Struct bdk_chain::bitcoin::pow::CompactTarget

pub struct CompactTarget(/* private fields */);

Encoding of 256-bit target as 32-bit float.

This is used to encode a target into the block header. Satoshi made this part of consensus code in the original version of Bitcoin, likely copying an idea from OpenSSL.

OpenSSL’s bignum (BN) type has an encoding, which is even called “compact” as in bitcoin, which is exactly this format.

Implementations

impl CompactTarget

pub fn from_hex(s: &str) -> Result<CompactTarget, PrefixedHexError>

Creates a CompactTarget from an prefixed hex string.

pub fn from_unprefixed_hex(s: &str) -> Result<CompactTarget, UnprefixedHexError>

Creates a CompactTarget from an unprefixed hex string.

pub fn from_next_work_required( last: CompactTarget, timespan: u64, params: impl AsRef<Params> ) -> CompactTarget

Computes the CompactTarget from a difficulty adjustment.

ref: https://github.com/bitcoin/bitcoin/blob/0503cbea9aab47ec0a87d34611e5453158727169/src/pow.cpp

Given the previous Target, represented as a CompactTarget, the difficulty is adjusted by taking the timespan between them, and multipling the current CompactTarget by a factor of the net timespan and expected timespan. The CompactTarget may not adjust by more than a factor of 4, or adjust beyond the maximum threshold for the network.

Note

Under the consensus rules, the difference in the number of blocks between the headers does not equate to the difficulty_adjustment_interval of Params. This is due to an off-by-one error, and, the expected number of blocks in between headers is difficulty_adjustment_interval - 1 when calculating the difficulty adjustment.

Take the example of the first difficulty adjustment. Block 2016 introduces a new CompactTarget, which takes the net timespan between Block 2015 and Block 0, and recomputes the difficulty.

Returns

The expected CompactTarget recalculation.

pub fn from_header_difficulty_adjustment( last_epoch_boundary: Header, current: Header, params: impl AsRef<Params> ) -> CompactTarget

Computes the CompactTarget from a difficulty adjustment, assuming these are the relevant block headers.

Given two headers, representing the start and end of a difficulty adjustment epoch, compute the CompactTarget based on the net time between them and the current CompactTarget.

Note

See CompactTarget::from_next_work_required

For example, to successfully compute the first difficulty adjustment on the Bitcoin network, one would pass the header for Block 2015 as current and the header for Block 0 as last_epoch_boundary.

Returns

The expected CompactTarget recalculation.

pub fn from_consensus(bits: u32) -> CompactTarget

Creates a CompactTarget from a consensus encoded u32.

pub fn to_consensus(self) -> u32

Returns the consensus encoded u32 representation of this CompactTarget.

Trait Implementations

impl Clone for CompactTarget

fn clone(&self) -> CompactTarget

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CompactTarget

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Decodable for CompactTarget

fn consensus_decode<R>(r: &mut R) -> Result<CompactTarget, Error>

where R: Read + ?Sized,

Decode an object with a well-defined format.

fn consensus_decode_from_finite_reader<R>(reader: &mut R) -> Result<Self, Error>

where R: Read + ?Sized,

Decode Self from a size-limited reader.

impl Default for CompactTarget

fn default() -> CompactTarget

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for CompactTarget

fn deserialize<__D>( __deserializer: __D ) -> Result<CompactTarget, <__D as Deserializer<'de>>::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Encodable for CompactTarget

fn consensus_encode<W>(&self, w: &mut W) -> Result<usize, Error>

where W: Write + ?Sized,

Encodes an object with a well-defined format.

impl From<CompactTarget> for Target

fn from(c: CompactTarget) -> Target

Converts to this type from the input type.

impl Hash for CompactTarget

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl LowerHex for CompactTarget

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Ord for CompactTarget

fn cmp(&self, other: &CompactTarget) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for CompactTarget

fn eq(&self, other: &CompactTarget) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for CompactTarget

fn partial_cmp(&self, other: &CompactTarget) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for CompactTarget

fn serialize<__S>( &self, __serializer: __S ) -> Result<<__S as Serializer>::Ok, <__S as Serializer>::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl UpperHex for CompactTarget

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Copy for CompactTarget

impl Eq for CompactTarget

impl StructuralPartialEq for CompactTarget