Convert big ruby integers to js bigints (#350)

Numbers outside the range that double-precision floating-point numbers
can represent exactly are now converted to JS BigInts instead of being
rejected outright. Said range corresponds to `Number.MIN_SAFE_INTEGER`
and `Number.MAX_SAFE_INTEGER` on the JS side.

Refs: #348

Author: bnoordhuis

ext/mini_racer_extension/mini_racer_extension.c

@@ -327,8 +327,19 @@ static void des_bigint(void *arg, const void *p, size_t n, int sign)
     if (t >> 63)
         *a++ = 0; // suppress sign extension
     v = rb_big_unpack(limbs, a-limbs);
-    if (sign < 0)
-        v = rb_big_mul(v, LONG2FIX(-1));
+    if (sign < 0) {
+        // rb_big_unpack returns T_FIXNUM for smallish bignums
+        switch (TYPE(v)) {
+        case T_BIGNUM:
+            v = rb_big_mul(v, LONG2FIX(-1));
+            break;
+        case T_FIXNUM:
+            v = LONG2FIX(-1 * FIX2LONG(v));
+            break;
+        default:
+            abort();
+        }
+    }
     put(c, v);
 }
 
@@ -620,14 +631,16 @@ static int serialize1(Ser *s, VALUE refs, VALUE v)
             struct timeval tv = rb_time_timeval(v);
             ser_date(s, tv.tv_sec*1e3 + tv.tv_usec/1e3);
         } else {
-	    snprintf(s->err, sizeof(s->err), "unsupported type %s", rb_class2name(CLASS_OF(v)));
-	    return -1;
+            snprintf(s->err, sizeof(s->err), "unsupported type %s", rb_class2name(CLASS_OF(v)));
+            return -1;
         }
         break;
     default:
         snprintf(s->err, sizeof(s->err), "unsupported type %x", TYPE(v));
         return -1;
     }
+    if (*s->err)
+        return -1;
     return 0;
 }
 

ext/mini_racer_extension/serde.c

@@ -239,15 +239,44 @@ static void ser_num(Ser *s, double v)
     }
 }
 
+// ser_bigint: |n| is in bytes, not quadwords
+static void ser_bigint(Ser *s, const uint64_t *p, size_t n, int sign)
+{
+    if (*s->err)
+        return;
+    if (n % 8) {
+        snprintf(s->err, sizeof(s->err), "bad bigint");
+        return;
+    }
+    w_byte(s, 'Z');
+    // chop off high all-zero words
+    n /= 8;
+    while (n--)
+        if (p[n])
+            break;
+    if (n == (size_t)-1) {
+        w_byte(s, 0); // normalized zero
+    } else {
+        n = 8*n + 8;
+        w_varint(s, 2*n + (sign < 0));
+        w(s, p, n);
+    }
+}
+
 static void ser_int(Ser *s, int64_t v)
 {
+    uint64_t t;
+    int sign;
+
     if (*s->err)
         return;
     if (v < INT32_MIN || v > INT32_MAX) {
         if (v > INT64_MIN/1024)
             if (v <= INT64_MAX/1024)
                 return ser_num(s, v);
-        snprintf(s->err, sizeof(s->err), "out of range: %lld", (long long)v);
+        t = v < 0 ? -v : v;
+        sign = v < 0 ? -1 : 1;
+        ser_bigint(s, &t, sizeof(t), sign);
     } else {
         w_byte(s, 'I');
         w_zigzag(s, v);
@@ -265,30 +294,6 @@ static void ser_date(Ser *s, double v)
     }
 }
 
-// ser_bigint: |n| is in bytes, not quadwords
-static void ser_bigint(Ser *s, const uint64_t *p, size_t n, int sign)
-{
-    if (*s->err)
-        return;
-    if (n % 8) {
-        snprintf(s->err, sizeof(s->err), "bad bigint");
-        return;
-    }
-    w_byte(s, 'Z');
-    // chop off high all-zero words
-    n /= 8;
-    while (n--)
-        if (p[n])
-            break;
-    if (n == (size_t)-1) {
-        w_byte(s, 0); // normalized zero
-    } else {
-        n = 8*n + 8;
-        w_varint(s, 2*n + (sign < 0));
-        w(s, p, n);
-    }
-}
-
 // string must be utf8
 static void ser_string(Ser *s, const char *p, size_t n)
 {

test/mini_racer_test.rb

@@ -1153,5 +1153,19 @@ def test_large_integer
       assert_equal(result.class, big_int.class)
       assert_equal(result, big_int)
     }
+    types = []
+    [2**63/1024-1, 2**63/1024, -2**63/1024+1, -2**63/1024].each { |big_int|
+      context = MiniRacer::Context.new
+      context.attach("test", proc { big_int })
+      context.attach("type", proc { |arg| types.push(arg) })
+      result = context.eval("const t = test(); type(typeof t); t")
+      assert_equal(result.class, big_int.class)
+      assert_equal(result, big_int)
+    }
+    if RUBY_ENGINE == "truffleruby"
+      assert_equal(types, %w[number number number number])
+    else
+      assert_equal(types, %w[number bigint number bigint])
+    end
   end
 end