1 files changed, 78 insertions, 0 deletions
diff --git a/libcharconv_negative.c b/libcharconv_negative.c
new file mode 100644
index 0000000..dfdc353
--- /dev/null
+++ b/libcharconv_negative.c
@@ -0,0 +1,78 @@
+/* See LICENSE file for copyright and license details. */
+#include "lib-common.h"
+
+
+static struct {
+	uint_least32_t a;
+	uint_least32_t b;
+} pairs[] = {
+	{UINT32_C(0x0020), UINT32_C(0x2588)},
+	{UINT32_C(0x1FBA3), UINT32_C(0x1FBBE)},
+	{UINT32_C(0x1FBAE), UINT32_C(0x1FBBF)},
+	{UINT32_C(0x1FBBD), UINT32_C(0x2573)},
+	{UINT32_C(0x1F030), UINT32_C(0x1F031)},
+	{UINT32_C(0x1F062), UINT32_C(0x1F063)},
+	{UINT32_C(0x2686), UINT32_C(0x2688)},
+	{UINT32_C(0x2687), UINT32_C(0x2689)},
+	{UINT32_C(0x2616), UINT32_C(0x26C9)},
+	{UINT32_C(0x2617), UINT32_C(0x26CA)},
+	{UINT32_C(0x26C0), UINT32_C(0x26C2)},
+	{UINT32_C(0x26C1), UINT32_C(0x26C3)}
+};
+
+
+enum libcharconv_result
+libcharconv_negative(const char *s, size_t slen, size_t *n, uint_least32_t *cp, size_t *ncp)
+{
+	uint_least32_t c;
+	size_t i, clen;
+	*n = 0;
+	while (slen) {
+		clen = libcharconv_decode_utf8_(s, slen, &c);
+		if (clen > slen) {
+			if (*n)
+				goto no_conv;
+			return LIBCHARCONV_INDETERMINATE;
+		}
+		if (!clen) {
+			*n += 1u;
+			slen -= 1u;
+			s = &s[1];
+			continue;
+		}
+
+		if (UINT32_C(0x1FA60) <= c && c <= UINT32_C(0x1FA66)) {
+			c += 7u;
+			goto conv;
+		} else if (UINT32_C(0x1FA67) <= c && c <= UINT32_C(0x1FA6D)) {
+			c -= 7u;
+			goto conv;
+		} else {
+			for (i = 0u; i < sizeof(pairs) / sizeof(*pairs); i++) {
+				if (c == pairs[i].a) {
+					c = pairs[i].b;
+					goto conv;
+				}
+				if (c == pairs[i].b) {
+					c = pairs[i].a;
+					goto conv;
+				}
+			}
+		}
+
+		*n += clen;
+		s = &s[clen];
+		slen -= clen;
+	}
+no_conv:
+	return LIBCHARCONV_NO_CONVERT;
+
+conv:
+	if (*n)
+		goto no_conv;
+	if (*ncp)
+		*cp = c;
+	*n += clen;
+	*ncp = 1u;
+	return LIBCHARCONV_CONVERTED;
+}