blockchain

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 Go to latest Published: Nov 30, 2015 License: ISC Imports: 17 Imported by: 0

README

blockchain

[Build Status] (https://travis-ci.org/btcsuite/btcd) ![ISC License] (http://img.shields.io/badge/license-ISC-blue.svg) [GoDoc] (http://godoc.org/github.com/btcsuite/btcd/blockchain)

Package blockchain implements bitcoin block handling and chain selection rules. The test coverage is currently only around 60%, but will be increasing over time. See test_coverage.txt for the gocov coverage report. Alternatively, if you are running a POSIX OS, you can run the cov_report.sh script for a real-time report. Package blockchain is licensed under the liberal ISC license.

There is an associated blog post about the release of this package here.

This package has intentionally been designed so it can be used as a standalone package for any projects needing to handle processing of blocks into the bitcoin block chain.

Installation and Updating

$ go get -u github.com/btcsuite/btcd/blockchain

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

Examples

GPG Verification Key

All official release tags are signed by Conformal so users can ensure the code has not been tampered with and is coming from the btcsuite developers. To verify the signature perform the following:

  • Download the public key from the Conformal website at https://opensource.conformal.com/GIT-GPG-KEY-conformal.txt

  • Import the public key into your GPG keyring:

    gpg --import GIT-GPG-KEY-conformal.txt

  • Verify the release tag with the following command where TAG_NAME is a placeholder for the specific tag:

    git tag -v TAG_NAME

License

Package blockchain is licensed under the copyfree ISC License.

Documentation

Overview

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)

Index

Examples

Constants

View Source 
const (
	// MaxSigOpsPerBlock is the maximum number of signature operations
	// allowed for a block.  It is a fraction of the max block payload size.
	MaxSigOpsPerBlock = wire.MaxBlockPayload / 50

	// MaxTimeOffsetSeconds is the maximum number of seconds a block time
	// is allowed to be ahead of the current time.  This is currently 2
	// hours.
	MaxTimeOffsetSeconds = 2 * 60 * 60

	// MinCoinbaseScriptLen is the minimum length a coinbase script can be.
	MinCoinbaseScriptLen = 2

	// MaxCoinbaseScriptLen is the maximum length a coinbase script can be.
	MaxCoinbaseScriptLen = 100

	// CoinbaseMaturity is the number of blocks required before newly
	// mined bitcoins (coinbase transactions) can be spent.
	CoinbaseMaturity = 100
)
View Source 
const (

	// BlocksPerRetarget is the number of blocks between each difficulty
	// retarget.  It is calculated based on the desired block generation
	// rate.
	BlocksPerRetarget = int32(targetTimespan / targetSpacing)
)
View Source 
const CheckpointConfirmations = 2016

CheckpointConfirmations is the number of blocks before the end of the current best block chain that a good checkpoint candidate must be.

Variables

View Source 
var ErrIndexAlreadyInitialized = errors.New("the block index can only be " +
	"initialized before it has been modified")

ErrIndexAlreadyInitialized describes an error that indicates the block index is already initialized.

Functions

func BigToCompact 

func BigToCompact(n *big.Int) uint32

BigToCompact converts a whole number N to a compact representation using an unsigned 32-bit number. The compact representation only provides 23 bits of precision, so values larger than (2^23 - 1) only encode the most significant digits of the number. See CompactToBig for details.

Example

This example demonstrates how to convert a target difficulty into the compact "bits" in a block header which represent that target difficulty . 

package main

import (
	"fmt"
	"math/big"

	"github.com/btcsuite/btcd/blockchain"

	_ "github.com/btcsuite/btcd/database/memdb"
)

func main() {
	// Convert the target difficulty from block 300000 in the main block
	// chain to compact form.
	t := "0000000000000000896c00000000000000000000000000000000000000000000"
	targetDifficulty, success := new(big.Int).SetString(t, 16)
	if !success {
		fmt.Println("invalid target difficulty")
		return
	}
	bits := blockchain.BigToCompact(targetDifficulty)

	fmt.Println(bits)

}

Output:

419465580

func BuildMerkleTreeStore 

func BuildMerkleTreeStore(transactions []*btcutil.Tx) []*wire.ShaHash

BuildMerkleTreeStore creates a merkle tree from a slice of transactions, stores it using a linear array, and returns a slice of the backing array. A linear array was chosen as opposed to an actual tree structure since it uses about half as much memory. The following describes a merkle tree and how it is stored in a linear array.

