From 7b1e170e7ca2407e2d35a043dc34af29551ef7c2 Mon Sep 17 00:00:00 2001
From: Ash Vardanian <1983160+ashvardanian@users.noreply.github.com>
Date: Mon, 9 Oct 2023 19:08:48 -0700
Subject: [PATCH] Improve: BitScan dispatch on Windows

---
 stringzilla/stringzilla.h | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/stringzilla/stringzilla.h b/stringzilla/stringzilla.h
index 57d17b89..136d93c5 100644
--- a/stringzilla/stringzilla.h
+++ b/stringzilla/stringzilla.h
@@ -714,19 +714,26 @@ inline static sz_u64_t sz_u64_byte_reverse(sz_u64_t val) {
 inline static sz_size_t sz_log2i(sz_size_t n) {
     if (n == 0) return 0;
 
-#if defined(__LP64__) || defined(_WIN64) // 64-bit
+#ifdef _WIN64
 #ifdef _MSC_VER
     unsigned long index;
-    _BitScanReverse64(&index, n);
-    return index;
+    if (_BitScanReverse64(&index, n)) return index;
+    return 0; // This line might be redundant due to the initial check, but it's safer to include it.
 #else
     return 63 - __builtin_clzll(n);
 #endif
-#else // 32-bit
+#elif defined(_WIN32)
 #ifdef _MSC_VER
     unsigned long index;
-    _BitScanReverse(&index, n);
-    return index;
+    if (_BitScanReverse(&index, n)) return index;
+    return 0; // Same note as above.
+#else
+    return 31 - __builtin_clz(n);
+#endif
+#else
+// Handle non-Windows platforms. You can further differentiate between 32-bit and 64-bit if needed.
+#if defined(__LP64__)
+    return 63 - __builtin_clzll(n);
 #else
     return 31 - __builtin_clz(n);
 #endif