2 files changed, 96 insertions, 0 deletions

diff --git a/include/wchar.h b/include/wchar.h
index 27f00166..c3d8b045 100644
--- a/include/wchar.h
+++ b/include/wchar.h
@@ -133,6 +133,7 @@ size_t wcsftime (wchar_t *, size_t, const wchar_t *, const struct tm *);
 
 #if defined(_POSIX_SOURCE) || defined(_POSIX_C_SOURCE) \
  || defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE)
+FILE *open_wmemstream(wchar_t **, size_t *);
 size_t mbsnrtowcs(wchar_t *, const char **, size_t, size_t, mbstate_t *);
 size_t wcsnrtombs(char *, const wchar_t **, size_t, size_t, mbstate_t *);
 #endif
diff --git a/src/stdio/open_wmemstream.c b/src/stdio/open_wmemstream.c
new file mode 100644
index 00000000..5402ca1a
--- /dev/null
+++ b/src/stdio/open_wmemstream.c
@@ -0,0 +1,95 @@
+#include "stdio_impl.h"
+
+struct cookie {
+	wchar_t **bufp;
+	size_t *sizep;
+	size_t pos;
+	wchar_t *buf;
+	size_t len;
+	size_t space;
+	mbstate_t mbs;
+};
+
+static off_t wms_seek(FILE *f, off_t off, int whence)
+{
+	ssize_t base;
+	struct cookie *c = f->cookie;
+	switch (whence) {
+	case SEEK_SET:
+		base = 0;
+		break;
+	case SEEK_CUR:
+		base = c->pos;
+		break;
+	case SEEK_END:
+		base = c->len;
+		break;
+	default:
+	fail:
+		errno = EINVAL;
+		return -1;
+	}
+	if (-off > base || off > SSIZE_MAX/4-base) goto fail;
+	memset(&c->mbs, 0, sizeof c->mbs);
+	return c->pos = base+off;
+}
+
+static size_t wms_write(FILE *f, const unsigned char *buf, size_t len)
+{
+	struct cookie *c = f->cookie;
+	size_t len2;
+	wchar_t *newbuf;
+	if (len > c->space - c->pos) {
+		len2 = 2*c->space+1 | c->space+len+1;
+		if (len2 > SSIZE_MAX/4) return 0;
+		newbuf = realloc(c->buf, len2*4);
+		if (!newbuf) return 0;
+		*c->bufp = c->buf = newbuf;
+		memset(c->buf + c->space, 0, len2 - c->space);
+		c->space = len2;
+	}
+	
+	len2 = mbsnrtowcs(c->buf+c->pos, (void *)&buf, len, c->space-c->pos, &c->mbs);
+	if (len2 == -1) return 0;
+	c->pos += len2;
+	if (c->pos >= c->len) c->len = c->pos;
+	*c->sizep = c->pos;
+	return len;
+}
+
+static int wms_close(FILE *f)
+{
+	return 0;
+}
+
+FILE *open_wmemstream(wchar_t **bufp, size_t *sizep)
+{
+	FILE *f;
+	struct cookie *c;
+	if (!(f=malloc(sizeof *f + sizeof *c))) return 0;
+	memset(f, 0, sizeof *f + sizeof *c);
+	f->cookie = c = (void *)(f+1);
+
+	c->bufp = bufp;
+	c->sizep = sizep;
+	c->pos = c->len = c->space = 0;
+	c->buf = 0;
+
+	f->flags = F_NORD;
+	f->fd = -1;
+	f->buf = (void *)(c+1);
+	f->buf_size = 0;
+	f->lbf = EOF;
+	f->write = wms_write;
+	f->seek = wms_seek;
+	f->close = wms_close;
+
+	if (!libc.threaded) {
+		f->lock = -1;
+		f->next = libc.ofl_head;
+		if (libc.ofl_head) libc.ofl_head->prev = f;
+		libc.ofl_head = f;
+	}
+
+	return f;
+}