Add wcsrtombs(3).

libc/Makefile

@@ -142,6 +142,7 @@ wcslen.o \
 wcsncat.o \
 wcsncpy.o \
 wcsrchr.o \
+wcsrtombs.o \
 wcsspn.o \
 wcstok.o \
 wctomb.o \

libc/include/wchar.h

@@ -74,6 +74,7 @@ size_t wcslen(const wchar_t*);
 wchar_t* wcsncat(wchar_t* restrict, const wchar_t* restrict, size_t);
 wchar_t* wcsncpy(wchar_t* restrict, const wchar_t* restrict, size_t);
 wchar_t* wcsrchr(const wchar_t*, wchar_t);
+size_t wcsrtombs(char* restrict, const wchar_t** restrict, size_t, mbstate_t* restrict);
 size_t wcsspn(const wchar_t*, const wchar_t*);
 wchar_t* wcstok(wchar_t* restrict, const wchar_t* restrict, wchar_t** restrict);
 
@@ -108,7 +109,6 @@ long long wcstoll(const wchar_t* restrict, wchar_t** restrict, int);
 long wcstol(const wchar_t* restrict, wchar_t** restrict, int);
 size_t mbrlen(const char* restrict, size_t, mbstate_t* restrict);
 size_t wcsftime(wchar_t* restrict, size_t, const wchar_t* restrict, const struct tm* restrict);
-size_t wcsrtombs(char* restrict, const wchar_t** restrict, size_t, mbstate_t* restrict);
 size_t wcsxfrm(wchar_t* restrict, const wchar_t* restrict, size_t);
 unsigned long long wcstoull(const wchar_t* restrict, wchar_t** restrict, int);
 unsigned long wcstoul(const wchar_t* restrict, wchar_t** restrict, int);

libc/wcsrtombs.cpp

@@ -0,0 +1,76 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library is distributed in the hope that it will be useful, but
+    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    wcsrtombs.cpp
+    Convert a wide-character string to multibyte string.
+
+*******************************************************************************/
+
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+extern "C" size_t wcsrtombs(char* dst, const wchar_t** src_ptr, size_t dst_len,
+                            mbstate_t* ps)
+{
+	assert(src_ptr && *src_ptr);
+	// Avoid changing *src_ptr if dst is NULL.
+	const wchar_t* local_src_ptr = *src_ptr;
+	if ( !dst )
+		src_ptr = &local_src_ptr;
+	// For some reason, the standards don't mandate that the secret ps variable
+	// is reset when ps is NULL, unlike mbstowcs that always resets this
+	// variable. We'll avoid resetting the variable here in case any programs
+	// actually take advantage of this fact.
+	static mbstate_t static_ps;
+	if ( !ps )
+		ps = &static_ps;
+	size_t ret = 0;
+	size_t src_len = wcslen(*src_ptr);
+	char buf[MB_CUR_MAX];
+	while ( !dst || dst_len )
+	{
+		mbstate_t saved_ps = *ps;
+		size_t produced = wcrtomb(buf, **src_ptr, ps);
+		if ( produced == (size_t) -1 )
+			return (size_t) -1;
+		if ( dst && dst_len < produced )
+		{
+			*ps  = saved_ps;
+			break;
+		}
+		memcpy(dst, buf, produced);
+		if ( **src_ptr == L'\0' )
+		{
+			ret += produced - 1; // Don't count the '\0' byte.
+			*src_ptr = NULL;
+			break;
+		}
+		ret += produced;
+		(*src_ptr)++;
+		src_len--;
+		if ( dst )
+			dst += produced,
+			dst_len -= produced;
+		ret++;
+	}
+	return ret;
+}