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package org.pdfbox.ttf;
import java.io.EOFException;
import java.io.IOException;
import java.util.Calendar;
import java.util.GregorianCalendar;
import org.pdfbox.pdmodel.common.PDStream;
/**
* An interface into a data stream.
*
* @author Ben Litchfield (ben@benlitchfield.com)
* @version $Revision: 1.5 $
*/
public abstract class TTFDataStream
{
/**
* Read a 16.16 fixed value, where the first 16 bits are the decimal and the last
* 16 bits are the fraction.
* @return A 32 bit value.
* @throws IOException If there is an error reading the data.
*/
public float read32Fixed() throws IOException
{
float retval = 0;
retval = readSignedShort();
retval += (readUnsignedShort()/65536);
return retval;
}
/**
* Read a fixed length ascii string.
* @param length The length of the string to read.
* @return A string of the desired length.
* @throws IOException If there is an error reading the data.
*/
public String readString( int length ) throws IOException
{
return readString( length, "ISO-8859-1" );
}
/**
* Read a fixed length ascii string.
* @param length The length of the string to read in bytes.
* @param charset The expected character set of the string.
* @return A string of the desired length.
* @throws IOException If there is an error reading the data.
*/
public String readString( int length, String charset ) throws IOException
{
byte[] buffer = read( length );
return new String(buffer, charset);
}
/**
* Read an unsigned byte.
* @return An unsigned byte.
* @throws IOException If there is an error reading the data.
*/
public abstract int read() throws IOException;
/**
* Read an unsigned byte.
* @return An unsigned byte.
* @throws IOException If there is an error reading the data.
*/
public abstract long readLong() throws IOException;
/**
* Read a signed byte.
* @return A signed byte.
* @throws IOException If there is an error reading the data.
*/
public int readSignedByte() throws IOException
{
int signedByte = read();
return signedByte < 127 ? signedByte : signedByte-256;
}
/**
* Read an unsigned integer.
* @return An unsiged integer.
* @throws IOException If there is an error reading the data.
*/
public long readUnsignedInt() throws IOException
{
long byte1 = read();
long byte2 = read();
long byte3 = read();
long byte4 = read();
if( byte4 < 0 )
{
throw new EOFException();
}
return (byte1 << 24) + (byte2 << 16) + (byte3 << 8) + (byte4 << 0);
}
/**
* Read an unsigned short.
*
* @return An unsigned short.
* @throws IOException If there is an error reading the data.
*/
public abstract int readUnsignedShort() throws IOException;
/**
* Read an unsigned short array.
*
* @param length The length of the array to read.
* @return An unsigned short array.
* @throws IOException If there is an error reading the data.
*/
public int[] readUnsignedShortArray( int length ) throws IOException
{
int[] array = new int[ length ];
for( int i=0; i<length; i++ )
{
array[i] = readUnsignedShort();
}
return array;
}
/**
* Read an signed short.
*
* @return An signed short.
* @throws IOException If there is an error reading the data.
*/
public abstract short readSignedShort() throws IOException;
/**
* Read an eight byte international date.
*
* @return An signed short.
* @throws IOException If there is an error reading the data.
*/
public Calendar readInternationalDate() throws IOException
{
long secondsSince1904 = readLong();
GregorianCalendar cal = new GregorianCalendar( 1904, 0, 1 );
long millisFor1904 = cal.getTimeInMillis();
millisFor1904 += (secondsSince1904*1000);
cal.setTimeInMillis( millisFor1904 );
return cal;
}
/**
* Close the underlying resources.
*
* @throws IOException If there is an error closing the resources.
*/
public abstract void close() throws IOException;
/**
* Seek into the datasource.
*
* @param pos The position to seek to.
* @throws IOException If there is an error seeking to that position.
*/
public abstract void seek(long pos) throws IOException;
/**
* Read a specific number of bytes from the stream.
* @param numberOfBytes The number of bytes to read.
* @return The byte buffer.
* @throws IOException If there is an error while reading.
*/
public byte[] read( int numberOfBytes ) throws IOException
{
byte[] data = new byte[ numberOfBytes ];
int amountRead = 0;
int totalAmountRead = 0;
while( (amountRead = read( data, totalAmountRead, numberOfBytes-totalAmountRead ) ) != -1 &&
totalAmountRead < numberOfBytes )
{
totalAmountRead += amountRead;
//read at most numberOfBytes bytes from the stream.
}
return data;
}
/**
* @see java.io.InputStream#read( byte[], int, int )
*
* @param b The buffer to write to.
* @param off The offset into the buffer.
* @param len The length into the buffer.
*
* @return The number of bytes read.
*
* @throws IOException If there is an error reading from the stream.
*/
public abstract int read(byte[] b,
int off,
int len)
throws IOException;
/**
* Get the current position in the stream.
* @return The current position in the stream.
* @throws IOException If an error occurs while reading the stream.
*/
public abstract long getCurrentPosition() throws IOException;
/**
* Get a COSStream from this TTFDataStream
* This permit to pass the data read from an
* external source to the COSObjects to keep
* a certain persistence layer between specialized
* objects like the TTF package and the pdmodel package.
*
* Created by Pascal Allain
* Vertical7 Inc.
*
* @return COSStream describing this stream
*/
public abstract PDStream getPDStream();
}