[9fans] Small program "PlanKey" (paraphrase of DOSKey)

["pavel.klinkovsky@gmail.com" <pavel.klinkovsky@gmail.com>]

Hi all,

In Plan9 I missed the simple way to repeat previous (or previous of
previous etc.) command in the terminal.
I prepared a very small (an stupid) program to allow that.

Compile the following source code and run it in that way:
8.out | rc -i

You can insert the commands, and if you want to walk through the
"history", just press CTRL+K (backward) or CTRL+L (foreward).

That is all, folks. ;-)

Pavel


#include <u.h>
#include <libc.h>

enum
{
	KCtrlD = 0x04,
	KCtrlK = 0x0B,
	KCtrlL = 0x0C,
	KDelete = 0x7F,

	MaxLen = 128,
	MaxDepth = 10
};

struct Line
{
	int len;
	char buf[MaxLen];
};
typedef struct Line Line;

void
main(void)
{
	// Console control file descriptor
	int cfd;
	// End flag
	int end = 0;
	// Actual read character
	char c;
	// Array of BackSpaces
	char bs[MaxLen];
	// Array of Lines
	Line line[MaxDepth];
	// Index of actual line
	int act = 0;
	// Index of stored line
	int stored = 0;

	memset(bs, '\b', sizeof(bs));
	memset(line, 0, sizeof(line));

	cfd = open("/dev/consctl", OWRITE);
	if (cfd < 0)
		sysfatal("%r");
	write(cfd, "rawon", 5);

	while (!end) {
		if (read(0, &c, sizeof(c)) < 0)
			sysfatal("%r");

		switch (c) {
		case KCtrlD:
		case KDelete:
			end++;
			break;

		case '\b':
			if (line[act].len > 0) {
				line[act].len--;
				write(2, &c, sizeof(c));
			}
			break;

		case '\n':
			if (line[act].len > 0)
				write(1, line[act].buf, line[act].len);
			write(1, &c, sizeof(c));
			write(2, &c, sizeof(c));
			act = stored = (act + 1) % MaxDepth;
			line[act].len = 0;
			break;

		case KCtrlK:
			write(2, bs, line[act].len);
			stored = (stored + MaxDepth - 1) % MaxDepth;
			line[act] = line[stored];
			write(2, line[act].buf, line[act].len);
			break;

		case KCtrlL:
			write(2, bs, line[act].len);
			stored = (stored + 1) % MaxDepth;
			line[act] = line[stored];
			write(2, line[act].buf, line[act].len);
			break;

		case -0x11:
			read(0, &c, sizeof(c));
			read(0, &c, sizeof(c));
			break;

		default:
			if (line[act].len < MaxLen) {
				line[act].buf[line[act].len++] = c;
				write(2, &c, sizeof(c));
			}
			break;
		}
	}

	close(cfd);

	exits(nil);
}