7 files changed, 46 insertions, 3 deletions
diff --git a/src/multibyte/btowc.c b/src/multibyte/btowc.c
index 29cb798d..8acd0a2c 100644
--- a/src/multibyte/btowc.c
+++ b/src/multibyte/btowc.c
@@ -1,8 +1,10 @@
 #include <stdio.h>
 #include <wchar.h>
+#include <stdlib.h>
+#include "internal.h"
 
 wint_t btowc(int c)
 {
-	c = (unsigned char)c;
-	return c<128U ? c : EOF;
+	int b = (unsigned char)c;
+	return b<128U ? b : (MB_CUR_MAX==1 && c!=EOF) ? CODEUNIT(c) : WEOF;
 }
diff --git a/src/multibyte/internal.h b/src/multibyte/internal.h
index cc017fa2..53d62eda 100644
--- a/src/multibyte/internal.h
+++ b/src/multibyte/internal.h
@@ -23,3 +23,10 @@ extern const uint32_t bittab[];
 
 #define SA 0xc2u
 #define SB 0xf4u
+
+/* Arbitrary encoding for representing code units instead of characters. */
+#define CODEUNIT(c) (0xdfff & (signed char)(c))
+#define IS_CODEUNIT(c) ((unsigned)(c)-0xdf80 < 0x80)
+
+/* Get inline definition of MB_CUR_MAX. */
+#include "locale_impl.h"
diff --git a/src/multibyte/mbrtowc.c b/src/multibyte/mbrtowc.c
index e7b36540..ca7da700 100644
--- a/src/multibyte/mbrtowc.c
+++ b/src/multibyte/mbrtowc.c
@@ -4,6 +4,7 @@
  * unnecessary.
  */
 
+#include <stdlib.h>
 #include <wchar.h>
 #include <errno.h>
 #include "internal.h"
@@ -27,6 +28,7 @@ size_t mbrtowc(wchar_t *restrict wc, const char *restrict src, size_t n, mbstate
 	if (!n) return -2;
 	if (!c) {
 		if (*s < 0x80) return !!(*wc = *s);
+		if (MB_CUR_MAX==1) return (*wc = CODEUNIT(*s)), 1;
 		if (*s-SA > SB-SA) goto ilseq;
 		c = bittab[*s++-SA]; n--;
 	}
diff --git a/src/multibyte/mbsrtowcs.c b/src/multibyte/mbsrtowcs.c
index 3c1343ae..e23083d2 100644
--- a/src/multibyte/mbsrtowcs.c
+++ b/src/multibyte/mbsrtowcs.c
@@ -7,6 +7,8 @@
 #include <stdint.h>
 #include <wchar.h>
 #include <errno.h>
+#include <string.h>
+#include <stdlib.h>
 #include "internal.h"
 
 size_t mbsrtowcs(wchar_t *restrict ws, const char **restrict src, size_t wn, mbstate_t *restrict st)
@@ -24,6 +26,23 @@ size_t mbsrtowcs(wchar_t *restrict ws, const char **restrict src, size_t wn, mbs
 		}
 	}
 
+	if (MB_CUR_MAX==1) {
+		if (!ws) return strlen((const char *)s);
+		for (;;) {
+			if (!wn) {
+				*src = (const void *)s;
+				return wn0;
+			}
+			if (!*s) break;
+			c = *s++;
+			*ws++ = CODEUNIT(c);
+			wn--;
+		}
+		*ws = 0;
+		*src = 0;
+		return wn0-wn;
+	}
+
 	if (!ws) for (;;) {
 		if (*s-1u < 0x7f && (uintptr_t)s%4 == 0) {
 			while (!(( *(uint32_t*)s | *(uint32_t*)s-0x01010101) & 0x80808080)) {
diff --git a/src/multibyte/mbtowc.c b/src/multibyte/mbtowc.c
index 803d2213..71a95066 100644
--- a/src/multibyte/mbtowc.c
+++ b/src/multibyte/mbtowc.c
@@ -4,6 +4,7 @@
  * unnecessary.
  */
 
+#include <stdlib.h>
 #include <wchar.h>
 #include <errno.h>
 #include "internal.h"
@@ -19,6 +20,7 @@ int mbtowc(wchar_t *restrict wc, const char *restrict src, size_t n)
 	if (!wc) wc = &dummy;
 
 	if (*s < 0x80) return !!(*wc = *s);
+	if (MB_CUR_MAX==1) return (*wc = CODEUNIT(*s)), 1;
 	if (*s-SA > SB-SA) goto ilseq;
 	c = bittab[*s++-SA];
 
diff --git a/src/multibyte/wcrtomb.c b/src/multibyte/wcrtomb.c
index 59f733db..ddc37a57 100644
--- a/src/multibyte/wcrtomb.c
+++ b/src/multibyte/wcrtomb.c
@@ -4,8 +4,10 @@
  * unnecessary.
  */
 
+#include <stdlib.h>
 #include <wchar.h>
 #include <errno.h>
+#include "internal.h"
 
 size_t wcrtomb(char *restrict s, wchar_t wc, mbstate_t *restrict st)
 {
@@ -13,6 +15,13 @@ size_t wcrtomb(char *restrict s, wchar_t wc, mbstate_t *restrict st)
 	if ((unsigned)wc < 0x80) {
 		*s = wc;
 		return 1;
+	} else if (MB_CUR_MAX == 1) {
+		if (!IS_CODEUNIT(wc)) {
+			errno = EILSEQ;
+			return -1;
+		}
+		*s = wc;
+		return 1;
 	} else if ((unsigned)wc < 0x800) {
 		*s++ = 0xc0 | (wc>>6);
 		*s = 0x80 | (wc&0x3f);
diff --git a/src/multibyte/wctob.c b/src/multibyte/wctob.c
index d6353ee1..4aeda6a1 100644
--- a/src/multibyte/wctob.c
+++ b/src/multibyte/wctob.c
@@ -1,8 +1,10 @@
-#include <stdio.h>
 #include <wchar.h>
+#include <stdlib.h>
+#include "internal.h"
 
 int wctob(wint_t c)
 {
 	if (c < 128U) return c;
+	if (MB_CUR_MAX==1 && IS_CODEUNIT(c)) return (unsigned char)c;
 	return EOF;
 }