Now prints "Hello, World" on boot

build/OSDev_18/compile_commands.json

@@ -8,5 +8,10 @@
   "directory": "/workspaces/AdvOpSys/build/OSDev_18",
   "command": "/usr/local/bin/i686-elf-gcc -I/workspaces/AdvOpSys/src/OSDev_18/include -g -Wall -Wextra -nostdinc -nostdlib -fno-builtin -fno-stack-protector -fno-stack-check -fno-lto -fPIE -m32 -march=i386 -mno-mmx -mno-sse -mno-sse2 -mno-red-zone -Wno-main -g -Wno-unused-variable -Wno-unused-parameter -std=gnu99 -o CMakeFiles/uiaos-kernel.dir/src/kernel.c.o -c /workspaces/AdvOpSys/src/OSDev_18/src/kernel.c",
   "file": "/workspaces/AdvOpSys/src/OSDev_18/src/kernel.c"
+},
+{
+  "directory": "/workspaces/AdvOpSys/build/OSDev_18",
+  "command": "/usr/local/bin/i686-elf-gcc -I/workspaces/AdvOpSys/src/OSDev_18/include -g -Wall -Wextra -nostdinc -nostdlib -fno-builtin -fno-stack-protector -fno-stack-check -fno-lto -fPIE -m32 -march=i386 -mno-mmx -mno-sse -mno-sse2 -mno-red-zone -Wno-main -g -Wno-unused-variable -Wno-unused-parameter -std=gnu99 -o CMakeFiles/uiaos-kernel.dir/src/terminal.c.o -c /workspaces/AdvOpSys/src/OSDev_18/src/terminal.c",
+  "file": "/workspaces/AdvOpSys/src/OSDev_18/src/terminal.c"
 }
 ]

src/OSDev_18/CMakeLists.txt

@@ -60,6 +60,7 @@ set(OS_KERNEL_LINKER "${CMAKE_CURRENT_SOURCE_DIR}/src/arch/${OS_ARCH_TARGET}/lin
 add_executable(uiaos-kernel 
 	src/multiboot2.asm # TODO: Add multiboot2 support
     src/kernel.c
+	src/terminal.c
 )
 
 # Include directories for the kernel target

src/OSDev_18/include/kernel/terminal.h

@@ -1,16 +1,36 @@
-#include <libc/stdio.h>
-#include <libc/stdint.h>
-#include <libc/limits.h>
+#ifndef KERNEL_TERMINAL_H
+#define KERNEL_TERMINAL_H
+
 #include <libc/stddef.h>
+#include <libc/stdint.h>
 
-const size_t VGA_HEIGHT = 25;
-const size_t VGA_WIDTH = 80;
+enum vga_colour{
+    VGA_COLOR_BLACK = 0,
+    VGA_COLOR_BLUE = 1,
+    VGA_COLOR_GREEN = 2,
+    VGA_COLOR_CYAN = 3,
+    VGA_COLOR_RED = 4,
+    VGA_COLOR_MAGENTA = 5,
+    VGA_COLOR_BROWN = 6,
+    VGA_COLOR_LIGHT_GREY = 7,
+    VGA_COLOR_DARK_GREY = 8,
+    VGA_COLOR_LIGHT_BLUE = 9,
+    VGA_COLOR_LIGHT_GREEN = 10,
+    VGA_COLOR_LIGHT_CYAN = 11,
+    VGA_COLOR_LIGHT_RED = 12,
+    VGA_COLOR_LIGHT_MAGENTA = 13,
+    VGA_COLOR_LIGHT_BROWN = 14,
+    VGA_COLOR_WHITE = 15,
+};
 
-static uint16_t* terminalBuffer = (uint16_t*) 0xB8000;
+uint8_t vgaEntryColour(enum vga_colour fg, enum vga_colour bg);
+uint16_t vgaEntry(unsigned char uc, uint8_t color);
 
+void terminalEntryAt(char c, uint8_t colour, size_t x, size_t y);
+void terminalInitialize(void);
+void terminalSetColour(uint8_t colour);
+void terminalPutChar(char c);
+void terminalWrite(const char* data, size_t size);
+void terminalWriteString(const char* data);
 
-
-void terminalEntryAt(char c, uint8_t colour, size_t x, size_t y){
-    size_t index = y * VGA_WIDTH + x;
-    terminalBuffer[index] = vgaEntry(c, colour);
-}
+#endif

src/OSDev_18/src/kernel.c

@@ -1,6 +1,10 @@
 #include <libc/stdint.h>
+#include <kernel/terminal.h>
 
 void main(void) {
+    terminalInitialize();
+    terminalWriteString("Hello, World!\n");
+    
     for (;;) {
         __asm__ volatile ("hlt");
     }

src/OSDev_18/src/terminal.c

@@ -0,0 +1,78 @@
+#include <kernel/terminal.h>
+
+const size_t VGA_HEIGHT = 25;
+const size_t VGA_WIDTH = 80;
+
+static size_t terminal_row;
+static size_t terminal_column;
+
+static uint8_t terminal_colour;
+static uint16_t* terminal_buffer = (uint16_t*) 0xB8000;
+
+// Builds the colour byte
+uint8_t vgaEntryColour(enum vga_colour fg, enum vga_colour bg) {
+    return fg | bg << 4;
+}
+
+// Builds the full cell
+uint16_t vgaEntry(unsigned char uc, uint8_t color) {
+    return (uint16_t) uc | (uint16_t) color << 8;
+}
+
+void terminalEntryAt(char c, uint8_t colour, size_t x, size_t y){
+    size_t index = y * VGA_WIDTH + x;
+    terminal_buffer[index] = vgaEntry(c, colour);
+}
+
+void terminalInitialize(void) {
+    terminal_row = 0;
+    terminal_column = 0;
+    terminal_colour = vgaEntryColour(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
+    terminal_buffer = (uint16_t*) 0xB8000;
+
+    for (size_t y = 0; y < VGA_HEIGHT; y++) {
+        for (size_t x = 0; x < VGA_WIDTH; x++) {
+            terminalEntryAt(' ', terminal_colour, x, y);
+        }
+    }
+}
+
+void terminalSetColour(uint8_t colour) {
+    terminal_colour = colour;
+}
+
+void terminalPutChar(char c) {
+    if (c == '\n') {
+        terminal_column = 0;
+        terminal_row++;
+        return;
+    }
+    terminalEntryAt(c, terminal_colour,terminal_column, terminal_row);
+    terminal_column++;
+
+    if (terminal_column == VGA_WIDTH) {
+        terminal_column = 0;
+        terminal_row++;
+    }
+
+    if (terminal_row == VGA_HEIGHT) {
+        terminal_row = 0;
+    }
+}
+
+void terminalWrite(const char* data, size_t size) {
+    for (size_t i = 0; i < size; i++) {
+        terminalPutChar(data[i]);
+    }
+}
+
+void terminalWriteString(const char* data) {
+    size_t len = 0;
+
+    while (data[len] != '\0') {
+        len++;
+    }
+
+    terminalWrite(data, len);
+}
+