Return proper errors from UtxoSet::update

src/blockdata/utxoset.rs

@@ -28,6 +28,7 @@ use blockdata::transaction::{Transaction, TxOut};
 use blockdata::constants::genesis_block;
 use blockdata::block::Block;
 use blockdata::script::read_scriptbool;
+use blockdata::script::ScriptError;
 use network::constants::Network;
 use network::serialize::BitcoinHash;
 use util::hash::{DumbHasher, Sha256dHash};
@@ -47,6 +48,25 @@ pub enum ValidationLevel {
   ScriptValidation
 }
 
+/// An error returned from a UTXO set operation
+#[deriving(PartialEq, Eq, Clone, Show)]
+pub enum UtxoSetError {
+  /// prevhash of the new block is not the hash of the old block (expected, actual)
+  BadPrevHash(Sha256dHash, Sha256dHash),
+  /// A TXID was duplicated
+  DuplicatedTxid(Sha256dHash),
+  /// Concatenated script failed in the input half (txid, script error)
+  InputScriptFailure(Sha256dHash, ScriptError),
+  /// Concatenated script failed in the output half (txid, script error)
+  OutputScriptFailure(Sha256dHash, ScriptError),
+  /// Script ended with false at the top of the stock (txid)
+  ScriptReturnedFalse(Sha256dHash),
+  /// Script ended with nothing in the stack (txid)
+  ScriptReturnedEmptyStack(Sha256dHash),
+  /// Script ended with nothing in the stack (txid, input txid, input vout)
+  InputNotFound(Sha256dHash, Sha256dHash, u32),
+}
+
 /// Vector of outputs; None indicates a nonexistent or already spent output
 type UtxoNode = ThinVec<Option<TxOut>>;
 
@@ -152,11 +172,12 @@ impl UtxoSet {
   }
 
   /// Apply the transactions contained in a block
-  pub fn update(&mut self, block: &Block, validation: ValidationLevel) -> bool {
+  pub fn update(&mut self, block: &Block, validation: ValidationLevel)
+                -> Result<(), UtxoSetError> {
     // Make sure we are extending the UTXO set in order
     if validation >= ChainValidation &&
        self.last_hash != block.header.prev_blockhash {
-      return false;
+      return Err(BadPrevHash(self.last_hash, block.header.prev_blockhash));
     }
 
     // Set the next hash immediately so that if anything goes wrong,
@@ -196,7 +217,7 @@ impl UtxoSet {
             }
             // Otherwise fail the block
             self.rewind(block);
-            return false;
+            return Err(DuplicatedTxid(txid));
           }
         }
         // Didn't replace anything? Good.
@@ -220,40 +241,47 @@ impl UtxoSet {
         future_vec.push(Future::spawn(proc() {
           let txes = unsafe {&*txes};
           for tx in txes.slice(start, end).iter() {
+            let txid = tx.bitcoin_hash();
             for (n, input) in tx.input.iter().enumerate() {
               let txo = unsafe { (*s).get_utxo(input.prev_hash, input.prev_index) };
               match txo {
                 Some(txo) => {
                   let mut stack = Vec::with_capacity(6);
-                  if input.script_sig.evaluate(&mut stack, Some((tx, n))).is_err() {
-                    println!("txid was {}", tx.bitcoin_hash());
-                    return false;
+                  match input.script_sig.evaluate(&mut stack, Some((tx, n))) {
+                    Ok(_) => {}
+                    Err(e) => { return Err(InputScriptFailure(txid, e)); }
                   }
-                  if txo.script_pubkey.evaluate(&mut stack, Some((tx, n))).is_err() {
-                    println!("txid was {}", tx.bitcoin_hash());
-                    return false;
+                  match txo.script_pubkey.evaluate(&mut stack, Some((tx, n))) {
+                    Ok(_) => {}
+                    Err(e) => { return Err(OutputScriptFailure(txid, e)); }
                   }
                   match stack.pop() {
                     Some(v) => {
                       if !read_scriptbool(v.as_slice()) {
-                        use serialize::json::ToJson;
-                        println!("txid was {}", tx.bitcoin_hash());
-                        println!("tx was {}", tx.to_json().to_string());
-                        println!("script ended with stack {}", stack);
-                        return false;
+                        return Err(ScriptReturnedFalse(txid));
                       }
                     }
-                    None => { return false; }
+                    None => { return Err(ScriptReturnedEmptyStack(txid)); }
                   }
                 }
-                None => { return false; }
+                None => { return Err(InputNotFound(txid, input.prev_hash, input.prev_index)); }
               }
             }
           }
-          true
+          Ok(())
         }));
       }
-      if !future_vec.mut_iter().map(|f| f.get()).all(|x| x) { return false; }
+      // Return the last error since we need to finish every future before
+      // leaving this function, and given that, it's easier to return the last.
+      let mut last_error = Ok(());
+      for res in future_vec.mut_iter().map(|f| f.get()) {
+        if res.is_err() {
+          last_error = res;
+        }
+      }
+      if last_error.is_err() {
+        return last_error;
+      }
     }
 
     let mut skipped_genesis = false;
@@ -266,7 +294,12 @@ impl UtxoSet {
           let taken = self.take_utxo(input.prev_hash, input.prev_index);
           match taken {
             Some(txo) => { self.spent_txos.get_mut(spent_idx).push(((txid, n as u32), txo)); }
-            None => { if validation >= TxoValidation { self.rewind(block); return false; } }
+            None => {
+              if validation >= TxoValidation {
+                self.rewind(block);
+                return Err(InputNotFound(txid, input.prev_hash, input.prev_index));
+              }
+            }
           }
         }
       }
@@ -274,7 +307,7 @@ impl UtxoSet {
 
     }
     // If we made it here, success!
-    true
+    Ok(())
   }
 
   /// Unapply the transactions contained in a block
@@ -389,7 +422,7 @@ mod tests {
     let new_block: Block = deserialize("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".from_hex().unwrap()).unwrap();
 
     // Make sure we can't add the block directly, since we are missing the inputs
-    assert!(!empty_set.update(&new_block, TxoValidation));
+    assert!(empty_set.update(&new_block, TxoValidation).is_err());
     assert_eq!(empty_set.n_utxos(), 0);
     // Add the block manually so that we'll have some UTXOs for the rest of the test
     for tx in new_block.txdata.iter() {
@@ -409,7 +442,7 @@ mod tests {
 
     // Check again that we can't add the block, and that this doesn't mess up the
     // existing UTXOs
-    assert!(!empty_set.update(&new_block, TxoValidation));
+    assert!(empty_set.update(&new_block, TxoValidation).is_err());
     assert_eq!(empty_set.n_utxos(), 2);
     for tx in new_block.txdata.iter() {
       let hash = tx.bitcoin_hash();