Improve get_descriptor() (#380)

* Fix log in get_descriptor

* Change formatting

* Apply comments

* Remove clones in get_descriptor

zero_bin/ops/src/lib.rs

@@ -116,13 +116,20 @@ struct SegmentProofSpan {
 impl SegmentProofSpan {
     /// Get a unique id for the transaction proof.
     fn get_id(ir: &GenerationInputs, segment_index: usize) -> String {
-        format!(
-            "b{} - {}_{} ({})",
-            ir.block_metadata.block_number,
-            ir.txn_number_before,
-            ir.txn_number_before + ir.signed_txns.len(),
-            segment_index
-        )
+        if ir.signed_txns.len() == 1 {
+            format!(
+                "b{} - {} ({})",
+                ir.block_metadata.block_number, ir.txn_number_before, segment_index
+            )
+        } else {
+            format!(
+                "b{} - {}_{} ({})",
+                ir.block_metadata.block_number,
+                ir.txn_number_before,
+                ir.txn_number_before + ir.signed_txns.len(),
+                segment_index
+            )
+        }
     }
 
     /// Get a textual descriptor for the transaction proof.
@@ -132,18 +139,25 @@ impl SegmentProofSpan {
     fn get_descriptor(ir: &GenerationInputs) -> String {
         if ir.signed_txns.is_empty() {
             "Dummy".to_string()
+        } else if ir.signed_txns.len() == 1 {
+            format!(
+                "{:x?}",
+                u64::from_be_bytes(keccak(&ir.signed_txns[0][..])[0..8].try_into().unwrap())
+            )
         } else {
-            let first_encoding: [u8; 8] =
-                keccak(ir.signed_txns[0].clone())[..8].try_into().unwrap();
-            let last_encoding: [u8; 8] = keccak(
-                ir.signed_txns
-                    .last()
-                    .expect("the vector of transactions is not empty")
-                    .clone(),
-            )[..8]
-                .try_into()
-                .unwrap();
-            format!("{:x?}..{:x?}", first_encoding, last_encoding)
+            let first_encoding =
+                u64::from_be_bytes(keccak(&ir.signed_txns[0][..])[0..8].try_into().unwrap());
+            let last_encoding = u64::from_be_bytes(
+                keccak(
+                    ir.signed_txns
+                        .last()
+                        .expect("the vector of transactions is not empty"),
+                )[0..8]
+                    .try_into()
+                    .unwrap(),
+            );
+
+            format!("[0x{:x?}..0x{:x?}]", first_encoding, last_encoding)
         }
     }