feat: added printf

kernel/libc/kprintf.c

@@ -0,0 +1,84 @@
+//
+// Created by rick on 06-02-21.
+//
+
+#include "kprintf.h"
+#include "libc.h"
+#include <libc/string.h>
+#include <libc/va_list.h>
+#include <kprint.h>
+#include <libk.h>
+#include <types.h>
+
+/*
+ * Integer to string
+ */
+void print_int(u32 value, u32 width, char* buf, u32 *ptr, u8 base) {
+    // u32 in binary is 32 digits, so never longer than 33 digits
+    char msg[33];
+    itoa(value, msg, base);
+    u32 digits = strlen(msg);
+    if (digits < width) {
+        for (u32 i = 0; i < (width - digits); ++i) {
+            buf[*ptr] = '0';
+            *ptr += 1;
+        }
+    }
+    for (u32 i = 0; i < digits; ++i) {
+        buf[*ptr] = msg[i];
+        *ptr += 1;
+    }
+}
+
+u32 vasprintf(char *buf, const char *fmt, va_list args) {
+    u32 ptr = 0;
+    for (int i = 0; i < strlen(fmt); ++i) {
+        if (fmt[i] != '%') {
+            buf[ptr++] = fmt[i];
+            continue;
+        }
+        ++i;
+        u32 arg_width = 0;
+        while (fmt[i] >= '0' && fmt[i] <= '9') {
+            arg_width *= 10;
+            arg_width += fmt[i] - '0';
+            ++i;
+        }
+        switch (fmt[i]) {
+            case 's': { // string
+                char *s_fmt = (char *) va_arg(args, char*);
+                while (*s_fmt) {
+                    buf[ptr++] = *s_fmt++;
+                }
+                break;
+            }
+            case 'c':
+                buf[ptr++] = (char)va_arg(args, int);
+                break;
+            case 'x':
+                print_int((u32)va_arg(args, u32), arg_width, buf, &ptr, 16);
+                break;
+            case 'd':
+                print_int((u32)va_arg(args, u32), arg_width, buf, &ptr, 10);
+                break;
+            case '%':
+                buf[ptr++] = '%';
+                break;
+            default:
+                printf("FMT '%c' is not supported\n", fmt[i]);
+                k_panic();
+                break;
+        }
+    }
+    buf[ptr] = 0;
+    return ptr;
+}
+
+void printf(const char *fmt, ...) {
+    char buf[1024] = {-1};
+    va_list args;
+    va_start(args, fmt);
+    vasprintf(buf, fmt, args);
+    va_end(args);
+    kprint(buf);
+}