// NewMerkleBlock returns a new *wire.MsgMerkleBlock and an array of the matched
// transaction index numbers based on the passed block and filter.
func NewMerkleBlock(block *coinutil.Block, filter *Filter) (*wire.MsgMerkleBlock, []uint32) {
numTx := uint32(len(block.Transactions()))
mBlock := merkleBlock{
numTx: numTx,
allHashes: make([]*wire.ShaHash, 0, numTx),
matchedBits: make([]byte, 0, numTx),
}
// Find and keep track of any transactions that match the filter.
var matchedIndices []uint32
for txIndex, tx := range block.Transactions() {
if filter.MatchTxAndUpdate(tx) {
mBlock.matchedBits = append(mBlock.matchedBits, 0x01)
matchedIndices = append(matchedIndices, uint32(txIndex))
} else {
mBlock.matchedBits = append(mBlock.matchedBits, 0x00)
}
mBlock.allHashes = append(mBlock.allHashes, tx.Sha())
}
// Calculate the number of merkle branches (height) in the tree.
height := uint32(0)
for mBlock.calcTreeWidth(height) > 1 {
height++
}
// Build the depth-first partial merkle tree.
mBlock.traverseAndBuild(height, 0)
// Create and return the merkle block.
msgMerkleBlock := wire.MsgMerkleBlock{
Header: block.MsgBlock().Header,
Transactions: uint32(mBlock.numTx),
Hashes: make([]*wire.ShaHash, 0, len(mBlock.finalHashes)),
Flags: make([]byte, (len(mBlock.bits)+7)/8),
}
for _, sha := range mBlock.finalHashes {
msgMerkleBlock.AddTxHash(sha)
}
for i := uint32(0); i < uint32(len(mBlock.bits)); i++ {
msgMerkleBlock.Flags[i/8] |= mBlock.bits[i] << (i % 8)
}
return &msgMerkleBlock, matchedIndices
}
