Java tutorial
/***************************************************************************** * * 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. * ****************************************************************************/ package org.apache.padaf.preflight.helpers; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; import org.apache.commons.io.IOUtils; import org.apache.padaf.preflight.DocumentHandler; import org.apache.padaf.preflight.ValidationConstants; import org.apache.padaf.preflight.ValidationException; import org.apache.padaf.preflight.ValidationResult; import org.apache.padaf.preflight.ValidatorConfig; import org.apache.padaf.preflight.ValidationResult.ValidationError; import org.apache.padaf.preflight.utils.COSUtils; import org.apache.padaf.preflight.utils.FilterHelper; import org.apache.pdfbox.cos.COSArray; import org.apache.pdfbox.cos.COSBase; import org.apache.pdfbox.cos.COSDocument; import org.apache.pdfbox.cos.COSName; import org.apache.pdfbox.cos.COSObject; import org.apache.pdfbox.cos.COSStream; import org.apache.pdfbox.pdmodel.PDDocument; import org.apache.pdfbox.persistence.util.COSObjectKey; /** * @author eric * */ public class StreamValidationHelper extends AbstractValidationHelper { public StreamValidationHelper(ValidatorConfig cfg) throws ValidationException { super(cfg); } /* * (non-Javadoc) * * @see * net.awl.edoc.pdfa.validation.helpers.AbstractValidationHelper#innerValidate * (net.awl.edoc.pdfa.validation.DocumentHandler) */ @Override public List<ValidationError> innerValidate(DocumentHandler handler) throws ValidationException { List<ValidationError> result = new ArrayList<ValidationError>(0); PDDocument pdfDoc = handler.getDocument(); COSDocument cDoc = pdfDoc.getDocument(); List<?> lCOSObj = cDoc.getObjects(); for (Object o : lCOSObj) { COSObject cObj = (COSObject) o; // If this object represents a Stream, the Dictionary must contain the // Length key COSBase cBase = cObj.getObject(); if (cBase instanceof COSStream) { // it is a stream result.addAll(validateStreamObject(handler, cObj)); } } return result; } public List<ValidationError> validateStreamObject(DocumentHandler handler, COSObject cObj) throws ValidationException { List<ValidationError> result = new ArrayList<ValidationError>(0); COSStream streamObj = (COSStream) cObj.getObject(); // ---- Check dictionary entries // ---- Only the Length entry is mandatory // ---- In a PDF/A file, F, FFilter and FDecodeParms are forbidden checkDictionaryEntries(streamObj, result); // ---- check stream length checkStreamLength(handler, cObj, result); // ---- Check the Filter value(s) checkFilters(streamObj, handler, result); return result; } /** * This method checks if one of declared Filter is LZWdecode. If LZW is found, * the result list is updated with an error code. * * @param stream * @param handler * @param result */ protected void checkFilters(COSStream stream, DocumentHandler handler, List<ValidationError> result) { COSDocument cDoc = handler.getDocument().getDocument(); COSBase bFilter = stream.getItem(COSName.getPDFName(STREAM_DICTIONARY_KEY_FILTER)); if (bFilter != null) { if (COSUtils.isArray(bFilter, cDoc)) { COSArray afName = (COSArray) bFilter; for (int i = 0; i < afName.size(); ++i) { if (!FilterHelper.isAuthorizedFilter(afName.getString(i), result)) { return; } } } else if (bFilter instanceof COSName) { String fName = ((COSName) bFilter).getName(); if (!FilterHelper.isAuthorizedFilter(fName, result)) { return; } } else { // ---- The filter type is invalid result.add(new ValidationError(ERROR_SYNTAX_STREAM_INVALID_FILTER, "Filter should be a Name or an Array")); } } // else Filter entry is optional } private boolean readUntilStream(InputStream ra) throws IOException { boolean search = true; // String stream = ""; boolean maybe = false; int lastChar = -1; do { int c = ra.read(); switch (c) { case 's': // stream = "s"; maybe = true; lastChar = c; break; case 't': // if (maybe && stream.endsWith("s")) { if (maybe && lastChar == 's') { // stream = stream + "t"; lastChar = c; } else { maybe = false; lastChar = -1; } break; case 'r': // if (maybe && stream.endsWith("t")) { if (maybe && lastChar == 't') { // stream = stream + "r"; lastChar = c; } else { maybe = false; lastChar = -1; } break; case 'e': // if (maybe && stream.endsWith("r")) { if (maybe && lastChar == 'r') { lastChar = c; // stream = stream + "e"; } else { maybe = false; } break; case 'a': // if (maybe && stream.endsWith("e")) { if (maybe && lastChar == 'e') { lastChar = c; // stream = stream + "a"; } else { maybe = false; } break; case 'm': // if (maybe && stream.endsWith("a")) { if (maybe && lastChar == 'a') { return true; } else { maybe = false; } break; case -1: search = false; break; default: maybe = false; break; } } while (search); return false; } protected void checkStreamLength(DocumentHandler handler, COSObject cObj, List<ValidationError> result) throws ValidationException { COSStream streamObj = (COSStream) cObj.getObject(); int length = streamObj.getInt(COSName.getPDFName(STREAM_DICTIONARY_KEY_LENGHT)); InputStream ra = null; try { ra = handler.getSource().getInputStream(); Long offset = handler.getDocument().getDocument().getXrefTable().get(new COSObjectKey(cObj)); // ---- go to the beginning of the object long skipped = 0; if (offset != null) { while (skipped != offset) { long curSkip = ra.skip(offset - skipped); if (curSkip < 0) { throw new ValidationException("Unable to skip bytes in the PDFFile to check stream length"); } skipped += curSkip; } // ---- go to the stream key word if (readUntilStream(ra)) { int c = ra.read(); if (c == '\r') { ra.read(); } // else c is '\n' no more character to read // ---- Here is the true beginning of the Stream Content. // ---- Read the given length of bytes and check the 10 next bytes // ---- to see if there are endstream. byte[] buffer = new byte[1024]; int nbBytesToRead = length; do { int cr = 0; if (nbBytesToRead > 1024) { cr = ra.read(buffer, 0, 1024); } else { cr = ra.read(buffer, 0, nbBytesToRead); } if (cr == -1) { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); return; } else { nbBytesToRead = nbBytesToRead - cr; } } while (nbBytesToRead > 0); int len = "endstream".length() + 2; byte[] buffer2 = new byte[len]; for (int i = 0; i < len; ++i) { buffer2[i] = (byte) ra.read(); } // ---- check the content of 10 last characters String endStream = new String(buffer2); if (buffer2[0] == '\r' && buffer2[1] == '\n') { if (!endStream.contains("endstream")) { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); } } else if (buffer2[0] == '\r' && buffer2[1] == 'e') { if (!endStream.contains("endstream")) { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); } } else if (buffer2[0] == '\n' && buffer2[1] == 'e') { if (!endStream.contains("endstream")) { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); } } else { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); } } else { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_INVALID, "Stream length is invalide")); } } else { /* * * Offset is null. The stream isn't used, check is useless. * * TODO : Is it the truth? */ } } catch (IOException e) { throw new ValidationException("Unable to read a stream to validate it due to : " + e.getMessage(), e); } finally { if (ra != null) { IOUtils.closeQuietly(ra); } } } /** * Check dictionary entries. Only the Length entry is mandatory. In a PDF/A * file, F, FFilter and FDecodeParms are forbidden * * @param streamObj * @param result */ protected void checkDictionaryEntries(COSStream streamObj, List<ValidationError> result) { boolean len = false; boolean f = false; boolean ffilter = false; boolean fdecParams = false; for (Object key : streamObj.keyList()) { if (!(key instanceof COSName)) { result.add(new ValidationResult.ValidationError( ValidationConstants.ERROR_SYNTAX_DICTIONARY_KEY_INVALID, "Invalid key in The Stream dictionary")); return; } COSName cosName = (COSName) key; if (cosName.getName().equals(STREAM_DICTIONARY_KEY_LENGHT)) { len = true; } if (cosName.getName().equals(STREAM_DICTIONARY_KEY_F)) { f = true; } if (cosName.getName().equals(STREAM_DICTIONARY_KEY_FFILTER)) { ffilter = true; } if (cosName.getName().equals(STREAM_DICTIONARY_KEY_FDECODEPARAMS)) { fdecParams = true; } } if (!len) { result.add(new ValidationResult.ValidationError(ValidationConstants.ERROR_SYNTAX_STREAM_LENGTH_MISSING, "Stream length is missing")); } if (f || ffilter || fdecParams) { result.add(new ValidationResult.ValidationError(ValidationConstants.ERROR_SYNTAX_STREAM_FX_KEYS, "F, FFilter or FDecodeParms keys are present in the stream dictionary")); } } }