82 lines
4.1 KiB
Go
82 lines
4.1 KiB
Go
|
// Copyright (c) 2013-2014 The btcsuite developers
|
||
|
|
// Use of this source code is governed by an ISC
|
||
|
|
// license that can be found in the LICENSE file.
|
||
|
|
|
||
|
|
/*
|
||
|
|
Package blockchain implements bitcoin block handling and chain selection rules.
|
||
|
|
|
||
|
|
The bitcoin block handling and chain selection rules are an integral, and quite
|
||
|
|
likely the most important, part of bitcoin. Unfortunately, at the time of
|
||
|
|
this writing, these rules are also largely undocumented and had to be
|
||
|
|
ascertained from the bitcoind source code. At its core, bitcoin is a
|
||
|
|
distributed consensus of which blocks are valid and which ones will comprise the
|
||
|
|
main block chain (public ledger) that ultimately determines accepted
|
||
|
|
transactions, so it is extremely important that fully validating nodes agree on
|
||
|
|
all rules.
|
||
|
|
|
||
|
|
At a high level, this package provides support for inserting new blocks into
|
||
|
|
the block chain according to the aforementioned rules. It includes
|
||
|
|
functionality such as rejecting duplicate blocks, ensuring blocks and
|
||
|
|
transactions follow all rules, orphan handling, and best chain selection along
|
||
|
|
with reorganization.
|
||
|
|
|
||
|
|
Since this package does not deal with other bitcoin specifics such as network
|
||
|
|
communication or wallets, it provides a notification system which gives the
|
||
|
|
caller a high level of flexibility in how they want to react to certain events
|
||
|
|
such as orphan blocks which need their parents requested and newly connected
|
||
|
|
main chain blocks which might result in wallet updates.
|
||
|
|
|
||
|
|
Bitcoin Chain Processing Overview
|
||
|
|
|
||
|
|
Before a block is allowed into the block chain, it must go through an intensive
|
||
|
|
series of validation rules. The following list serves as a general outline of
|
||
|
|
those rules to provide some intuition into what is going on under the hood, but
|
||
|
|
is by no means exhaustive:
|
||
|
|
|
||
|
|
- Reject duplicate blocks
|
||
|
|
- Perform a series of sanity checks on the block and its transactions such as
|
||
|
|
verifying proof of work, timestamps, number and character of transactions,
|
||
|
|
transaction amounts, script complexity, and merkle root calculations
|
||
|
|
- Compare the block against predetermined checkpoints for expected timestamps
|
||
|
|
and difficulty based on elapsed time since the checkpoint
|
||
|
|
- Save the most recent orphan blocks for a limited time in case their parent
|
||
|
|
blocks become available
|
||
|
|
- Stop processing if the block is an orphan as the rest of the processing
|
||
|
|
depends on the block's position within the block chain
|
||
|
|
- Perform a series of more thorough checks that depend on the block's position
|
||
|
|
within the block chain such as verifying block difficulties adhere to
|
||
|
|
difficulty retarget rules, timestamps are after the median of the last
|
||
|
|
several blocks, all transactions are finalized, checkpoint blocks match, and
|
||
|
|
block versions are in line with the previous blocks
|
||
|
|
- Determine how the block fits into the chain and perform different actions
|
||
|
|
accordingly in order to ensure any side chains which have higher difficulty
|
||
|
|
than the main chain become the new main chain
|
||
|
|
- When a block is being connected to the main chain (either through
|
||
|
|
reorganization of a side chain to the main chain or just extending the
|
||
|
|
main chain), perform further checks on the block's transactions such as
|
||
|
|
verifying transaction duplicates, script complexity for the combination of
|
||
|
|
connected scripts, coinbase maturity, double spends, and connected
|
||
|
|
transaction values
|
||
|
|
- Run the transaction scripts to verify the spender is allowed to spend the
|
||
|
|
coins
|
||
|
|
- Insert the block into the block database
|
||
|
|
|
||
|
|
Errors
|
||
|
|
|
||
|
|
Errors returned by this package are either the raw errors provided by underlying
|
||
|
|
calls or of type blockchain.RuleError. This allows the caller to differentiate
|
||
|
|
between unexpected errors, such as database errors, versus errors due to rule
|
||
|
|
violations through type assertions. In addition, callers can programmatically
|
||
|
|
determine the specific rule violation by examining the ErrorCode field of the
|
||
|
|
type asserted blockchain.RuleError.
|
||
|
|
|
||
|
|
Bitcoin Improvement Proposals
|
||
|
|
|
||
|
|
This package includes spec changes outlined by the following BIPs:
|
||
|
|
|
||
|
|
BIP0016 (https://en.bitcoin.it/wiki/BIP_0016)
|
||
|
|
BIP0030 (https://en.bitcoin.it/wiki/BIP_0030)
|
||
|
|
BIP0034 (https://en.bitcoin.it/wiki/BIP_0034)
|
||
|
|
*/
|
||
|
|
package blockchain
|