A merkle tree is a tree in which every non-leaf node is the hash of its children nodes. A diagram depicting how this works for bitcoin transactions where h(x) is a double sha256 follows: 

         root = h1234 = h(h12 + h34)
        /                           \
  h12 = h(h1 + h2)            h34 = h(h3 + h4)
   /            \              /            \
h1 = h(tx1)  h2 = h(tx2)    h3 = h(tx3)  h4 = h(tx4)

The above stored as a linear array is as follows: 

[h1 h2 h3 h4 h12 h34 root]

As the above shows, the merkle root is always the last element in the array.

The number of inputs is not always a power of two which results in a balanced tree structure as above. In that case, parent nodes with no children are also zero and parent nodes with only a single left node are calculated by concatenating the left node with itself before hashing. Since this function uses nodes that are pointers to the hashes, empty nodes will be nil.

func CalcBlockSubsidy 

func CalcBlockSubsidy(height int32, chainParams *chaincfg.Params) int64

CalcBlockSubsidy returns the subsidy amount a block at the provided height should have. This is mainly used for determining how much the coinbase for newly generated blocks awards as well as validating the coinbase for blocks has the expected value.

The subsidy is halved every SubsidyHalvingInterval blocks. Mathematically this is: baseSubsidy / 2^(height/subsidyHalvingInterval)

At the target block generation rate for the main network, this is approximately every 4 years.

func CalcWork 

func CalcWork(bits uint32) *big.Int

CalcWork calculates a work value from difficulty bits. Bitcoin increases the difficulty for generating a block by decreasing the value which the generated hash must be less than. This difficulty target is stored in each block header using a compact representation as described in the documenation for CompactToBig. The main chain is selected by choosing the chain that has the most proof of work (highest difficulty). Since a lower target difficulty value equates to higher actual difficulty, the work value which will be accumulated must be the inverse of the difficulty. Also, in order to avoid potential division by zero and really small floating point numbers, the result adds 1 to the denominator and multiplies the numerator by 2^256.

func CheckBlockSanity 

func CheckBlockSanity(block *btcutil.Block, powLimit *big.Int, timeSource MedianTimeSource) error

CheckBlockSanity performs some preliminary checks on a block to ensure it is sane before continuing with block processing. These checks are context free.

func CheckProofOfWork 

func CheckProofOfWork(block *btcutil.Block, powLimit *big.Int) error

CheckProofOfWork ensures the block header bits which indicate the target difficulty is in min/max range and that the block hash is less than the target difficulty as claimed.

func CheckTransactionInputs 

func CheckTransactionInputs(tx *btcutil.Tx, txHeight int32, txStore TxStore) (int64, error)

CheckTransactionInputs performs a series of checks on the inputs to a transaction to ensure they are valid. An example of some of the checks include verifying all inputs exist, ensuring the coinbase seasoning requirements are met, detecting double spends, validating all values and fees are in the legal range and the total output amount doesn't exceed the input amount, and verifying the signatures to prove the spender was the owner of the bitcoins and therefore allowed to spend them. As it checks the inputs, it also calculates the total fees for the transaction and returns that value.

func CheckTransactionSanity 

func CheckTransactionSanity(tx *btcutil.Tx) error

CheckTransactionSanity performs some preliminary checks on a transaction to ensure it is sane. These checks are context free.

func CompactToBig 

func CompactToBig(compact uint32) *big.Int

CompactToBig converts a compact representation of a whole number N to an unsigned 32-bit number. The representation is similar to IEEE754 floating point numbers.

Like IEEE754 floating point, there are three basic components: the sign, the exponent, and the mantissa. They are broken out as follows:

  • the most significant 8 bits represent the unsigned base 256 exponent

  • bit 23 (the 24th bit) represents the sign bit

  • the least significant 23 bits represent the mantissa

    ------------------------------------------------- | Exponent | Sign | Mantissa | ------------------------------------------------- | 8 bits [31-24] | 1 bit [23] | 23 bits [22-00] | -------------------------------------------------

The formula to calculate N is: 

N = (-1^sign) * mantissa * 256^(exponent-3)

This compact form is only used in bitcoin to encode unsigned 256-bit numbers which represent difficulty targets, thus there really is not a need for a sign bit, but it is implemented here to stay consistent with bitcoind.

