eth/erc20_params: do more efficient lookup

log-n binary search on sorted list instead of linear search on
unsorted list. Sorting happens at compile time, so that has no runtime
impact.

Author: benma

src/rust/erc20_params/build.rs

@@ -69,7 +69,10 @@ fn main() {
         .open(out_filename)
         .unwrap();
 
-    for ((decimals, unit_len), tokens) in &grouped_tokens {
+    for ((decimals, unit_len), tokens) in &mut grouped_tokens {
+        // Sort by contract address so we can look up by contract
+        // address more efficiently.
+        tokens.sort_by_key(|token| token.contract_address);
         writeln!(
             output_file,
             "const PARAMS_D{}_U{}: &[P] = &[",

src/rust/erc20_params/src/lib.rs

@@ -57,9 +57,9 @@ pub fn get(chain_id: u64, contract_address: [u8; 20]) -> Option<Params> {
     }
     for &(decimals, unit_len, params) in ALL.iter() {
         let result = params
-            .iter()
-            .find(|p| p.contract_address == contract_address)
-            .map(|p| Params::from_p(p, decimals, unit_len));
+            .binary_search_by_key(&contract_address, |p| p.contract_address)
+            .ok()
+            .map(|idx| Params::from_p(&params[idx], decimals, unit_len));
         if result.is_some() {
             return result;
         }