add native-json-parser module for comparison

.dir-locals.el

@@ -0,0 +1,4 @@
+;;; Directory Local Variables         -*- no-byte-compile: t; -*-
+;;; For more information see (info "(emacs) Directory Variables")
+
+((rust-mode . ((lsp-rust-analyzer-proc-macro-enable . nil))))

Cargo.toml

@@ -11,3 +11,10 @@ anyhow = "1.0"
 lazy_static = "1.4"
 smallvec = "1.11"
 tempfile = "3.9"
+
+[[example]]
+name = "native-json-parser"
+crate-type = ["cdylib"]
+
+[dev-dependencies]
+emacs = "0.18"

examples/native-json-parser.rs

@@ -0,0 +1,53 @@
+use emacs::{defun, Env, Result, Value, IntoLisp};
+use serde_json as json;
+
+// Emacs won't load the module without this.
+emacs::plugin_is_GPL_compatible!();
+
+// Register the initialization hook that Emacs will call when it loads the module.
+#[emacs::module]
+fn init(env: &Env) -> Result<Value<'_>> {
+    env.message("Done loading!")
+}
+
+fn json_to_lisp<'a>(env: &'a Env, val: &json::Value) -> Result<Value<'a>> {
+    match val {
+        &json::Value::Null | &json::Value::Bool(false) =>
+            ().into_lisp(env),
+        &json::Value::Bool(true) =>
+            true.into_lisp(env),
+        &json::Value::Number(ref num) =>
+            if num.is_f64() {
+                num.as_f64().unwrap().into_lisp(env)
+            } else if num.is_i64() {
+                num.as_i64().unwrap().into_lisp(env)
+            } else {
+                num.as_u64().unwrap().into_lisp(env)
+            },
+        &json::Value::String(ref s) =>
+            s.into_lisp(env),
+        &json::Value::Array(ref arr) => {
+            let vals = arr.iter().map(|x| json_to_lisp(env, x)).collect::<Result<Vec<_>>>()?;
+            env.vector(&vals)
+        },
+        &json::Value::Object(ref map) => {
+            let mut vals: Vec<Value<'a>> = Vec::new();
+            for (k, v) in map {
+                vals.push(env.intern(&format!(":{}", k))?);
+                vals.push(json_to_lisp(env, v)?);
+            }
+            env.list(&vals)
+        },
+    }
+}
+
+
+#[defun]
+fn parse(env: &Env, s: String) -> Result<Value<'_>> {
+    let start = std::time::Instant::now();
+    let json_val = json::from_str(&s)?;
+    let end = std::time::Instant::now();
+    env.message(format!("json parsing took {:?}", end.duration_since(start)))?;
+
+    json_to_lisp(env, &json_val)
+}