Example

This example demonstrates how to convert the compact "bits" in a block header which represent the target difficulty to a big integer and display it using the typical hex notation. 

package main

import (
	"fmt"

	"github.com/btcsuite/btcd/blockchain"

	_ "github.com/btcsuite/btcd/database/memdb"
)

func main() {
	// Convert the bits from block 300000 in the main block chain.
	bits := uint32(419465580)
	targetDifficulty := blockchain.CompactToBig(bits)

	// Display it in hex.
	fmt.Printf("%064x\n", targetDifficulty.Bytes())

}

Output:

0000000000000000896c00000000000000000000000000000000000000000000

func CountP2SHSigOps 

func CountP2SHSigOps(tx *btcutil.Tx, isCoinBaseTx bool, txStore TxStore) (int, error)

CountP2SHSigOps returns the number of signature operations for all input transactions which are of the pay-to-script-hash type. This uses the precise, signature operation counting mechanism from the script engine which requires access to the input transaction scripts.

func CountSigOps 

func CountSigOps(tx *btcutil.Tx) int

CountSigOps returns the number of signature operations for all transaction input and output scripts in the provided transaction. This uses the quicker, but imprecise, signature operation counting mechanism from txscript.

func DisableLog 

func DisableLog()

DisableLog disables all library log output. Logging output is disabled by default until either UseLogger or SetLogWriter are called.

func ExtractCoinbaseHeight 

func ExtractCoinbaseHeight(coinbaseTx *btcutil.Tx) (int32, error)

ExtractCoinbaseHeight attempts to extract the height of the block from the scriptSig of a coinbase transaction. Coinbase heights are only present in blocks of version 2 or later. This was added as part of BIP0034.

func HashMerkleBranches 

func HashMerkleBranches(left *wire.ShaHash, right *wire.ShaHash) *wire.ShaHash

HashMerkleBranches takes two hashes, treated as the left and right tree nodes, and returns the hash of their concatenation. This is a helper function used to aid in the generation of a merkle tree.

func IsCoinBase 

func IsCoinBase(tx *btcutil.Tx) bool

IsCoinBase determines whether or not a transaction is a coinbase. A coinbase is a special transaction created by miners that has no inputs. This is represented in the block chain by a transaction with a single input that has a previous output transaction index set to the maximum value along with a zero hash.

This function only differs from IsCoinBaseTx in that it works with a higher level util transaction as opposed to a raw wire transaction.

func IsCoinBaseTx 

func IsCoinBaseTx(msgTx *wire.MsgTx) bool

IsCoinBaseTx determines whether or not a transaction is a coinbase. A coinbase is a special transaction created by miners that has no inputs. This is represented in the block chain by a transaction with a single input that has a previous output transaction index set to the maximum value along with a zero hash.

This function only differs from IsCoinBase in that it works with a raw wire transaction as opposed to a higher level util transaction.

func IsFinalizedTransaction 

func IsFinalizedTransaction(tx *btcutil.Tx, blockHeight int32, blockTime time.Time) bool

IsFinalizedTransaction determines whether or not a transaction is finalized.

func SetLogWriter 

func SetLogWriter(w io.Writer, level string) error

SetLogWriter uses a specified io.Writer to output package logging info. This allows a caller to direct package logging output without needing a dependency on seelog. If the caller is also using btclog, UseLogger should be used instead.

func ShaHashToBig 

func ShaHashToBig(hash *wire.ShaHash) *big.Int

ShaHashToBig converts a wire.ShaHash into a big.Int that can be used to perform math comparisons.

func ShouldHaveSerializedBlockHeight 

func ShouldHaveSerializedBlockHeight(header *wire.BlockHeader) bool

ShouldHaveSerializedBlockHeight determines if a block should have a serialized block height embedded within the scriptSig of its coinbase transaction. Judgement is based on the block version in the block header. Blocks with version 2 and above satisfy this criteria. See BIP0034 for further information.

func UseLogger 

func UseLogger(logger btclog.Logger)

UseLogger uses a specified Logger to output package logging info. This should be used in preference to SetLogWriter if the caller is also using btclog.

func ValidateTransactionScripts 

func ValidateTransactionScripts(tx *btcutil.Tx, txStore TxStore, flags txscript.ScriptFlags, sigCache *txscript.SigCache) error

ValidateTransactionScripts validates the scripts for the passed transaction using multiple goroutines.

