Add zlsh and zrsh

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 48 insertions, 0 deletions

diff --git a/src/zrsh.c b/src/zrsh.c
new file mode 100644
index 0000000..649ebb3
--- /dev/null
+++ b/src/zrsh.c
@@ -0,0 +1,48 @@
+/* See LICENSE file for copyright and license details. */
+#include "internals"
+
+#include <stdlib.h>
+#include <string.h>
+
+
+void
+zrsh(z_t a, z_t b, size_t bits)
+{
+	size_t i, chars, cbits;
+
+	if (!bits) {
+		if (a != b)
+			zset(a, b);
+		return;
+	}
+
+	chars = FLOOR_BITS_TO_CHARS(bits);
+
+	if (zzero(b) || chars >= b->used || zbits(b) <= bits) {
+		SET_SIGNUM(a, 0);
+		return;
+	}
+
+	bits = BITS_IN_LAST_CHAR(bits)
+	cbits = BITS_PER_CHAR - 1 - bits;
+
+	if (chars && a == b) {
+		a->used -= chars;
+		memmove(a->chars, a->chars + chars, a->used * sizeof(*(a->chars)));
+	} else if (a != b) {
+		a->used = b->used - chars;
+		if (a->alloced < a->used) {
+			a->alloced = a->used;
+			a->chars = realloc(a->chars, a->used * sizeof(*(a->chars)));
+		}
+		memcpy(a->chars, b->chars + chars, a->used * sizeof(*(a->chars)));
+	}
+
+	a->chars[0] >>= bits;
+	for (i = 1; i < a->used; i++) {
+		a->chars[i - 1] |= a->chars[i] >> cbits;
+		a->chars[i] >>= bits;
+	}
+
+	SET_SIGNUM(a, zsignum(b));
+}