From 3f730a8a94b4f759ae64fb96b183aa94947cd922 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Tue, 27 Jun 2023 00:02:15 +1000
Subject: [PATCH] AP_Math: add crc_sum_of_bytes

sums the values of the bytes in a buffer and returns that sum modulus 256
---
 libraries/AP_Math/crc.cpp | 11 +++++++++++
 libraries/AP_Math/crc.h   |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/libraries/AP_Math/crc.cpp b/libraries/AP_Math/crc.cpp
index ff320588ff..0b283b0515 100644
--- a/libraries/AP_Math/crc.cpp
+++ b/libraries/AP_Math/crc.cpp
@@ -598,3 +598,14 @@ uint8_t parity(uint8_t byte)
 
     return p;
 }
+
+// sums the bytes in the supplied buffer, returns that sum mod 256
+// (i.e. shoved into a uint8_t)
+uint8_t crc_sum_of_bytes(uint8_t *data, uint16_t count)
+{
+    uint8_t ret = 0;
+    for (uint32_t i=0; i<count; i++) {
+        ret += data[i];
+    }
+    return ret;
+}
diff --git a/libraries/AP_Math/crc.h b/libraries/AP_Math/crc.h
index cf994a5c23..b0d3ceccce 100644
--- a/libraries/AP_Math/crc.h
+++ b/libraries/AP_Math/crc.h
@@ -61,3 +61,7 @@ uint64_t crc_crc64(const uint32_t *data, uint16_t num_words);
 // return the parity of byte - "1" if there is an odd number of bits
 // set, "0" if there is an even number of bits set
 uint8_t parity(uint8_t byte);
+
+// sums the bytes in the supplied buffer, returns that sum mod 256
+// (i.e. shoved into a uint8_t)
+uint8_t crc_sum_of_bytes(uint8_t *data, uint16_t count);