/**
* 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);
}
}
/**
* Checks availability of a classpath resource.
*
* @param name Resource name.
* @return {@code true} if resource is available and ready for read, {@code false} otherwise.
*/
private boolean resourceAvailable(String name) {
InputStream cfgStream =
Thread.currentThread().getContextClassLoader().getResourceAsStream(name);
if (cfgStream == null) {
log.error("Classpath resource not found: " + name);
return false;
}
try {
// Read a single byte to force actual content access by JVM.
cfgStream.read();
return true;
} catch (IOException e) {
log.error("Failed to read classpath resource: " + name, e);
return false;
} finally {
U.close(cfgStream, log);
}
}