From: Keith Packard <keithp@keithp.com>
Date: Mon, 2 Oct 2017 23:58:53 +0000 (-0700)
Subject: altoslib: Allow early bail-out on bad telemetry CRC
X-Git-Tag: 1.8.3~1^2~81
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=c6be13e8ef80e5afc836e04cbfe4cb17631540e4

altoslib: Allow early bail-out on bad telemetry CRC

Check the CRC status in the packet before creating a new telemetry
object.

Signed-off-by: Keith Packard <keithp@keithp.com>
---

diff --git a/altoslib/AltosTelemetry.java b/altoslib/AltosTelemetry.java
index fe536c6a..a374519d 100644
--- a/altoslib/AltosTelemetry.java
+++ b/altoslib/AltosTelemetry.java
@@ -28,8 +28,11 @@ public abstract class AltosTelemetry implements AltosDataProvider {
 	int[]	bytes;
 
 	/* All telemetry packets have these fields */
-	public int rssi() { return AltosConvert.telem_to_rssi(AltosLib.int8(bytes, bytes.length - 3)); }
-	public int status() { return AltosLib.uint8(bytes, bytes.length - 2); }
+	static public int rssi(int[] bytes) { return AltosConvert.telem_to_rssi(AltosLib.int8(bytes, bytes.length - 3)); }
+	static public int status(int[] bytes) { return AltosLib.uint8(bytes, bytes.length - 2); }
+
+	public int rssi() { return rssi(bytes); }
+	public int status() { return status(bytes); }
 
 	/* All telemetry packets report these fields in some form */
 	public abstract int serial();
@@ -96,6 +99,9 @@ public abstract class AltosTelemetry implements AltosDataProvider {
 		if (!cksum(bytes))
 			throw new ParseException(String.format("invalid line \"%s\"", hex), 0);
 
+		if ((status(bytes) & PKT_APPEND_STATUS_1_CRC_OK) == 0)
+			throw new AltosCRCException(rssi(bytes));
+
 		/* length, data ..., rssi, status, checksum -- 4 bytes extra */
 		switch (bytes.length) {
 		case AltosLib.ao_telemetry_standard_len + 4: