1 files changed, 53 insertions, 0 deletions
diff --git a/src/init/stdlib.c b/src/init/stdlib.c
index 6ed5a0a..a60854b 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 +12,54 @@ int memcmp(const void *s1, const void *s2, size_t n) {
 	}
 	return 0;
 }
+
+size_t strlen(const char *s) {
+	size_t c = 0;
+	while (*s++) c++;
+	return c;
+}
+
+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 - 1, 0);
+				return total + (fmt - seg - 1);
+
+			case '%':
+				_syscall_write(0, seg, fmt - seg - 1, 0);
+				total += fmt - seg - 1;
+				c = *fmt++;
+				switch (c) {
+					case 's':
+						const char *s = va_arg(argp, char*);
+						_syscall_write(0, s, strlen(s), 0);
+						total += strlen(s);
+						break;
+
+					case 'x':
+						unsigned int n = va_arg(argp, int);
+						size_t i = 4; // nibbles * 4
+						while (n >> i && i < (sizeof(int) * 8))
+							i += 4;
+
+						while (i > 0) {
+							i -= 4;
+							char h = '0' + ((n >> i) & 0xf);
+							if (h > '9') h += 'a' - '9' - 1;
+							_syscall_write(0, &h, 1, 0);
+							total++;
+						}
+						break;
+				}
+				seg = fmt;
+				break;
+		}
+	}
+}