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ref: 313e86a65b33fb0c9f4c05789e2e93de19fb61bc
parent: 7db7502fee313e42ccf0506a0f0a65db26aa883a
author: Roberto E. Vargas Caballero <[email protected]>
date: Wed Mar 16 08:10:43 EDT 2022

libc: Add mbtowc()

--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -11,7 +11,7 @@
 
 #define _ATEXIT_MAX 32
 
-#define MB_CUR_MAX 1
+#define MB_CUR_MAX 6
 #define RAND_MAX 32767
 
 typedef struct {
--- a/src/libc/stdlib/Makefile
+++ b/src/libc/stdlib/Makefile
@@ -18,6 +18,7 @@
 	labs.$O\
 	llabs.$O\
 	malloc.$O\
+	mbtowc.$O\
 	qsort.$O\
 	rand.$O\
 	realloc.$O\
--- /dev/null
+++ b/src/libc/stdlib/mbtowc.c
@@ -1,0 +1,34 @@
+#include <stdlib.h>
+
+#undef mbtowc
+
+int
+mbtowc(wchar_t *restrict pwc, const char *restrict s, size_t n)
+{
+	const char *t = s;
+	unsigned long wc;
+	unsigned c;
+	size_t len;
+
+	if (s == NULL)
+		return 0;
+
+	wc = c = *t++;
+	for (len = 0; n > 0 && c & 0x80; --n, ++len)
+		c <<= 1;
+	if (n == 0 || len == 1 || len == 8)
+		return -1;
+	if (len == 0)
+		goto return_code;
+
+	for (wc = (c & 0xFF) >> len; len--; wc |= c & 0x3F) {
+		if ((c = *t++) & 0xC0 != 0x80)
+			return -1;
+		wc <<= 6;
+	}
+
+return_code:
+	if (pwc)
+		*pwc = wc;
+	return (*s) ? t - s : 0;
+}