From 28288545db27127065910908f6335a511a3a5467 Mon Sep 17 00:00:00 2001
From: nigel <nigel@LinuxDevMachine.LinuxDevMachine>
Date: Sun, 2 May 2021 13:14:31 -0400
Subject: [PATCH] Implemented terminal scrolling

---
 README.md    |  2 +-
 build.sh     |  3 +++
 src/kernel.c | 63 ++++++++++++++++++++++++++++++++++++++++------------
 3 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/README.md b/README.md
index 1aae946..c07f211 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ I hope to soon have the basic output and booting sequence with multiboot done.
 
 ### Planning
 
-[ ] Muliboot to kernel \
+[x] Muliboot to kernel \
 [ ] Printing strings and integer numbers (both decimal and hex) on the screen is certainly a must. This is one of most basic ways of debugging, and virtually all of us have gone through a kprint() or kout in version 0.01. \
 [ ] Outputting to a serial port will save you a lot of debugging time. You don't have to fear losing information due to scrolling. You will be able to test your OS from a console, filter interesting debug messages, and automatize some tests. \
 [ ] Having a working and reliable interrupt/exception handling system that can dump the contents of the registers (and perhaps the address of the fault) will be very useful. \
diff --git a/build.sh b/build.sh
index 75f630a..8a15692 100755
--- a/build.sh
+++ b/build.sh
@@ -9,6 +9,9 @@ SRC_DIR=src
 BUILD_DIR=build
 
 
+# clean old build 
+rm build/*
+
 # Execute build
 i686-elf-as $SRC_DIR/boot.s -o $BUILD_DIR/boot.o
 i686-elf-gcc -c $SRC_DIR/kernel.c -o $BUILD_DIR/kernel.o -std=gnu99 -ffreestanding -O2 -Wall -Wextra
diff --git a/src/kernel.c b/src/kernel.c
index f75f1b4..c06aa3a 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -46,20 +46,36 @@ void kterm_putat (char c, uint8_t color, size_t x, size_t y ) {
 
 }
 
-void kterm_put (char c) {
-    // add newline support 
-    if ( c == '\n'){
-        kterm_column = 0;
-        kterm_row++;
-        return;
-    }
 
-    kterm_putat ( c, kterm_color, kterm_column, kterm_row);
-    if(kterm_column++ == VGA_WIDTH ){
+/**
+ *  With the help from:
+ * https://whiteheadsoftware.dev/operating-systems-development-for-dummies/
+ **/ 
+void kterm_scrollup(){
+    size_t i ;
+    for(i=0; i < (VGA_WIDTH * VGA_HEIGHT - VGA_WIDTH); i++)
+        kterm_buffer[i] = kterm_buffer[i+VGA_WIDTH];
+
+    for( i=0; i< VGA_WIDTH; i++)
+        kterm_buffer[(VGA_HEIGHT -1) * VGA_WIDTH + i ] = vga_entry(' ', kterm_color); 
+
+}
+
+void kterm_put (char c) {
+ 
+    if(++kterm_column == VGA_WIDTH || c == '\n' ) {
         kterm_column = 0;
-        if(kterm_row++ == VGA_HEIGHT)
-            kterm_row = 0;
+        if(kterm_row == VGA_HEIGHT-1) {       
+            kterm_scrollup();
+        } else {
+            kterm_row ++;
+        }
+            
     }
+    
+    if(c == '\n') return;
+    kterm_putat ( c, kterm_color, kterm_column, kterm_row);
+    
 
 }
 
@@ -71,15 +87,34 @@ void kterm_write(const char* data, size_t size) {
 
 
 void kterm_writestring(const char* data ){
+    
+    //#define KernelTag "[Kernel]: "
+    //kterm_write(KernelTag, strlen(KernelTag));
+
     kterm_write(data, strlen(data));
 }
 
+/**
+ *      simple delay function 
+ **/
+void delay(int t){
+    volatile int i,j;
+    for(i=0;i<t;i++)
+        for(j=0;j<25000;j++)
+            asm("NOP");
+}
 
 void kernel_main (void) {
     /** initialize terminal interface */ 
     init_kterm();
 
-    kterm_writestring("K: Hello world!\n");
-    kterm_writestring("K: We got newline support!");
-    
+    /** Wrtite stuff to the screen to test the terminal**/ 
+    kterm_writestring("Hello world!\n");
+    kterm_writestring("We got newline support!\n");
+    for(;;){
+        delay(100);
+        kterm_writestring("We have implemented terminal scrolling!");
+    }
+   
+   
 }   
\ No newline at end of file