--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/pcm-br/xconn.c	Wed Aug 28 05:00:38 2024 +0000
@@ -0,0 +1,52 @@
+/*
+ * The two functions in this module get called from Osmocom select loop
+ * whenever each timeslot data socket to osmo-e1d is ready for reading;
+ * the cross-connect of the two timeslots is implemented here.
+ */
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <osmocom/core/select.h>
+
+#include "globals.h"
+
+uint8_t readbuf_a[160], readbuf_b[160];
+FILE *rec_file_a, *rec_file_b;
+
+int tsa_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	int rc;
+
+	rc = read(tsa_fd, readbuf_a, 160);
+	if (rc != 160) {
+		fprintf(stderr,
+			"error: read from ts A returned %d instead of 160\n",
+			rc);
+		exit(1);
+	}
+	if (rec_file_a)
+		fwrite(readbuf_a, 1, 160, rec_file_a);
+	write(tsb_fd, readbuf_a, 160);
+	return 0;
+}
+
+int tsb_fd_cb(struct osmo_fd *ofd, unsigned int what)
+{
+	int rc;
+
+	rc = read(tsb_fd, readbuf_b, 160);
+	if (rc != 160) {
+		fprintf(stderr,
+			"error: read from ts B returned %d instead of 160\n",
+			rc);
+		exit(1);
+	}
+	if (rec_file_b)
+		fwrite(readbuf_b, 1, 160, rec_file_b);
+	write(tsa_fd, readbuf_b, 160);
+	return 0;
+}