How can i get record by data block not by sql? - Mailing list pgsql-general

How can i get record by data block not by sql?
 
I want to read and write lots of data by data blocks, so i can form a disk-resident tree by recording the block address. But i don't know  how to implement in postgresql.
Is there system function can do this? 
Can someone help me?? Thank you very very much!!!!1

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