76 lines
2.8 KiB
Rust
76 lines
2.8 KiB
Rust
// Bitcoin Dev Kit
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// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
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//
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// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
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//
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// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
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// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
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// You may not use this file except in accordance with one or both of these
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// licenses.
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//! Additional functions on the `rust-bitcoin` `Psbt` structure.
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use alloc::vec::Vec;
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use bitcoin::Amount;
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use bitcoin::FeeRate;
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use bitcoin::Psbt;
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use bitcoin::TxOut;
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// TODO upstream the functions here to `rust-bitcoin`?
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/// Trait to add functions to extract utxos and calculate fees.
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pub trait PsbtUtils {
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/// Get the `TxOut` for the specified input index, if it doesn't exist in the PSBT `None` is returned.
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fn get_utxo_for(&self, input_index: usize) -> Option<TxOut>;
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/// The total transaction fee amount, sum of input amounts minus sum of output amounts, in sats.
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/// If the PSBT is missing a TxOut for an input returns None.
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fn fee_amount(&self) -> Option<u64>;
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/// The transaction's fee rate. This value will only be accurate if calculated AFTER the
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/// `Psbt` is finalized and all witness/signature data is added to the
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/// transaction.
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/// If the PSBT is missing a TxOut for an input returns None.
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fn fee_rate(&self) -> Option<FeeRate>;
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}
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impl PsbtUtils for Psbt {
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fn get_utxo_for(&self, input_index: usize) -> Option<TxOut> {
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let tx = &self.unsigned_tx;
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let input = self.inputs.get(input_index)?;
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match (&input.witness_utxo, &input.non_witness_utxo) {
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(Some(_), _) => input.witness_utxo.clone(),
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(_, Some(_)) => input.non_witness_utxo.as_ref().map(|in_tx| {
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in_tx.output[tx.input[input_index].previous_output.vout as usize].clone()
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}),
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_ => None,
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}
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}
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fn fee_amount(&self) -> Option<u64> {
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let tx = &self.unsigned_tx;
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let utxos: Option<Vec<TxOut>> = (0..tx.input.len()).map(|i| self.get_utxo_for(i)).collect();
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utxos.map(|inputs| {
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let input_amount: u64 = inputs.iter().map(|i| i.value.to_sat()).sum();
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let output_amount: u64 = self
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.unsigned_tx
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.output
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.iter()
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.map(|o| o.value.to_sat())
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.sum();
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input_amount
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.checked_sub(output_amount)
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.expect("input amount must be greater than output amount")
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})
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}
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fn fee_rate(&self) -> Option<FeeRate> {
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let fee_amount = self.fee_amount();
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let weight = self.clone().extract_tx().ok()?.weight();
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fee_amount.map(|fee| Amount::from_sat(fee) / weight)
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}
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}
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