Renamed ktypes.h to types.h, added missing directories in make prepare, implemented text scrolling and added util module with a few test functions

.vscode/settings.json

@@ -1,5 +1,6 @@
 {
     "files.associations": {
-        "ktypes.h": "c"
+        "ktypes.h": "c",
+        "ports.h": "c"
     }
 }

Makefile

@@ -32,7 +32,7 @@ BUILD_PATHS += $(subst src/,$(OBJDIR),$(dir $(DRIVERS_OBJS)))
 
 
 prepare:
-	mkdir -p $(BUILD_PATHS)
+	mkdir -p $(BUILD_PATHS) build obj dist 
 
 
 clean:

include/kernel/drivers/ports/ports.h

@@ -18,7 +18,7 @@ limitations under the License.
 #define TSOS_DRV_PORTS_H
 
 
-#include "kernel/ktypes.h"
+#include "kernel/types.h"
 
 
 byte readByte(u16 port);

include/kernel/drivers/vga/screen.h

@@ -18,7 +18,7 @@ limitations under the License.
 #ifndef TSOS_DRV_VGA_SCREEN
 #define TSOS_DRV_VGA_SCREEN
 
-#include "kernel/ktypes.h"
+#include "kernel/types.h"
 #include "kernel/drivers/ports/ports.h"
 
 

include/kernel/types.h

@@ -19,12 +19,14 @@ limitations under the License.
 #ifndef TSOS_KTYPES
 #define TSOS_KTYPES
 
+#define true 1
+#define false 0
 
 typedef unsigned char byte;
 typedef unsigned short int u16;
 typedef short int i16;
-typedef unsigned int uint;
 typedef unsigned int u32;
 typedef int i32;
+typedef unsigned char bool;
 
 #endif

include/kernel/util.h

@@ -0,0 +1,25 @@
+/*
+Copyright 2022 Mattia Giambirtone & Contributors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifndef TSOS_UTIL_H
+#define TSOS_UTIL_H
+
+#include "kernel/types.h"
+
+void copystr(const char* source, char* dest, i32 n);
+void itoa(i32 i, char* a);
+
+#endif

src/boot/mbr.s

@@ -47,7 +47,7 @@ jmp $ ; Keeps jumping at the current address (loops forever)
 
 ; Here we define our variables: They need to be defined after the
 ; halting because otherwise they will be executed as code
-real_mode_msg: db "TSOS is starting up", 0
+real_mode_msg: db "TSBL is starting up", 0
 protected_mode_msg: db "Switched to protected mode", 0
 loading_kernel_msg: db "Loading kernel into memory", 0
 boot_drive: db 0
@@ -58,7 +58,7 @@ load_kernel:    ; Loads the kernel into memory
     mov si, loading_kernel_msg
     call bios_println
     mov bx, kernel_offset
-    mov dh, 3
+    mov dh, 4
     mov dl, [boot_drive]
     call load_disk
     ret

src/kernel/drivers/vga/screen.c

@@ -16,7 +16,8 @@ limitations under the License.
 
 // Implementation of a simple text-only VGA driver
 #include "kernel/drivers/vga/screen.h"
-#include "kernel/ktypes.h"
+#include "kernel/types.h"
+#include "kernel/util.h"
 
 
 i32 getCursorOffset(void);
@@ -82,12 +83,22 @@ i32 putchar(byte ch, i32 col, i32 row, byte attr) {
     - '\n' -> Goes to the next line
     - '\t' -> Prints VGA_TABSIZE spaces
     - '\r' -> Resets the cursor's column, but not the row
+    Upon error, a negative value is returned; The possible
+    errors are codes are
+        - -1 -> Column out of bounds
+        - -2 -> Row out of bounds
     */
     
