refactor and test ts start search

solanaceae/ngc_hs2/ts_find_start.hpp

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <algorithm>
+#include <cstdint>
+
+#include <iostream>
+
+// perform binary search to find the first message not newer than ts_start
+template<typename View>
+auto find_start_by_ts(const View& view, uint64_t ts_start) {
+	std::cout << "!!!! starting msg ts search, ts_start:" << ts_start << "\n";
+
+	// -> first value smaller than start ts
+	auto res = std::lower_bound(
+		view.begin(), view.end(),
+		ts_start,
+		[&view](const auto& a, const auto& b) {
+			const auto& [a_comp] = view.get(a);
+			return a_comp.ts > b; // > bc ts is sorted high to low?
+		}
+	);
+
+	if (res != view.end()) {
+		const auto& [ts_comp] = view.get(*res);
+		std::cout << "!!!! first value not newer than start ts is " << ts_comp.ts << "\n";
+	} else {
+		std::cout << "!!!! no first value not newer than start ts\n";
+	}
+	return res;
+}
+