Add zlsh and zrsh

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

1 files changed, 51 insertions, 0 deletions

diff --git a/src/zlsh.c b/src/zlsh.c
new file mode 100644
index 0000000..bc1aa0b
--- /dev/null
+++ b/src/zlsh.c
@@ -0,0 +1,51 @@
+/* See LICENSE file for copyright and license details. */
+#include "internals"
+
+#include <stdlib.h>
+#include <string.h>
+
+
+void
+zlsh(z_t a, z_t b, size_t bits)
+{
+	size_t i, chars, cbits;
+	zahl_char_t carry[] = {0, 0};
+
+	if (zzero(b)) {
+		SET_SIGNUM(a, 0);
+		return;
+	}
+	if (!bits) {
+		if (a != b)
+			zset(a, b);
+		return;
+	}
+
+	chars = FLOOR_BITS_TO_CHARS(bits);
+	bits = BITS_IN_LAST_CHAR(bits)
+	cbits = BITS_PER_CHAR - 1 - bits;
+
+	a->used = b->used + chars;
+	if (a->alloced < a->used) {
+		a->alloced = a->used;
+		a->chars = realloc(a->chars, a->used * sizeof(*(a->chars)));
+	}
+	(a == b ? memmove : memcpy)(a->chars + chars, b->chars, a->used * sizeof(*(a->chars)));
+	memset(a->chars, 0, chars * sizeof(*(a->chars)));
+
+	for (i = chars; i < a->used; i++) {
+		carry[~i & 1] = a->chars[i] >> cbits;
+		a->chars[i] <<= bits;
+		a->chars[i] |= carry[i & 1];
+	}
+	if (carry[i & 1]) {
+		if (a->alloced == a->used) {
+			a->alloced <<= 1;
+			a->chars = realloc(a->chars, a->alloced * sizeof(*(a->chars)));
+		}
+		a->chars[i] = carry[i & 1];
+		a->used++;
+	}
+
+	SET_SIGNUM(a, zsignum(b));
+}