     if (!attr) {
         // No color data provided? We supply our own
         attr = LIGHT_GREY_ON_BLACK;
     }
+    if (col >= MAX_COLS) {
+        return -1;
+    }
+    if (row >= MAX_ROWS) {
+        return -2;
+    }
     i32 offset = (col >= 0 && row >= 0)? getOffset(col, row): getCursorOffset();
     switch (ch) {
         // Note the difference between a carriage return (which
@@ -112,6 +123,26 @@ i32 putchar(byte ch, i32 col, i32 row, byte attr) {
             offset += 2;
             break;
     }
+    // We check if we reached the end of the screen, in which
+    // case we scroll
+    if (offset >= SCREEN_SIZE * 2) {
+        for (i32 i = 1; i < MAX_ROWS; i ++) {
+            // This loop will take the bytes of row i and copy
+            // them to row i - 1, effectively erasing the first
+            // one and causing the text on the screen to scroll!
+            copystr((char *)(getOffset(0, i) + VMEM_ADDRESS), 
+                    (char*)(getOffset(0, i - 1) + VMEM_ADDRESS), 
+                    MAX_COLS * 2);
+        }
+        // We empty the last line
+        char* last = (char*)(getOffset(0, MAX_ROWS - 1) + VMEM_ADDRESS);
+        for (i32 i = 0; i < MAX_COLS * 2; i++) {
+            last[i] = 0;
+        }
+
+        offset -= 2 * MAX_COLS;
+    }
+
     setCursorOffset(offset);
     return offset;
 }

src/kernel/main.c

@@ -14,13 +14,28 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-// Entry point of the TSOS kernel
-#include "kernel/ktypes.h"
+#include "kernel/types.h"
 #include "kernel/drivers/vga/screen.h"
+#include "kernel/util.h"
 
 
 void kmain(void) {
+    /*
+    The kernel entry point of TSOS
+    */
+
     // Newline so we skip the log
     // messages from the bootloader
     kprint("\nTSOS Kernel is starting up");
+    // TODO: Sleep
+    clearScreen();
+    char str[255];
+    /* Fill up the screen */
+    for (i32 i = 0; i < 24; i++) {
+        itoa(i, str);
+        kprintAt(str, 0, i);
+    }
+
+    kprintAt("This text forces the kernel to scroll. Row 0 will disappear.", 60, 24);
+    kprint("\nAnd with this text, the kernel will scroll again, and row 1 will disappear too!");
 }

src/kernel/util.c

@@ -0,0 +1,74 @@
+/*
+Copyright 2022 Mattia Giambirtone & Contributors
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#include "kernel/types.h"
+#include "kernel/util.h"
+
+void copystr(const char* restrict source, char* restrict dest, i32 n) {
+    /*
+    Copies n bytes from source to dest. The two memory locations may
+    not overlap: if they do, the behavior is undefined. This function's
+    behavior is also undefined if:
+    - n is larger than source's or dest's actual size
+    - dest is smaller than source
+    The caller should make sure these conditions are checked for before
+    calling this function 
+    */
+    int i;
+    for (i = 0; i < n; i++) {
+        *(dest + i) = *(source + i);
+    }
+}
+
+
+i32 countDigits(i32 n) {
+    /*
+    Returns the number of digits
+    of n
+    */
+    i32 result = 0;
+    while (n) {
+        n /= 10;
+        result++;
+    }
+    return result;
+
+}
+
+
+void itoa(i32 n, char* a) {
+    /*
+    Converts the integer n to
+    a string. The result is written
+    to a, which is assumed to be large
+    enough to accomodate an optional
+    negative sign, the number itself
+    and a null byte at the end (if the
+    buffer is not large enough, the 
+    behavior is undefined)
+    */
+    int i, sign;
+    if ((sign = n) < 0) n = -n;
+    i = countDigits(n);
+    do {
+        a[--i] = n % 10 + '0';
+    } while ((n /= 10) > 0);
+
+    if (sign < 0) a[--i] = '-';
+    a[--i] = '\0';
+
+    /* TODO: implement "reverse" */
+}