1 files changed, 44 insertions, 0 deletions
diff --git a/libterminput_encode_utf8__.c b/libterminput_encode_utf8__.c
new file mode 100644
index 0000000..7e83a04
--- /dev/null
+++ b/libterminput_encode_utf8__.c
@@ -0,0 +1,44 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+void
+libterminput_encode_utf8__(unsigned long long int codepoint, char buffer[7])
+{
+	static const char masks[6] = {
+		(char)0x00, /* 1 byte = 0 high set bits, */
+		(char)0xC0, /* 2 bytes = 2 high set bits, */
+		(char)0xE0, /* 3 bytes = 3 high set bits, ... */
+		(char)0xF0,
+		(char)0xF8,
+		(char)0xFC  /* 6 bytes = 3 high set bits */
+	};
+	static const unsigned long long int limits[6] = {
+		1ULL << (7 + 0 * 6), /* 1 byte has room for 7 codepoint encoding bits, */
+		1ULL << (5 + 1 * 6), /* 2 bytes has room for 5 bits in the first by and 6 bits the rest, */
+		1ULL << (4 + 2 * 6), /* 3 bytes has room for 4 bits in the first by and 6 bits the rest, ... */
+		1ULL << (3 + 3 * 6),
+		1ULL << (2 + 4 * 6),
+		1ULL << (1 + 5 * 6)  /* 6 bytes has room for 1 bits in the first by and 6 bits the rest */
+	};
+
+	size_t len;
+
+	/* Get encoding length for codepoint */
+	for (len = 0; codepoint >= limits[len]; len++);
+
+	/* Set the `len` (but 0 if 1) high bits in the first byte
+	 * to encode the encoding length of the codepoint */
+	buffer[0] = masks[len];
+
+	/* NUL terminate the encoding buffer,
+	 * to mark the encode of the encoding */
+	buffer[++len] = '\0';
+
+	/* Encode the bites representing the code point
+	 * and the length continuation marker bits in
+	 * the non-first bytes */
+	for (; --len; codepoint >>= 6)
+		buffer[len] = (char)((codepoint & 0x3FULL) | 0x80ULL);
+	buffer[0] |= (char)codepoint;
+}