Types

type BehaviorFlags 

type BehaviorFlags uint32

BehaviorFlags is a bitmask defining tweaks to the normal behavior when performing chain processing and consensus rules checks. 

const (
	// BFFastAdd may be set to indicate that several checks can be avoided
	// for the block since it is already known to fit into the chain due to
	// already proving it correct links into the chain up to a known
	// checkpoint.  This is primarily used for headers-first mode.
	BFFastAdd BehaviorFlags = 1 << iota

	// BFNoPoWCheck may be set to indicate the proof of work check which
	// ensures a block hashes to a value less than the required target will
	// not be performed.
	BFNoPoWCheck

	// BFDryRun may be set to indicate the block should not modify the chain
	// or memory chain index.  This is useful to test that a block is valid
	// without modifying the current state.
	BFDryRun

	// BFNone is a convenience value to specifically indicate no flags.
	BFNone BehaviorFlags = 0
)

type BlockChain 

type BlockChain struct {
	// contains filtered or unexported fields
}

BlockChain provides functions for working with the bitcoin block chain. It includes functionality such as rejecting duplicate blocks, ensuring blocks follow all rules, orphan handling, checkpoint handling, and best chain selection with reorganization.

func New 

func New(db database.Db, params *chaincfg.Params, c NotificationCallback, sigCache *txscript.SigCache) *BlockChain

New returns a BlockChain instance for the passed bitcoin network using the provided backing database. It accepts a callback on which notifications will be sent when various events take place. See the documentation for Notification and NotificationType for details on the types and contents of notifications. The provided callback can be nil if the caller is not interested in receiving notifications.

func (*BlockChain) BlockLocatorFromHash 

func (b *BlockChain) BlockLocatorFromHash(hash *wire.ShaHash) BlockLocator

BlockLocatorFromHash returns a block locator for the passed block hash. See BlockLocator for details on the algotirhm used to create a block locator.

In addition to the general algorithm referenced above, there are a couple of special cases which are handled:

  • If the genesis hash is passed, there are no previous hashes to add and therefore the block locator will only consist of the genesis hash
  • If the passed hash is not currently known, the block locator will only consist of the passed hash

func (*BlockChain) CalcNextRequiredDifficulty 

func (b *BlockChain) CalcNextRequiredDifficulty(timestamp time.Time) (uint32, error)

CalcNextRequiredDifficulty calculates the required difficulty for the block after the end of the current best chain based on the difficulty retarget rules.

This function is NOT safe for concurrent access.

func (*BlockChain) CalcPastMedianTime 

func (b *BlockChain) CalcPastMedianTime() (time.Time, error)

CalcPastMedianTime calculates the median time of the previous few blocks prior to, and including, the end of the current best chain. It is primarily used to ensure new blocks have sane timestamps.

This function is NOT safe for concurrent access.

func (*BlockChain) CheckConnectBlock 

func (b *BlockChain) CheckConnectBlock(block *btcutil.Block) error

CheckConnectBlock performs several checks to confirm connecting the passed block to the main chain does not violate any rules. An example of some of the checks performed are ensuring connecting the block would not cause any duplicate transaction hashes for old transactions that aren't already fully spent, double spends, exceeding the maximum allowed signature operations per block, invalid values in relation to the expected block subsidy, or fail transaction script validation.

