feat: some extensions to kernel standard c library. Other minor

improvements and formats

kernel/libc/kprintf.c

@@ -33,28 +33,51 @@ void print_int(uint32_t value, uint32_t width, char *buf, uint32_t *ptr, uint8_t
     }
 }
 
+void vasprintf_unsupported(char c) {
+    char *msg = "FMT '%x' is not supported\n";
+    msg[6] = c;
+    k_panics(msg);
+}
+
 uint32_t vasprintf(char *buf, const char *fmt, va_list args) {
     uint32_t ptr = 0;
-    for (int i = 0; i < strlen(fmt); ++i) {
+    for (size_t i = 0; i < strlen(fmt); ++i) {
         if (fmt[i] != '%') {
             buf[ptr++] = fmt[i];
             continue;
         }
         ++i;
-        uint32_t arg_width = 0;
-        while (fmt[i] >= '0' && fmt[i] <= '9') {
-            arg_width *= 10;
-            arg_width += fmt[i] - '0';
+        uint32_t field_width = 0;
+        uint32_t precision = 0; // todo
+        bool negative_field_width = false; // todo
+        if (fmt[i] == '-') {
+            // invert
+            negative_field_width = true;
             ++i;
         }
+        while (fmt[i] >= '0' && fmt[i] <= '9') {
+            field_width *= 10;
+            field_width += fmt[i] - '0';
+            ++i;
+        }
+        if (fmt[i] == '.') {
+            ++i;
+            while (fmt[i] >= '0' && fmt[i] <= '9') {
+                precision *= 10;
+                precision += fmt[i] - '0';
+                ++i;
+            }
+        }
         switch (fmt[i]) {
             case 's': { // string
+                uint32_t j = 0;
                 const char *s_fmt = (char *) va_arg(args, char*);
                 if (s_fmt == NULL) {
                     s_fmt = printf_null_str;
                 }
-                while (*s_fmt) {
+                while (*s_fmt && (precision == 0 || j != precision)) {
                     buf[ptr++] = *s_fmt++;
+                    j++;
                 }
                 break;
             }
@@ -62,18 +85,19 @@ uint32_t vasprintf(char *buf, const char *fmt, va_list args) {
                 buf[ptr++] = (char) va_arg(args, int);
                 break;
             case 'x':
-                print_int((uint32_t) va_arg(args, uint32_t), arg_width, buf, &ptr, 16);
+            case 'X': // todo capitalize
+                print_int((uint32_t) va_arg(args, uint32_t), field_width, buf, &ptr, 16);
                 break;
             case 'i':
             case 'd':
-                print_int((uint32_t) va_arg(args, uint32_t), arg_width, buf, &ptr, 10);
+            case 'u':
+                print_int((uint32_t) va_arg(args, uint32_t), field_width, buf, &ptr, 10);
                 break;
             case '%':
                 buf[ptr++] = '%';
                 break;
             default:
-                printf("FMT '%c' is not supported\n", fmt[i]);
-                k_panic();
+                vasprintf_unsupported(fmt[i]);
                 break;
         }
     }
@@ -81,14 +105,20 @@ uint32_t vasprintf(char *buf, const char *fmt, va_list args) {
     return ptr;
 }
 
-int printf(const char *fmt, ...) {
+int vprintf(const char *fmt, va_list args) {
     int result;
     char buf[1024] = {-1};
+    result = vasprintf(buf, fmt, args);
+    kprint(buf);
+    return result;
+}
+
+int printf(const char *fmt, ...) {
+    int result;
     va_list args;
     va_start(args, fmt);
-    result = vasprintf(buf, fmt, args);
+    result = vprintf(fmt, args);
     va_end(args);
-    kprint(buf);
     return result;
 }