FetchBlockHeaders returns the raw serialized bytes for the block headers identified by the given hashes. The raw bytes are in the format returned by Serialize on a wire.BlockHeader.
Returns the following errors as required by the interface contract:
- ErrBlockNotFound if the any of the requested block hashes do not exist - ErrTxClosed if the transaction has already been closed - ErrCorruption if the database has somehow become corrupted
NOTE: The data returned by this function is only valid during a database transaction. Attempting to access it after a transaction has ended results in undefined behavior. This constraint prevents additional data copies and allows support for memory-mapped database implementations.
This function is part of the database.Tx interface implementation.