/** Read checksums and feed compressed block data into decompressor. */
@Override
protected int getCompressedData() throws IOException {
checkStream();
// Get the size of the compressed chunk
int compressedLen = readInt(in, buf, 4);
noCompressedBytes += 4;
// Get the checksum of the compressed chunk
int checksum = readInt(in, buf, 4);
noCompressedBytes += 4;
if (compressedLen > FourMcCodec.FOURMC_MAX_BLOCK_SIZE) {
throw new IOException(
"Compressed length "
+ compressedLen
+ " exceeds max block size "
+ FourMcCodec.FOURMC_MAX_BLOCK_SIZE);
}
Lz4Decompressor lz4dec = (Lz4Decompressor) decompressor;
// if compressed len == uncompressedBlockSize, 4mc wrote data w/o compression
lz4dec.setCurrentBlockUncompressed(compressedLen >= uncompressedBlockSize);
// Read len bytes from underlying stream
if (compressedLen > buffer.length) {
buffer = new byte[compressedLen];
}
readFully(in, buffer, 0, compressedLen);
noCompressedBytes += compressedLen;
// checksum check
if (checksum != Lz4Decompressor.xxhash32(buffer, 0, compressedLen, 0)) {
if (lz4dec.isCurrentBlockUncompressed()) {
throw new IOException("Corrupted uncompressed block (invalid checksum)");
} else {
throw new IOException("Corrupted compressed block (invalid checksum)");
}
}
// Send the read data to the decompressor.
lz4dec.setInput(buffer, 0, compressedLen);
return compressedLen;
}
static {
if (FourMcNativeCodeLoader.isNativeCodeLoaded()) {
boolean nativeLoaded = Lz4Decompressor.isNativeLoaded();
if (!nativeLoaded) {
LOG.error("Failed to load/initialize native-4mc library");
}
} else {
LOG.error("Cannot load native-4mc without native-hadoop");
}
}
@Override
public void close() throws IOException {
if (decompressor == null) {
return;
}
byte[] b = new byte[4096];
while (!decompressor.finished()) {
decompressor.decompress(b, 0, b.length);
}
super.close();
// force release direct buffers of decompressor
((Lz4Decompressor) decompressor).releaseDirectBuffers();
decompressor = null;
}
/** Read and verify 4mc header. */
protected void readHeader(InputStream in) throws IOException {
readFully(in, buf, 0, 12);
int magic = getInt(buf, 0);
if (magic != FourMcCodec.FOURMC_MAGIC) {
throw new IOException("Invalid 4mc header (wrong magic)");
}
int version = getInt(buf, 4);
if (version != FourMcCodec.FOURMC_VERSION) {
throw new IOException("Invalid 4mc header (wrong version)");
}
int hdrChecksum = getInt(buf, 8);
if (hdrChecksum != Lz4Decompressor.xxhash32(buf, 0, 8, 0)) {
throw new IOException("Invalid 4mc header (invalid checksum)");
}
}
/**
* Reads blocks index at tail of file.
*
* @param fs filesystem
* @param file path to 4mc file
* @return block index
* @throws IOException
*/
public static FourMcBlockIndex readIndex(FileSystem fs, Path file) throws IOException {
long fileSize = fs.getFileStatus(file).getLen();
if (fileSize < (12 + 20)) { // file too small
return new FourMcBlockIndex();
}
FSDataInputStream indexIn = fs.open(file);
/*
4mc Footer:
Footer size: 4 bytes
Footer version: 4 byte (1)
Block index offset: 4 bytes delta offset for each stored block, the delta between offset between previous file position and next block
Footer size: 4 bytes (repeated to be able to read from end of file)
MAGIC SIGNATURE: 4 bytes: "4MC\0"
Footer checksum: 4 bytes (always in XXHASH32)
*/
/**
* jump to file tail and read-ahead last 4KB of file which should be enough in most cases
* Improvement: we could estimate a best case compression factor of 10% and calc forecast based
* on filesize and blocksize, to see if better to read-head more.
*/
int readTailSize = 4 * 1024;
if (readTailSize > (fileSize - 12)) readTailSize = (int) (fileSize - 12);
indexIn.seek(fileSize - readTailSize);
byte[] buf = new byte[readTailSize];
readFully(indexIn, buf, 0, buf.length);
int footerSize = getInt(buf, buf.length - 12);
int magic = getInt(buf, buf.length - 8);
int checksum = getInt(buf, buf.length - 4);
if (magic != FourMcCodec.FOURMC_MAGIC) {
throw new IOException("Invalid 4mc footer magic");
}
if (footerSize >= (fileSize - 12)) {
throw new IOException("Invalid 4mc footer checksum");
}
// very rare case: read head was not enough! seek back and read it all
if (footerSize > readTailSize) {
readTailSize = footerSize;
indexIn.seek(fileSize - readTailSize);
buf = new byte[readTailSize];
readFully(indexIn, buf, 0, buf.length);
}
indexIn.close();
int startFooterOffset = readTailSize - footerSize;
if (getInt(buf, startFooterOffset) != footerSize) { // size again
throw new IOException("Invalid 4mc footer size");
}
if (getInt(buf, startFooterOffset + 4) != FourMcCodec.FOURMC_VERSION) { // version
throw new IOException(
"Invalid 4mc footer version (" + getInt(buf, startFooterOffset + 4) + ")");
}
if (checksum != Lz4Decompressor.xxhash32(buf, startFooterOffset, footerSize - 4, 0)) {
throw new IOException("Invalid 4mc footer checksum");
}
int totalBlocks = (footerSize - 20) / 4;
FourMcBlockIndex index = new FourMcBlockIndex(totalBlocks);
long curOffset = 0;
for (int i = 0; i < totalBlocks; ++i) {
curOffset += getInt(buf, startFooterOffset + 8 + (i * 4));
index.set(i, curOffset);
}
return index;
}
