1 files changed, 61 insertions, 0 deletions
diff --git a/src/zstr.c b/src/zstr.c
new file mode 100644
index 0000000..a1d4d13
--- /dev/null
+++ b/src/zstr.c
@@ -0,0 +1,61 @@
+/* See LICENSE file for copyright and license details. */
+#include "internals"
+
+#define num  libzahl_tmp_str_num
+#define rem  libzahl_tmp_str_rem
+
+/* All 9 you see here is derived from that 10⁹ is the largest
+ * power of than < 2³², and 32 is the number of bits in
+ * zahl_char_t. If zahl_char_t is chanced, the value 9, and
+ * the cast to unsigned long must be changed accordingly. */
+
+
+char *
+zstr(z_t a, char *b)
+{
+	size_t n;
+	char overridden;
+	int neg;
+
+	if (zzero(a)) {
+		if (!b) {
+			b = malloc(2);
+			if (!b)
+				FAILURE_JUMP();
+		}
+		b[0] = '0';
+		b[1] = 0;
+		return b;
+	}
+
+	n = zstr_length(a, 10);
+	if (!b) {
+		b = malloc(n + 1);
+		if (!b)
+			FAILURE_JUMP();
+	}
+
+	neg = zsignum(a) < 0;
+	zabs(num, a);
+	n -= neg;
+	n = n > 9 ? (n - 9) : 0;
+	b[0] = '-';
+	b += neg;
+	overridden = 0;
+
+	for (;;) {
+		zdivmod(num, rem, num, libzahl_const_1e9);
+		if (!zzero(num)) {
+			sprintf(b + n, "%09lu", (unsigned long)(rem->chars[0]));
+			b[n + 9] = overridden;
+			overridden = b[n + (9 - 1)];
+			n = n > 9 ? (n - 9) : 0;
+		} else {
+			n += sprintf(b + n, "%lu", (unsigned long)(rem->chars[0]));
+			b[n] = overridden;
+			break;
+		}
+	}
+
+	return b - neg;
+}