From 6a4877d52cc3941d2658e4e23c2f8757203122ff Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Mon, 9 Mar 2026 23:46:55 +0000
Subject: [PATCH] Implement .param directive

---
 asm.js | 54 ++++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/asm.js b/asm.js
index 3f71387..c687de7 100644
--- a/asm.js
+++ b/asm.js
@@ -47,10 +47,12 @@ class Tokenizer {
 }
 
 const State = Object.freeze({
-    TOP:    0,
-    EXPORT: 1,
-    FUNC:   2,
-    RESULT: 3,
+    TOP:        0,
+    EXPORT:     1,
+    FUNC:       2,
+    RESULT:     3,
+    PARAM_NAME: 4,
+    PARAM_TYPE: 5,
 });
 
 const Action = Object.freeze({
@@ -58,6 +60,7 @@ const Action = Object.freeze({
     EXPORT: 1,
     FUNC:   2,
     RESULT: 3,
+    PARAM:  4,
 });
 
 const types = {
@@ -67,6 +70,7 @@ const types = {
 
 const opcodes = {
     "end":       0x0b,
+    "local.get": 0x20,
     "i32.const": 0x41,
     "i32.mul":   0x6c,
 };
@@ -80,15 +84,19 @@ class Parser {
             ".export": State.EXPORT,
             ".func":   State.FUNC,
             ".result": State.RESULT,
+            ".param":  State.PARAM_NAME,
         };
         this.handlers = {
-            [State.TOP]:    (token) => this.token_top(token),
-            [State.EXPORT]: (token) => this.token_export(token),
-            [State.FUNC]:   (token) => this.token_func(token),
-            [State.RESULT]: (token) => this.token_result(token),
+            [State.TOP]:        (token) => this.token_top(token),
+            [State.EXPORT]:     (token) => this.token_export(token),
+            [State.FUNC]:       (token) => this.token_func(token),
+            [State.RESULT]:     (token) => this.token_result(token),
+            [State.PARAM_NAME]: (token) => this.token_param_name(token),
+            [State.PARAM_TYPE]: (token) => this.token_param_type(token),
         };
 
         this.results = [];
+        this.params = {};
 	}
 
     translate_code(token) {
@@ -132,6 +140,31 @@ class Parser {
         }
     }
 
+    token_param_name(token) {
+        if (token == LINE_END) {
+            const action = { type: Action.PARAM, params: this.params };
+            this.state = State.TOP;
+            this.params = {};
+            return action;
+        } else {
+            this.current_param = token;
+            this.state = State.PARAM_TYPE;
+        }
+    }
+
+    token_param_type(token) {
+        if (token == LINE_END) {
+            console.error(
+                "ERROR: Unexpected newline in .params: expected type");
+            this.state = State.TOP;
+            this.params = {};
+        } else {
+            this.params[this.current_param] = types[token];
+            this.current_param = undefined;
+            this.state = State.PARAM_NAME;
+        }
+    }
+
 	*handle(src) {
         let action;
 		for (const token of this.tokenizer.handle(src)) {
@@ -158,6 +191,7 @@ export class Assembler {
             [Action.EXPORT]: (action) => this.action_export(action),
             [Action.FUNC]:   (action) => this.action_func(action),
             [Action.RESULT]: (action) => this.action_result(action),
+            [Action.PARAM]:  (action) => this.action_param(action),
         };
 
         this.exports = [];
@@ -187,6 +221,10 @@ export class Assembler {
         this.funcs[this.current_func].results.push(...action.results);
     }
 
+    action_param(action) {
+        Object.assign(this.funcs[this.current_func].params, action.params);
+    }
+
 	push(chunk) {
 		const text = this.decoder.decode(chunk, { stream: true });
 		for (const action of this.parser.handle(text))