Remove repeated coinbase tx in each exported block's data.
Add resume from last exported height to blockchain_export, making it the
default behavior when the file already exists.
Start reorganizing the utilities.
Various cleanup.
Update output, including referring to both height and block numbers as
zero-based instead of one-based. This better matches the block data,
rather than just some parts of the existing codebase.
Use smaller default batch sizes for importer when verifying, so progress
is saved more frequently.
Use small default batch size (1000) for importer on Windows, due to
current issue with big transaction sizes on LMDB.
file format
-----------
[4-byte magic | variable-length header | block data]
header
------
4-byte file_info length
file_info struct
file format major version
file format minor version
header length (includes file_info struct)
[rest of header, padded with 0 bytes up to header length]
block data
----------
4-byte chunk/block_package length
block_package struct
block
txs (coinbase/miner tx included already in block)
block_size
cumulative_difficulty
coins_generated
4-byte chunk/block_package length
block_package struct
[...]
