1 files changed, 46 insertions, 0 deletions
diff --git a/libcharconv_yijing_tetragrams.c b/libcharconv_yijing_tetragrams.c
new file mode 100644
index 0000000..8286417
--- /dev/null
+++ b/libcharconv_yijing_tetragrams.c
@@ -0,0 +1,46 @@
+/* See LICENSE file for copyright and license details. */
+#include "lib-common.h"
+
+
+enum libcharconv_result
+libcharconv_yijing_tetragrams(const char *s, size_t slen, size_t *n, uint_least32_t *cp, size_t *ncp)
+{
+	uint_least32_t c;
+	*n = 0;
+	for (; slen--; s++) {
+		if ('1' <= s[0] && s[0] <= '3') {
+			if (slen == 0u)
+				return LIBCHARCONV_INDETERMINATE;
+			if ('1' > s[1] || s[1] > '3')
+				goto no_match;
+			if (slen == 1u)
+				return LIBCHARCONV_INDETERMINATE;
+			if ('1' > s[2] || s[2] > '3')
+				goto no_match;
+			if (slen == 2u)
+				return LIBCHARCONV_INDETERMINATE;
+			if ('1' > s[3] || s[3] > '3')
+				goto no_match;
+			c = UINT32_C(0x1D306);
+			c += (uint_least32_t)(s[3] - '1') *  1u;
+			c += (uint_least32_t)(s[2] - '1') *  3u;
+			c += (uint_least32_t)(s[1] - '1') *  9u;
+			c += (uint_least32_t)(s[0] - '1') * 27u;
+			goto conv;
+		} else {
+		no_match:
+			*n += 1u;
+		}
+	}
+no_conv:
+	return LIBCHARCONV_NO_CONVERT;
+
+conv:
+	if (*n)
+		goto no_conv;
+	if (*ncp)
+		*cp = c;
+	*n += 4u;
+	*ncp = 1u;
+	return LIBCHARCONV_CONVERTED;
+}