Refactor DAH creation to better accommodate celestia-node use case

[evan-forbes]

Description

This PR is a quick refactor of #524 so that the user has more control over what happens to the extended data square after it is used to generate a data availability header. Note that this PR was built on top of the branch used for #537, so that should probably merged first.

Closes: #538
blocked by #536 #537

[evan-forbes]

instead of generating the extended data square for the user, accept it as input to create a data availability header

[evan-forbes]

the diff make it's difficult to see the differences... I reccomend simply looking at the file. The previous NewDataAvailabilityHeader function has been split in two. This provides the user with direct access to the extended data square.

celestia-core/pkg/da/data_availability_header.go

Lines 40 to 74 in 422eb4d

	// NewDataAvailabilityHeader generates a DataAvailability header using the provided square size and shares
	func NewDataAvailabilityHeader(eds *rsmt2d.ExtendedDataSquare) DataAvailabilityHeader {
	// generate the row and col roots using the EDS
	dah := DataAvailabilityHeader{
	RowsRoots: eds.RowRoots(),
	ColumnRoots: eds.ColRoots(),
	}
	// generate the hash of the data using the new roots
	dah.Hash()
	return dah
	}
	func ExtendShares(squareSize uint64, shares [][]byte) (*rsmt2d.ExtendedDataSquare, error) {
	// Check that square size is with range
	if squareSize < consts.MinSquareSize || squareSize > consts.MaxSquareSize {
	return nil, fmt.Errorf(
	"invalid square size: min %d max %d provided %d",
	consts.MinSquareSize,
	consts.MaxSquareSize,
	squareSize,
	)
	}
	// check that valid number of shares have been provided
	if squareSize*squareSize != uint64(len(shares)) {
	return nil, fmt.Errorf(
	"must provide valid number of shares for square size: got %d wanted %d",
	len(shares),
	squareSize*squareSize,
	)
	}
	tree := wrapper.NewErasuredNamespacedMerkleTree(squareSize)
	return rsmt2d.ComputeExtendedDataSquare(shares, consts.DefaultCodec(), tree.Constructor)
	}

[liamsi]

So this is the main change and the somewhere else mentioned celestia-node use-case is to re-use this function, right?

[evan-forbes]

yep, this is the main change, and celestia-node would use both of the new functions outlined here. This way they would have access to the rsmt2d.DataSquare

[evan-forbes]

the diff make it's difficult to see the differences... I reccomend simply looking at the file. The previous NewDataAvailabilityHeader function has been split in two. This provides the user with direct access to the extended data square.

celestia-core/pkg/da/data_availability_header.go

Lines 40 to 74 in 422eb4d

	// NewDataAvailabilityHeader generates a DataAvailability header using the provided square size and shares
	func NewDataAvailabilityHeader(eds *rsmt2d.ExtendedDataSquare) DataAvailabilityHeader {
	// generate the row and col roots using the EDS
	dah := DataAvailabilityHeader{
	RowsRoots: eds.RowRoots(),
	ColumnRoots: eds.ColRoots(),
	}
	// generate the hash of the data using the new roots
	dah.Hash()
	return dah
	}
	func ExtendShares(squareSize uint64, shares [][]byte) (*rsmt2d.ExtendedDataSquare, error) {
	// Check that square size is with range
	if squareSize < consts.MinSquareSize || squareSize > consts.MaxSquareSize {
	return nil, fmt.Errorf(
	"invalid square size: min %d max %d provided %d",
	consts.MinSquareSize,
	consts.MaxSquareSize,
	squareSize,
	)
	}
	// check that valid number of shares have been provided
	if squareSize*squareSize != uint64(len(shares)) {
	return nil, fmt.Errorf(
	"must provide valid number of shares for square size: got %d wanted %d",
	len(shares),
	squareSize*squareSize,
	)
	}
	tree := wrapper.NewErasuredNamespacedMerkleTree(squareSize)
	return rsmt2d.ComputeExtendedDataSquare(shares, consts.DefaultCodec(), tree.Constructor)
	}

[renaynay]

This LGTM @evan-forbes ! Thank you so much for the quick PR, this will be very helpful for celestia node.

[liamsi]

👍🏼