From a39228c45393175bbb866d5681e80e5cd049949a Mon Sep 17 00:00:00 2001
From: murata <ma2maru@gmail.com>
Date: Fri, 12 Jul 2019 10:52:37 +0200
Subject: [PATCH] AP_Common: Make hexadecimal character number conversion
 method common

---
 libraries/AP_Common/AP_Common.cpp | 34 +++++++++++++++++++++++++++++++
 libraries/AP_Common/AP_Common.h   |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/libraries/AP_Common/AP_Common.cpp b/libraries/AP_Common/AP_Common.cpp
index 217841cb39..94cdc4f10f 100644
--- a/libraries/AP_Common/AP_Common.cpp
+++ b/libraries/AP_Common/AP_Common.cpp
@@ -36,3 +36,37 @@ bool is_bounded_int32(int32_t value, int32_t lower_bound, int32_t upper_bound)
     return false;
 
 }
+
+/**
+ * return the numeric value of an ascii hex character
+ *
+ * @param [in]  a   Hexa character
+ * @param [out] res uint8 value
+ * @retval true  Conversion OK
+ * @retval false Input value error
+ * @Note Input character is 0-9, A-F, a-f
+ *  A 0x41, a 0x61, 0 0x30
+ */
+bool hex_to_uint8(uint8_t a, uint8_t &res)
+{
+    uint8_t nibble_low  = a & 0xf;
+
+    switch (a & 0xf0) {
+    case 0x30:  // 0-
+        if (nibble_low > 9) {
+            return false;
+        }
+        res = nibble_low;
+        break;
+    case 0x40:  // uppercase A-
+    case 0x60:  // lowercase a-
+        if (nibble_low == 0 || nibble_low > 6) {
+            return false;
+        }
+        res = nibble_low + 9;
+        break;
+    default:
+        return false;
+    }
+    return true;
+}
diff --git a/libraries/AP_Common/AP_Common.h b/libraries/AP_Common/AP_Common.h
index d6fb0f5890..8883bd164d 100644
--- a/libraries/AP_Common/AP_Common.h
+++ b/libraries/AP_Common/AP_Common.h
@@ -133,3 +133,5 @@ template<typename s, size_t t> struct assert_storage_size {
   False otherwise.
 */
 bool is_bounded_int32(int32_t value, int32_t lower_bound, int32_t upper_bound);
+
+bool hex_to_uint8(uint8_t a, uint8_t &res);  // return the uint8 value of an ascii hex character