nano

commit 1c010d8ec9a788a3065f52331daee584fda1c158
parent b02093747526cc6a8978960855cf3a7b3ecc6c83
Author: Benno Schulenberg <bensberg@telfort.nl>
Date:   Sun, 28 Mar 2021 12:23:35 +0200

chars: implement mbtowc() ourselves, for more efficiency

This saves a function call, and the passing and checking of the
MAXCHARLEN parameter, and the checking whether wc is maybe NULL
(which for nano is never the case), and who knows what other
overheads mbtowc() has, and our workaround for glibc.

Code was written after looking at gnulib/lib/mbrtowc-impl-utf8.h.

Diffstat:
M
src/chars.c
 | 
47
++++++++++++++++++++++++++++++++++++++++++-----

1 file changed, 42 insertions(+), 5 deletions(-)
diff --git a/src/chars.c b/src/chars.c
@@ -180,12 +180,49 @@ char control_mbrep(const char *c, bool isdata)
  * the number of bytes in the sequence, or -1 for an invalid sequence. */
 int mbtowide(wchar_t *wc, const char *c)
 {
-	int count = mbtowc(wc, c, MAXCHARLEN);
+#ifdef ENABLE_UTF8
+	if ((signed char)*c < 0 && use_utf8) {
+		unsigned char v1 = (unsigned char)c[0];
+		unsigned char v2 = (unsigned char)c[1] ^ 0x80;
 
-	if (count < 0 || *wc > 0x10FFFF)
-		return -1;
-	else
-		return count;
+		if (v2 > 0x3F || v1 < 0xC2)
+			return -1;
+
+		if (v1 < 0xE0) {
+			*wc = (((unsigned int)(v1 & 0x1F) << 6) | (unsigned int)v2);
+			return 2;
+		}
+
+		unsigned char v3 = (unsigned char)c[2] ^ 0x80;
+
+		if (v3 > 0x3F)
+			return -1;
+
+		if (v1 < 0xF0) {
+			if ((v1 > 0xE0 || v2 >= 0x20) && (v1 != 0xED || v2 < 0x20)) {
+				*wc = (((unsigned int)(v1 & 0x0F) << 12) |
+							((unsigned int)v2 << 6) | (unsigned int)v3);
+				return 3;
+			} else
+				return -1;
+		}
+
+		unsigned char v4 = (unsigned char)c[3] ^ 0x80;
+
+		if (v4 > 0x3F || v1 > 0xF4)
+			return -1;
+
+		if ((v1 > 0xF0 || v2 >= 0x10) && (v1 != 0xF4 || v2 < 0x10)) {
+			*wc = (((unsigned int)(v1 & 0x07) << 18) | ((unsigned int)v2 << 12) |
+							((unsigned int)v3 << 6) | (unsigned int)v4);
+			return 4;
+		} else
+			return -1;
+	}
+#endif
+
+	*wc = (unsigned int)*c;
+	return 1;
 }
 
 /* Return the width in columns of the given (multibyte) character. */