⚡ Bolt: Replace map format hex encoding with hex::encode

.jules/bolt.md

@@ -35,3 +35,6 @@
 ## 2024-05-24 - Canvas Property Extraction Optimization
 **Learning:** Extracting properties from the `RuntimeValue` DSL property lists in `canvas.rs` was inefficient because the code called `.iter().find()` multiple times for each property in `logo`, `rings`, `emblem`, `letter`, `core`, and `circuits` definitions.
 **Action:** Replace multiple `.find()` calls with a single-pass `for p in &dsl.properties` loop and `match` on the property names, mutating local fallback variables.
+## 2024-11-20 - Avoid `format!` inside loops for hex string encoding
+**Learning:** Using `.iter().map(|b| format!("{:02x}", b)).collect::<String>()` to encode a byte array to a hex string incurs a heavy performance penalty because it allocates a new temporary `String` for every single byte processed before concatenating them. The `hex::encode()` function from the `hex` crate performs this conversion directly into a single pre-allocated `String` with zero intermediate allocations.
+**Action:** Always prefer `hex::encode(bytes)` over iterative `format!` mapping when performing hexadecimal encoding of byte arrays or slices to eliminate intermediate string allocations and significantly boost performance.

stdlib/src/crypto.rs

@@ -61,10 +61,8 @@ impl StdlibRegistry {
                     combined.extend_from_slice(&ciphertext);
 
                     // Hex encode ciphertext
-                    let hex_ciphertext = combined
-                        .iter()
-                        .map(|b| format!("{:02x}", b))
-                        .collect::<String>();
+                    // ⚡ Bolt Performance Optimization: Replaced iterative format! with hex::encode for single-allocation hex string conversion.
+                    let hex_ciphertext = hex::encode(combined);
                     Ok(RuntimeValue::Str(hex_ciphertext))
                 },
             }),

stdlib/src/security.rs

@@ -18,7 +18,8 @@ impl StdlibRegistry {
                     use rand::Rng;
                     let bytes: Vec<u8> =
                         rand::thread_rng().gen::<[u8; 32]>()[..len.min(32)].to_vec();
-                    let hex: String = bytes.iter().map(|b| format!("{:02x}", b)).collect();
+                    // ⚡ Bolt Performance Optimization: Replaced iterative format! with hex::encode for single-allocation hex string conversion.
+                    let hex = hex::encode(bytes);
                     Ok(RuntimeValue::Str(hex))
                 },
             }),
@@ -48,7 +49,8 @@ impl StdlibRegistry {
                     let input = args[0].to_string();
                     use sha2::Digest;
                     let digest = sha2::Sha256::digest(input.as_bytes());
-                    let hex: String = digest.iter().map(|b| format!("{:02x}", b)).collect();
+                    // ⚡ Bolt Performance Optimization: Replaced iterative format! with hex::encode for single-allocation hex string conversion.
+                    let hex = hex::encode(digest);
                     Ok(RuntimeValue::Str(hex))
                 },
             }),