meta: move photon/libc to root

libc/stdio/vsnprintf.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include "__printf.h"
+
+struct __vsnprintf_arg {
+    char *buf;
+    size_t idx;
+    size_t max;
+};
+
+static void _out_buf(struct __printf_backend *bk, char ch)
+{
+    struct __vsnprintf_arg *arg = bk->arg;
+    if (arg->idx < arg->max) {
+        arg->buf[arg->idx] = ch;
+    }
+
+    arg->idx++;
+}
+
+int vsnprintf(char *buf, size_t sz, const char *restrict format, va_list arg)
+{
+    struct __vsnprintf_arg bk_arg = {};
+    bk_arg.buf = buf;
+    bk_arg.max = sz;
+
+    struct __printf_backend bk = {};
+    bk.out = _out_buf;
+    bk.arg = &bk_arg;
+
+    __xprintf(&bk, format, arg);
+    if (!bk_arg.idx) {
+        return 0;
+    }
+
+    return bk_arg.idx - 1;
+}