init: printf base

3 files changed, 23 insertions, 0 deletions

diff --git a/src/init/main.c b/src/init/main.c
index ec6d5be..a819152 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -1,3 +1,4 @@
+#include <init/stdlib.h>
 #include <init/tar.h>
 #include <shared/flags.h>
 #include <shared/syscalls.h>
@@ -28,6 +29,8 @@ int main(void) {
 	fs_test();
 	test_await();
 
+	printf("printf test\n");
+
 	char c;
 	while (_syscall_read(tty_fd, &c, 1, 0))
 		_syscall_write(tty_fd, &c, 1, 0);
diff --git a/src/init/stdlib.c b/src/init/stdlib.c
index 6ed5a0a..ac80c28 100644
--- a/src/init/stdlib.c
+++ b/src/init/stdlib.c
@@ -1,4 +1,6 @@
 #include <init/stdlib.h>
+#include <shared/syscalls.h>
+#include <stdarg.h>
 
 int memcmp(const void *s1, const void *s2, size_t n) {
 	const unsigned char *c1 = s1, *c2 = s2;
@@ -10,3 +12,19 @@ int memcmp(const void *s1, const void *s2, size_t n) {
 	}
 	return 0;
 }
+
+int printf(const char *fmt, ...) {
+	const char *seg = fmt; // beginning of the current segment
+	int total = 0;
+	va_list argp;
+	va_start(argp, fmt);
+	for (;;) {
+		char c = *fmt++;
+		switch (c) {
+			case '\0':
+				// TODO don't assume that stdout is @ fd 0
+				_syscall_write(0, seg, fmt - seg, 0);
+				return total + (fmt - seg);
+		}
+	}
+}
diff --git a/src/init/stdlib.h b/src/init/stdlib.h
index 1cabc7a..357a396 100644
--- a/src/init/stdlib.h
+++ b/src/init/stdlib.h
@@ -5,3 +5,5 @@
 //      stb-style header file
 
 int memcmp(const void *s1, const void *s2, size_t n);
+
+int printf(const char *fmt, ...);