add lab answers

labcodes_answer/lab2_result/kern/libs/readline.c

@@ -0,0 +1,50 @@
+#include <stdio.h>
+
+#define BUFSIZE 1024
+static char buf[BUFSIZE];
+
+/* *
+ * readline - get a line from stdin
+ * @prompt:     the string to be written to stdout
+ *
+ * The readline() function will write the input string @prompt to
+ * stdout first. If the @prompt is NULL or the empty string,
+ * no prompt is issued.
+ *
+ * This function will keep on reading characters and saving them to buffer
+ * 'buf' until '\n' or '\r' is encountered.
+ *
+ * Note that, if the length of string that will be read is longer than
+ * buffer size, the end of string will be discarded.
+ *
+ * The readline() function returns the text of the line read. If some errors
+ * are happened, NULL is returned. The return value is a global variable,
+ * thus it should be copied before it is used.
+ * */
+char *
+readline(const char *prompt) {
+    if (prompt != NULL) {
+        cprintf("%s", prompt);
+    }
+    int i = 0, c;
+    while (1) {
+        c = getchar();
+        if (c < 0) {
+            return NULL;
+        }
+        else if (c >= ' ' && i < BUFSIZE - 1) {
+            cputchar(c);
+            buf[i ++] = c;
+        }
+        else if (c == '\b' && i > 0) {
+            cputchar(c);
+            i --;
+        }
+        else if (c == '\n' || c == '\r') {
+            cputchar(c);
+            buf[i] = '\0';
+            return buf;
+        }
+    }
+}
+

labcodes_answer/lab2_result/kern/libs/stdio.c

@@ -0,0 +1,78 @@
+#include <defs.h>
+#include <stdio.h>
+#include <console.h>
+
+/* HIGH level console I/O */
+
+/* *
+ * 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) {
+    cons_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, &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;
+    int cnt;
+    va_start(ap, fmt);
+    cnt = vcprintf(fmt, ap);
+    va_end(ap);
+    return cnt;
+}
+
+/* cputchar - writes a single character to stdout */
+void
+cputchar(int c) {
+    cons_putc(c);
+}
+
+/* *
+ * 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;
+}
+
+/* getchar - reads a single non-zero character from stdin */
+int
+getchar(void) {
+    int c;
+    while ((c = cons_getc()) == 0)
+        /* do nothing */;
+    return c;
+}
+