payload = new byte[sublen]; | ||
| System.arraycopy(ba, pos, f.payload, 0, sublen); | ||
| pos += sublen; | ||
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| e.fieldsList.add(f); | ||
| e.totalSize = pos; | ||
| } | ||
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| if (pos < ba.length) { | ||
| throw new IOException("" + (ba.length - pos) + " remaining bytes not used to parse an extra subfield."); | ||
| } | ||
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| return e; | ||
| } | ||
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| // -------------- | ||
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| private final List<SubField> fieldsList = new ArrayList<>(); | ||
| private int totalSize = 0; | ||
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| public Extra() { | ||
| } | ||
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| public boolean isEmpty() { | ||
| return fieldsList.isEmpty(); | ||
| } | ||
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| public void clear() { | ||
| fieldsList.clear(); | ||
| totalSize = 0; | ||
| } | ||
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| /** | ||
| * The bytes count of this extra payload when encoded. This does not include its | ||
| * own 16 bits size. For N sub fields, the total is all subfields payloads + 4N. | ||
| */ | ||
| public int getEncodedSize() { | ||
| return totalSize; | ||
| } | ||
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| /** | ||
| * The count of subfields contained in this extra. | ||
| */ | ||
| public int getSize() { | ||
| return fieldsList.size(); | ||
| } | ||
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| /** | ||
| * @return an unmodifiable copy of the subfields list. | ||
| */ | ||
| public List<SubField> getFieldsList() { | ||
| return Collections.unmodifiableList(fieldsList); | ||
| } | ||
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| /** | ||
| * Append a subfield by a 2-chars ISO-8859-1 string. The char at index 0 and 1 | ||
| * are respectiovely si1 and si2 (subfield id 1 and 2). | ||
| * | ||
| * @throws IllegalArgumentException if the subfield is not 2-chars or the | ||
| * payload is null | ||
| * | ||
| * @throws IOException if appending this subfield would exceed the | ||
| * max size 65535 of the extra header. | ||
| */ | ||
| public Extra appendSubField(String subfieldId, byte[] payload) throws IOException { | ||
| if (subfieldId.length() != 2) { | ||
| throw new IllegalArgumentException("subfield id must be a 2-chars iso-8859-1 string."); | ||
| } | ||
| if (payload == null) { | ||
| throw new IllegalArgumentException("payload was null"); | ||
| } | ||
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| char si1 = subfieldId.charAt(0); | ||
| char si2 = subfieldId.charAt(1); | ||
| if ((si1 & 0xff00) != 0 || (si2 & 0xff00) != 0) { | ||
| throw new IllegalArgumentException("subfield id must be a 2-chars iso-8859-1 string."); | ||
| } | ||
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| SubField f = new SubField((byte) (si1 & 0xff), (byte) (si2 & 0xff), payload); | ||
| int len = 4 + payload.length; | ||
| if (totalSize + len > MAX_SIZE) { | ||
| throw new IOException("extra subfield '" + f.getId() + "' too big (extras total size is already at " + totalSize + ")"); | ||
| } | ||
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| fieldsList.add(f); | ||
| totalSize += len; | ||
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| return this; | ||
| } | ||
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| byte[] toBytes() { | ||
| if (fieldsList.isEmpty()) { | ||
| return ZERO_BYTES; | ||
| } | ||
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| byte[] ba = new byte[totalSize]; | ||
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| int pos = 0; | ||
| for (SubField f : fieldsList) { | ||
| ba[pos++] = f.si1; | ||
| ba[pos++] = f.si2; | ||
| ba[pos++] = (byte) (f.payload.length & 0xff); // little endian expected | ||
| ba[pos++] = (byte) (f.payload.length >>> 8); | ||
| System.arraycopy(f.payload, 0, ba, pos, f.payload.length); | ||
| pos += f.payload.length; | ||
| } | ||
| return ba; | ||
| } | ||
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| /** | ||
| * Give all 2-chars ISO-8859-1 strings denoting the subfields. Note that this is | ||
| * imprecise as ids can repeat. Use the methods with indexes to find a specific | ||
| * occurence. | ||
| */ | ||
| public List<String> listIds() { | ||
| return fieldsList.stream().map(SubField::getId).collect(Collectors.toList()); | ||
| } | ||
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| /** | ||
| * Find the 1st subfield that matches the id. | ||
| * | ||
| * @return the SubField if found, null otherwise. | ||
| */ | ||
| public SubField findFirstSubField(String subfieldId) { | ||
| return fieldsList.stream().filter(f -> f.getId().equals(subfieldId)).findFirst().orElse(null); | ||
| } | ||
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| /** | ||
| * Find the subfield at the given index. | ||
| */ | ||
| public SubField subFieldAt(int i) { | ||
| return fieldsList.get(i); | ||
| } | ||
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| /** | ||
| * The carrier for a subfield in the gzip extra. | ||
| */ | ||
| public static class SubField { | ||
| byte si1; | ||
| byte si2; | ||
| byte[] payload; | ||
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| SubField() { | ||
| } | ||
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| SubField(byte si1, byte si2, byte[] payload) { | ||
| this.si1 = si1; | ||
| this.si2 = si2; | ||
| this.payload = payload; | ||
| } | ||
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| /** | ||
| * The 2 char iso-8859-1 string made from the si1 and si2 bytes of the sub field | ||
| * id. | ||
| */ | ||
| public String getId() { | ||
| return "" + ((char) (si1 & 0xff)) + ((char) (si2 & 0xff)); | ||
| } | ||
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| /** | ||
| * The subfield payload. | ||
| */ | ||
| public byte[] getPayload() { | ||
| return payload; | ||
| } | ||
| } | ||
|
|
||
| } |
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