[Sync] Move //sync to //components/sync.

sync/internal_api/public/base/ordinal.h

Index: sync/internal_api/public/base/ordinal.h
diff --git a/sync/internal_api/public/base/ordinal.h b/sync/internal_api/public/base/ordinal.h
deleted file mode 100644
index 81798a4ea8d348185727dddb97d0145c1f3f1a56..0000000000000000000000000000000000000000
--- a/sync/internal_api/public/base/ordinal.h
+++ /dev/null
@@ -1,489 +0,0 @@
-// Copyright (c) 2012 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 SYNC_INTERNAL_API_PUBLIC_BASE_ORDINAL_H_
-#define SYNC_INTERNAL_API_PUBLIC_BASE_ORDINAL_H_
-
-#include <stdint.h>
-
-#include <algorithm>
-#include <cstddef>
-#include <string>
-
-#include "base/json/string_escape.h"
-#include "base/logging.h"
-
-namespace syncer {
-
-// An Ordinal<T> is an object that can be used for ordering. The
-// Ordinal<T> class has an unbounded dense strict total order, which
-// mean for any Ordinal<T>s a, b and c:
-//
-//  - a < b and b < c implies a < c (transitivity);
-//  - exactly one of a < b, b < a and a = b holds (trichotomy);
-//  - if a < b, there is a Ordinal<T> x such that a < x < b (density);
-//  - there are Ordinals<T> x and y such that x < a < y (unboundedness).
-//
-// This means that when Ordinal<T> is used for sorting a list, if any
-// item changes its position in the list, only its Ordinal<T> value
-// has to change to represent the new order, and all the other values
-// can stay the same.
-//
-// An Ordinal<T> is internally represented as an array of bytes, so it
-// can be serialized to and deserialized from disk.
-//
-// The Traits class should look like the following:
-//
-//   // Don't forget to #include <stdint.h> and <stddef.h>.
-//   struct MyOrdinalTraits {
-//     // There must be at least two distinct values greater than kZeroDigit
-//     // and less than kMaxDigit.
-//     static const uint8_t kZeroDigit = '0';
-//     static const uint8_t kMaxDigit = '9';
-//     // kMinLength must be positive.
-//     static const size_t kMinLength = 1;
-//   };
-//
-// An Ordinal<T> is valid iff its corresponding string has at least
-// kMinLength characters, does not contain any characters less than
-// kZeroDigit or greater than kMaxDigit, is not all zero digits, and
-// does not have any unnecessary trailing zero digits.
-//
-// Note that even if the native char type is signed, strings still
-// compare as if their they are unsigned.  (This is explicitly in
-// C++11 but not in C++98, even though all implementations do so
-// anyway in practice.)  Thus, it is safe to use any byte range for
-// Ordinal<T>s.
-template <typename Traits>
-class Ordinal {
- public:
-  // Functors for use with STL algorithms and containers.
-  class LessThanFn {
-   public:
-    LessThanFn();
-
-    bool operator()(const Ordinal<Traits>& lhs,
-                    const Ordinal<Traits>& rhs) const;
-  };
-
-  class EqualsFn {
-   public:
-    EqualsFn();
-
-    bool operator()(const Ordinal<Traits>& lhs,
-                    const Ordinal<Traits>& rhs) const;
-  };
-
-  // Creates an Ordinal from the given string of bytes. The Ordinal
-  // may be valid or invalid.
-  explicit Ordinal(const std::string& bytes);
-
-  // Creates an invalid Ordinal.
-  Ordinal();
-
-  // Creates a valid initial Ordinal. This is called to create the first
-  // element of Ordinal list (i.e. before we have any other values we can
-  // generate from).
-  static Ordinal CreateInitialOrdinal();
-
-  // Returns true iff this Ordinal is valid.  This takes constant
-  // time.
-  bool IsValid() const;
-
-  // Returns true iff |*this| == |other| or |*this| and |other|
-  // are both invalid.
-  bool EqualsOrBothInvalid(const Ordinal& other) const;
-
-  // Returns a printable string representation of the Ordinal suitable
-  // for logging.
-  std::string ToDebugString() const;
-
-  // All remaining functions can only be called if IsValid() holds.
-  // It is an error to call them if IsValid() is false.
-
-  // Order-related functions.
-
-  // Returns true iff |*this| < |other|.
