Fragmented stdio.h header

2026-11-04 02:23:10 +00:00 · 2024-08-26 14:54:47 +02:00
parent 9388457774
commit d6c4682f52
3 changed files with 169 additions and 150 deletions
@@ -0,0 +1,74 @@
+#ifndef _PRINTF_H
+#define _PRINTF_H
+
+#include <string.h>
+#include <stdlib.h>
+
+// TODO: Support negative numbers
+int printf(const char* fmt, ...) {
+    unsigned int* argPtr = (unsigned int*)&fmt + 1; // First arg after fmt
+    
+    // Printing buffer
+    static char* buffer;
+    static unsigned int len;
+    int max = 256;
+
+    buffer = malloc(max);
+    len = 0;
+    
+    int state = 0;
+    for (int i = 0; fmt[i] != '\0'; i++) {
+        if (len > max) {
+            max *= 2;
+            // Reallocate larger buffer TODO: Use realloc();
+            char* temp = malloc(max);
+            strcpy(temp, buffer);
+            free(buffer);
+            buffer = temp;
+        }
+        buffer[len] = '\0';
+
+        char c = fmt[i];
+        if (state == 0) {
+             if (c == '%') state = '%';
+             else buffer[len++] = c;
+        } else if (state == '%') {
+            switch (c) {
+                case 'd': // Decimal number
+                    strcat(buffer, itoa(*argPtr++, 10));
+                    len += strlen(&buffer[len]); // Add the remaining length
+                    break;
+                case 'x': // Hex number
+                    strcat(buffer, itoa(*argPtr++, 16));
+                    len += strlen(&buffer[len]);
+                    break;
+                case 's': // String
+                    char* s = *(char**)argPtr++;
+                    
+                    while (*s != '\0') {
+                        buffer[len++] = *s++;
+                    }
+                    break;
+                case 'c': // Char
+                    buffer[len++] = *(char*)argPtr;
+                    argPtr++;
+                    break;
+                default: // This looks insane
+                    buffer[len++] = '%';
+                case '%': // Just print '%'
+                    buffer[len++] = c;
+                    break;
+            }  
+            state = 0;
+        }
+    }
+
+    buffer[len] = '\0';
+    write(1, buffer, len);
+    free(buffer);
+
+    return 0;
+}
+
+#endif
+