From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/multibyte/c16rtomb.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 src/multibyte/c16rtomb.c

(limited to 'src/multibyte/c16rtomb.c')

diff --git a/src/multibyte/c16rtomb.c b/src/multibyte/c16rtomb.c
new file mode 100644
index 0000000..39ca375
--- /dev/null
+++ b/src/multibyte/c16rtomb.c
@@ -0,0 +1,35 @@
+#include <uchar.h>
+#include <errno.h>
+#include <wchar.h>
+
+size_t c16rtomb(char *restrict s, char16_t c16, mbstate_t *restrict ps)
+{
+	static unsigned internal_state;
+	if (!ps) ps = (void *)&internal_state;
+	unsigned *x = (unsigned *)ps;
+	wchar_t wc;
+
+	if (!s) {
+		if (*x) goto ilseq;
+		return 1;
+	}
+
+	if (!*x && c16 - 0xd800u < 0x400) {
+		*x = c16 - 0xd7c0 << 10;
+		return 0;
+	}
+
+	if (*x) {
+		if (c16 - 0xdc00u >= 0x400) goto ilseq;
+		else wc = *x + c16 - 0xdc00;
+		*x = 0;
+	} else {
+		wc = c16;
+	}
+	return wcrtomb(s, wc, 0);
+
+ilseq:
+	*x = 0;
+	errno = EILSEQ;
+	return -1;
+}
-- 
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