Use preprocessor macros instead of autoconf to detect endianness

[secp256k1.git] / src / util.h

diff --git a/src/util.h b/src/util.h
index d5fa39c02c30606bc4a01a645c0bf4f18d27a8a9..befb9dccdb414f1e23475e096f31f7b18697b338 100644 (file)
--- a/src/util.h
+++ b/src/util.h
@@ -69,6 +69,25 @@ static SECP256K1_INLINE void secp256k1_callback_call(const secp256k1_callback *
 #define VERIFY_SETUP(stmt)
 #endif
 
+/* Define `VG_UNDEF` and `VG_CHECK` when VALGRIND is defined  */
+#if !defined(VG_CHECK)
+# if defined(VALGRIND)
+#  include <valgrind/memcheck.h>
+#  define VG_UNDEF(x,y) VALGRIND_MAKE_MEM_UNDEFINED((x),(y))
+#  define VG_CHECK(x,y) VALGRIND_CHECK_MEM_IS_DEFINED((x),(y))
+# else
+#  define VG_UNDEF(x,y)
+#  define VG_CHECK(x,y)
+# endif
+#endif
+
+/* Like `VG_CHECK` but on VERIFY only */
+#if defined(VERIFY)
+#define VG_CHECK_VERIFY(x,y) VG_CHECK((x), (y))
+#else
+#define VG_CHECK_VERIFY(x,y)
+#endif
+
 static SECP256K1_INLINE void *checked_malloc(const secp256k1_callback* cb, size_t size) {
     void *ret = malloc(size);
     if (ret == NULL) {
@@ -160,4 +179,47 @@ static SECP256K1_INLINE void *manual_alloc(void** prealloc_ptr, size_t alloc_siz
 SECP256K1_GNUC_EXT typedef unsigned __int128 uint128_t;
 #endif
 
+#if defined(__BYTE_ORDER__)
+# if defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ && !defined(SECP256K1_LITTLE_ENDIAN)
+#  define SECP256K1_LITTLE_ENDIAN
+# elif defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ && !defined(SECP256K1_BIG_ENDIAN)
+#  define SECP256K1_BIG_ENDIAN
+# endif
+#endif
+#if defined(_MSC_VER) && defined(_WIN32) && !defined(SECP256K1_LITTLE_ENDIAN)
+# define SECP256K1_LITTLE_ENDIAN
+#endif
+#if defined(SECP256K1_LITTLE_ENDIAN) == defined(SECP256K1_BIG_ENDIAN)
+# error Please make sure that either SECP256K1_LITTLE_ENDIAN or SECP256K1_BIG_ENDIAN is set, see src/util.h.
+#endif
+
+/* Zero memory if flag == 1. Flag must be 0 or 1. Constant time. */
+static SECP256K1_INLINE void memczero(void *s, size_t len, int flag) {
+    unsigned char *p = (unsigned char *)s;
+    /* Access flag with a volatile-qualified lvalue.
+       This prevents clang from figuring out (after inlining) that flag can
+       take only be 0 or 1, which leads to variable time code. */
+    volatile int vflag = flag;
+    unsigned char mask = -(unsigned char) vflag;
+    while (len) {
+        *p &= ~mask;
+        p++;
+        len--;
+    }
+}
+
+/** If flag is true, set *r equal to *a; otherwise leave it. Constant-time.  Both *r and *a must be initialized and non-negative.*/
+static SECP256K1_INLINE void secp256k1_int_cmov(int *r, const int *a, int flag) {
+    unsigned int mask0, mask1, r_masked, a_masked;
+    /* Casting a negative int to unsigned and back to int is implementation defined behavior */
+    VERIFY_CHECK(*r >= 0 && *a >= 0);
+
+    mask0 = (unsigned int)flag + ~0u;
+    mask1 = ~mask0;
+    r_masked = ((unsigned int)*r & mask0);
+    a_masked = ((unsigned int)*a & mask1);
+
+    *r = (int)(r_masked | a_masked);
+}
+
 #endif /* SECP256K1_UTIL_H */