This function is NOT safe for concurrent access.

func (*BlockChain) Checkpoints 

func (b *BlockChain) Checkpoints() []chaincfg.Checkpoint

Checkpoints returns a slice of checkpoints (regardless of whether they are already known). When checkpoints are disabled or there are no checkpoints for the active network, it will return nil.

func (*BlockChain) DisableCheckpoints 

func (b *BlockChain) DisableCheckpoints(disable bool)

DisableCheckpoints provides a mechanism to disable validation against checkpoints which you DO NOT want to do in production. It is provided only for debug purposes.

func (*BlockChain) DisableVerify 

func (b *BlockChain) DisableVerify(disable bool)

DisableVerify provides a mechanism to disable transaction script validation which you DO NOT want to do in production as it could allow double spends and othe undesirable things. It is provided only for debug purposes since script validation is extremely intensive and when debugging it is sometimes nice to quickly get the chain.

func (*BlockChain) FetchTransactionStore 

func (b *BlockChain) FetchTransactionStore(tx *btcutil.Tx, includeSpent bool) (TxStore, error)

FetchTransactionStore fetches the input transactions referenced by the passed transaction from the point of view of the end of the main chain. It also attempts to fetch the transaction itself so the returned TxStore can be examined for duplicate transactions.

func (*BlockChain) GenerateInitialIndex 

func (b *BlockChain) GenerateInitialIndex() error

GenerateInitialIndex is an optional function which generates the required number of initial block nodes in an optimized fashion. This is optional because the memory block index is sparse and previous nodes are dynamically loaded as needed. However, during initial startup (when there are no nodes in memory yet), dynamically loading all of the required nodes on the fly in the usual way is much slower than preloading them.

This function can only be called once and it must be called before any nodes are added to the block index. ErrIndexAlreadyInitialized is returned if the former is not the case. In practice, this means the function should be called directly after New.

func (*BlockChain) GetOrphanRoot 

func (b *BlockChain) GetOrphanRoot(hash *wire.ShaHash) *wire.ShaHash

GetOrphanRoot returns the head of the chain for the provided hash from the map of orphan blocks.

This function is safe for concurrent access.

func (*BlockChain) HaveBlock 

func (b *BlockChain) HaveBlock(hash *wire.ShaHash) (bool, error)

HaveBlock returns whether or not the chain instance has the block represented by the passed hash. This includes checking the various places a block can be like part of the main chain, on a side chain, or in the orphan pool.

This function is NOT safe for concurrent access.

func (*BlockChain) IsCheckpointCandidate 

func (b *BlockChain) IsCheckpointCandidate(block *btcutil.Block) (bool, error)

IsCheckpointCandidate returns whether or not the passed block is a good checkpoint candidate.

The factors used to determine a good checkpoint are:

  • The block must be in the main chain
  • The block must be at least 'CheckpointConfirmations' blocks prior to the current end of the main chain
  • The timestamps for the blocks before and after the checkpoint must have timestamps which are also before and after the checkpoint, respectively (due to the median time allowance this is not always the case)
  • The block must not contain any strange transaction such as those with nonstandard scripts

The intent is that candidates are reviewed by a developer to make the final decision and then manually added to the list of checkpoints for a network.

func (*BlockChain) IsCurrent 

func (b *BlockChain) IsCurrent(timeSource MedianTimeSource) bool

IsCurrent returns whether or not the chain believes it is current. Several factors are used to guess, but the key factors that allow the chain to believe it is current are:

  • Latest block height is after the latest checkpoint (if enabled)
  • Latest block has a timestamp newer than 24 hours ago

This function is NOT safe for concurrent access.

func (*BlockChain) IsKnownOrphan 

func (b *BlockChain) IsKnownOrphan(hash *wire.ShaHash) bool

IsKnownOrphan returns whether the passed hash is currently a known orphan. Keep in mind that only a limited number of orphans are held onto for a limited amount of time, so this function must not be used as an absolute way to test if a block is an orphan block. A full block (as opposed to just its hash) must be passed to ProcessBlock for that purpose. However, calling ProcessBlock with an orphan that already exists results in an error, so this function provides a mechanism for a caller to intelligently detect *recent* duplicate orphans and react accordingly.

This function is safe for concurrent access.

func (*BlockChain) LatestBlockLocator 

func (b *BlockChain) LatestBlockLocator() (BlockLocator, error)

LatestBlockLocator returns a block locator for the latest known tip of the main (best) chain.

func (*BlockChain) LatestCheckpoint 

func (b *BlockChain) LatestCheckpoint() *chaincfg.Checkpoint

LatestCheckpoint returns the most recent checkpoint (regardless of whether it is already known). When checkpoints are disabled or there are no checkpoints for the active network, it will return nil.

func (*BlockChain) ProcessBlock 

func (b *BlockChain) ProcessBlock(block *btcutil.Block, timeSource MedianTimeSource, flags BehaviorFlags) (bool, error)

ProcessBlock is the main workhorse for handling insertion of new blocks into the block chain. It includes functionality such as rejecting duplicate blocks, ensuring blocks follow all rules, orphan handling, and insertion into the block chain along with best chain selection and reorganization.

