V.27ter Modem emulation (partly)

2020-02-22 21:07:00 +01:00
parent 5070bc70bd
commit 6a18c924fb
12 changed files with 946 additions and 2 deletions
--- a/src/test/test_v27scrambler.c
+++ b/src/test/test_v27scrambler.c
@@ -0,0 +1,133 @@
+#include "stdio.h"
+#include "stdint.h"
+#include "string.h"
+#include "../libv27/scrambler.h"
+
+static int show_bin(uint8_t *data1, uint8_t *data2, int len)
+{
+	int i, j, error = 0;;
+	uint8_t bit1, bit2;
+
+	for (i = 0; i < len; i++) {
+		printf(".");
+		for (j = 0; j < 8; j++) {
+			bit1 = (data1[i] >> j) & 1;
+			bit2 = (data2[i] >> j) & 1;
+			if (bit1 == bit2)
+				printf("%d", bit1);
+			else {
+				printf("X");
+				error++;
+			}
+		}
+	}
+
+	printf("\n");
+
+	return error;
+}
+
+static int check_repetition(uint8_t *data, int len, int repeat, int start)
+{
+	int i;
+	uint8_t b1, b2;
+
+	for (i = start; i < (len * 8 - repeat); i++) {
+		b1 = (data[i >> 3] >> (i & 7)) & 1;
+		b2 = (data[(i+repeat) >> 3] >> ((i+repeat) & 7)) & 1;
+		if (b1 != b2)
+			return i - start + repeat;
+	}
+
+	return 0;
+}
+
+int main(void)
+{
+	v27scrambler_t scram, descram;
+
+	char message[] = "Jolly Roger~~~~";
+	int len = strlen(message);
+	uint8_t data[len];
+	int ret;
+
+	printf("Message: %s\n", message);
+
+	memcpy(data, message, len);
+	show_bin(data, (uint8_t *)message, len);
+
+	v27_scrambler_init(&scram, 1, 0);
+	v27_scrambler_block(&scram, data, len);
+
+	printf("Scrambled:\n");
+	show_bin(data, data, len);
+
+	v27_scrambler_init(&descram, 1, 1);
+	v27_scrambler_block(&descram, data, len);
+	
+	printf("Descramble without corruption?\n");
+
+	ret = show_bin(data, (uint8_t *)message, len);
+	if (ret) {
+		printf("Descrambling failed!\n");
+		return 1;
+	}
+	printf("Yes!\n");
+
+	printf("\n");
+
+	v27_scrambler_init(&scram, 1, 0);
+	v27_scrambler_block(&scram, data, len);
+
+	data[0] = 'B';
+	data[1] = 'U';
+	data[2] = 'G';
+
+	v27_scrambler_init(&descram, 1, 1);
+	v27_scrambler_block(&descram, data, len);
+	
+	printf("Descramble with 3 bytes corruption: (should fix itself after 4 bytes)\n");
+
+	show_bin(data, (uint8_t *)message, len);
+
+	printf("\n");
+
+	printf("Descramble a scrambled sequence of 8 bit repetitions with V.27: 01111110\n");
+
+	memset(data, 0x7e, len);
+
+	v27_scrambler_init(&descram, 0, 1);
+	v27_scrambler_block(&descram, data, len);
+
+	show_bin(data, (uint8_t *)data, len);
+
+	/* note at position 6 we have no more change towards 8 bit offset */
+	ret = check_repetition(data, len, 8, 6);
+	if (ret) {
+		printf("Theres is a change of repetition after %d bits after start %d, please fix!\n", ret, 6);
+		return 1;
+	}
+	printf("Repetition not detected, good!\n");
+	
+	printf("\n");
+
+	printf("Descramble a scrambled sequence of 8 bit repetitions with V.27bis/ter: 01111110\n");
+
+	memset(data, 0x7e, len);
+
+	v27_scrambler_init(&descram, 1, 1);
+	v27_scrambler_block(&descram, data, len);
+
+	show_bin(data, (uint8_t *)data, len);
+
+	/* note at position 6 we have no more change towards 8 bit offset */
+	ret = check_repetition(data, len, 8, 6);
+	if (ret != 34) {
+		printf("Theres is NO change of repetition after 34 bits, but after %d bits, which should not happen!\n", ret);
+		return 1;
+	}
+	printf("Repetition detected after %d bits from start %d, good!\n", ret, 6);
+	
+	return 0;
+}
+