From c1c9c0136625fdf262735abbb8712b8a629207b5 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Wed, 19 Feb 2020 22:58:34 +0100
Subject: [PATCH] BSB: Provisional parser and generator of packets

---
 test-bsb/gen.c   | 41 +++++++++++++++++++++++
 test-bsb/parse.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+)
 create mode 100644 test-bsb/gen.c
 create mode 100644 test-bsb/parse.c

diff --git a/test-bsb/gen.c b/test-bsb/gen.c
new file mode 100644
index 0000000..fb4fdbf
--- /dev/null
+++ b/test-bsb/gen.c
@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <stdint.h>
+
+typedef unsigned char byte;
+typedef unsigned int uint;
+typedef uint16_t u16;
+
+u16 crc_update(u16 crc, byte data)
+{
+	crc = crc ^ (data << 8);
+	for (uint i=0; i<8; i++) {
+		if (crc & 0x8000)
+			crc = (crc << 1) ^ 0x1021;
+		else
+			crc <<= 1;
+	}
+	return crc;
+}
+
+byte msg[] = {
+	0xdc,			// sync
+	0x80 | 0x42,		// src
+	0x00,			// dest
+	0x00,			// length (will be filled)
+	0x06,			// command
+	0x3d, 0x2e, 0x11, 0x25,
+};
+
+int main(void)
+{
+	msg[3] = sizeof(msg) + 2;
+
+	u16 crc = 0;
+	for (uint i=0; i < sizeof(msg); i++) {
+		printf("%02x ", msg[i]);
+		crc = crc_update(crc, msg[i]);
+	}
+	printf("%02x %02x\n", crc >> 8, crc & 0xff);
+
+	return 0;
+}
diff --git a/test-bsb/parse.c b/test-bsb/parse.c
new file mode 100644
index 0000000..bec15a1
--- /dev/null
+++ b/test-bsb/parse.c
@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+typedef unsigned char byte;
+typedef unsigned int uint;
+typedef uint16_t u16;
+
+uint rd(void)
+{
+	uint x;
+	if (scanf("%x", &x) == 1)
+		return x;
+	else {
+		puts("EOF");
+		exit(1);
+	}
+}
+
+u16 crc_update(u16 crc, byte data)
+{
+	crc = crc ^ (data << 8);
+	for (uint i=0; i<8; i++) {
+		if (crc & 0x8000)
+			crc = (crc << 1) ^ 0x1021;
+		else
+			crc <<= 1;
+	}
+	return crc;
+}
+
+int main(void)
+{
+	byte pkt[256];
+
+	for (;;) {
+		pkt[0] = rd();
+		if (pkt[0] != 0xdc) {
+			printf("# Bad sync: %02x\n", pkt[0]);
+			continue;
+		}
+
+		int len = 1;
+		while (len < 4 || len < pkt[3]) {
+			pkt[len++] = rd();
+		}
+
+		for (int i=0; i<len; i++)
+			printf("%02x ", pkt[i]);
+
+		u16 crc = 0;
+		for (int i=0; i<len; i++)
+			crc = crc_update(crc, pkt[i]);
+		if (crc) {
+			printf("[BAD CRC]\n");
+			continue;
+		}
+		len -= 2;
+
+		if (len < 9) {
+			printf("[TOO SHORT]\n");
+			continue;
+		}
+
+		printf("\n\t%02x -> %02x: ", pkt[1], pkt[2]);
+		switch (pkt[4]) {
+			case 2:
+				printf("INFO %04x:%04x =", (pkt[5]<<8) | pkt[6], (pkt[7]<<8) | pkt[8]);
+				for (int i=9; i<len; i++)
+					printf(" %02x", pkt[i]);
+				putchar('\n');
+				break;
+			case 6:
+				printf("GET %04x:%04x\n", (pkt[6]<<8) | pkt[5], (pkt[7]<<8) | pkt[8]);
+				break;
+			case 7:
+				printf("RET %04x:%04x =", (pkt[5]<<8) | pkt[6], (pkt[7]<<8) | pkt[8]);
+				for (int i=9; i<len; i++)
+					printf(" %02x", pkt[i]);
+				putchar('\n');
+				break;
+			default:
+				printf("??? type=%02x\n", pkt[4]);
+		}
+	}
+}
-- 
2.39.2