Split utils function from main

src/utils.c

@@ -0,0 +1,28 @@
+/*******************************************************************************
+*   Ledger Ethereum App
+*   (c) 2016-2019 Ledger
+*
+*  Licensed under the Apache License, Version 2.0 (the "License");
+*  you may not use this file except in compliance with the License.
+*  You may obtain a copy of the License at
+*
+*      http://www.apache.org/licenses/LICENSE-2.0
+*
+*  Unless required by applicable law or agreed to in writing, software
+*  distributed under the License is distributed on an "AS IS" BASIS,
+*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+*  See the License for the specific language governing permissions and
+*  limitations under the License.
+********************************************************************************/
+
+static const unsigned char hex_digits[] = {'0', '1', '2', '3', '4', '5', '6', '7',
+                                           '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
+
+void array_hexstr(char *strbuf, const void *bin, unsigned int len) {
+    while (len--) {
+        *strbuf++ = hex_digits[((*((char *)bin)) >> 4) & 0xF];
+        *strbuf++ = hex_digits[(*((char *)bin)) & 0xF];
+        bin = (const void *)((unsigned int)bin + 1);
+    }
+    *strbuf = 0; // EOS
+}