rpc: enable passing decimals to AmountFromValue, add doxygen

src/rpc/util.cpp

@@ -74,12 +74,12 @@ void RPCTypeCheckObj(const UniValue& o,
     }
 }
 
-CAmount AmountFromValue(const UniValue& value)
+CAmount AmountFromValue(const UniValue& value, int decimals)
 {
     if (!value.isNum() && !value.isStr())
         throw JSONRPCError(RPC_TYPE_ERROR, "Amount is not a number or string");
     CAmount amount;
-    if (!ParseFixedPoint(value.getValStr(), 8, &amount))
+    if (!ParseFixedPoint(value.getValStr(), decimals, &amount))
         throw JSONRPCError(RPC_TYPE_ERROR, "Invalid amount");
     if (!MoneyRange(amount))
         throw JSONRPCError(RPC_TYPE_ERROR, "Amount out of range");

src/rpc/util.h

@@ -77,7 +77,14 @@ extern uint256 ParseHashO(const UniValue& o, std::string strKey);
 extern std::vector<unsigned char> ParseHexV(const UniValue& v, std::string strName);
 extern std::vector<unsigned char> ParseHexO(const UniValue& o, std::string strKey);
 
-extern CAmount AmountFromValue(const UniValue& value);
+/**
+ * Validate and return a CAmount from a UniValue number or string.
+ *
+ * @param[in] value     UniValue number or string to parse.
+ * @param[in] decimals  Number of significant digits (default: 8).
+ * @returns a CAmount if the various checks pass.
+ */
+extern CAmount AmountFromValue(const UniValue& value, int decimals = 8);
 
 using RPCArgList = std::vector<std::pair<std::string, UniValue>>;
 extern std::string HelpExampleCli(const std::string& methodname, const std::string& args);