initial import of Osmocom TETRA phy and lower MAC code

src/float_to_bits.c

@@ -0,0 +1,117 @@
+/* Convert floating point symbols in the range +3/-3 to hard bits,
+ * in the 1-bit-per-byte format */
+
+/* (C) 2011 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+
+#include <stdint.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+static int process_sym_fl(float offset, float fl)
+{
+	int ret;
+	fl += offset;
+
+	/* very simplistic scheme */
+	if (fl > 2)
+		ret = 3;
+	else if (fl > 0)
+		ret = 1;
+	else if (fl < -2)
+		ret = -3;
+	else
+		ret = -1;
+
+	return ret;
+}
+
+static void sym_int2bits(int sym, uint8_t *ret)
+{
+	switch (sym) {
+	case -3:
+		ret[0] = 1;
+		ret[1] = 1;
+		break;
+	case 1:
+		ret[0] = 0;
+		ret[1] = 0;
+		break;
+	//case -1:
+	case 3:
+		ret[0] = 0;
+		ret[1] = 1;
+		break;
+	//case 3:
+	case -1:
+		ret[0] = 1;
+		ret[1] = 0;
+		break;
+	}
+}
+
+int main(int argc, char **argv)
+{
+	int fd, fd_out;
+
+	if (argc < 3) {
+		fprintf(stderr, "Usage: %s <infile> <outfile>\n", argv[0]);
+		exit(2);
+	}
+
+	fd = open(argv[1], O_RDONLY);
+	if (fd < 0) {
+		perror("open infile");
+		exit(1);
+	}
+	fd_out = creat(argv[2], 0660);
+	if (fd_out < 0) {
+		perror("open outfile");
+		exit(1);
+	}
+	while (1) {
+		int rc;
+		float fl;
+		uint8_t bits[2];
+		rc = read(fd, &fl, sizeof(fl));
+		if (rc < 0) {
+			perror("read");
+			exit(1);
+		} else if (rc == 0)
+			break;
+		rc = process_sym_fl(0.3f, fl);
+		sym_int2bits(rc, bits);
+		//printf("%2d %1u %1u  %f\n", rc, bits[0], bits[1], fl);
+		//printf("%1u%1u", bits[0], bits[1]);
+
+		rc = write(fd_out, bits, 2);
+		if (rc < 0) {
+			perror("write");
+			exit(1);
+		} else if (rc == 0)
+			break;
+	}
+	exit(0);
+}