Bugfix/read range trend log buffer (#947)

* Fixed ReadRange app to read and pretty-print a Trend Log log-buffer

src/bacnet/bacdcode.c

@@ -1274,6 +1274,41 @@ int bacnet_boolean_application_decode(
     return apdu_len;
 }
 
+/**
+ * @brief Decode a context boolean value.
+ * @param apdu  Pointer to the encode buffer.
+ * @param apdu_size  Number of bytes in the buffer.
+ * @param boolean_value  Pointer to a boolean variable
+ * @note The Boolean datatype differs from the other datatypes
+ * in that the encoding of a context-tagged Boolean value is not the
+ * same as the encoding of an application-tagged Boolean value.
+ * This is done so that the application-tagged value may be encoded
+ * in a single octet, without a contents octet. While this same encoding
+ * could have been used for the context-tagged case, doing
+ * so would require that the context be known in order to distinguish
+ * between a length or a value in the length/value/type field.
+ * This was considered to be undesirable.
+ * @return number of bytes decoded, or 0 if errors occur
+ */
+int bacnet_boolean_context_value_decode(
+    const uint8_t *apdu, uint32_t apdu_size, bool *boolean_value)
+{
+    int len = 0;
+
+    if (apdu && (apdu_size > 0)) {
+        if (boolean_value) {
+            if (apdu[0]) {
+                *boolean_value = true;
+            } else {
+                *boolean_value = false;
+            }
+        }
+        len = 1;
+    }
+
+    return len;
+}
+
 /**
  * @brief Decode the Boolean Value when context encoded
  * From clause 20.2.3 Encoding of a Boolean Value
@@ -1314,11 +1349,10 @@ int bacnet_boolean_context_decode(
     if (len > 0) {
         if (tag.context && (tag.number == tag_value)) {
             apdu_len = len;
-            if (apdu_len < apdu_size) {
-                if (boolean_value) {
-                    *boolean_value = decode_context_boolean(&apdu[apdu_len]);
-                }
-                apdu_len++;
+            len = bacnet_boolean_context_value_decode(
+                &apdu[apdu_len], apdu_size - apdu_len, boolean_value);
+            if (len > 0) {
+                apdu_len += len;
             } else {
                 apdu_len = BACNET_STATUS_ERROR;
             }