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/*
 * Copyright 2008 by Kevin Day.
 *
 * The contents of this file are subject to the Mozilla Public License Version 1.1
 * (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.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the License.
 *
 * The Original Code is 'iText, a free JAVA-PDF library'.
 *
 * The Initial Developer of the Original Code is Bruno Lowagie. Portions created by
 * the Initial Developer are Copyright (C) 1999-2008 by Bruno Lowagie.
 * All Rights Reserved.
 * Co-Developer of the code is Paulo Soares. Portions created by the Co-Developer
 * are Copyright (C) 2000-2008 by Paulo Soares. All Rights Reserved.
 *
 * Contributor(s): all the names of the contributors are added in the source code
 * where applicable.
 *
 * Alternatively, the contents of this file may be used under the terms of the
 * LGPL license (the "GNU LIBRARY GENERAL PUBLIC LICENSE"), in which case the
 * provisions of LGPL are applicable instead of those above.  If you wish to
 * allow use of your version of this file only under the terms of the LGPL
 * License and not to allow others to use your version of this file under
 * the MPL, indicate your decision by deleting the provisions above and
 * replace them with the notice and other provisions required by the LGPL.
 * If you do not delete the provisions above, a recipient may use your version
 * of this file under either the MPL or the GNU LIBRARY GENERAL PUBLIC LICENSE.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the MPL as stated above or under the terms of the GNU
 * Library General Public License as published by the Free Software Foundation;
 * either version 2 of the License, or 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 Library general Public License for more
 * details.
 *
 * If you didn't download this code from the following link, you should check if
 * you aren't using an obsolete version:
 * http://www.lowagie.com/iText/
 */
package com.lowagie.text.pdf;

import com.lowagie.text.error_messages.MessageLocalization;
import com.lowagie.text.pdf.fonts.cmaps.CMap;
import com.lowagie.text.pdf.fonts.cmaps.CMapParser;

import java.io.ByteArrayInputStream;
import java.io.IOException;

/**
 * Implementation of DocumentFont used while parsing PDF streams.
 * 
 * @since 2.1.4
 */
public class CMapAwareDocumentFont extends DocumentFont {

	/** The font dictionary. */
	private PdfDictionary fontDic;
	/** the width of a space for this font, in normalized 1000 point units */
	private int spaceWidth;
	/**
	 * The CMap constructed from the ToUnicode map from the font's dictionary,
	 * if present. This CMap transforms CID values into unicode equivalent
	 */
	private CMap toUnicodeCmap;
	/**
	 * Mapping between CID code (single byte only for now) and unicode
	 * equivalent as derived by the font's encoding. Only needed if the
	 * ToUnicode CMap is not provided.
	 */
	private char[] cidbyte2uni;

	/**
	 * Creates an instance of a CMapAwareFont based on an indirect reference to
	 * a font.
	 * 
	 * @param refFont
	 *            the indirect reference to a font
	 */
	public CMapAwareDocumentFont(PRIndirectReference refFont) {
		super(refFont);
		fontDic = (PdfDictionary) PdfReader.getPdfObjectRelease(refFont);

		processToUnicode();
		if (toUnicodeCmap == null) {
			processUni2Byte();
		}

		spaceWidth = super.getWidth(' ');
		if (spaceWidth == 0) {
			spaceWidth = computeAverageWidth();
		}

	}

	/**
	 * Parses the ToUnicode entry, if present, and constructs a CMap for it
	 * 
	 * @since 2.1.7
	 */
	private void processToUnicode() {

		PdfObject toUni = fontDic.get(PdfName.TOUNICODE);
		if (toUni != null) {

			try {
				byte[] touni = PdfReader.getStreamBytes((PRStream) PdfReader
						.getPdfObjectRelease(toUni));

				CMapParser cmapParser = new CMapParser();
				toUnicodeCmap = cmapParser
						.parse(new ByteArrayInputStream(touni));
			} catch (IOException e) {
				throw new Error("Unable to process ToUnicode map - "
						+ e.getMessage(), e);
			}
		}
	}

