1 files changed, 50 insertions, 0 deletions
diff --git a/string32.c b/string32.c
new file mode 100644
index 0000000..9b14e30
--- /dev/null
+++ b/string32.c
@@ -0,0 +1,50 @@
+// UTF-32 string
+typedef struct {
+	size_t len;
+	char32_t *str;
+} String32;
+
+void s32_free(String32 *s) {
+	free(s->str);
+	s->str = NULL;
+	s->len = 0;
+}
+
+// the string returned should be s32_free'd.
+// this will return an empty string if the allocation failed or the string is invalid UTF-8
+String32 s32_from_utf8(char const *utf8) {
+	String32 string = {0, NULL};
+	size_t len = strlen(utf8);
+	if (len) {
+		// the wide string uses at most as many "characters" (elements?) as the UTF-8 string
+		char32_t *widestr = calloc(len, sizeof *widestr);
+		if (widestr) {
+			char32_t *wide_p = widestr;
+			char const *utf8_p = utf8;
+			char const *utf8_end = utf8_p + len;
+			mbstate_t mbstate = {0};
+			while (utf8_p < utf8_end) {
+				char32_t c = 0;
+				size_t n = mbrtoc32(&c, utf8_p, (size_t)(utf8_end - utf8_p), &mbstate);
+				if (n == 0// null character. this shouldn't happen.
+					|| n == (size_t)(-2) // incomplete character
+					|| n == (size_t)(-1) // invalid UTF-8
+					) {
+					free(widestr);
+					widestr = wide_p = NULL;
+					break;
+				} else if (n == (size_t)(-3)) { // no bytes consumed, but a character was produced
+					*wide_p++ = c;
+				} else {
+					// n bytes consumed
+					*wide_p++ = c;
+					utf8_p += n;
+				}
+			}
+			string.str = widestr;
+			string.len = (size_t)(wide_p - widestr);
+		}
+	}
+	return string;
+}
+