[eth] Add parsePriceFeedUpdates method (#392)

* Add the implementation with tests and benchmark

* Refactor the contract to reduce redundancy

* Reduce optimization runs as the contract was huge

It has 177 more gas usage on some benchmark tests

Author: ali-behjati

ethereum/contracts/pyth/Pyth.sol

@@ -86,8 +86,7 @@ contract GasBenchmark is Test, WormholeTestUtils, PythTestUtils {
 
     function generateUpdateDataAndFee(PythStructs.Price[] memory prices) internal returns (bytes[] memory updateData, uint updateFee) {
         bytes memory vaa = generatePriceFeedUpdateVAA(
-            priceIds,
-            prices,
+            pricesToPriceAttestations(priceIds, prices),
             sequence,
             NUM_GUARDIAN_SIGNERS
         );
@@ -122,6 +121,29 @@ contract GasBenchmark is Test, WormholeTestUtils, PythTestUtils {
         pyth.updatePriceFeedsIfNecessary{value: cachedPricesUpdateFee}(cachedPricesUpdateData, priceIds, cachedPricesPublishTimes);
     }
 
+    function testBenchmarkParsePriceFeedUpdatesForOnePriceFeed() public {
+        bytes32[] memory ids = new bytes32[](1);
+        ids[0] = priceIds[0];
+
+        pyth.parsePriceFeedUpdates{value: freshPricesUpdateFee}(freshPricesUpdateData, ids, 0, 50);
+    }
+
+    function testBenchmarkParsePriceFeedUpdatesForTwoPriceFeed() public {
+        bytes32[] memory ids = new bytes32[](2);
+        ids[0] = priceIds[0];
+        ids[1] = priceIds[1];
+
+        pyth.parsePriceFeedUpdates{value: freshPricesUpdateFee}(freshPricesUpdateData, ids, 0, 50);
+    }
+
+    function testBenchmarkParsePriceFeedUpdatesForOnePriceFeedNotWithinRange() public {
+        bytes32[] memory ids = new bytes32[](1);
+        ids[0] = priceIds[0];
+
+        vm.expectRevert(bytes("1 or more price feeds are not found in the updateData or they are out of the given time range"));
+        pyth.parsePriceFeedUpdates{value: freshPricesUpdateFee}(freshPricesUpdateData, ids, 50, 100);
+    }
+
     function testBenchmarkGetPrice() public {
         // Set the block timestamp to 0. As prices have < 10 timestamp and staleness 
         // is set to 60 seconds, the getPrice should work as expected.