Merge #664: Return Weight type for max_weight_to_satisfy methods

7c5f3dc Return Weight type for max_weight_to_satisfy methods (yancy)

Pull request description:

  Return Weight type for max_weight_to_satisfy methods.

ACKs for top commit:
  apoelstra:
    ACK 7c5f3dc

Tree-SHA512: 7e6f32dc1f55927b90ed739f54460546229f1958136bf67418fd738f30c51f674469cf69d2b24cf5e8ff99b152461b289682446f881f6ad6640deb057e3624d3

Author: apoelstra

embedded/src/main.rs

@@ -51,7 +51,7 @@ fn main() -> ! {
     assert!(desc.sanity_check().is_ok());
 
     // Estimate the satisfaction cost
-    assert_eq!(desc.max_weight_to_satisfy().unwrap(), 288);
+    assert_eq!(desc.max_weight_to_satisfy().unwrap().to_wu(), 288);
     // end miniscript test
 
     // exit QEMU

examples/sign_multisig.rs

@@ -20,7 +20,7 @@ fn main() {
     // Check weight for witness satisfaction cost ahead of time.
     // 106 (serialized witnessScript)
     // + 73*2 (signature length + signatures + sighash bytes) + 1 (dummy byte) = 253
-    assert_eq!(descriptor.max_weight_to_satisfy().unwrap(), 253);
+    assert_eq!(descriptor.max_weight_to_satisfy().unwrap().to_wu(), 253);
 
     // Sometimes it is necessary to have additional information to get the
     // `bitcoin::PublicKey` from the `MiniscriptKey` which can be supplied by

examples/taproot.rs

@@ -102,7 +102,7 @@ fn main() {
     //     max_witness_size = varint(control_block_size) + control_block size +
     //                        varint(script_size) + script_size + max_satisfaction_size
     //                      = 1 + 65 + 1 + 68 + 132 = 269
-    let max_sat_wt = real_desc.max_weight_to_satisfy().unwrap();
+    let max_sat_wt = real_desc.max_weight_to_satisfy().unwrap().to_wu();
     assert_eq!(max_sat_wt, 267);
 
     // Compute the bitcoin address and check if it matches

src/descriptor/bare.rs

@@ -10,7 +10,7 @@
 use core::fmt;
 
 use bitcoin::script::{self, PushBytes};
-use bitcoin::{Address, Network, ScriptBuf};
+use bitcoin::{Address, Network, ScriptBuf, Weight};
 
 use super::checksum::verify_checksum;
 use crate::descriptor::{write_descriptor, DefiniteDescriptorKey};
@@ -67,11 +67,12 @@ impl<Pk: MiniscriptKey> Bare<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> Result<usize, Error> {
+    pub fn max_weight_to_satisfy(&self) -> Result<Weight, Error> {
         let scriptsig_size = self.ms.max_satisfaction_size()?;
         // scriptSig varint difference between non-satisfied (0) and satisfied
         let scriptsig_varint_diff = varint_len(scriptsig_size) - varint_len(0);
-        Ok(4 * (scriptsig_varint_diff + scriptsig_size))
+        Weight::from_vb((scriptsig_varint_diff + scriptsig_size) as u64)
+            .ok_or(Error::CouldNotSatisfy)
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the
@@ -240,12 +241,12 @@ impl<Pk: MiniscriptKey> Pkh<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> usize {
+    pub fn max_weight_to_satisfy(&self) -> Weight {
         // OP_72 + <sig(71)+sigHash(1)> + OP_33 + <pubkey>
         let scriptsig_size = 73 + BareCtx::pk_len(&self.pk);
         // scriptSig varint different between non-satisfied (0) and satisfied
         let scriptsig_varint_diff = varint_len(scriptsig_size) - varint_len(0);
-        4 * (scriptsig_varint_diff + scriptsig_size)
+        Weight::from_vb((scriptsig_varint_diff + scriptsig_size) as u64).unwrap()
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the

