package gov.nasa.gsfc.spdf.cdfj; import java.nio.*; import java.nio.channels.*; import java.io.*; import java.net.*; /** * ReaderFactory creates an instance of CDFReader from a CDF source. * Uses array backed ByteBuffer for CDFReader. * The source CDF can be a file, or a URL. */ public final class ReaderFactory { /** * creates CDFReader object from a file using array backed ByteBuffer. */ static int preamble = 3000; /** * Return a reader for the CDF file. This looks at the CDF file internals * to calculate the version and returns an implementation. * @param fname * @return a reader for the CDF file * @throws CDFException.ReaderError if there is an issue while reading the file * @throws IllegalArgumentException if the file is not a CDF file */ public static CDFReader getReader(String fname) throws CDFException.ReaderError { CDFImpl cdf = null; File file = new File(fname); try { RandomAccessFile raf = new RandomAccessFile(file, "r"); long len = raf.length(); if (len > preamble) len = preamble; byte[] ba = new byte[(int)len]; raf.readFully(ba); ByteBuffer buf = ByteBuffer.wrap(ba); cdf = getVersion(buf, raf.getChannel()); } catch (Throwable th) { CDFException.ReaderError ex= new CDFException.ReaderError("I/O Error reading " + fname,th); throw ex; } if ( cdf==null ) { throw new IllegalArgumentException("File is not a CDF-format file."); } final String _fname = file.getPath(); cdf.setSource(new CDFFactory.CDFSource() { public String getName() {return _fname;}; public boolean isFile() {return true;}; }); CDFReader rdr = new CDFReader(); rdr.setImpl(cdf); return rdr; } /** * creates CDFReader object from a URL using array backed ByteBuffer. */ public static CDFReader getReader(URL url) throws CDFException.ReaderError { CDFImpl cdf = null; try { URLConnection con = new CDFUrl(url).openConnection(); int remaining = con.getContentLength(); InputStream is = con.getInputStream(); byte [] ba = new byte[remaining]; int offset = 0; while (remaining > 0) { int got = is.read(ba, offset, remaining); offset += got; remaining -= got; } ((HttpURLConnection)con).disconnect(); ByteBuffer buf = ByteBuffer.wrap(ba); cdf = CDFFactory.getVersion(buf); if ( cdf==null ) { throw new IllegalArgumentException("File is not a CDF-format file."); } } catch (Throwable th) { throw new CDFException.ReaderError("I/O Error reading " + url,th); } CDFReader rdr = new CDFReader(); rdr.setImpl(cdf); final String _url = url.toString(); cdf.setSource(new CDFFactory.CDFSource() { public String getName() {return _url;}; public boolean isFile() {return false;}; }); return rdr; } /** * returns an implementation for reading the CDF, or null if the file * does not have magic numbers indicating it is a CDF. * @param buf the buffer containing the CDF data. * @param ch the file channel for the data. * @return the implementation for reading the CDF, or null. * @throws Throwable */ static CDFImpl getVersion(ByteBuffer buf, FileChannel ch) throws Throwable { LongBuffer lbuf = buf.asLongBuffer(); long magic = lbuf.get(); if (magic == CDFFactory.CDF3_MAGIC) { return new CDF3Impl(buf, ch); } if (magic == CDFFactory.CDF3_COMPRESSED_MAGIC) { ByteBuffer mbuf = CDFFactory.uncompressed(buf, 3); return new CDF3Impl(mbuf); } if (magic == CDFFactory.CDF2_MAGIC_DOT5) { int release = buf.getInt(24); return new CDF2Impl(buf, release, ch); } else { ShortBuffer sbuf = buf.asShortBuffer(); if (sbuf.get() == (short)0xcdf2) { if (sbuf.get() == (short)0x6002) { short x = sbuf.get(); if (x == 0) { if (sbuf.get() == -1) { return new CDF2Impl(buf, 6, ch); } } else { if ((x == (short)0xcccc) && (sbuf.get() == 1)) { // is compressed - positioned at CCR ByteBuffer mbuf = CDFFactory.uncompressed(buf, 2); return new CDF2Impl(mbuf, 6, ch); } } } } } return null; } public static CDFReader getReader(String fname, boolean map) throws CDFException.ReaderError { CDFImpl cdf = null; File file = new File(fname); try { int len = (int)file.length(); byte[] ba = new byte[len]; int rem = len; FileInputStream fis = new FileInputStream(file); int n = 0; while (rem > 0) { len = fis.read(ba, n, rem); n += len; rem -= len; } fis.close(); cdf = CDFFactory.getCDF(ba); if ( cdf==null ) { throw new IllegalArgumentException("File is not a CDF-format file: "+fname); } } catch (Throwable th) { throw new CDFException.ReaderError("I/O Error reading " + fname); } final String _fname = file.getPath(); cdf.setSource(new CDFFactory.CDFSource() { public String getName() {return _fname;}; public boolean isFile() {return true;}; }); CDFReader rdr = new CDFReader(); rdr.setImpl(cdf); return rdr; } }