Move plugins to external folder

applications/external/protoview/crc.c

@@ -0,0 +1,36 @@
+/* Copyright (C) 2022-2023 Salvatore Sanfilippo -- All Rights Reserved
+ * See the LICENSE file for information about the license. */
+
+#include <stdint.h>
+#include <stddef.h>
+
+/* CRC8 with the specified initialization value 'init' and
+ * polynomial 'poly'. */
+uint8_t crc8(const uint8_t* data, size_t len, uint8_t init, uint8_t poly) {
+    uint8_t crc = init;
+    size_t i, j;
+    for(i = 0; i < len; i++) {
+        crc ^= data[i];
+        for(j = 0; j < 8; j++) {
+            if((crc & 0x80) != 0)
+                crc = (uint8_t)((crc << 1) ^ poly);
+            else
+                crc <<= 1;
+        }
+    }
+    return crc;
+}
+
+/* Sum all the specified bytes modulo 256.
+ * Initialize the sum with 'init' (usually 0). */
+uint8_t sum_bytes(const uint8_t* data, size_t len, uint8_t init) {
+    for(size_t i = 0; i < len; i++) init += data[i];
+    return init;
+}
+
+/* Perform the bitwise xor of all the specified bytes.
+ * Initialize xor value with 'init' (usually 0). */
+uint8_t xor_bytes(const uint8_t* data, size_t len, uint8_t init) {
+    for(size_t i = 0; i < len; i++) init ^= data[i];
+    return init;
+}