clickOS/kprintf.c at main · printedz/clickOS · GitHub

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#include "kprintf.h"
#include "terminal.h"

#include <stdarg.h>
#include <stdint.h>

/* Print unsigned integer in any base (2–16) */
static void print_uint(uint32_t n, uint32_t base, const char* digits) {
    if (n == 0) {
        terminal_putchar('0');
        return;
    }
    char buf[32];
    int  i = 0;
    while (n > 0) {
        buf[i++] = digits[n % base];
        n /= base;
    }
    while (i > 0) terminal_putchar(buf[--i]);
}

/* Print signed 32-bit integer — handles INT32_MIN safely */
static void print_int(int32_t n) {
    if (n < 0) {
        terminal_putchar('-');
        /* ~n + 1 gives the magnitude as uint32_t without overflow */
        print_uint((uint32_t)(~n) + 1u, 10, "0123456789");
    } else {
        print_uint((uint32_t)n, 10, "0123456789");
    }
}

void kprintf(const char* fmt, ...) {
    va_list args;
    va_start(args, fmt);

    for (const char* p = fmt; *p; p++) {
        if (*p != '%') {
            terminal_putchar(*p);
            continue;
        }

        p++; /* consume '%' */

        /* Parse optional flags and width: %-12s etc. */
        int left_justify = 0;
        int pad_width = 0;

        if (*p == '-') {
            left_justify = 1;
            p++;
        }
        while (*p >= '0' && *p <= '9') {
            pad_width = pad_width * 10 + (*p - '0');
            p++;
        }

        switch (*p) {
            case 's': {
                const char* s = va_arg(args, const char*);
                if (!s) s = "(null)";
                int slen = 0;
                while (s[slen]) slen++;
                if (left_justify) {
                    terminal_writestring(s);
                    for (int i = slen; i < pad_width; i++) terminal_putchar(' ');
                } else {
                    for (int i = slen; i < pad_width; i++) terminal_putchar(' ');
                    terminal_writestring(s);
                }
                break;
            }
            case 'c':
                terminal_putchar((char)va_arg(args, int));
                break;
            case 'd':
                print_int(va_arg(args, int32_t));
                break;
            case 'u':
                print_uint(va_arg(args, uint32_t), 10, "0123456789");
                break;
            case 'x':
                print_uint(va_arg(args, uint32_t), 16, "0123456789abcdef");
                break;
            case 'X':
                print_uint(va_arg(args, uint32_t), 16, "0123456789ABCDEF");
                break;
            case 'b':
                print_uint(va_arg(args, uint32_t), 2, "01");
                break;
            case 'p':
                terminal_writestring("0x");
                print_uint((uint32_t)va_arg(args, void*), 16, "0123456789abcdef");
                break;
            case '%':
                terminal_putchar('%');
                break;
            default:
                /* Pass through unknown specifiers verbatim */
                terminal_putchar('%');
                terminal_putchar(*p);
                break;
        }
    }

    va_end(args);
}