[GitHub] [trafficserver] bneradt commented on a diff in pull request #9485: Unit parser

["bneradt (via GitHub)" <gi...@apache.org>]

bneradt commented on code in PR #9485:
URL: https://github.com/apache/trafficserver/pull/9485#discussion_r1128445563


##########
include/tscpp/util/ts_unit_parser.h:
##########
@@ -0,0 +1,103 @@
+/** @file
+
+  Parse strings with units.
+
+  @section license License
+
+  Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.
+  See the NOTICE file distributed with this work for additional information regarding copyright
+  ownership.  The ASF licenses this file to you 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.
+*/
+
+#pragma once
+
+#include <cstdint>
+
+#include "swoc/Lexicon.h"
+#include "swoc/Errata.h"
+
+namespace ts
+{
+
+using swoc::TextView;
+using swoc::Lexicon;
+using swoc::Errata;
+using swoc::Rv;
+
+/** Parse a string that consists of counts and units.
+ *
+ * Give a set of units, each of which is a list of names and a multiplier, parse a string. The
+ * string contents must consist of (optional whitespace) with alternating counts and units,
+ * starting with a count. Each count is multiplied by the value of the subsequent unit. Optionally
+ * the parser can be set to allow counts without units, which are not multiplied.
+ *
+ * For example, if the units were [ "X", 10 ] , [ "L", 50 ] , [ "C", 100 ] , [ "M", 1000 ]
+ * then the following strings would be parsed as
+ *
+ * - "1X" : 10
+ * - "1L3X" : 80
+ * - "2C" : 200
+ * - "1M 4C 4X" : 1,440
+ * - "3M 5 C3 X" : 3,530
+ */
+class UnitParser
+{
+  using self_type = UnitParser; ///< Self reference type.
+public:
+  using value_type = uintmax_t;                 ///< Integral type returned.
+  using Units      = swoc::Lexicon<value_type>; ///< Unit definition type.
+
+  /// Symbolic name for setting whether units are required.
+  static constexpr bool UNITS_REQUIRED = true;
+  /// Symbolic name for setting whether units are required.
+  static constexpr bool UNITS_NOT_REQUIRED = false;
+
+  /** Constructor.
+   *
+   * @param units A @c Lexicon of unit definitions.
+   * @param unit_required_p Whether valid input requires units on all values.
+   */
+  UnitParser(Units &&units, bool unit_required_p = true) noexcept;
+
+  /** Set whether a unit is required.
+   *
+   * @param flag @c true if a unit is required, @c false if not.
+   * @return @a this.
+   */
+  self_type &unit_required(bool flag);
+
+  /** Parse a string.
+   *
+   * @param src Input string.
+   * @return The computed value if the input it valid, or an error report.

Review Comment:
   "it valid" -> "is valid"



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