hexdump method to speed runtime protocol debugging

src/utility.c

@@ -1,4 +1,7 @@
+#include <errno.h>
 #include <stdint.h>
+#include <stdio.h>
+#include <string.h>
 #include <unistd.h>
 
 #include "utility.h"
@@ -23,3 +26,28 @@ float poly_battery_level(const double terms[], const size_t numterms, uint16_t v
         percent = 0;
     return percent;
 }
+
+size_t hexdump(char* out, size_t out_size, unsigned char* data, size_t data_size)
+{
+    size_t i;
+    size_t used_buf = 0;
+    int rc;
+    for (i = 0; i < data_size; ++i) {
+        if (used_buf >= out_size) {
+            return 0;
+        }
+        rc = snprintf(out + used_buf, out_size - used_buf, "0x%02X ", data[i]);
+        if (rc < 0) {
+#ifdef _WIN32
+            printf("hexdump formatting failed\n");
+#elif __APPLE__
+            printf("%s\n", strerror(errno));
+#else //__linux__
+            printf("%s\n", strerror_l(errno, NULL));
+#endif
+        } else {
+            used_buf += rc;
+        }
+    }
+    return i;
+}

src/utility.h

@@ -21,3 +21,14 @@ int map(int x, int in_min, int in_max, int out_min, int out_max);
  * @return battery level in percent
  */
 float poly_battery_level(const double terms[], const size_t numterms, uint16_t voltage);
+
+/**
+ * @brief Helper function used during debugging for printing out binary data
+ *
+ * @param out buffer to write output example char tmp[128];
+ * @param out_size sizeof(out)
+ * @param data data to be represented as hex string
+ * @param data_size sizeof(data) or sizeof(*data);
+ * @return 0 on failure or filled size of out
+ */
+size_t hexdump(char* out, size_t out_size, unsigned char* data, size_t data_size);