Read data from Postgres table pages - Mailing list pgsql-hackers

I'm trying to build a postgres export tool that reads data from table pages and exports it to an S3 bucket. I'd like to avoid manual commands like pg_dump, I need access to the raw data.

Can you please point me to the postgres source header / cc files that encapsulate this functionality?

 - List all pages for a table

- Read a given page for a table

Any pointers to the relevant source code would be appreciated.

Thanks,

Sushrut