Add deserialize json benchmark

Author: khvzak

benches/serde.rs

@@ -1,6 +1,7 @@
-use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
 use std::time::Duration;
 
+use criterion::{criterion_group, criterion_main, BatchSize, Criterion};
+
 use mlua::prelude::*;
 
 fn collect_gc_twice(lua: &Lua) {
@@ -43,6 +44,38 @@ fn encode_json(c: &mut Criterion) {
     });
 }
 
+fn decode_json(c: &mut Criterion) {
+    let lua = Lua::new();
+
+    let decode = lua
+        .create_function(|lua, s: String| {
+            lua.to_value(&serde_json::from_str::<serde_json::Value>(&s).unwrap())
+        })
+        .unwrap();
+    let json = r#"{
+        "name": "Clark Kent",
+        "address": {
+            "city": "Smallville",
+            "state": "Kansas",
+            "country": "USA"
+        },
+        "age": 22,
+        "parents": ["Jonathan Kent", "Martha Kent"],
+        "superman": true,
+        "interests": ["flying", "saving the world", "kryptonite"]
+    }"#;
+
+    c.bench_function("deserialize json", |b| {
+        b.iter_batched(
+            || collect_gc_twice(&lua),
+            |_| {
+                decode.call::<_, LuaTable>(json).unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
 criterion_group! {
     name = benches;
     config = Criterion::default()
@@ -51,6 +84,7 @@ criterion_group! {
         .noise_threshold(0.02);
     targets =
         encode_json,
+        decode_json,
 }
 
 criterion_main!(benches);