kernel print and mem

makefile

@@ -7,12 +7,18 @@ run: build/os.bin
 build/os.bin: build/boot.bin build/kernel.bin build/zeroes.bin
 	cat build/boot.bin build/kernel.bin build/zeroes.bin > build/os.bin
 
-build/kernel.bin: build/kernel.o build/kernel_entry.o
-	i386-elf-ld -o build/kernel.bin -Ttext 0x1000 build/kernel_entry.o build/kernel.o --oformat binary
+build/kernel.bin: build/kernel_entry.o build/kernel.o build/mem.o build/print.o
+	i386-elf-ld -o build/kernel.bin -Ttext 0x1000 build/kernel_entry.o build/kernel.o build/mem.o build/print.o --oformat binary
 
 build/kernel.o: src/kernel.c
 	i386-elf-gcc -ffreestanding -m32 -c -o build/kernel.o src/kernel.c
 
+build/mem.o: src/mem.c
+	i386-elf-gcc -ffreestanding -m32 -c -o build/mem.o src/mem.c
+
+build/print.o: src/print.c
+	i386-elf-gcc -ffreestanding -m32 -c -o build/print.o src/print.c
+
 build/kernel_entry.o: src/kernel_entry.asm
 	nasm -f elf -o build/kernel_entry.o src/kernel_entry.asm
 

src/kernel.c

@@ -1,5 +1,7 @@
-int main(void)
+#include "print.h"
+
+void init(void)
 {
-    *(char*)0xb8000 = 'A';
-    return 0;
+    print_init();
+    print("Starting nub-os\n", VGA_FG_WHITE, VGA_BG_BLACK);
 }

src/kernel_entry.asm

@@ -1,5 +1,5 @@
 section .text
     [bits 32]
-    [extern main]
-    call main
+    [extern init]
+    call init
     jmp $

src/mem.c

@@ -0,0 +1,26 @@
+#include "mem.h"
+
+void* memcpy(void* dest, const void* src, long n)
+{
+    char* d = dest;
+    const char* s = src;
+    for (long i = 0; i < n; i++)
+        d[i] = s[i];
+    return dest;
+}
+
+void* memset(void* dest, int val, long n)
+{
+    char* d = dest;
+    for (long i = 0; i < n; i++)
+        d[i] = val;
+    return dest;
+}
+
+long strlen(const char* str)
+{
+    long len = 0;
+    while (str[len])
+        len++;
+    return len;
+}

src/mem.h

@@ -0,0 +1,3 @@
+void* memcpy(void* dest, const void* src, long n);
+void* memset(void* dest, int val, long n);
+long strlen(const char* str);

src/print.c

@@ -0,0 +1,94 @@
+#include "print.h"
+
+#define VGA_WIDTH 80
+#define VGA_HEIGHT 25
+
+char* vga_text_pos;
+
+void print_init(void)
+{
+    vga_text_pos = (char*)0xb8000;
+}
+
+void print(char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color)
+{
+    for (int i = 0; string[i]; i++)
+    {
+        char c = string[i];
+
+        switch (c)
+        {
+        case '\n':
+        {
+
+            vga_text_pos += 160 - ((vga_text_pos - (char*)0xb8000) % 160);
+            break;
+        }
+        case '\r':
+        {
+            vga_text_pos -= ((vga_text_pos - (char*)0xb8000) % 160);
+            break;
+        }
+        case '\t':
+        {
+            int offset = (vga_text_pos - (char*)0xb8000) % 160;
+            int next_tab = ((offset / 16) + 1) * 16;
+            vga_text_pos += next_tab - offset;
+            break;
+        }
+        case '\b':
+        {
+            if (vga_text_pos > (char*)0xb8000)
+            {
+                vga_text_pos -= 2;
+                *vga_text_pos = ' ';
+                *(vga_text_pos + 1) = (bg_color << 4) | fg_color;
+            }
+            break;
+        }
+        case '\f':
+        {
+            char* start = (char*)0xb8000;
+            for (int j = 0; j < 80 * 25 * 2; j += 2)
+            {
+                start[j] = ' ';
+                start[j + 1] = (bg_color << 4) | fg_color;
+            }
+            vga_text_pos = (char*)0xb8000;
+            break;
+        }
+        case '\a':
+        {
+            break;
+        }
+        default:
+        {
+            *vga_text_pos++ = c;
+            *vga_text_pos++ = (bg_color << 4) | fg_color;
+            break;
+        }
+        }
+
+        if (vga_text_pos >= (char*)0xb8000 + VGA_WIDTH * VGA_HEIGHT * 2)
+        {
+            char* start = (char*)0xb8000;
+
+            for (int row = 1; row < VGA_HEIGHT; row++)
+            {
+                for (int col = 0; col < VGA_WIDTH * 2; col++)
+                {
+                    start[(row - 1) * VGA_WIDTH * 2 + col] = start[row * VGA_WIDTH * 2 + col];
+                }
+            }
+
+            char* last_row = start + (VGA_HEIGHT - 1) * VGA_WIDTH * 2;
+            for (int col = 0; col < VGA_WIDTH * 2; col += 2)
+            {
+                last_row[col] = ' ';
+                last_row[col + 1] = (VGA_BG_BLACK << 4) | VGA_FG_WHITE;
+            }
+
+            vga_text_pos -= VGA_WIDTH * 2;
+        }
+    }
+}

src/print.h

@@ -0,0 +1,34 @@
+enum VGA_FG_COLOR
+{
+    VGA_FG_BLACK = 0x0,
+    VGA_FG_BLUE = 0x1,
+    VGA_FG_GREEN = 0x2,
+    VGA_FG_CYAN = 0x3,
+    VGA_FG_RED = 0x4,
+    VGA_FG_MAGENTA = 0x5,
+    VGA_FG_BROWN = 0x6,
+    VGA_FG_LIGHT_GRAY = 0x7,
+    VGA_FG_DARK_GRAY = 0x8,
+    VGA_FG_LIGHT_BLUE = 0x9,
+    VGA_FG_LIGHT_GREEN = 0xA,
+    VGA_FG_LIGHT_CYAN = 0xB,
+    VGA_FG_LIGHT_RED = 0xC,
+    VGA_FG_LIGHT_MAGENTA = 0xD,
+    VGA_FG_YELLOW = 0xE,
+    VGA_FG_WHITE = 0xF,
+};
+
+enum VGA_BG_COLOR
+{
+    VGA_BG_BLACK = 0x0,
+    VGA_BG_BLUE = 0x1,
+    VGA_BG_GREEN = 0x2,
+    VGA_BG_CYAN = 0x3,
+    VGA_BG_RED = 0x4,
+    VGA_BG_MAGENTA = 0x5,
+    VGA_BG_BROWN = 0x6,
+    VGA_BG_LIGHT_GRAY = 0x7,
+};
+
+void print(char* string, enum VGA_FG_COLOR fg_color, enum VGA_BG_COLOR bg_color);
+void print_init(void);