1 files changed, 31 insertions, 0 deletions
diff --git a/src/ztrunc.c b/src/ztrunc.c
new file mode 100644
index 0000000..d4c31de
--- /dev/null
+++ b/src/ztrunc.c
@@ -0,0 +1,31 @@
+/* See LICENSE file for copyright and license details. */
+#include "internals"
+
+#include <stdlib.h>
+#include <string.h>
+
+
+void
+ztrunc(z_t a, z_t b, size_t bits)
+{
+	zahl_char_t mask = 1;
+	size_t chars;
+	if (zzero(b)) {
+		SET_SIGNUM(a, 0);
+	} else {
+		chars = CEILING_BITS_TO_CHARS(bits);
+		a->sign = b->sign;
+		a->used = chars < b->used ? chars : b->used;
+		if (a->alloced < b->alloced) {
+			a->alloced = b->alloced;
+			a->chars = realloc(a->chars, b->alloced * sizeof(*(a->chars)));
+		}
+		memcpy(a->chars, b->chars, a->used * sizeof(*(a->chars)));
+		bits = BITS_IN_LAST_CHAR(bits);
+		if (bits) {
+			mask <<= bits;
+			mask -= 1;
+			a->chars[a->used - 1] &= mask;
+		}
+	}
+}