It returns a bool which indicates whether or not the block is an orphan and any errors that occurred during processing. The returned bool is only valid when the error is nil.

Example

This example demonstrates how to create a new chain instance and use ProcessBlock to attempt to attempt add a block to the chain. As the package overview documentation describes, this includes all of the Bitcoin consensus rules. This example intentionally attempts to insert a duplicate genesis block to illustrate how an invalid block is handled. 

package main

import (
	"fmt"

	"github.com/btcsuite/btcd/blockchain"
	"github.com/btcsuite/btcd/chaincfg"
	"github.com/btcsuite/btcd/database"
	"github.com/btcsuite/btcutil"

	_ "github.com/btcsuite/btcd/database/memdb"
)

func main() {
	// Create a new database to store the accepted blocks into.  Typically
	// this would be opening an existing database and would not use memdb
	// which is a memory-only database backend, but we create a new db
	// here so this is a complete working example.
	db, err := database.CreateDB("memdb")
	if err != nil {
		fmt.Printf("Failed to create database: %v\n", err)
		return
	}
	defer db.Close()

	// Insert the main network genesis block.  This is part of the initial
	// database setup.  Like above, this typically would not be needed when
	// opening an existing database.
	genesisBlock := btcutil.NewBlock(chaincfg.MainNetParams.GenesisBlock)
	_, err = db.InsertBlock(genesisBlock)
	if err != nil {
		fmt.Printf("Failed to insert genesis block: %v\n", err)
		return
	}

	// Create a new BlockChain instance without an initialized signature
	// verification cache, using the underlying database for the main
	// bitcoin network and ignore notifications.
	chain := blockchain.New(db, &chaincfg.MainNetParams, nil, nil)

	// Create a new median time source that is required by the upcoming
	// call to ProcessBlock.  Ordinarily this would also add time values
	// obtained from other peers on the network so the local time is
	// adjusted to be in agreement with other peers.
	timeSource := blockchain.NewMedianTime()

	// Process a block.  For this example, we are going to intentionally
	// cause an error by trying to process the genesis block which already
	// exists.
	isOrphan, err := chain.ProcessBlock(genesisBlock, timeSource, blockchain.BFNone)
	if err != nil {
		fmt.Printf("Failed to process block: %v\n", err)
		return
	}
	fmt.Printf("Block accepted. Is it an orphan?: %v", isOrphan)

}

Output:

Failed to process block: already have block 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f

type BlockLocator 

type BlockLocator []*wire.ShaHash

BlockLocator is used to help locate a specific block. The algorithm for building the block locator is to add the hashes in reverse order until the genesis block is reached. In order to keep the list of locator hashes to a reasonable number of entries, first the most recent previous 10 block hashes are added, then the step is doubled each loop iteration to exponentially decrease the number of hashes as a function of the distance from the block being located.

For example, assume you have a block chain with a side chain as depicted below: 

genesis -> 1 -> 2 -> ... -> 15 -> 16  -> 17  -> 18
                              \-> 16a -> 17a

The block locator for block 17a would be the hashes of blocks: [17a 16a 15 14 13 12 11 10 9 8 6 2 genesis]

type ErrorCode 

type ErrorCode int

ErrorCode identifies a kind of error. 

const (
	// ErrDuplicateBlock indicates a block with the same hash already
	// exists.
	ErrDuplicateBlock ErrorCode = iota

	// ErrBlockTooBig indicates the serialized block size exceeds the
	// maximum allowed size.
	ErrBlockTooBig

	// ErrBlockVersionTooOld indicates the block version is too old and is
	// no longer accepted since the majority of the network has upgraded
	// to a newer version.
	ErrBlockVersionTooOld

	// ErrInvalidTime indicates the time in the passed block has a precision
	// that is more than one second.  The chain consensus rules require
	// timestamps to have a maximum precision of one second.
	ErrInvalidTime

