git-compat-util: introduce more size_t helpers
We will use them in the next commit.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-compat-util.h b/git-compat-util.h
index a508dbe..1f41e56 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -113,6 +113,14 @@
#define unsigned_mult_overflows(a, b) \
((a) && (b) > maximum_unsigned_value_of_type(a) / (a))
+/*
+ * Returns true if the left shift of "a" by "shift" bits will
+ * overflow. The type of "a" must be unsigned.
+ */
+#define unsigned_left_shift_overflows(a, shift) \
+ ((shift) < bitsizeof(a) && \
+ (a) > maximum_unsigned_value_of_type(a) >> (shift))
+
#ifdef __GNUC__
#define TYPEOF(x) (__typeof__(x))
#else
@@ -859,6 +867,23 @@ static inline size_t st_sub(size_t a, size_t b)
return a - b;
}
+static inline size_t st_left_shift(size_t a, unsigned shift)
+{
+ if (unsigned_left_shift_overflows(a, shift))
+ die("size_t overflow: %"PRIuMAX" << %u",
+ (uintmax_t)a, shift);
+ return a << shift;
+}
+
+static inline unsigned long cast_size_t_to_ulong(size_t a)
+{
+ if (a != (unsigned long)a)
+ die("object too large to read on this platform: %"
+ PRIuMAX" is cut off to %lu",
+ (uintmax_t)a, (unsigned long)a);
+ return (unsigned long)a;
+}
+
#ifdef HAVE_ALLOCA_H
# include <alloca.h>
# define xalloca(size) (alloca(size))
