Add lib-c functions usage option

Author: abderraouf-adjal

src/SpritzCipher.c

@@ -254,8 +254,8 @@ spritz_compare(const uint8_t *data_a, const uint8_t *data_b, uint16_t len)
   else {
     d = 1U;
   }
-# endif
-#endif
+# endif /* !defined(__GNUC__) && !defined(__clang__) */
+#endif /* SPRITZ_WIPE_TRACES_PARANOID */
 
   return d;
 }
@@ -276,11 +276,15 @@ __attribute__ ((optnone))
 #endif
 spritz_memzero(uint8_t *buf, uint16_t len)
 {
+#ifdef SPRITZ_USE_LIBC
+  memset(buf, 0, len * sizeof(uint8_t));
+#else
   uint16_t i;
 
   for (i = 0; i < len; i++) {
     buf[i] = 0;
   }
+#endif
 }
 
 /** spritz_state_memzero()
@@ -298,12 +302,15 @@ __attribute__ ((optnone))
 #endif
 spritz_state_memzero(spritz_ctx *ctx)
 {
+#ifdef SPRITZ_USE_LIBC
+  memset(ctx->s, 0, SPRITZ_N);
+#else
   uint8_t i = 0;
-
   /* Loop for SPRITZ_N=256 */
   do {
     ctx->s[i] = 0;
   } while (++i);
+#endif
 
   ctx->i = 0;
   ctx->j = 0;

src/SpritzCipher.h

@@ -27,6 +27,18 @@ extern "C" {
 #include <stdint.h> /* uint8_t, uint16_t, uint32_t */
 
 
+/** SPRITZ_USE_LIBC
+ * Use C standard library functions such as `memset()` to zero buffers.
+ * It can be useful for performnce if the lib-C functions are optimized in low-level.
+ */
+#if 0
+# define SPRITZ_USE_LIBC
+# include <string.h>
+# if !defined(__GNUC__) && !defined(__clang__) /* Not GCC or Clang. */
+#  warning "SPRITZ_USE_LIBC warning: Code optimization isn't off in some security functions."
+# endif /* Not GCC or Clang. */
+#endif
+
 /** SPRITZ_TIMING_SAFE_CRUSH
  * If defined, the equal time crush() will be used.
  * This may NOT be useful in some compilers with optimization (except GCC and Clang).
@@ -69,7 +81,7 @@ extern "C" {
 /** SPRITZ_N
  * Present the value of N in this spritz implementation, DO NOT change SPRITZ_N value.
  */
-#define SPRITZ_N 256
+#define SPRITZ_N 256U
 
 /* `Semantic Versioning` of this library */
 #define SPRITZ_LIBRARY_VERSION_STRING "1.1.0"