bdk_wallet/psbt/
mod.rs

1// Bitcoin Dev Kit
2// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
3//
4// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
5//
6// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
7// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
8// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
9// You may not use this file except in accordance with one or both of these
10// licenses.
11
12//! Additional functions on the `rust-bitcoin` `Psbt` structure.
13
14use alloc::vec::Vec;
15use bitcoin::Amount;
16use bitcoin::FeeRate;
17use bitcoin::Psbt;
18use bitcoin::TxOut;
19
20// TODO upstream the functions here to `rust-bitcoin`?
21
22/// Trait to add functions to extract utxos and calculate fees.
23pub trait PsbtUtils {
24    /// Get the `TxOut` for the specified input index, if it doesn't exist in the PSBT `None` is
25    /// returned.
26    fn get_utxo_for(&self, input_index: usize) -> Option<TxOut>;
27
28    /// The total transaction fee amount, sum of input amounts minus sum of output amounts, in sats.
29    /// If the PSBT is missing a TxOut for an input returns None.
30    fn fee_amount(&self) -> Option<Amount>;
31
32    /// The transaction's fee rate. This value will only be accurate if calculated AFTER the
33    /// `Psbt` is finalized and all witness/signature data is added to the
34    /// transaction.
35    /// If the PSBT is missing a TxOut for an input returns None.
36    fn fee_rate(&self) -> Option<FeeRate>;
37}
38
39impl PsbtUtils for Psbt {
40    fn get_utxo_for(&self, input_index: usize) -> Option<TxOut> {
41        let tx = &self.unsigned_tx;
42        let input = self.inputs.get(input_index)?;
43
44        match (&input.witness_utxo, &input.non_witness_utxo) {
45            (Some(_), _) => input.witness_utxo.clone(),
46            (_, Some(_)) => input.non_witness_utxo.as_ref().map(|in_tx| {
47                in_tx.output[tx.input[input_index].previous_output.vout as usize].clone()
48            }),
49            _ => None,
50        }
51    }
52
53    fn fee_amount(&self) -> Option<Amount> {
54        let tx = &self.unsigned_tx;
55        let utxos: Option<Vec<TxOut>> = (0..tx.input.len()).map(|i| self.get_utxo_for(i)).collect();
56
57        utxos.map(|inputs| {
58            let input_amount: Amount = inputs.iter().map(|i| i.value).sum();
59            let output_amount: Amount = self.unsigned_tx.output.iter().map(|o| o.value).sum();
60            input_amount
61                .checked_sub(output_amount)
62                .expect("input amount must be greater than output amount")
63        })
64    }
65
66    fn fee_rate(&self) -> Option<FeeRate> {
67        let fee_amount = self.fee_amount();
68        let weight = self.clone().extract_tx().ok()?.weight();
69        fee_amount.map(|fee| fee / weight)
70    }
71}
bdk_wallet/psbt/mod.rs

bdk_wallet/psbt/
mod.rs
