Add mnimalistic command line interface "command.c"

This is a very simplistic command line interface parser which
various parts of the code can use to register textual commands
on the debug UART.

Change-Id: I2d289228fb97ecde5602e9756f3d7c51fa65a3b7
diff --git a/sysmoOCTSIM/command.c b/sysmoOCTSIM/command.c
new file mode 100644
index 0000000..9502f05
--- /dev/null
+++ b/sysmoOCTSIM/command.c
@@ -0,0 +1,101 @@
+#include <string.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include <utils.h>
+
+#include "atmel_start.h"
+#include "command.h"
+
+struct cmd_state {
+	const char *prompt;
+	char buf[128];
+	unsigned int buf_idx;
+	const struct command_fn *cmd[32];
+	unsigned int cmd_idx;
+};
+
+static struct cmd_state g_cmds;
+
+int command_register(const struct command_fn *cmd)
+{
+	if (g_cmds.cmd_idx >= ARRAY_SIZE(g_cmds.cmd))
+		return -1;
+	g_cmds.cmd[g_cmds.cmd_idx++] = cmd;
+	return 0;
+}
+
+DEFUN(help, help_cmd, "help", "Print command reference")
+{
+	unsigned int i;
+	printf("Help:\r\n");
+	printf(" Command          Help\r\n");
+	printf(" ---------------- ----\r\n");
+	for (i = 0; i < g_cmds.cmd_idx; i++)
+		printf(" %-16s %s\r\n", g_cmds.cmd[i]->command, g_cmds.cmd[i]->help);
+}
+
+static void cmd_execute()
+{
+	char *argv[16];
+	unsigned int i;
+	int argc = 0;
+	char *cur;
+
+	printf("\r\n");
+	memset(argv, 0, sizeof(argv));
+
+	for (cur = strtok(g_cmds.buf, " "); cur; cur = strtok(NULL, " ")) {
+		if (argc >= ARRAY_SIZE(argv))
+			break;
+		argv[argc++] = cur;
+	}
+
+	for (i = 0; i < g_cmds.cmd_idx; i++) {
+		if (!strcmp(g_cmds.cmd[i]->command, argv[0])) {
+			g_cmds.cmd[i]->fn(argc, argv);
+			return;
+		}
+	}
+	printf("Unknown command: '%s'\r\n", argv[0]);
+}
+
+static void cmd_buf_reset(void)
+{
+	memset(g_cmds.buf, 0, sizeof(g_cmds.buf));
+	g_cmds.buf_idx = 0;
+}
+
+static void cmd_buf_append(char c)
+{
+	g_cmds.buf[g_cmds.buf_idx++] = c;
+}
+
+void command_try_recv(void)
+{
+	unsigned int i = 0;
+
+	/* yield CPU after maximum of 10 received characters */
+	while (usart_sync_is_rx_not_empty(&UART_debug) && (i < 10)) {
+		int c = getchar();
+		if (c < 0)
+			return;
+		putchar(c);
+		if (c == '\r' || c == '\n' || g_cmds.buf_idx >= sizeof(g_cmds.buf)-1) {
+			cmd_execute();
+			cmd_buf_reset();
+			printf(g_cmds.prompt);
+			return;
+		}
+		/* append character */
+		cmd_buf_append(c);
+
+		i++;
+	}
+}
+
+void command_init(const char *prompt)
+{
+	g_cmds.prompt = prompt;
+	command_register(&help_cmd);
+}