From 00ad163cc353a9e69b5e1e00c6f7a9a1e15f3e7a Mon Sep 17 00:00:00 2001
From: Quinten Kock <quinten@quinten.space>
Date: Fri, 4 Dec 2020 03:07:27 +0100
Subject: [PATCH] implement platform-agnostic printf

---
 kernel/src/arch/x86/vga.c | 14 +++----
 kernel/src/hal/print.h    |  1 +
 kernel/src/main.c         | 10 +----
 kernel/src/print/print.c  | 77 +++++++++++++++++++++++++++++++++++++++
 kernel/src/print/print.h  |  5 +++
 5 files changed, 90 insertions(+), 17 deletions(-)
 create mode 100644 kernel/src/hal/print.h
 create mode 100644 kernel/src/print/print.c
 create mode 100644 kernel/src/print/print.h

diff --git a/kernel/src/arch/x86/vga.c b/kernel/src/arch/x86/vga.c
index 03c06fc..3bb5fb7 100644
--- a/kernel/src/arch/x86/vga.c
+++ b/kernel/src/arch/x86/vga.c
@@ -11,6 +11,10 @@ static volatile size_t terminal_column;
 static volatile uint8_t current_color = VGA_WHITE;
 static uint16_t *terminal_buffer = (uint16_t*)0xb8000;
 
+void putchar(char c) {
+	vga_putc(c);
+}
+
 void vga_putc(char c) {
 	size_t index = terminal_row*VGA_WIDTH + terminal_column;
 	if(c == '\t') {
@@ -30,14 +34,6 @@ void vga_putc(char c) {
 	}
 }
 
-void vga_puts(const char *c) {
-	char cur = *(c++);
-	while(cur != '\0') {
-		vga_putc(cur);
-		cur = *(c++);
-	}
-}
-
 void vga_setcolor(uint8_t new_color) {
 	current_color = new_color;
 }
@@ -47,7 +43,7 @@ void vga_write_elsewhere(const char *c, size_t y, size_t x) {
 	size_t old_column = terminal_column;
 	terminal_row = y;
 	terminal_column = x;
-	vga_puts(c);
+	puts(c);
 	terminal_row=old_row;
 	terminal_column=old_column;
 }
diff --git a/kernel/src/hal/print.h b/kernel/src/hal/print.h
new file mode 100644
index 0000000..f8c2025
--- /dev/null
+++ b/kernel/src/hal/print.h
@@ -0,0 +1 @@
+void putchar(char);
diff --git a/kernel/src/main.c b/kernel/src/main.c
index d1db8e2..f140678 100644
--- a/kernel/src/main.c
+++ b/kernel/src/main.c
@@ -2,14 +2,8 @@
 #include "hal/ops.h"
 
 void kmain(int argc, char **argv) {
-	vga_puts("Kernel initialized! Platform: ");
-	vga_puts(arch);
-	vga_putc('\n');
-	vga_puts("Bootloader information:\t");
-	for(int i = 0; i < argc; i++) {
-		vga_puts(argv[i]);
-		vga_putc('\t');
-	}
+	printf("Kernel initialized! Platform: %s\n", arch);
+	printf("Bootloader type: %s (%s %s)\n", argv[0], argv[1], argv[2]);
 
 	vga_setcolor(VGA_DARK_GRAY);
 	vga_write_elsewhere("(c) Quinten Kock 2020 (MIT License)", 24, 0);
diff --git a/kernel/src/print/print.c b/kernel/src/print/print.c
new file mode 100644
index 0000000..8e1dea5
--- /dev/null
+++ b/kernel/src/print/print.c
@@ -0,0 +1,77 @@
+#include <stddef.h>
+#include <stdarg.h>
+
+#include "print.h"
+
+void puts(const char* c) {
+    for(size_t i = 0; c[i]; i++)
+        putchar(c[i]);
+}
+
+void print(const char* c) {
+    puts(c);
+    putchar('\n');;
+}
+
+static const char CONVERSION_TABLE[] = "0123456789abcdef";
+
+static void printhex(size_t num) {
+    int i;
+    char buf[17];
+
+    if (!num) {
+        puts("0x0");
+        return;
+    }
+
+    buf[16] = 0;
+
+    for (i = 15; num; i--) {
+        buf[i] = CONVERSION_TABLE[num % 16];
+        num /= 16;
+    }
+
+    i++;
+    puts("0x");
+    puts(&buf[i]);
+}
+
+static void printdec(size_t num) {
+    int i;
+    char buf[21] = {0};
+
+    if (!num) {
+        putchar('0');
+        return;
+    }
+
+    for (i = 19; num; i--) {
+        buf[i] = (num % 10) + 0x30;
+        num = num / 10;
+    }
+
+    i++;
+    puts(buf + i);
+}
+
+void printf(const char *format, ...) {
+    va_list argp;
+    va_start(argp, format);
+
+    while (*format != '\0') {
+        if (*format == '%') {
+            format++;
+            if (*format == 'x') {
+                printhex(va_arg(argp, size_t));
+            } else if (*format == 'd') {
+                printdec(va_arg(argp, size_t));
+            } else if (*format == 's') {
+                puts(va_arg(argp, char*));
+            } 
+        } else {
+            putchar(*format);
+        }
+        format++;
+    }
+    va_end(argp);
+}
diff --git a/kernel/src/print/print.h b/kernel/src/print/print.h
new file mode 100644
index 0000000..4e4be31
--- /dev/null
+++ b/kernel/src/print/print.h
@@ -0,0 +1,5 @@
+#include "../hal/print.h"
+
+void puts(const char*);
+void print(const char*);
+void printf(const char *format, ...);