erlang: register binary_to_list/1 + list_to_binary/1 BIFs (+9 ffi tests, 738/738)

lib/erlang/runtime.sx

@@ -1561,7 +1561,66 @@
     (er-register-pure-bif! "crypto" "hash" 2 er-bif-crypto-hash)
     (er-register-pure-bif! "cid" "from_bytes" 1 er-bif-cid-from-bytes)
     (er-register-pure-bif! "cid" "to_string" 1 er-bif-cid-to-string)
+
+;; ── binary_to_list / list_to_binary (Step 3b — term codec) ──────
+;; Standard Erlang semantics:
+;;   binary_to_list(<<B1,B2,...>>) -> [B1, B2, ...]   (Erlang cons of ints)
+;;   list_to_binary(IoList)        -> <<...>>         (flattens nested
+;;     iolists; elements are byte ints 0-255 or binaries)
+;; Bad arg / out-of-range byte / non-iolist element -> error:badarg.
+
+(define er-bif-binary-to-list
+  (fn (vs)
+    (let ((v (nth vs 0)))
+      (cond
+        (not (er-binary? v))
+          (raise (er-mk-error-marker (er-mk-atom "badarg")))
+        :else
+          (let ((bs (get v :bytes)) (out (er-mk-nil)))
+            (for-each
+              (fn (i)
+                (set! out (er-mk-cons (nth bs (- (- (len bs) 1) i)) out)))
+              (range 0 (len bs)))
+            out)))))
+
+;; Walk an Erlang iolist, appending bytes to `acc` (a mutable SX list).
+;; Accepts: nil, cons-of-X, binary, integer in 0..255. Anything else
+;; signals failure by setting (nth fail 0) to true.
+(define er-iolist-walk!
+  (fn (v acc fail)
+    (cond
+      (nth fail 0) nil
+      (er-nil? v) nil
+      (er-cons? v)
+        (do (er-iolist-walk! (get v :head) acc fail)
+            (er-iolist-walk! (get v :tail) acc fail))
+      (er-binary? v)
+        (for-each
+          (fn (i) (append! acc (nth (get v :bytes) i)))
+          (range 0 (len (get v :bytes))))
+      (= (type-of v) "number")
+        (cond
+          (and (>= v 0) (<= v 255)) (append! acc v)
+          :else (set-nth! fail 0 true))
+      :else (set-nth! fail 0 true))))
+
+(define er-bif-list-to-binary
+  (fn (vs)
+    (let ((v (nth vs 0)) (acc (list)) (fail (list false)))
+      (cond
+        (not (or (er-nil? v) (er-cons? v) (er-binary? v)))
+          (raise (er-mk-error-marker (er-mk-atom "badarg")))
+        :else
+          (do
+            (er-iolist-walk! v acc fail)
+            (cond
+              (nth fail 0)
+                (raise (er-mk-error-marker (er-mk-atom "badarg")))
+              :else (er-mk-binary acc)))))))
+
     (er-register-bif! "file" "list_dir" 1 er-bif-file-list-dir)
+    (er-register-pure-bif! "erlang" "binary_to_list" 1 er-bif-binary-to-list)
+    (er-register-pure-bif! "erlang" "list_to_binary"  1 er-bif-list-to-binary)
     (er-mk-atom "ok")))
 
 ;; Register everything at load time.

lib/erlang/scoreboard.json

@@ -1,7 +1,7 @@
 {
   "language": "erlang",
-  "total_pass": 729,
+  "total_pass": 738,
-  "total": 729,
+  "total": 738,
   "suites": [
     {"name":"tokenize","pass":62,"total":62,"status":"ok"},
     {"name":"parse","pass":52,"total":52,"status":"ok"},
@@ -12,7 +12,7 @@
     {"name":"bank","pass":8,"total":8,"status":"ok"},
     {"name":"echo","pass":7,"total":7,"status":"ok"},
     {"name":"fib","pass":8,"total":8,"status":"ok"},
-    {"name":"ffi","pass":28,"total":28,"status":"ok"},
+    {"name":"ffi","pass":37,"total":37,"status":"ok"},
     {"name":"vm","pass":78,"total":78,"status":"ok"}
   ]
 }

lib/erlang/scoreboard.md

@@ -1,6 +1,6 @@
 # Erlang-on-SX Scoreboard
 
-**Total: 729 / 729 tests passing**
+**Total: 738 / 738 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
@@ -13,7 +13,7 @@
 | ✅ | bank | 8 | 8 |
 | ✅ | echo | 7 | 7 |
 | ✅ | fib | 8 | 8 |
-| ✅ | ffi | 28 | 28 |
+| ✅ | ffi | 37 | 37 |
 | ✅ | vm | 78 | 78 |
 
 

lib/erlang/tests/ffi.sx

@@ -160,6 +160,51 @@
   (ffi-nm (ffi-ev "element(2, file:list_dir(\"/no/such/dir/xyz\"))"))
   "enoent")
 
+(er-ffi-test
+  "binary_to_list <<1,2,3>> length"
+  (ffi-ev "length(binary_to_list(<<1,2,3,4,5>>))")
+  5)
+
+(er-ffi-test
+  "binary_to_list hd byte"
+  (ffi-ev "hd(binary_to_list(<<7,8,9>>))")
+  7)
+
+(er-ffi-test
+  "binary_to_list empty -> []"
+  (ffi-nm (ffi-ev "case binary_to_list(<<>>) of [] -> empty end"))
+  "empty")
+
+(er-ffi-test
+  "list_to_binary flat list bytes"
+  (ffi-ev "byte_size(list_to_binary([1,2,3]))")
+  3)
+
+(er-ffi-test
+  "list_to_binary nested iolist"
+  (ffi-ev "byte_size(list_to_binary([1, <<2,3>>, [4, [5]]]))")
+  5)
+
+(er-ffi-test
+  "list_to_binary round-trip via binary_to_list"
+  (ffi-nm (ffi-ev "list_to_binary(binary_to_list(<<10,20,30>>)) =:= <<10,20,30>>"))
+  "true")
+
+(er-ffi-test
+  "binary_to_list non-binary -> error:badarg"
+  (ffi-nm (ffi-ev "try binary_to_list(42) catch error:badarg -> ok end"))
+  "ok")
+
+(er-ffi-test
+  "list_to_binary out-of-range byte -> error:badarg"
+  (ffi-nm (ffi-ev "try list_to_binary([300]) catch error:badarg -> ok end"))
+  "ok")
+
+(er-ffi-test
+  "list_to_binary non-iolist -> error:badarg"
+  (ffi-nm (ffi-ev "try list_to_binary(42) catch error:badarg -> ok end"))
+  "ok")
+
 ;; ── Still deferred (no host primitive): httpc (HTTP client, v2),
 ;; sqlite-* (v2 indexes). Assert NOT registered so a future iteration
 ;; that wires them without updating this suite fails fast.