private IndexEntry parseEntry(final ByteBuffer buffer, final int n) {
        final int pos = this.header.getHeaderSize() + n * getIndexSize();
        buffer.position(pos);
        final IndexEntry indexEntry = IndexEntry.newInstance();
        indexEntry.decode(buffer);
        return indexEntry;
    }
Parse an index entry from this index file
jraft-extension/java-log-storage-impl/src/main/java/com/alipay/sofa/jraft/storage/file/index/IndexFile.java