1 files changed, 72 insertions, 0 deletions
diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..3653252
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,72 @@
+#include <assert.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include "types.h"
+#include "instset.h"
+#include "common.h"
+
+static boolean g_is_init;
+static int g_file_desc;
+
+void _sal_comm_init(string pipe)
+{
+	/* Initialize the common pipe. This module is the only one on Salis that
+	makes use of Linux specific headers and types. If you want, feel free to
+	port this code into other platforms (should be easy). If you do so, let me
+	know and we can incorporate it into the Salis repository.
+	*/
+	assert(!g_is_init);
+	mkfifo(pipe, 0666);
+	g_is_init = TRUE;
+
+	/* It's important to open the FIFO file in non-blocking mode, or else the
+	simulators might halt if the pipe becomes empty.
+	*/
+	g_file_desc = open(pipe, O_RDWR | O_NONBLOCK);
+	assert(g_file_desc != -1);
+}
+
+void _sal_comm_quit(void)
+{
+	/* Close the common pipe FIFO file from within this instance. An empty pipe
+	file will remain unless it gets manually deleted.
+	*/
+	assert(g_is_init);
+	close(g_file_desc);
+	g_is_init = FALSE;
+	g_file_desc = 0;
+}
+
+void _sal_comm_send(uint8 inst)
+{
+	/* Send a single byte (instruction) to the common pipe. This function is
+	called by processes that execute the SEND instruction. Hopefully, some of
+	them 'learn' to use this as an advantage.
+
+	In the future, I want to make the common pipe able to communicate across
+	local networks (LANs) and over the Internet.
+	*/
+	assert(g_is_init);
+	assert(sal_is_inst(inst));
+	write(g_file_desc, &inst, 1);
+}
+
+uint8 _sal_comm_receive(void)
+{
+	/* Receive a single byte (instruction) from the common pipe. This function
+	is called by processes that execute the RCVE instruction. If the pipe is
+	empty, this function returns the NOP0 instruction.
+	*/
+	uint8 inst;
+	ssize_t res;
+	assert(g_is_init);
+	res = read(g_file_desc, &inst, 1);
+
+	if (res) {
+		assert(sal_is_inst(inst));
+		return inst;
+	} else {
+		return NOP0;
+	}
+}