Add `LTC_ALIGN_BUF()`

Signed-off-by: Steffen Jaeckel <[email protected]>

demos/gcm-file/gcm_filehandle.c

@@ -98,9 +98,7 @@ int gcm_filehandle(      int           cipher,
     * but again it's only for SSE2 anyways, so who cares?
     */
 #ifdef LTC_GCM_TABLES_SSE2
-   if ((unsigned long)gcm & 15) {
-      gcm = (gcm_state *)((unsigned long)gcm + (16 - ((unsigned long)gcm & 15)));
-   }
+    gcm = LTC_ALIGN_BUF(gcm, 16);
 #endif
 
     if ((err = gcm_init(gcm, cipher, key, keylen)) != CRYPT_OK) {

src/encauth/gcm/gcm_memory.c

@@ -70,9 +70,7 @@ int gcm_memory(      int           cipher,
     * but again it's only for SSE2 anyways, so who cares?
     */
 #ifdef LTC_GCM_TABLES_SSE2
-   if ((unsigned long)gcm & 15) {
-      gcm = (gcm_state *)((unsigned long)gcm + (16 - ((unsigned long)gcm & 15)));
-   }
+    gcm = LTC_ALIGN_BUF(gcm, 16);
 #endif
 
     if ((err = gcm_init(gcm, cipher, key, keylen)) != CRYPT_OK) {

src/headers/tomcrypt_cfg.h

@@ -209,7 +209,7 @@ LTC_EXPORT int   LTC_CALL XSTRCMP(const char *s1, const char *s2);
    typedef unsigned __int64 ulong64;
    typedef __int64 long64;
 #else
-   #define CONST64(n) n ## ULL
+   #define CONST64(n) n ## uLL
    typedef unsigned long long ulong64;
    typedef long long long64;
 #endif

src/headers/tomcrypt_private.h

@@ -6,9 +6,30 @@
 /*
  * Internal Macros
  */
+/* Static assertion */
+#define LTC_STATIC_ASSERT(msg, cond) typedef char ltc_static_assert_##msg[(cond) ? 1 : -1];
 
 #define LTC_PAD_MASK       (0xF000U)
 
+#if defined(ENDIAN_64BITWORD)
+   #define CONSTPTR(n) CONST64(n)
+#else
+   #define CONSTPTR(n) n ## uL
+#endif
+
+LTC_STATIC_ASSERT(correct_CONSTPTR_size, sizeof(CONSTPTR(1)) == sizeof(void*))
+
+/* Poor-man's `uintptr_t` since we can't use stdint.h
+ * c.f. https://github.com/DCIT/perl-CryptX/issues/95#issuecomment-1745280962 */
+typedef size_t ltc_uintptr;
+
+LTC_STATIC_ASSERT(correct_ltc_uintptr_size, sizeof(ltc_uintptr) == sizeof(void*))
+
+/* Aligns a `unsigned char` buffer `buf` to `n` bytes and returns that aligned address.
+ * Make sure that the buffer that is passed is huge enough.
+ */
+#define LTC_ALIGN_BUF(buf, n) ((void*)((ltc_uintptr)&((unsigned char*)(buf))[n - 1] & (~(CONSTPTR(n) - CONSTPTR(1)))))
+
 /* `NULL` as defined by the standard is not guaranteed to be of a pointer
  * type. In order to make sure that in vararg API's a pointer type is used,
  * define our own version and use that one internally.