-  bool LessThan(const Ordinal& other) const;
-
-  // Returns true iff |*this| > |other|.
-  bool GreaterThan(const Ordinal& other) const;
-
-  // Returns true iff |*this| == |other| (i.e. |*this| < |other| and
-  // |other| < |*this| are both false).
-  bool Equals(const Ordinal& other) const;
-
-  // Given |*this| != |other|, returns a Ordinal x such that
-  // min(|*this|, |other|) < x < max(|*this|, |other|). It is an error
-  // to call this function when |*this| == |other|.
-  Ordinal CreateBetween(const Ordinal& other) const;
-
-  // Returns a Ordinal |x| such that |x| < |*this|.
-  Ordinal CreateBefore() const;
-
-  // Returns a Ordinal |x| such that |*this| < |x|.
-  Ordinal CreateAfter() const;
-
-  // Returns the string of bytes representing the Ordinal.  It is
-  // guaranteed that an Ordinal constructed from the returned string
-  // will be valid.
-  std::string ToInternalValue() const;
-
-  // Use of copy constructor and default assignment for this class is allowed.
-
-  // Constants for Ordinal digits.
-  static const uint8_t kZeroDigit = Traits::kZeroDigit;
-  static const uint8_t kMaxDigit = Traits::kMaxDigit;
-  static const size_t kMinLength = Traits::kMinLength;
-  static const uint8_t kOneDigit = kZeroDigit + 1;
-  static const uint8_t kMidDigit = kOneDigit + (kMaxDigit - kOneDigit) / 2;
-  static const unsigned int kMidDigitValue = kMidDigit - kZeroDigit;
-  static const unsigned int kMaxDigitValue = kMaxDigit - kZeroDigit;
-  static const unsigned int kRadix = kMaxDigitValue + 1;
-
-  static_assert(kOneDigit > kZeroDigit, "incorrect ordinal one digit");
-  static_assert(kMidDigit > kOneDigit, "incorrect ordinal mid digit");
-  static_assert(kMaxDigit > kMidDigit, "incorrect ordinal max digit");
-  static_assert(kMinLength > 0, "incorrect ordinal min length");
-  static_assert(kMidDigitValue > 1, "incorrect ordinal mid digit");
-  static_assert(kMaxDigitValue > kMidDigitValue, "incorrect ordinal max digit");
-  static_assert(kRadix == kMaxDigitValue + 1, "incorrect ordinal radix");
-
- private:
-  // Returns true iff the given byte string satisfies the criteria for
-  // a valid Ordinal.
-  static bool IsValidOrdinalBytes(const std::string& bytes);
-
-  // Returns the length that bytes.substr(0, length) would be with
-  // trailing zero digits removed.
-  static size_t GetLengthWithoutTrailingZeroDigits(
-      const std::string& bytes,
-      size_t length);
-
-  // Returns the digit at position i, padding with zero digits if
-  // required.
-  static uint8_t GetDigit(const std::string& bytes, size_t i);
-
-  // Returns the digit value at position i, padding with 0 if required.
-  static int GetDigitValue(const std::string& bytes, size_t i);
-
-  // Adds the given value to |bytes| at position i, carrying when
-  // necessary.  Returns the left-most carry.
-  static int AddDigitValue(std::string* bytes, size_t i, int digit_value);
-
-  // Returns the proper length |bytes| should be resized to, i.e. the
-  // smallest length such that |bytes| is still greater than
-  // |lower_bound| and is still valid.  |bytes| should be greater than
-  // |lower_bound|.
-  static size_t GetProperLength(const std::string& lower_bound,
-                                const std::string& bytes);
-
-  // Compute the midpoint ordinal byte string that is between |start|
-  // and |end|.
-  static std::string ComputeMidpoint(const std::string& start,
-                                     const std::string& end);
-
-  // Create a Ordinal that is lexigraphically greater than |start| and
-  // lexigraphically less than |end|. The returned Ordinal will be roughly
-  // between |start| and |end|.
-  static Ordinal<Traits> CreateOrdinalBetween(const Ordinal<Traits>& start,
-                                              const Ordinal<Traits>& end);
-
-  // The internal byte string representation of the Ordinal.  Never
-  // changes after construction except for assignment.
-  std::string bytes_;
-
-  // A cache of the result of IsValidOrdinalBytes(bytes_).
