init/stdlib: implement snprintf

2 files changed, 21 insertions, 0 deletions

diff --git a/src/init/stdlib.c b/src/init/stdlib.c
index 9b7a329..cbaed61 100644
--- a/src/init/stdlib.c
+++ b/src/init/stdlib.c
@@ -18,6 +18,26 @@ int printf(const char *fmt, ...) {
 	return ret;
 }
 
+static void backend_buf(void *arg, const char *buf, size_t len) {
+	char **ptrs = arg;
+	size_t space = ptrs[1] - ptrs[0];
+	if (len > space) len = space;
+	memcpy(ptrs[0], buf, len);
+	ptrs[0] += len;
+}
+
+int snprintf(char *str, size_t len, const char *fmt, ...) {
+	int ret = 0;
+	char *ptrs[2] = {str, str + len};
+	va_list argp;
+	va_start(argp, fmt);
+	ret = __printf_internal(fmt, argp, backend_buf, &ptrs);
+	va_end(argp);
+	if (ptrs[0] < ptrs[1]) *ptrs[0] = '\0';
+	return ret;
+}
+
+
 int file_open(libc_file *f, const char *path, int flags) {
 	f->pos = 0;
 	f->eof = false;
diff --git a/src/init/stdlib.h b/src/init/stdlib.h
index 3dc1c81..03e1717 100644
--- a/src/init/stdlib.h
+++ b/src/init/stdlib.h
@@ -5,6 +5,7 @@
 #include <stddef.h>
 
 int printf(const char *fmt, ...);
+int snprintf(char *str, size_t len, const char *fmt, ...);
 
 typedef struct {
 	int fd;