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.pdfbox.cos; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.util.Arrays; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.pdfbox.util.Charsets; import org.apache.pdfbox.util.Hex; /** * A string object, which may be a text string, a PDFDocEncoded string, ASCII string, or byte string. * * <p>Text strings are used for character strings that contain information intended to be * human-readable, such as text annotations, bookmark names, article names, document information, * and so forth. * * <p>PDFDocEncoded strings are used for characters that are represented in a single byte. * * <p>ASCII strings are used for characters that are represented in a single byte using ASCII * encoding. * * <p>Byte strings are used for binary data represented as a series of bytes, but the encoding is * not known. The bytes of the string need not represent characters. * * @author Ben Litchfield * @author John Hewson */ public final class COSString extends COSBase { private static final Log LOG = LogFactory.getLog(COSString.class); // legacy behaviour for old PDFParser public static final boolean FORCE_PARSING = Boolean.getBoolean("org.apache.pdfbox.forceParsing"); /** * This will create a COS string from a string of hex characters. * * @param hex A hex string. * @return A cos string with the hex characters converted to their actual bytes. * @throws IOException If there is an error with the hex string. */ public static COSString parseHex(String hex) throws IOException { ByteArrayOutputStream bytes = new ByteArrayOutputStream(); StringBuilder hexBuffer = new StringBuilder(hex.trim()); // if odd number then the last hex digit is assumed to be 0 if (hexBuffer.length() % 2 != 0) { hexBuffer.append('0'); } int length = hexBuffer.length(); for (int i = 0; i < length; i += 2) { try { bytes.write(Integer.parseInt(hexBuffer.substring(i, i + 2), 16)); } catch (NumberFormatException e) { if (FORCE_PARSING) { LOG.warn("Encountered a malformed hex string"); bytes.write('?'); // todo: what does Acrobat do? Any example PDFs? } else { throw new IOException("Invalid hex string: " + hex, e); } } } return new COSString(bytes.toByteArray()); } private byte[] bytes; private boolean forceHexForm; /** * Creates a new PDF string from a byte array. This method can be used to read a string from * an existing PDF file, or to create a new byte string. * * @param bytes The raw bytes of the PDF text string or byte string. */ public COSString(byte[] bytes) { setValue(bytes); } /** * Creates a new <i>text string</i> from a Java String. * * @param text The string value of the object. */ public COSString(String text) { // check whether the string uses only characters available in PDFDocEncoding boolean isOnlyPDFDocEncoding = true; for (char c : text.toCharArray()) { if (!PDFDocEncoding.containsChar(c)) { isOnlyPDFDocEncoding = false; break; } } if (isOnlyPDFDocEncoding) { // PDFDocEncoded string bytes = PDFDocEncoding.getBytes(text); } else { // UTF-16BE encoded string with a leading byte order marker byte[] data = text.getBytes(Charsets.UTF_16BE); ByteArrayOutputStream out = new ByteArrayOutputStream(data.length + 2); out.write(0xFE); // BOM out.write(0xFF); // BOM try { out.write(data); } catch (IOException e) { // should never happen throw new RuntimeException(e); } bytes = out.toByteArray(); } } /** * Sets the raw value of this string. * * @param value The raw bytes of the PDF text string or byte string. */ public void setValue(byte[] value) { bytes = value.clone(); } /** * Sets whether or not to force the string is to be written in hex form. * This is needed when signing PDF files. * * @param value True to force hex. */ public void setForceHexForm(boolean value) { this.forceHexForm = value; } /** * Returns true if the string is to be written in hex form. */ public boolean getForceHexForm() { return forceHexForm; } /** * Returns the content of this string as a PDF <i>text string</i>. */ public String getString() { // text string - BOM indicates Unicode if (bytes.length > 2) { if ((bytes[0] & 0xff) == 0xFE && (bytes[1] & 0xff) == 0xFF) { // UTF-16BE return new String(bytes, 2, bytes.length - 2, Charsets.UTF_16BE); } else if ((bytes[0] & 0xff) == 0xFF && (bytes[1] & 0xff) == 0xFE) { // UTF-16LE - not in the PDF spec! return new String(bytes, 2, bytes.length - 2, Charsets.UTF_16LE); } } // otherwise use PDFDocEncoding return PDFDocEncoding.toString(bytes); } /** * Returns the content of this string as a PDF <i>ASCII string</i>. */ public String getASCII() { // ASCII string return new String(bytes, Charsets.US_ASCII); } /** * Returns the raw bytes of the string. Best used with a PDF <i>byte string</i>. */ public byte[] getBytes() { return bytes; } /** * This will take this string and create a hex representation of the bytes that make the string. * * @return A hex string representing the bytes in this string. */ public String toHexString() { StringBuilder sb = new StringBuilder(bytes.length * 2); for (byte b : bytes) { sb.append(Hex.getString(b)); } return sb.toString(); } /** * Visitor pattern double dispatch method. * * @param visitor The object to notify when visiting this object. * @return any object, depending on the visitor implementation, or null * @throws IOException If an error occurs while visiting this object. */ @Override public Object accept(ICOSVisitor visitor) throws IOException { return visitor.visitFromString(this); } @Override public boolean equals(Object obj) { if (obj instanceof COSString) { COSString strObj = (COSString) obj; return getString().equals(strObj.getString()) && forceHexForm == strObj.forceHexForm; } return false; } @Override public int hashCode() { int result = Arrays.hashCode(bytes); return result + (forceHexForm ? 17 : 0); } @Override public String toString() { return "COSString{" + getString() + "}"; } }