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