Create StringOrdinal to allow placement of strings in sorted lists

chrome/common/string_index.h

+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_STRING_INDEX_H_
+#define CHROME_COMMON_STRING_INDEX_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+
+namespace StringIndex {

[akalin, 2011/10/12 18:50:14]

static functions in a namespace isn't a great interface.  I feel like we're
going in circles, so I'll just outline what I think would be a workable
interface:

class StringIndex {
 public:
  // Creates a valid StringIndex if str matches [A-Z]*[B-Z]
  StringIndex(const std::string& str);

  // Invalid StringIndex.
  StringIndex();

  bool IsValid() const;

  bool LessThan(const StringIndex& other) const;

  // LessThan(other) must hold.  Returns a StringIndex x s.t. LessThan(x) holds,
and x.LessThan(other) holds.
  StringIndex CreateBetween(const StringIndex& other) const;

  // Returns a StringIndex x s.t. x.LessThan(*this) holds.
  StringIndex CreateBefore() const;

  // Returns a StringIndex x s.t. LessThan(x) holds.
  StringIndex CreateAfter() const;

  std::string ToString() const;
};

+
+// Create a string that is lexigraphically greater than start and
+// lexigraphically less than end, ideally the string will be a
+// middle value between the two strings.
+// Use an empty string to signify no ending or starting limit.
+// The range of values returns from here are (A..K*).
+std::string CreateStringBetween(const std::string& start,
+                                const std::string& end);
+
+// Used to add kMidDigitValue to the value at position index because
+// the previous index values had an odd difference, so their correct
+// middle value is x and a half, so we are inserting the half here.

[akalin, 2011/10/12 18:50:14]

why is this public?

+void AddHalf(size_t position, std::string& value);
+
+// Remove all trailing zeros from a value as they provide no value.
+std::string RemoveTrailingZeros(const std::string& value);

[akalin, 2011/10/12 18:50:14]

why is this public?

+
+// Ensure that given string matches the format with asserts.
+// The format is [A-Z][B-Z]*
+void ValidateString(const std::string& value);
+
+static const char kZeroDigit = 'A';

[akalin, 2011/10/12 18:50:14]

why are these in the header?

+static const char kMinDigit = 'B';
+static const char kMidDigit = 'N';
+static const char kMaxDigit = 'Z';
+
+static const int kMaxDigitValue = kMaxDigit - kZeroDigit;
+static const int kMidDigitValue = kMidDigit - kZeroDigit;
+static const int kFullDigitValue = (kMaxDigit + 1) - kZeroDigit;
+}
+#endif  // CHROME_COMMON_STRING_INDEX_H_