Fix crc32 code warning

examples/Crc32.cpp

@@ -15,19 +15,19 @@
 #include <cstdint>
 #include <cstddef>
 
-uint32_t crc32(const char *s,size_t n, uint32_t crc=0xFFFFFFFF) {
-	
-	for(size_t i=0;i<n;i++) {
-		char ch=s[i];
-		for(size_t j=0;j<8;j++) {
-			uint32_t b=(ch^crc)&1;
-			crc>>=1;
-			if(b) crc=crc^0xEDB88320;
-			ch>>=1;
-		}
-	}
-	
-	return crc;
+uint32_t crc32(const char *s, size_t n, uint32_t crc = 0xFFFFFFFF) {
+
+    for (size_t i = 0; i < n; i++) {
+        unsigned char ch = static_cast<unsigned char>(s[i]);
+        for (size_t j = 0; j < 8; j++) {
+            uint32_t b = (ch ^ crc) & 1;
+            crc >>= 1;
+            if (b) crc = crc ^ 0xEDB88320;
+            ch >>= 1;
+        }
+    }
+
+    return crc;
 }
 
 int main() {