public static ProcedureWALTrailer readTrailer(FSDataInputStream stream, long startPos, long size)
throws IOException {
// Beginning of the Trailer Jump. 17 = 1 byte version + 8 byte magic + 8 byte offset
long trailerPos = size - 17;
if (trailerPos < startPos) {
throw new InvalidWALDataException("Missing trailer: size=" + size + " startPos=" + startPos);
}
stream.seek(trailerPos);
int version = stream.read();
if (version != TRAILER_VERSION) {
throw new InvalidWALDataException(
"Invalid Trailer version. got " + version + " expected " + TRAILER_VERSION);
}
long magic = StreamUtils.readLong(stream);
if (magic != TRAILER_MAGIC) {
throw new InvalidWALDataException(
"Invalid Trailer magic. got " + magic + " expected " + TRAILER_MAGIC);
}
long trailerOffset = StreamUtils.readLong(stream);
stream.seek(trailerOffset);
ProcedureWALEntry entry = readEntry(stream);
if (entry.getType() != ProcedureWALEntry.Type.PROCEDURE_WAL_EOF) {
throw new InvalidWALDataException("Invalid Trailer begin");
}
ProcedureWALTrailer trailer =
ProcedureWALTrailer.newBuilder().setVersion(version).setTrackerPos(stream.getPos()).build();
return trailer;
}