	// ErrTimeTooOld indicates the time is either before the median time of
	// the last several blocks per the chain consensus rules or prior to the
	// most recent checkpoint.
	ErrTimeTooOld

	// ErrTimeTooNew indicates the time is too far in the future as compared
	// the current time.
	ErrTimeTooNew

	// ErrDifficultyTooLow indicates the difficulty for the block is lower
	// than the difficulty required by the most recent checkpoint.
	ErrDifficultyTooLow

	// ErrUnexpectedDifficulty indicates specified bits do not align with
	// the expected value either because it doesn't match the calculated
	// valued based on difficulty regarted rules or it is out of the valid
	// range.
	ErrUnexpectedDifficulty

	// ErrHighHash indicates the block does not hash to a value which is
	// lower than the required target difficultly.
	ErrHighHash

	// ErrBadMerkleRoot indicates the calculated merkle root does not match
	// the expected value.
	ErrBadMerkleRoot

	// ErrBadCheckpoint indicates a block that is expected to be at a
	// checkpoint height does not match the expected one.
	ErrBadCheckpoint

	// ErrForkTooOld indicates a block is attempting to fork the block chain
	// before the most recent checkpoint.
	ErrForkTooOld

	// ErrCheckpointTimeTooOld indicates a block has a timestamp before the
	// most recent checkpoint.
	ErrCheckpointTimeTooOld

	// ErrNoTransactions indicates the block does not have a least one
	// transaction.  A valid block must have at least the coinbase
	// transaction.
	ErrNoTransactions

	// ErrTooManyTransactions indicates the block has more transactions than
	// are allowed.
	ErrTooManyTransactions

	// ErrNoTxInputs indicates a transaction does not have any inputs.  A
	// valid transaction must have at least one input.
	ErrNoTxInputs

	// ErrNoTxOutputs indicates a transaction does not have any outputs.  A
	// valid transaction must have at least one output.
	ErrNoTxOutputs

	// ErrTxTooBig indicates a transaction exceeds the maximum allowed size
	// when serialized.
	ErrTxTooBig

	// ErrBadTxOutValue indicates an output value for a transaction is
	// invalid in some way such as being out of range.
	ErrBadTxOutValue

	// ErrDuplicateTxInputs indicates a transaction references the same
	// input more than once.
	ErrDuplicateTxInputs

	// ErrBadTxInput indicates a transaction input is invalid in some way
	// such as referencing a previous transaction outpoint which is out of
	// range or not referencing one at all.
	ErrBadTxInput

	// ErrMissingTx indicates a transaction referenced by an input is
	// missing.
	ErrMissingTx

	// ErrUnfinalizedTx indicates a transaction has not been finalized.
	// A valid block may only contain finalized transactions.
	ErrUnfinalizedTx

	// ErrDuplicateTx indicates a block contains an identical transaction
	// (or at least two transactions which hash to the same value).  A
	// valid block may only contain unique transactions.
	ErrDuplicateTx

	// ErrOverwriteTx indicates a block contains a transaction that has
	// the same hash as a previous transaction which has not been fully
	// spent.
	ErrOverwriteTx

	// ErrImmatureSpend indicates a transaction is attempting to spend a
	// coinbase that has not yet reached the required maturity.
	ErrImmatureSpend

	// ErrDoubleSpend indicates a transaction is attempting to spend coins
	// that have already been spent.
	ErrDoubleSpend

	// ErrSpendTooHigh indicates a transaction is attempting to spend more
	// value than the sum of all of its inputs.
	ErrSpendTooHigh

	// ErrBadFees indicates the total fees for a block are invalid due to
	// exceeding the maximum possible value.
	ErrBadFees

	// ErrTooManySigOps indicates the total number of signature operations
	// for a transaction or block exceed the maximum allowed limits.
	ErrTooManySigOps

	// ErrFirstTxNotCoinbase indicates the first transaction in a block
	// is not a coinbase transaction.
	ErrFirstTxNotCoinbase

	// ErrMultipleCoinbases indicates a block contains more than one
	// coinbase transaction.
	ErrMultipleCoinbases

	// ErrBadCoinbaseScriptLen indicates the length of the signature script
	// for a coinbase transaction is not within the valid range.
	ErrBadCoinbaseScriptLen

