From 639fca0157a08e07805847e64862388f63223b40 Mon Sep 17 00:00:00 2001
From: Leif Scholz <Leif-Ulrik.Scholz@telekom.de>
Date: Sun, 19 Apr 2026 14:42:58 +0200
Subject: [PATCH] Fix: Enable MSVC build on Windows

Replaces compiler-specific function calls with a compatible MSVC implementation.

Removes unsupported '-std=gnu99' compile argument to allow clean compilation on Windows.
---
 setup.py                 |  2 +-
 src/pidng/liblj92/lj92.c | 21 ++++++++++++++-------
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/setup.py b/setup.py
index 49ee496..0562fca 100644
--- a/setup.py
+++ b/setup.py
@@ -5,7 +5,7 @@
     long_description = fh.read()
 
 ljpeg92 = Extension('ljpegCompress', sources=[
-                    "src/pidng/bitunpack.c", "src/pidng/liblj92/lj92.c"],  extra_compile_args=['-std=gnu99'], extra_link_args=[])
+                    "src/pidng/bitunpack.c", "src/pidng/liblj92/lj92.c"],  extra_compile_args=[], extra_link_args=[])
 
 setup(
     name="pidng",
diff --git a/src/pidng/liblj92/lj92.c b/src/pidng/liblj92/lj92.c
index b46a68f..6908ab5 100644
--- a/src/pidng/liblj92/lj92.c
+++ b/src/pidng/liblj92/lj92.c
@@ -35,14 +35,21 @@ typedef uint32_t u32;
 //#define SLOW_HUFF
 //#define DEBUG
 
-#if defined(__clang__)
-    #define _clz __builtin_clz
-#elif defined(__GNUC__) || defined(__GNUG__)
-    #define _clz __builtin_clz
-#elif defined(_MSC_VER)
-    #define _clz __lzcnt
+#if defined(_MSC_VER)
+#include <intrin.h>
+static inline int __msvc_clz(unsigned int x) {
+    unsigned long leading_zero;
+    if (_BitScanReverse(&leading_zero, x)) {
+        return 31 - leading_zero;
+    } else {
+        return 32;
+    }
+}
+#define _clz __msvc_clz
+#elif defined(__GNUC__) || defined(__clang__)
+#define _clz __builtin_clz
 #else
-    #error Could not find builtin clz function
+#error Could not find builtin clz function
 #endif
 
 typedef struct _ljp {