Initial Spring 2016 commit.

kern/lib/kgets.c

@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2001
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+
+#include <types.h>
+#include <lib.h>
+
+/*
+ * Do a backspace in typed input.
+ * We overwrite the current character with a space in case we're on
+ * a terminal where backspace is nondestructive.
+ */
+static
+void
+backsp(void)
+{
+	putch('\b');
+	putch(' ');
+	putch('\b');
+}
+
+/*
+ * Read a string off the console. Support a few of the more useful
+ * common control characters. Do not include the terminating newline
+ * in the buffer passed back.
+ */
+void
+kgets(char *buf, size_t maxlen)
+{
+	size_t pos = 0;
+	int ch;
+
+	while (1) {
+		ch = getch();
+		if (ch=='\n' || ch=='\r') {
+			putch('\n');
+			break;
+		}
+
+		/* Only allow the normal 7-bit ascii */
+		if (ch>=32 && ch<127 && pos < maxlen-1) {
+			putch(ch);
+			buf[pos++] = ch;
+		}
+		else if ((ch=='\b' || ch==127) && pos>0) {
+			/* backspace */
+			backsp();
+			pos--;
+		}
+		else if (ch==3) {
+			/* ^C - return empty string */
+			putch('^');
+			putch('C');
+			putch('\n');
+			pos = 0;
+			break;
+		}
+		else if (ch==18) {
+			/* ^R - reprint input */
+			buf[pos] = 0;
+			kprintf("^R\n%s", buf);
+		}
+		else if (ch==21) {
+			/* ^U - erase line */
+			while (pos > 0) {
+				backsp();
+				pos--;
+			}
+		}
+		else if (ch==23) {
+			/* ^W - erase word */
+			while (pos > 0 && buf[pos-1]==' ') {
+				backsp();
+				pos--;
+			}
+			while (pos > 0 && buf[pos-1]!=' ') {
+				backsp();
+				pos--;
+			}
+		}
+		else {
+			beep();
+		}
+	}
+
+	buf[pos] = 0;
+}