	// ErrBadCoinbaseValue indicates the amount of a coinbase value does
	// not match the expected value of the subsidy plus the sum of all fees.
	ErrBadCoinbaseValue

	// ErrMissingCoinbaseHeight indicates the coinbase transaction for a
	// block does not start with the serialized block block height as
	// required for version 2 and higher blocks.
	ErrMissingCoinbaseHeight

	// ErrBadCoinbaseHeight indicates the serialized block height in the
	// coinbase transaction for version 2 and higher blocks does not match
	// the expected value.
	ErrBadCoinbaseHeight

	// ErrScriptMalformed indicates a transaction script is malformed in
	// some way.  For example, it might be longer than the maximum allowed
	// length or fail to parse.
	ErrScriptMalformed

	// ErrScriptValidation indicates the result of executing transaction
	// script failed.  The error covers any failure when executing scripts
	// such signature verification failures and execution past the end of
	// the stack.
	ErrScriptValidation
)

These constants are used to identify a specific RuleError.

func (ErrorCode) String 

func (e ErrorCode) String() string

String returns the ErrorCode as a human-readable name.

type MedianTimeSource 

type MedianTimeSource interface {
	// AdjustedTime returns the current time adjusted by the median time
	// offset as calculated from the time samples added by AddTimeSample.
	AdjustedTime() time.Time

	// AddTimeSample adds a time sample that is used when determining the
	// median time of the added samples.
	AddTimeSample(id string, timeVal time.Time)

	// Offset returns the number of seconds to adjust the local clock based
	// upon the median of the time samples added by AddTimeData.
	Offset() time.Duration
}

MedianTimeSource provides a mechanism to add several time samples which are used to determine a median time which is then used as an offset to the local clock.

func NewMedianTime 

func NewMedianTime() MedianTimeSource

NewMedianTime returns a new instance of concurrency-safe implementation of the MedianTimeSource interface. The returned implementation contains the rules necessary for proper time handling in the chain consensus rules and expects the time samples to be added from the timestamp field of the version message received from remote peers that successfully connect and negotiate.

type Notification 

type Notification struct {
	Type NotificationType
	Data interface{}
}

Notification defines notification that is sent to the caller via the callback function provided during the call to New and consists of a notification type as well as associated data that depends on the type as follows:

  • NTBlockAccepted: *btcutil.Block
  • NTBlockConnected: *btcutil.Block
  • NTBlockDisconnected: *btcutil.Block

type NotificationCallback 

type NotificationCallback func(*Notification)

NotificationCallback is used for a caller to provide a callback for notifications about various chain events.

type NotificationType 

type NotificationType int

NotificationType represents the type of a notification message. 

const (
	// NTBlockAccepted indicates the associated block was accepted into
	// the block chain.  Note that this does not necessarily mean it was
	// added to the main chain.  For that, use NTBlockConnected.
	NTBlockAccepted NotificationType = iota

	// NTBlockConnected indicates the associated block was connected to the
	// main chain.
	NTBlockConnected

	// NTBlockDisconnected indicates the associated block was disconnected
	// from the main chain.
	NTBlockDisconnected
)

Constants for the type of a notification message.

func (NotificationType) String 

func (n NotificationType) String() string

String returns the NotificationType in human-readable form.

type RuleError 

type RuleError struct {
	ErrorCode   ErrorCode // Describes the kind of error
	Description string    // Human readable description of the issue
}

RuleError identifies a rule violation. It is used to indicate that processing of a block or transaction failed due to one of the many validation rules. The caller can use type assertions to determine if a failure was specifically due to a rule violation and access the ErrorCode field to ascertain the specific reason for the rule violation.

func (RuleError) Error 

func (e RuleError) Error() string

Error satisfies the error interface and prints human-readable errors.

type TxData 

type TxData struct {
	Tx          *btcutil.Tx
	Hash        *wire.ShaHash
	BlockHeight int32
	Spent       []bool
	Err         error
}

TxData contains contextual information about transactions such as which block they were found in and whether or not the outputs are spent.

type TxStore 

type TxStore map[wire.ShaHash]*TxData

TxStore is used to store transactions needed by other transactions for things such as script validation and double spend prevention. This also allows the transaction data to be treated as a view since it can contain the information from the point-of-view of different points in the chain.

Source Files

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