	/**
	 * Inverts DocumentFont's uni2byte mapping to obtain a cid-to-unicode
	 * mapping based on the font's encoding
	 * 
	 * @since 2.1.7
	 */
	private void processUni2Byte() {
		IntHashtable uni2byte = getUni2Byte();
		int e[] = uni2byte.toOrderedKeys();

		cidbyte2uni = new char[256];
		for (int element : e) {
			int n = uni2byte.get(element);

			// this is messy, messy - an encoding can have multiple unicode
			// values mapping to the same cid - we are going to arbitrarily
			// choose the first one
			// what we really need to do is to parse the encoding, and handle
			// the differences info ourselves. This is a huge duplication of
			// code of what is already
			// being done in DocumentFont, so I really hate to go down that path
			// without seriously thinking about a change in the organization of
			// the Font class hierarchy
			if (cidbyte2uni[n] == 0) {
				cidbyte2uni[n] = (char) element;
			}
		}
	}

	/**
	 * For all widths of all glyphs, compute the average width in normalized
	 * 1000 point units. This is used to give some meaningful width in cases
	 * where we need an average font width (such as if the width of a space
	 * isn't specified by a given font)
	 * 
	 * @return the average width of all non-zero width glyphs in the font
	 */
	private int computeAverageWidth() {
		int count = 0;
		int total = 0;
		for (int i = 0; i < super.widths.length; i++) {
			if (super.widths[i] != 0) {
				total += super.widths[i];
				count++;
			}
		}
		return count != 0 ? total / count : 0;
	}

	/**
	 * @since 2.1.5 Override to allow special handling for fonts that don't
	 *        specify width of space character
	 * @see com.lowagie.text.pdf.DocumentFont#getWidth(int)
	 */
	@Override
	public int getWidth(int char1) {
		if (char1 == ' ') {
			return spaceWidth;
		}

		return super.getWidth(char1);
	}

	/**
	 * Decodes a single CID (represented by one or two bytes) to a unicode
	 * String.
	 * 
	 * @param bytes
	 *            the bytes making up the character code to convert
	 * @param offset
	 *            an offset
	 * @param len
	 *            a length
	 * @return a String containing the encoded form of the input bytes using the
	 *         font's encoding.
	 */
	private String decodeSingleCID(byte[] bytes, int offset, int len) {
		if (toUnicodeCmap != null) {
			if (offset + len > bytes.length) {
				throw new ArrayIndexOutOfBoundsException(
						MessageLocalization.getComposedMessage(
								"invalid.index.1", offset + len));
			}
			return toUnicodeCmap.lookup(bytes, offset, len);
		}

		if (len == 1) {
			return new String(cidbyte2uni, 0xff & bytes[offset], 1);
		}

		throw new Error("Multi-byte glyphs not implemented yet");
	}

	/**
	 * Decodes a string of bytes (encoded in the font's encoding) into a unicode
	 * string This will use the ToUnicode map of the font, if available,
	 * otherwise it uses the font's encoding
	 * 
	 * @param cidbytes
	 *            the bytes that need to be decoded
	 * @return the unicode String that results from decoding
	 * @since 2.1.7
	 */
	public String decode(byte[] cidbytes, final int offset, final int len) {
		StringBuffer sb = new StringBuffer(); // it's a shame we can't make this
												// StringBuilder
		for (int i = offset; i < offset + len; i++) {
			String rslt = decodeSingleCID(cidbytes, i, 1);
			if (rslt == null && i + 1 < offset + len) {
				rslt = decodeSingleCID(cidbytes, i, 2);
				i++;
			}
			if (rslt != null) {
				sb.append(rslt);
			}
		}

		return sb.toString();
	}

	/**
	 * Encodes bytes to a String.
	 * 
	 * @param bytes
	 *            the bytes from a stream
	 * @param offset
	 *            an offset
	 * @param len
	 *            a length
	 * @return a String encoded taking into account if the bytes are in unicode
	 *         or not.
	 * @deprecated method name is not indicative of what it does. Use
	 *             decode instead.
	 */
	@Deprecated
	public String encode(byte[] bytes, int offset, int len) {
		return decode(bytes, offset, len);
	}
}




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