From d3991147c77c86ff58defbfb4cae54533f8a995c Mon Sep 17 00:00:00 2001
From: FyloZ <fylozdev@gmail.com>
Date: Sun, 22 Feb 2026 22:50:35 -0500
Subject: [PATCH] Additional printf formats

---
 src/kernel/kernel.c            |  2 +-
 src/kernel/riscv64/qemu/uart.c | 82 ++++++++++++++++++++++++++++++++++
 2 files changed, 83 insertions(+), 1 deletion(-)

diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index 25c75cd..430651c 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -7,7 +7,7 @@
 void kmain(void) {
 	uart_init();
 
-	print("Hello world, %s!\n", ARCH);
+	print("Hello world, %x!\n", 0xff);
 
 	power_off();
 }
diff --git a/src/kernel/riscv64/qemu/uart.c b/src/kernel/riscv64/qemu/uart.c
index 3056318..a1ebc46 100644
--- a/src/kernel/riscv64/qemu/uart.c
+++ b/src/kernel/riscv64/qemu/uart.c
@@ -1,6 +1,8 @@
 #include <stdint.h>
 #include "../../uart.h"
 
+#include <limits.h>
+
 // QEMU emulates the NS16550A UART
 // The UART is memory mapped at 0x1000000
 #define UART_ADDR 0x10000000
@@ -36,9 +38,16 @@ void uart_puts(const char *line) {
     uart_putchar('\n');
 }
 
+#define DIGIT_TO_STR(digit) ('0' + (digit))
+#define DIGIT_TO_HEX(digit) ('0' + (digit) + ((digit < 10 ? 0 : 'a' - '0' - 10)))
+
 // Basic implementation of printf  supporting the following formats:
 //  - c: Character
 //  - s: String of characters
+//  - d, i: Signed integer
+//  - u: Unsigned integer
+//  - x: Unsigned hexadecimal
+//  - p: Pointer address
 //  - %: Literal '%'
 void uart_vprintf(const char *restrict format, va_list args) {
     while (*format) {
@@ -57,6 +66,79 @@ void uart_vprintf(const char *restrict format, va_list args) {
                 case 's': // String
                     uart_print(va_arg(args, char*));
                     break;
+                case 'd':
+                case 'i': {
+                    // TODO: This implementation breaks when the number starts with '0'. Check when debugging is possible?
+                    int num = va_arg(args, int);
+                    if (num == INT_MIN) {
+                        uart_print("-2147483648");
+                        break;
+                    }
+
+                    if (num < 0) {
+                        uart_putchar('-');
+                        num = -num;
+                    }
+
+                    const char lsh = DIGIT_TO_STR(num % 10);
+                    num /= 10;
+
+                    // Convert the number into a buffer of characters
+                    // The buffer will be reversed (the last digit will be first)
+                    char buf[9]; // There can't be more than 10 digits in an integer, -1 because of lsh
+                    char *buf_ptr = buf;
+                    while (num > 0) {
+                        *buf_ptr++ = DIGIT_TO_STR(num % 10);
+                        num /= 10;
+                    }
+
+                    // Print the characters in correct order
+                    while (buf_ptr != buf) {
+                        uart_putchar(*--buf_ptr);
+                    }
+
+                    uart_putchar(lsh);
+                }
+                break;
+                case 'u': {
+                    // Similar as the signed variant, without support for negatives
+                    unsigned int num = va_arg(args, unsigned int);
+                    const char lsh = DIGIT_TO_STR(num % 10);
+                    num /= 10;
+
+                    char buf[9];
+                    char *buf_ptr = buf;
+                    while (num > 0) {
+                        *buf_ptr++ = DIGIT_TO_STR(num % 10);
+                        num /= 10;
+                    }
+
+                    while (buf_ptr != buf) {
+                        uart_putchar(*--buf_ptr);
+                    }
+                    uart_putchar(lsh);
+                }
+                break;
+                case 'p':
+                    uart_print("0x");
+                case 'x': {
+                    unsigned int num = va_arg(args, unsigned int);
+                    const char lsh = DIGIT_TO_HEX(num % 16);
+                    num /= 16;
+
+                    char buf[7];
+                    char *buf_ptr = buf;
+                    while (num > 0) {
+                        *buf_ptr++ = DIGIT_TO_HEX(num % 16);
+                        num /= 16;
+                    }
+
+                    while (buf_ptr != buf) {
+                        uart_putchar(*--buf_ptr);
+                    }
+                    uart_putchar(lsh);
+                }
+                break;
                 case '%': // Literal '%'
                     uart_putchar('%');
                     break;