/**
* Read block from file.
*
* @param file - File to read.
* @param off - Marker position in file to start read from if {@code -1} read last blockSz bytes.
* @param blockSz - Maximum number of chars to read.
* @param lastModified - File last modification time.
* @return Read file block.
* @throws IOException In case of error.
*/
public static VisorFileBlock readBlock(File file, long off, int blockSz, long lastModified)
throws IOException {
RandomAccessFile raf = null;
try {
long fSz = file.length();
long fLastModified = file.lastModified();
long pos = off >= 0 ? off : Math.max(fSz - blockSz, 0);
// Try read more that file length.
if (fLastModified == lastModified && fSz != 0 && pos >= fSz)
throw new IOException(
"Trying to read file block with wrong offset: " + pos + " while file size: " + fSz);
if (fSz == 0)
return new VisorFileBlock(file.getPath(), pos, fLastModified, 0, false, EMPTY_FILE_BUF);
else {
int toRead = Math.min(blockSz, (int) (fSz - pos));
byte[] buf = new byte[toRead];
raf = new RandomAccessFile(file, "r");
raf.seek(pos);
int cntRead = raf.read(buf, 0, toRead);
if (cntRead != toRead)
throw new IOException(
"Count of requested and actually read bytes does not match [cntRead="
+ cntRead
+ ", toRead="
+ toRead
+ ']');
boolean zipped = buf.length > 512;
return new VisorFileBlock(
file.getPath(), pos, fSz, fLastModified, zipped, zipped ? zipBytes(buf) : buf);
}
} finally {
U.close(raf, null);
}
}
/**
* Decode file charset.
*
* @param f File to process.
* @return File charset.
* @throws IOException in case of error.
*/
public static Charset decode(File f) throws IOException {
SortedMap<String, Charset> charsets = Charset.availableCharsets();
String[] firstCharsets = {
Charset.defaultCharset().name(), "US-ASCII", "UTF-8", "UTF-16BE", "UTF-16LE"
};
Collection<Charset> orderedCharsets = U.newLinkedHashSet(charsets.size());
for (String c : firstCharsets)
if (charsets.containsKey(c)) orderedCharsets.add(charsets.get(c));
orderedCharsets.addAll(charsets.values());
try (RandomAccessFile raf = new RandomAccessFile(f, "r")) {
FileChannel ch = raf.getChannel();
ByteBuffer buf = ByteBuffer.allocate(4096);
ch.read(buf);
buf.flip();
for (Charset charset : orderedCharsets) {
CharsetDecoder decoder = charset.newDecoder();
decoder.reset();
try {
decoder.decode(buf);
return charset;
} catch (CharacterCodingException ignored) {
}
}
}
return Charset.defaultCharset();
}