-  bool is_valid_;
-};
-
-template <typename Traits>
-const uint8_t Ordinal<Traits>::kZeroDigit;
-template <typename Traits>
-const uint8_t Ordinal<Traits>::kMaxDigit;
-template <typename Traits> const size_t Ordinal<Traits>::kMinLength;
-template <typename Traits>
-const uint8_t Ordinal<Traits>::kOneDigit;
-template <typename Traits>
-const uint8_t Ordinal<Traits>::kMidDigit;
-template <typename Traits> const unsigned int Ordinal<Traits>::kMidDigitValue;
-template <typename Traits> const unsigned int Ordinal<Traits>::kMaxDigitValue;
-template <typename Traits> const unsigned int Ordinal<Traits>::kRadix;
-
-template <typename Traits>
-Ordinal<Traits>::LessThanFn::LessThanFn() {}
-
-template <typename Traits>
-bool Ordinal<Traits>::LessThanFn::operator()(const Ordinal<Traits>& lhs,
-                                             const Ordinal<Traits>& rhs) const {
-  return lhs.LessThan(rhs);
-}
-
-template <typename Traits>
-Ordinal<Traits>::EqualsFn::EqualsFn() {}
-
-template <typename Traits>
-bool Ordinal<Traits>::EqualsFn::operator()(const Ordinal<Traits>& lhs,
-                                           const Ordinal<Traits>& rhs) const {
-  return lhs.Equals(rhs);
-}
-
-template <typename Traits>
-Ordinal<Traits>::Ordinal(const std::string& bytes)
-    : bytes_(bytes),
-      is_valid_(IsValidOrdinalBytes(bytes_)) {}
-
-template <typename Traits>
-Ordinal<Traits>::Ordinal() : is_valid_(false) {}
-
-template <typename Traits>
-Ordinal<Traits> Ordinal<Traits>::CreateInitialOrdinal() {
-  std::string bytes(Traits::kMinLength, kZeroDigit);
-  bytes[0] = kMidDigit;
-  return Ordinal(bytes);
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::IsValid() const {
-  DCHECK_EQ(IsValidOrdinalBytes(bytes_), is_valid_);
-  return is_valid_;
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::EqualsOrBothInvalid(const Ordinal& other) const {
-  if (!IsValid() && !other.IsValid())
-    return true;
-
-  if (!IsValid() || !other.IsValid())
-    return false;
-
-  return Equals(other);
-}
-
-template <typename Traits>
-std::string Ordinal<Traits>::ToDebugString() const {
-  std::string debug_string =
-      base::EscapeBytesAsInvalidJSONString(bytes_, false /* put_in_quotes */);
-  if (!is_valid_) {
-    debug_string = "INVALID[" + debug_string + "]";
-  }
-  return debug_string;
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::LessThan(const Ordinal& other) const {
-  CHECK(IsValid());
-  CHECK(other.IsValid());
-  return bytes_ < other.bytes_;
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::GreaterThan(const Ordinal& other) const {
-  CHECK(IsValid());
-  CHECK(other.IsValid());
-  return bytes_ > other.bytes_;
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::Equals(const Ordinal& other) const {
-  CHECK(IsValid());
-  CHECK(other.IsValid());
-  return bytes_ == other.bytes_;
-}
-
-template <typename Traits>
-Ordinal<Traits> Ordinal<Traits>::CreateBetween(const Ordinal& other) const {
-  CHECK(IsValid());
-  CHECK(other.IsValid());
-  CHECK(!Equals(other));
-
-  if (LessThan(other)) {
-    return CreateOrdinalBetween(*this, other);
-  } else {
-    return CreateOrdinalBetween(other, *this);
-  }
-}
-
-template <typename Traits>
-Ordinal<Traits> Ordinal<Traits>::CreateBefore() const {
-  CHECK(IsValid());
-  // Create the smallest valid Ordinal of the appropriate length
-  // to be the minimum boundary.
-  const size_t length = bytes_.length();
-  std::string start(length, kZeroDigit);
-  start[length - 1] = kOneDigit;
-  if (start == bytes_) {
-    start[length - 1] = kZeroDigit;
-    start += kOneDigit;
-  }
-
-  // Even though |start| is already a valid Ordinal that is less
-  // than |*this|, we don't return it because we wouldn't have much space in
-  // front of it to insert potential future values.
