sender file adapter content conversion

Hello friends,

I have a scenario where I have to read fixed width file.

Header: field1, field2,field3 only one header (1:1)

Detail: fieldA,fieldB,fieldC multiple detail (1:n)

Key field in header is field2. There is no key field for Detail.

The file structure looks like below; how to read this file and what to configure in sender file adapter.

111 key 1127 header

111 234 ssss detail

111 646 ffsd detail

111 097 sfsf detail

112 key 1134 header

112 234 were detail

112 646 ffsr detail

112 097 sfsd detail

Thanks

Mukesh