TTFDataStream


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31  package org.pdfbox.ttf;
32  
33  import java.io.EOFException  ;
34  import java.io.IOException  ;
35  
36  import java.util.Calendar  ;
37  import java.util.GregorianCalendar  ;
38  
39  import org.pdfbox.cos.COSStream;
40  
41  /**
42   * An interface into a data stream.
43   * 
44   * @author Ben Litchfield (ben@csh.rit.edu)
45   * @version $Revision: 1.3 $
46   */
47  public abstract class TTFDataStream 
48  {
49  
50      /**
51       * Read a 16.16 fixed value, where the first 16 bits are the decimal and the last
52       * 16 bits are the fraction.
53       * @return A 32 bit value.
54       * @throws IOException If there is an error reading the data.
55       */
56      public float read32Fixed() throws IOException  
57      {
58          float retval = 0;
59          retval = readSignedShort();
60          retval += (readUnsignedShort()/65536);
61          return retval;
62      }
63      
64      /**
65       * Read a fixed length ascii string.
66       * @param length The length of the string to read.
67       * @return A string of the desired length.
68       * @throws IOException If there is an error reading the data.
69       */
70      public String   readString( int length ) throws IOException  
71      {
72          return readString( length, "ISO-8859-1" );
73      }
74      
75      /**
76       * Read a fixed length ascii string.
77       * @param length The length of the string to read in bytes.
78       * @param charset The expected character set of the string.
79       * @return A string of the desired length.
80       * @throws IOException If there is an error reading the data.
81       */
82      public String   readString( int length, String   charset ) throws IOException  
83      {
84          byte[] buffer = read( length );
85          return new String  (buffer, charset);
86      }
87      
88      /**
89       * Read an unsigned byte.
90       * @return An unsigned byte.
91       * @throws IOException If there is an error reading the data.
92       */
93      public abstract int read() throws IOException  ;
94      
95      /**
96       * Read an unsigned byte.
97       * @return An unsigned byte.
98       * @throws IOException If there is an error reading the data.
99       */
100     public abstract long readLong() throws IOException  ;
101     
102     
103     /**
104      * Read an unsigned byte.
105      * @return An unsigned byte.
106      * @throws IOException If there is an error reading the data.
107      */
108     public int readSignedByte() throws IOException  
109     {
110         return read() - 255;
111     }
112     
113     /**
114      * Read an unsigned integer.
115      * @return An unsiged integer.
116      * @throws IOException If there is an error reading the data.
117      */
118     public long readUnsignedInt() throws IOException  
119     {
120         long byte1 = read();
121         long byte2 = read();
122         long byte3 = read();
123         long byte4 = read();
124         if( byte4 < 0 )
125         {
126             throw new EOFException  ();
127         }
128         return (byte1 << 24) + (byte2 << 16) + (byte3 << 8) + (byte4 << 0);
129     }
130     
131     /**
132      * Read an unsigned short.
133      * 
134      * @return An unsigned short.
135      * @throws IOException If there is an error reading the data.
136      */
137     public abstract int readUnsignedShort() throws IOException  ;
138     
139     /**
140      * Read an unsigned short array.
141      * 
142      * @param length The length of the array to read.
143      * @return An unsigned short array.
144      * @throws IOException If there is an error reading the data.
145      */
146     public int[] readUnsignedShortArray( int length ) throws IOException  
147     {
148         int[] array = new int[ length ];
149         for( int i=0; i<length; i++ )
150         {
151             array[i] = readUnsignedShort();
152         }
153         return array;
154     }
155     
156     /**
157      * Read an signed short.
158      * 
159      * @return An signed short.
160      * @throws IOException If there is an error reading the data.
161      */
162     public abstract short readSignedShort() throws IOException  ;
163     
164     /**
165      * Read an eight byte international date.
166      * 
167      * @return An signed short.
168      * @throws IOException If there is an error reading the data.
169      */
170     public Calendar   readInternationalDate() throws IOException  
171     {
172         long secondsSince1904 = readLong();
173         GregorianCalendar   cal = new GregorianCalendar  ( 1904, 0, 1 );
174         long millisFor1904 = cal.getTimeInMillis();
175         millisFor1904 += (secondsSince1904*1000);
176         cal.setTimeInMillis( millisFor1904 );
177         return cal;
178     }
179     
180     /**
181      * Close the underlying resources.
182      * 
183      * @throws IOException If there is an error closing the resources.
184      */
185     public abstract void close() throws IOException  ;
186     
187     /**
188      * Seek into the datasource.
189      * 
190      * @param pos The position to seek to.
191      * @throws IOException If there is an error seeking to that position.
192      */
193     public abstract void seek(long pos) throws IOException  ;
194     
195     /**
196      * Read a specific number of bytes from the stream.
197      * @param numberOfBytes The number of bytes to read.
198      * @return The byte buffer.
199      * @throws IOException If there is an error while reading.
200      */
201     public byte[] read( int numberOfBytes ) throws IOException  
202     {
203         byte[] data = new byte[ numberOfBytes ];
204         int amountRead = 0;
205         int totalAmountRead = 0;
206         while( (amountRead = read( data, totalAmountRead, numberOfBytes-totalAmountRead ) ) != -1 && 
207                totalAmountRead < numberOfBytes )
208         {
209             totalAmountRead += amountRead;
210             //read at most numberOfBytes bytes from the stream.
211         }
212         return data;
213     }
214     
215     /**
216      * @see java.io.InputStream#read( byte[], int, int )
217      * 
218      * @param b The buffer to write to.
219      * @param off The offset into the buffer.
220      * @param len The length into the buffer.
221      * 
222      * @return The number of bytes read.
223      * 
224      * @throws IOException If there is an error reading from the stream.
225      */
226     public abstract int read(byte[] b,
227             int off,
228             int len)
229      throws IOException  ;
230     
231     /**
232      * Get the current position in the stream.
233      * @return The current position in the stream.
234      * @throws IOException If an error occurs while reading the stream.
235      */
236     public abstract long getCurrentPosition() throws IOException  ;
237     
238     /**
239      * Get a COSStream from this TTFDataStream
240      * This permit to pass the data read from an
241      * external source to the COSObjects to keep
242      * a certain persistence layer between specialized
243      * objects like the TTF package and the pdmodel package.
244      *
245      * Created by Pascal Allain
246      * Vertical7 Inc.
247      *
248      * @return COSStream describing this stream
249      */
250     public abstract COSStream getCOSStream();
251 
252 }
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