From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/stdio/vswprintf.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)
 create mode 100644 src/stdio/vswprintf.c

(limited to 'src/stdio/vswprintf.c')

diff --git a/src/stdio/vswprintf.c b/src/stdio/vswprintf.c
new file mode 100644
index 0000000..5e9a4da
--- /dev/null
+++ b/src/stdio/vswprintf.c
@@ -0,0 +1,58 @@
+#include "stdio_impl.h"
+#include <limits.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <wchar.h>
+
+struct cookie {
+	wchar_t *ws;
+	size_t l;
+};
+
+static size_t sw_write(FILE *f, const unsigned char *s, size_t l)
+{
+	size_t l0 = l;
+	int i = 0;
+	struct cookie *c = f->cookie;
+	if (s!=f->wbase && sw_write(f, f->wbase, f->wpos-f->wbase)==-1)
+		return -1;
+	while (c->l && l && (i=mbtowc(c->ws, (void *)s, l))>=0) {
+		if (!i) i=1;
+		s+=i;
+		l-=i;
+		c->l--;
+		c->ws++;
+	}
+	*c->ws = 0;
+	if (i < 0) {
+		f->wpos = f->wbase = f->wend = 0;
+		f->flags |= F_ERR;
+		return i;
+	}
+	f->wend = f->buf + f->buf_size;
+	f->wpos = f->wbase = f->buf;
+	return l0;
+}
+
+int vswprintf(wchar_t *restrict s, size_t n, const wchar_t *restrict fmt, va_list ap)
+{
+	int r;
+	unsigned char buf[256];
+	struct cookie c = { s, n-1 };
+	FILE f = {
+		.lbf = EOF,
+		.write = sw_write,
+		.lock = -1,
+		.buf = buf,
+		.buf_size = sizeof buf,
+		.cookie = &c,
+	};
+
+	if (!n) {
+		return -1;
+	}
+	r = vfwprintf(&f, fmt, ap);
+	sw_write(&f, 0, 0);
+	return r>=n ? -1 : r;
+}
-- 
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