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/* -*- Mode: java; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* Copyright (C) 2011 George Yunaev @ Ulduzsoft
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
http://www.ulduzsoft.com/2012/01/enumerating-the-fonts-on-android-platform/
*/
package org.jwz.xscreensaver;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.HashMap;
// The class which loads the TTF file, parses it and returns the TTF font name
class TTFAnalyzer
{
// This function parses the TTF file and returns the font name specified in the file
public String getTtfFontName( String fontFilename )
{
try
{
// Parses the TTF file format.
// See http://developer.apple.com/fonts/ttrefman/rm06/Chap6.html
m_file = new RandomAccessFile( fontFilename, "r" );
// Read the version first
int version = readDword();
// The version must be either 'true' (0x74727565) or 0x00010000 or 'OTTO' (0x4f54544f) for CFF style fonts.
if ( version != 0x74727565 && version != 0x00010000 && version != 0x4f54544f)
return null;
// The TTF file consist of several sections called "tables", and we need to know how many of them are there.
int numTables = readWord();
// Skip the rest in the header
readWord(); // skip searchRange
readWord(); // skip entrySelector
readWord(); // skip rangeShift
// Now we can read the tables
for ( int i = 0; i < numTables; i++ )
{
// Read the table entry
int tag = readDword();
readDword(); // skip checksum
int offset = readDword();
int length = readDword();
// Now here' the trick. 'name' field actually contains the textual string name.
// So the 'name' string in characters equals to 0x6E616D65
if ( tag == 0x6E616D65 )
{
// Here's the name section. Read it completely into the allocated buffer
byte[] table = new byte[ length ];
m_file.seek( offset );
read( table );
// This is also a table. See http://developer.apple.com/fonts/ttrefman/rm06/Chap6name.html
// According to Table 36, the total number of table records is stored in the second word, at the offset 2.
// Getting the count and string offset - remembering it's big endian.
int count = getWord( table, 2 );
int string_offset = getWord( table, 4 );
// Record starts from offset 6
for ( int record = 0; record < count; record++ )
{
// Table 37 tells us that each record is 6 words -> 12 bytes, and that the nameID is 4th word so its offset is 6.
// We also need to account for the first 6 bytes of the header above (Table 36), so...
int nameid_offset = record * 12 + 6;
int platformID = getWord( table, nameid_offset );
int nameid_value = getWord( table, nameid_offset + 6 );
// Table 42 lists the valid name Identifiers. We're interested in 4 but not in Unicode encoding (for simplicity).
// The encoding is stored as PlatformID and we're interested in Mac encoding
if ( nameid_value == 4 && platformID == 1 )
{
// We need the string offset and length, which are the word 6 and 5 respectively
int name_length = getWord( table, nameid_offset + 8 );
int name_offset = getWord( table, nameid_offset + 10 );
// The real name string offset is calculated by adding the string_offset
name_offset = name_offset + string_offset;
// Make sure it is inside the array
if ( name_offset >= 0 && name_offset + name_length < table.length )
return new String( table, name_offset, name_length );
}
}
}
}
return null;
}
catch (FileNotFoundException e)
{
// Permissions?
return null;
}
catch (IOException e)
{
// Most likely a corrupted font file
return null;
}
}
// Font file; must be seekable
private RandomAccessFile m_file = null;
// Helper I/O functions
private int readByte() throws IOException
{
return m_file.read() & 0xFF;
}
private int readWord() throws IOException
{
int b1 = readByte();
int b2 = readByte();
return b1 << 8 | b2;
}
private int readDword() throws IOException
{
int b1 = readByte();
int b2 = readByte();
int b3 = readByte();
int b4 = readByte();
return b1 << 24 | b2 << 16 | b3 << 8 | b4;
}
private void read( byte [] array ) throws IOException
{
if ( m_file.read( array ) != array.length )
throw new IOException();
}
// Helper
private int getWord( byte [] array, int offset )
{
int b1 = array[ offset ] & 0xFF;
int b2 = array[ offset + 1 ] & 0xFF;
return b1 << 8 | b2;
}
}
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