init/shell: basic readline()

1 files changed, 44 insertions, 0 deletions

diff --git a/src/init/shell.c b/src/init/shell.c
new file mode 100644
index 0000000..d61f46f
--- /dev/null
+++ b/src/init/shell.c
@@ -0,0 +1,44 @@
+#include <init/shell.h>
+#include <init/stdlib.h>
+#include <shared/syscalls.h>
+
+#define PROMPT "$ "
+
+static int tty_fd = 0; // TODO put in stdlib
+
+static int readline(char *buf, size_t max) {
+	char c;
+	size_t pos = 0;
+	while (_syscall_read(tty_fd, &c, 1, 0)) {
+		switch (c) {
+			case '\b':
+			case 0x7f:
+				/* for some reason backspace outputs 0x7f (DEL) */
+				if (pos != 0) {
+					printf("\b \b");
+					pos--;
+				}
+				break;
+			case '\r':
+				printf("\n");
+				buf[pos++] = '\0';
+				return pos;
+			default:
+				if (pos < max) {
+					_syscall_write(tty_fd, &c, 1, 0);
+					buf[pos] = c;
+					pos++;
+				}
+		}
+	}
+	return -1; // error
+}
+
+void shell_loop(void) {
+	static char cmd[256];
+	for (;;) {
+		printf(PROMPT);
+		readline(cmd, 256);
+		printf("  %s\n", cmd);
+	}
+}