src/descriptor/mod.rs

@@ -16,7 +16,9 @@ use core::ops::Range;
 use core::str::{self, FromStr};
 
 use bitcoin::hashes::{hash160, ripemd160, sha256};
-use bitcoin::{secp256k1, Address, Network, Script, ScriptBuf, TxIn, Witness, WitnessVersion};
+use bitcoin::{
+    secp256k1, Address, Network, Script, ScriptBuf, TxIn, Weight, Witness, WitnessVersion,
+};
 use sync::Arc;
 
 use self::checksum::verify_checksum;
@@ -320,7 +322,7 @@ impl<Pk: MiniscriptKey> Descriptor<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> Result<usize, Error> {
+    pub fn max_weight_to_satisfy(&self) -> Result<Weight, Error> {
         let weight = match *self {
             Descriptor::Bare(ref bare) => bare.max_weight_to_satisfy()?,
             Descriptor::Pkh(ref pkh) => pkh.max_weight_to_satisfy(),

src/descriptor/segwitv0.rs

@@ -7,7 +7,7 @@
 
 use core::fmt;
 
-use bitcoin::{Address, Network, ScriptBuf};
+use bitcoin::{Address, Network, ScriptBuf, Weight};
 
 use super::checksum::verify_checksum;
 use super::SortedMultiVec;
@@ -72,7 +72,7 @@ impl<Pk: MiniscriptKey> Wsh<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> Result<usize, Error> {
+    pub fn max_weight_to_satisfy(&self) -> Result<Weight, Error> {
         let (redeem_script_size, max_sat_elems, max_sat_size) = match self.inner {
             WshInner::SortedMulti(ref smv) => (
                 smv.script_size(),
@@ -89,7 +89,10 @@ impl<Pk: MiniscriptKey> Wsh<Pk> {
         // `max_sat_elems` is inclusive of the "witness script" (redeem script)
         let stack_varint_diff = varint_len(max_sat_elems) - varint_len(0);
 
-        Ok(stack_varint_diff + varint_len(redeem_script_size) + redeem_script_size + max_sat_size)
+        Ok(Weight::from_wu(
+            (stack_varint_diff + varint_len(redeem_script_size) + redeem_script_size + max_sat_size)
+                as u64,
+        ))
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the
@@ -347,12 +350,12 @@ impl<Pk: MiniscriptKey> Wpkh<Pk> {
     ///
     /// Assumes all ec-signatures are 73 bytes, including push opcode and
     /// sighash suffix.
-    pub fn max_weight_to_satisfy(&self) -> usize {
+    pub fn max_weight_to_satisfy(&self) -> Weight {
         // stack items: <varint(sig+sigHash)> <sig(71)+sigHash(1)> <varint(pubkey)> <pubkey>
         let stack_items_size = 73 + Segwitv0::pk_len(&self.pk);
         // stackLen varint difference between non-satisfied (0) and satisfied
         let stack_varint_diff = varint_len(2) - varint_len(0);
-        stack_varint_diff + stack_items_size
+        Weight::from_wu((stack_varint_diff + stack_items_size) as u64)
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the

src/descriptor/sh.rs

@@ -11,7 +11,7 @@ use core::convert::TryFrom;
 use core::fmt;
 
 use bitcoin::script::PushBytes;
-use bitcoin::{script, Address, Network, ScriptBuf};
+use bitcoin::{script, Address, Network, ScriptBuf, Weight};
 
