core/src/main/java/com/orientechnologies/orient/core/storage/fs/OFileClassic.java
private long checkRegions(final long iOffset, final long iLength) {
    acquireReadLock();
    try {
      if (iOffset < 0 || iOffset + iLength > size) {
        throw new OIOException(
            "You cannot access outside the file size (" + size + " bytes). You have requested portion " + iOffset + "-" + (iOffset
                + iLength) + " bytes. File: " + this);
      }

      return iOffset + HEADER_SIZE;
    } finally {
      releaseReadLock();
    }

  }
private long checkRegions(final long iOffset, final long iLength) {
    acquireReadLock();
    try {
      if (iOffset < 0 || iOffset + iLength > size) {
        throw new OIOException(
            "You cannot access outside the file size (" + size + " bytes). You have requested portion " + iOffset + "-" + (iOffset
                + iLength) + " bytes. File: " + this);
      }

      return iOffset + HEADER_SIZE;
    } finally {
      releaseReadLock();
    }

  }
ALWAYS ADD THE HEADER SIZE BECAUSE ON THIS TYPE IS ALWAYS NEEDED