1 files changed, 74 insertions, 0 deletions
diff --git a/kernel/log.c b/kernel/log.c
new file mode 100644
index 0000000..cfe2922
--- /dev/null
+++ b/kernel/log.c
@@ -0,0 +1,74 @@
+#include "io.h"
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define BOCHS_PUTCHAR(ch) (outb(0xe9, ch))
+
+static int eputchar(int ch)
+{
+    BOCHS_PUTCHAR(ch);
+    return 0;
+}
+
+static int eputs(const char* str)
+{
+    while(*str)
+        putchar(*str++);
+    return 0;
+}
+
+static char ehex_table[16] = { '0', '1', '2', '3', '4', '5', '6', '7',
+                              '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
+
+static void eprint_hex(unsigned int n)
+{
+    unsigned mask = 0xF0000000;
+    unsigned shift = 28;
+    while(mask)
+    {
+        eputchar(ehex_table[(n & mask) >> shift]);
+        mask >>= 4;
+        shift -= 4;
+    }
+}
+
+int klog(const char *fmt, ...)
+{
+    va_list ap;
+    va_start(ap, fmt);
+    while(*fmt)
+    {
+        char ch = *fmt++;
+        switch(ch)
+        {
+        case '%':
+        {
+            switch(*fmt++)
+            {
+            case 'c':
+                eputchar(va_arg(ap, int));
+                break;
+            case 's':
+                eputs(va_arg(ap, const char*));
+                break;
+            case 'x':
+                eprint_hex(va_arg(ap, unsigned));
+                break;
+            case 'd':
+                eputs(itoa(va_arg(ap, unsigned), 10));
+                break;
+            default:
+                eputs("klog: unknown format\n");
+                break;
+            }
+            break;
+        }
+        default:
+            eputchar(ch);
+            break;
+        }
+    }
+    va_end(ap);
+    return 0;
+}