 use super::checksum::verify_checksum;
 use super::{SortedMultiVec, Wpkh, Wsh};
@@ -185,7 +185,7 @@ impl<Pk: MiniscriptKey> Sh<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> Result<usize, Error> {
+    pub fn max_weight_to_satisfy(&self) -> Result<Weight, Error> {
         let (scriptsig_size, witness_size) = match self.inner {
             // add weighted script sig, len byte stays the same
             ShInner::Wsh(ref wsh) => {
@@ -198,7 +198,7 @@ impl<Pk: MiniscriptKey> Sh<Pk> {
                 let ss = smv.script_size();
                 let ps = push_opcode_size(ss);
                 let scriptsig_size = ps + ss + smv.max_satisfaction_size();
-                (scriptsig_size, 0)
+                (scriptsig_size, Weight::ZERO)
             }
             // add weighted script sig, len byte stays the same
             ShInner::Wpkh(ref wpkh) => {
@@ -211,14 +211,18 @@ impl<Pk: MiniscriptKey> Sh<Pk> {
                 let ss = ms.script_size();
                 let ps = push_opcode_size(ss);
                 let scriptsig_size = ps + ss + ms.max_satisfaction_size()?;
-                (scriptsig_size, 0)
+                (scriptsig_size, Weight::ZERO)
             }
         };
 
         // scriptSigLen varint difference between non-satisfied (0) and satisfied
         let scriptsig_varint_diff = varint_len(scriptsig_size) - varint_len(0);
 
-        Ok(4 * (scriptsig_varint_diff + scriptsig_size) + witness_size)
+        let wu = Weight::from_vb((scriptsig_varint_diff + scriptsig_size) as u64);
+        match wu {
+            Some(w) => Ok(w + witness_size),
+            None => Err(Error::CouldNotSatisfy),
+        }
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the

src/descriptor/tr.rs

@@ -9,7 +9,7 @@ use bitcoin::taproot::{
     LeafVersion, TaprootBuilder, TaprootSpendInfo, TAPROOT_CONTROL_BASE_SIZE,
     TAPROOT_CONTROL_MAX_NODE_COUNT, TAPROOT_CONTROL_NODE_SIZE,
 };
-use bitcoin::{opcodes, Address, Network, ScriptBuf};
+use bitcoin::{opcodes, Address, Network, ScriptBuf, Weight};
 use sync::Arc;
 
 use super::checksum::{self, verify_checksum};
@@ -261,7 +261,7 @@ impl<Pk: MiniscriptKey> Tr<Pk> {
     ///
     /// # Errors
     /// When the descriptor is impossible to safisfy (ex: sh(OP_FALSE)).
-    pub fn max_weight_to_satisfy(&self) -> Result<usize, Error> {
+    pub fn max_weight_to_satisfy(&self) -> Result<Weight, Error> {
         let tree = match self.tap_tree() {
             None => {
                 // key spend path
@@ -270,13 +270,14 @@ impl<Pk: MiniscriptKey> Tr<Pk> {
                 // 1 stack item
                 let stack_varint_diff = varint_len(1) - varint_len(0);
 
-                return Ok(stack_varint_diff + item_sig_size);
+                return Ok(Weight::from_wu((stack_varint_diff + item_sig_size) as u64));
             }
             // script path spend..
             Some(tree) => tree,
         };
 
-        tree.iter()
+        let wu = tree
+            .iter()
             .filter_map(|(depth, ms)| {
                 let script_size = ms.script_size();
                 let max_sat_elems = ms.max_satisfaction_witness_elements().ok()?;
@@ -299,7 +300,9 @@ impl<Pk: MiniscriptKey> Tr<Pk> {
                 )
             })
             .max()
-            .ok_or(Error::ImpossibleSatisfaction)
+            .ok_or(Error::ImpossibleSatisfaction)?;
+
+        Ok(Weight::from_wu(wu as u64))
     }
 
     /// Computes an upper bound on the weight of a satisfying witness to the

src/lib.rs

@@ -69,7 +69,7 @@
 //! // stackItem[Sig]: varint <sig+sighash>
 //! // = 1 + 73 = 74 WU
 //! // Expected satisfaction weight: 140 + 74 + 74 = 288
-//! assert_eq!(desc.max_weight_to_satisfy().unwrap(), 288);
+//! assert_eq!(desc.max_weight_to_satisfy().unwrap().to_wu(), 288);
 //! ```
 //!