kernel: make kprintf print to a ring buffer

The function kprintf should print to an internal ringbuffer instead of
directly to the framebuffer. This reduces dependence on the existence of
a framebuffer in the first place.

Signed-off-by: Danny Holman <dholman@gymli.org>

2 files changed, 52 insertions, 2 deletions

diff --git a/include/kernel/data/ringbuf.h b/include/kernel/data/ringbuf.h
new file mode 100644
index 0000000..4f30874
--- /dev/null
+++ b/include/kernel/data/ringbuf.h
@@ -0,0 +1,50 @@
+#ifndef KERNEL_RINGBUF_H
+#define KERNEL_RINGBUF_H
+
+#include <kernel/mem.h>
+#include <kernel/string.h>
+#include <stdint.h>
+
+struct ringbuf {
+        void *buffer;
+        void *buf_end;
+        uint32_t capacity;
+        uint32_t count;
+        uint32_t size;
+        void *head;
+        void *tail;
+};
+
+static inline void rb_init(struct ringbuf *rb, uint32_t capacity, uint32_t size) {
+        rb->buffer = kmalloc(capacity * size);
+        rb->buf_end = (char*)rb->buffer + (capacity * size);
+        rb->capacity = capacity;
+        rb->size = size;
+        rb->head = rb->buffer;
+        rb->tail = rb->buffer;
+}
+
+static inline int rb_push_back(struct ringbuf *rb, const void *item, size_t size) {
+        if (rb->count == rb->capacity)
+                return -1;
+        if (size > rb->size)
+                return -1;
+
+        void *tmp = rb->tail + rb->size;
+        if (tmp > rb->head + rb->capacity * rb->size)
+                rb->tail = rb->head;
+        memcpy(rb->tail, item, size);
+        rb->tail += rb->size;
+        rb->count++;
+        return 0;
+}
+
+static inline void rb_pop_front(struct ringbuf *rb, void *item) {
+        memcpy(item, rb->tail, rb->size);
+        rb->tail = (char*)rb->tail + rb->size;
+        if (rb->tail == rb->buf_end)
+                rb->tail = rb->buffer;
+        rb->count--;
+}
+
+#endif
diff --git a/include/kernel/io.h b/include/kernel/io.h
index 8f5fa59..cf8404a 100644
--- a/include/kernel/io.h
+++ b/include/kernel/io.h
@@ -1,5 +1,5 @@
-#ifndef IO_H
-#define IO_H
+#ifndef KERNEL_IO_H
+#define KERNEL_IO_H
 
 #include <stdarg.h>