From a267b8c076793cf59c2f6c80a31d7d094a215aab Mon Sep 17 00:00:00 2001
From: Danny Holman <dholman@gymli.org>
Date: Fri, 16 Feb 2024 12:32:40 -0600
Subject: 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>
---
 include/kernel/data/ringbuf.h | 50 +++++++++++++++++++++++++++++++++++++++++++
 include/kernel/io.h           |  4 ++--
 kernel/io.c                   | 34 +++++++++++++++++++----------
 3 files changed, 75 insertions(+), 13 deletions(-)
 create mode 100644 include/kernel/data/ringbuf.h

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>
 
diff --git a/kernel/io.c b/kernel/io.c
index 71b01bd..0a4ba6d 100644
--- a/kernel/io.c
+++ b/kernel/io.c
@@ -1,6 +1,10 @@
 #include <kernel/io.h>
+#include <kernel/framebuffer.h>
+#include <kernel/data/ringbuf.h>
 #include <kernel/string.h>
-#include <kernel/tty.h>
+
+static int ringbuf_init = 0;
+static struct ringbuf rb;
 
 char* convert(unsigned int num, int base) {
         static char rep[] = "0123456789ABCDEF";
@@ -19,12 +23,18 @@ char* convert(unsigned int num, int base) {
 }
 
 int vkprintf(const char *fmt, va_list args) {
+        if (ringbuf_init == 0) {
+                rb_init(&rb, 1024, 4096);
+                ringbuf_init = 1;
+        }
+
         char *s;
         int i;
 
+        char buffer[4096];
         for (size_t n = 0; n < strlen(fmt); n++) {
                 if (fmt[n] != '%') {
-                        tty_putchar(fmt[n]);
+                        buffer[strlen(buffer)] = fmt[n];
                         continue;
                 } else {
                         n++;
@@ -33,30 +43,32 @@ int vkprintf(const char *fmt, va_list args) {
                 switch (fmt[n]) {
                         case 'c':
                                 i = va_arg(args, int);
-                                tty_putchar(i);
+                                buffer[strlen(buffer)] = i;
+                                break;
+                        case 's':
+                                s = va_arg(args, char*);
+                                strcat(buffer, s);
                                 break;
                         case 'd':
                                 i = va_arg(args, int);
                                 if (i < 0) {
                                         i = -i;
-                                        tty_putchar('-');
+                                        strcat(buffer, "-");
                                 }
-                                tty_writestring(convert(i, 10));
+                                strcat(buffer, convert(i, 10));
                                 break;
                         case 'o':
                                 i = va_arg(args, unsigned int);
-                                tty_writestring(convert(i, 8));
-                                break;
-                        case 's':
-                                s = va_arg(args, char*);
-                                tty_writestring(s);
+                                strcat(buffer, convert(i, 10));
                                 break;
                         case 'x':
                                 i = va_arg(args, unsigned int);
-                                tty_writestring(convert(i, 16));
+                                strcat(buffer, convert(i, 16));
                                 break;
                 }
         }
+        rb_push_back(&rb, buffer, strlen(buffer));
+        memset(buffer, 0, 4096);
         return 0;
 }
 
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