usr: libc: Add initial vsnprintf() impl

- Support %x specifier for base 16 strings
- Support %d specifier for base 10 strings
- Support %p specifier for pointer strings
- Allow padding of %d strings

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/libc/include/stdio.h b/lib/libc/include/stdio.h
index cdb9c14..460b674 100644
--- a/lib/libc/include/stdio.h
+++ b/lib/libc/include/stdio.h
@@ -75,6 +75,7 @@ __BEGIN_DECLS
 size_t fread(void *__restrict ptr, size_t size, size_t n, FILE *__restrict stream);
 size_t fwrite(const void *__restrict ptr, size_t size, size_t n, FILE *__restrict stream);
 
+int vsnprintf(char *s, size_t size, const char *fmt, va_list ap);
 int fputc(int c, FILE *stream);
 int putchar(int c);