fixup! intn: add intn_to_integer_bytes and intn_required_unsigned_integer_bytes

Author: bettio

src/libAtomVM/intn.c

@@ -190,9 +190,9 @@ static size_t count16(const uint16_t *num, size_t num_len)
     return count;
 }
 
-static inline uint32_t nlz(uint32_t x)
+// make sure that x != 0 before calling this function
+static inline uint32_t uint32_nlz(uint32_t x)
 {
-    // This function is used only from divmnu, that doesn't allow 32 leading zeros
     ASSUME(x != 0);
 
 #ifdef __has_builtin
@@ -272,7 +272,7 @@ static int divmnu16(
     // same amount.  We may have to append a high-order
     // digit on the dividend; we do that unconditionally.
 
-    s = nlz(v[n - 1]) - 16; // 0 <= s <= 15.
+    s = uint32_nlz(v[n - 1]) - 16; // 0 <= s <= 15.
     uint16_t vn[INTN_DIVMNU_MAX_IN_LEN * (sizeof(intn_digit_t) / sizeof(uint16_t))];
     for (i = n - 1; i > 0; i--)
         vn[i] = (v[i] << s) | (v[i - 1] >> (16 - s));
@@ -778,14 +778,13 @@ int intn_to_integer_bytes(const intn_digit_t in[], size_t in_len, intn_integer_s
 
 size_t intn_required_unsigned_integer_bytes(const intn_digit_t in[], size_t in_len)
 {
-    uint8_t *in8 = (uint8_t *) in;
     int i;
-    for (i = in_len * sizeof(intn_digit_t) - 1; i >= 0; i--) {
-        if (in8[i] != 0) {
-            break;
+    for (i = in_len - 1; i >= 0; i--) {
+        uint32_t in_i = in[i];
+        if (in_i != 0) {
+            return (i + 1) * sizeof(uint32_t) - (uint32_nlz(in_i) / 8);
         }
     }
-    size_t count = i + 1;
 
-    return count;
+    return 0;
 }