add lab answers

labcodes_answer/lab8_result/user/libs/stdio.c

@@ -0,0 +1,89 @@
+#include <defs.h>
+#include <stdio.h>
+#include <syscall.h>
+#include <file.h>
+#include <ulib.h>
+#include <unistd.h>
+
+/* *
+ * cputch - writes a single character @c to stdout, and it will
+ * increace the value of counter pointed by @cnt.
+ * */
+static void
+cputch(int c, int *cnt) {
+    sys_putc(c);
+    (*cnt) ++;
+}
+
+/* *
+ * vcprintf - format a string and writes it to stdout
+ *
+ * The return value is the number of characters which would be
+ * written to stdout.
+ *
+ * Call this function if you are already dealing with a va_list.
+ * Or you probably want cprintf() instead.
+ * */
+int
+vcprintf(const char *fmt, va_list ap) {
+    int cnt = 0;
+    vprintfmt((void*)cputch, NO_FD, &cnt, fmt, ap);
+    return cnt;
+}
+
+/* *
+ * cprintf - formats a string and writes it to stdout
+ *
+ * The return value is the number of characters which would be
+ * written to stdout.
+ * */
+int
+cprintf(const char *fmt, ...) {
+    va_list ap;
+
+    va_start(ap, fmt);
+    int cnt = vcprintf(fmt, ap);
+    va_end(ap);
+
+    return cnt;
+}
+
+/* *
+ * cputs- writes the string pointed by @str to stdout and
+ * appends a newline character.
+ * */
+int
+cputs(const char *str) {
+    int cnt = 0;
+    char c;
+    while ((c = *str ++) != '\0') {
+        cputch(c, &cnt);
+    }
+    cputch('\n', &cnt);
+    return cnt;
+}
+
+
+static void
+fputch(char c, int *cnt, int fd) {
+    write(fd, &c, sizeof(char));
+    (*cnt) ++;
+}
+
+int
+vfprintf(int fd, const char *fmt, va_list ap) {
+    int cnt = 0;
+    vprintfmt((void*)fputch, fd, &cnt, fmt, ap);
+    return cnt;
+}
+
+int
+fprintf(int fd, const char *fmt, ...) {
+    va_list ap;
+
+    va_start(ap, fmt);
+    int cnt = vfprintf(fd, fmt, ap);
+    va_end(ap);
+
+    return cnt;
+}