Merge pull request #626 from visvirial/impl-vsize

Implement `Block.get_strippedsize()` and `Transaction.get_vsize()`

src/blockdata/block.rs

@@ -233,17 +233,27 @@ impl Block {
         bitcoin_merkle_root(hashes).into()
     }
 
+    /// The size of the header + the size of the varint with the tx count + the txs themselves
+    #[inline]
+    fn get_base_size(&self) -> usize {
+        80 + VarInt(self.txdata.len() as u64).len()
+    }
+
     /// Get the size of the block
     pub fn get_size(&self) -> usize {
-        // The size of the header + the size of the varint with the tx count + the txs themselves
-        let base_size = 80 + VarInt(self.txdata.len() as u64).len();
         let txs_size: usize = self.txdata.iter().map(Transaction::get_size).sum();
-        base_size + txs_size
+        self.get_base_size() + txs_size
+    }
+
+    /// Get the strippedsize of the block
+    pub fn get_strippedsize(&self) -> usize {
+        let txs_size: usize = self.txdata.iter().map(Transaction::get_strippedsize).sum();
+        self.get_base_size() + txs_size
     }
 
     /// Get the weight of the block
     pub fn get_weight(&self) -> usize {
-        let base_weight = WITNESS_SCALE_FACTOR * (80 + VarInt(self.txdata.len() as u64).len());
+        let base_weight = WITNESS_SCALE_FACTOR * self.get_base_size();
         let txs_weight: usize = self.txdata.iter().map(Transaction::get_weight).sum();
         base_weight + txs_weight
     }
@@ -372,6 +382,7 @@ mod tests {
         // [test] TODO: check the transaction data
 
         assert_eq!(real_decode.get_size(), some_block.len());
+        assert_eq!(real_decode.get_strippedsize(), some_block.len());
         assert_eq!(real_decode.get_weight(), some_block.len() * 4);
 
         // should be also ok for a non-witness block as commitment is optional in that case
@@ -406,6 +417,7 @@ mod tests {
         // [test] TODO: check the transaction data
 
         assert_eq!(real_decode.get_size(), segwit_block.len());
+        assert_eq!(real_decode.get_strippedsize(), 4283);
         assert_eq!(real_decode.get_weight(), 17168);
 
         assert!(real_decode.check_witness_commitment());

src/blockdata/transaction.rs

@@ -429,6 +429,39 @@ impl Transaction {
         self.get_scaled_size(1)
     }
 
+    /// Gets the "vsize" of this transaction. Will be `ceil(weight / 4.0)`.
+    #[inline]
+    pub fn get_vsize(&self) -> usize {
+        let weight = self.get_weight();
+        (weight + WITNESS_SCALE_FACTOR - 1) / WITNESS_SCALE_FACTOR
+    }
+
+    /// Gets the size of this transaction excluding the witness data.
+    pub fn get_strippedsize(&self) -> usize {
+        let mut input_size = 0;
+        for input in &self.input {
+            input_size += 32 + 4 + 4 + // outpoint (32+4) + nSequence
+                VarInt(input.script_sig.len() as u64).len() +
+                input.script_sig.len();
+        }
+        let mut output_size = 0;
+        for output in &self.output {
+            output_size += 8 + // value
+                VarInt(output.script_pubkey.len() as u64).len() +
+                output.script_pubkey.len();
+        }
+        let non_input_size =
+        // version:
+        4 +
+        // count varints:
+        VarInt(self.input.len() as u64).len() +
+        VarInt(self.output.len() as u64).len() +
+        output_size +
+        // lock_time
+        4;
+        non_input_size + input_size
+    }
+
     /// Internal utility function for get_{size,weight}
     fn get_scaled_size(&self, scale_factor: usize) -> usize {
         let mut input_weight = 0;
@@ -857,6 +890,8 @@ mod tests {
                    "a6eab3c14ab5272a58a5ba91505ba1a4b6d7a3a9fcbd187b6cd99a7b6d548cb7".to_string());
         assert_eq!(realtx.get_weight(), tx_bytes.len()*WITNESS_SCALE_FACTOR);
         assert_eq!(realtx.get_size(), tx_bytes.len());
+        assert_eq!(realtx.get_vsize(), tx_bytes.len());
+        assert_eq!(realtx.get_strippedsize(), tx_bytes.len());
     }
 
     #[test]
@@ -887,8 +922,24 @@ mod tests {
                    "f5864806e3565c34d1b41e716f72609d00b55ea5eac5b924c9719a842ef42206".to_string());
         assert_eq!(format!("{:x}", realtx.wtxid()),
                    "80b7d8a82d5d5bf92905b06f2014dd699e03837ca172e3a59d51426ebbe3e7f5".to_string());
-        assert_eq!(realtx.get_weight(), 442);
+        const EXPECTED_WEIGHT: usize = 442;
+        assert_eq!(realtx.get_weight(), EXPECTED_WEIGHT);
         assert_eq!(realtx.get_size(), tx_bytes.len());
+        assert_eq!(realtx.get_vsize(), 111);
+        // Since
+        //     size   =                        stripped_size + witness_size
+        //     weight = WITNESS_SCALE_FACTOR * stripped_size + witness_size
+        // then,
+        //     stripped_size = (weight - size) / (WITNESS_SCALE_FACTOR - 1)
+        let expected_strippedsize = (EXPECTED_WEIGHT - tx_bytes.len()) / (WITNESS_SCALE_FACTOR - 1);
+        assert_eq!(realtx.get_strippedsize(), expected_strippedsize);
+        // Construct a transaction without the witness data.
+        let mut tx_without_witness = realtx.clone();
+        tx_without_witness.input.iter_mut().for_each(|input| input.witness.clear());
+        assert_eq!(tx_without_witness.get_weight(), expected_strippedsize*WITNESS_SCALE_FACTOR);
+        assert_eq!(tx_without_witness.get_size(), expected_strippedsize);
+        assert_eq!(tx_without_witness.get_vsize(), expected_strippedsize);
+        assert_eq!(tx_without_witness.get_strippedsize(), expected_strippedsize);
     }
 
     #[test]