bench: add a small performance comparison script bench_json_vs_json2.v

vlib/v/tests/bench/bench_json_vs_json2.v

@@ -0,0 +1,54 @@
+import os
+import json
+import x.json2
+import time
+import benchmark
+
+//	assert json.decode[StructType[time.Time]]('{"val": "2022-03-11T13:54:25.000Z"}')!.val == fixed_time
+
+struct Person {
+	name       string
+	age        int
+	created_at time.Time
+}
+
+fn main() {
+	max_iterations := os.getenv_opt('MAX_ITERATIONS') or { '1000' }.int()
+	s := '{"name":"Bilbo Baggins","age":99,"created_at":1670840340}'
+	mut b := benchmark.start()
+
+	for _ in 0 .. max_iterations {
+		p := json2.decode[Person](s)!
+		if p.age != 99 {
+			println('error: ${p}')
+		}
+	}
+	b.measure('json2.decode')
+
+	for _ in 0 .. max_iterations {
+		p := json.decode(Person, s)!
+		if p.age != 99 {
+			println('error: ${p}')
+		}
+	}
+	b.measure('json.decode')
+
+	// encoding measurements:
+	p := json.decode(Person, s)!
+
+	for _ in 0 .. max_iterations {
+		es := json2.encode(p)
+		if es[0] != `{` {
+			println('json2.encode error: ${es}')
+		}
+	}
+	b.measure('json2.encode')
+
+	for _ in 0 .. max_iterations {
+		es := json.encode(p)
+		if es[0] != `{` {
+			println('json.encode error: ${es}')
+		}
+	}
+	b.measure('json.encode')
+}