Implement .align directive

asm.js

@@ -92,6 +92,7 @@ const State = Object.freeze({
     BYTE:         20,
     WORD:         21,
     UTF8:         22,
+    ALIGN:        23,
 });
 
 const Action = Object.freeze({
@@ -107,6 +108,7 @@ const Action = Object.freeze({
     GLOBAL: 9,
     AT:     10,
     DATA:   11,
+    ALIGN:  12,
 });
 
 const types = {
@@ -154,6 +156,7 @@ class Parser {
             ".byte":   State.BYTE,
             ".word":   State.WORD,
             ".utf8":   State.UTF8,
+            ".align":  State.ALIGN,
         };
         this.handlers = {
             [State.TOP]:          (token) => this.token_top(token),
@@ -179,6 +182,7 @@ class Parser {
             [State.BYTE]:         (token) => this.token_byte(token),
             [State.WORD]:         (token) => this.token_word(token),
             [State.UTF8]:         (token) => this.token_utf8(token),
+            [State.ALIGN]:        (token) => this.token_align(token),
         };
 
         this.results = [];
@@ -509,7 +513,7 @@ class Parser {
             return;
         } else if (token.string == undefined) {
             console.error(
-                `ERROR: unexpected token ${token}, expected string`);
+                `ERROR: Unexpected token ${token}, expected string`);
             return;
         }
         const value = this.encoder.encode(token.string);
@@ -517,6 +521,23 @@ class Parser {
         return action;
     }
 
+    token_align(token) {
+        const action = { type: Action.ALIGN };
+        if (token == LINE_END) {
+            action.alignment = 4;
+        } else {
+            action.alignment = this.integer(token);
+            if (action.alignment == null) {
+                console.error(
+                    `ERROR: Unexpected token ${token}, expected alignment`);
+                this.state = State.TOP;
+                return action;
+            }
+        }
+        this.state = State.TOP
+        return action;
+    }
+
     mem_action() {
         const action = {
             type: Action.MEM,
@@ -571,6 +592,7 @@ export class Assembler {
             [Action.GLOBAL]: (action) => this.action_global(action),
             [Action.AT]:     (action) => this.action_at(action),
             [Action.DATA]:   (action) => this.action_data(action),
+            [Action.ALIGN]:  (action) => this.action_align(action),
         };
 
         this.exports = [];
@@ -663,6 +685,15 @@ export class Assembler {
         this.pos.addr += action.size;
     }
 
+    action_align(action) {
+        const alignment = action.alignment;
+        const data = this.data.at(-1).data;
+        while (this.pos.addr % alignment != 0) {
+            data.push(0);
+            ++this.pos.addr;
+        }
+    }
+
 	push(chunk) {
 		const text = this.decoder.decode(chunk, { stream: true });
 		for (const action of this.parser.handle(text))