-  return CreateBetween(Ordinal(start));
-}
-
-template <typename Traits>
-Ordinal<Traits> Ordinal<Traits>::CreateAfter() const {
-  CHECK(IsValid());
-  // Create the largest valid Ordinal of the appropriate length to be
-  // the maximum boundary.
-  std::string end(bytes_.length(), kMaxDigit);
-  if (end == bytes_)
-    end += kMaxDigit;
-
-  // Even though |end| is already a valid Ordinal that is greater than
-  // |*this|, we don't return it because we wouldn't have much space after
-  // it to insert potential future values.
-  return CreateBetween(Ordinal(end));
-}
-
-template <typename Traits>
-std::string Ordinal<Traits>::ToInternalValue() const {
-  CHECK(IsValid());
-  return bytes_;
-}
-
-template <typename Traits>
-bool Ordinal<Traits>::IsValidOrdinalBytes(const std::string& bytes) {
-  const size_t length = bytes.length();
-  if (length < kMinLength)
-    return false;
-
-  bool found_non_zero = false;
-  for (size_t i = 0; i < length; ++i) {
-    const uint8_t byte = bytes[i];
-    if (byte < kZeroDigit || byte > kMaxDigit)
-      return false;
-    if (byte > kZeroDigit)
-      found_non_zero = true;
-  }
-  if (!found_non_zero)
-    return false;
-
-  if (length > kMinLength) {
-    const uint8_t last_byte = bytes[length - 1];
-    if (last_byte == kZeroDigit)
-      return false;
-  }
-
-  return true;
-}
-
-template <typename Traits>
-size_t Ordinal<Traits>::GetLengthWithoutTrailingZeroDigits(
-    const std::string& bytes, size_t length) {
-  DCHECK(!bytes.empty());
-  DCHECK_GT(length, 0U);
-
-  size_t end_position =
-      bytes.find_last_not_of(static_cast<char>(kZeroDigit), length - 1);
-
-  // If no non kZeroDigit is found then the string is a string of all zeros
-  // digits so we return 0 as the correct length.
-  if (end_position == std::string::npos)
-    return 0;
-
-  return end_position + 1;
-}
-
-template <typename Traits>
-uint8_t Ordinal<Traits>::GetDigit(const std::string& bytes, size_t i) {
-  return (i < bytes.length()) ? bytes[i] : kZeroDigit;
-}
-
-template <typename Traits>
-int Ordinal<Traits>::GetDigitValue(const std::string& bytes, size_t i) {
-  return GetDigit(bytes, i) - kZeroDigit;
-}
-
-template <typename Traits>
-int Ordinal<Traits>::AddDigitValue(std::string* bytes,
-                                   size_t i, int digit_value) {
-  DCHECK_GE(i, 0U);
-  DCHECK_LT(i, bytes->length());
-
-  for (int j = static_cast<int>(i); j >= 0 && digit_value > 0; --j) {
-    int byte_j_value = GetDigitValue(*bytes, j) + digit_value;
-    digit_value = byte_j_value / kRadix;
-    DCHECK_LE(digit_value, 1);
-    byte_j_value %= kRadix;
-    (*bytes)[j] = static_cast<char>(kZeroDigit + byte_j_value);
-  }
-  return digit_value;
-}
-
-template <typename Traits>
-size_t Ordinal<Traits>::GetProperLength(const std::string& lower_bound,
-                                        const std::string& bytes) {
-  CHECK_GT(bytes, lower_bound);
-
-  size_t drop_length =
-      GetLengthWithoutTrailingZeroDigits(bytes, bytes.length());
-  // See if the |ordinal| can be truncated after its last non-zero
-  // digit without affecting the ordering.
-  if (drop_length > kMinLength) {
-    size_t truncated_length =
-        GetLengthWithoutTrailingZeroDigits(bytes, drop_length - 1);
-
-    if (truncated_length > 0 &&
-        bytes.compare(0, truncated_length, lower_bound) > 0)
-      drop_length = truncated_length;
-  }
-  return std::max(drop_length, kMinLength);
-}
-
-template <typename Traits>
-std::string Ordinal<Traits>::ComputeMidpoint(
-    const std::string& start,
-    const std::string& end) {
-  size_t max_size = std::max(start.length(), end.length()) + 1;
-  std::string midpoint(max_size, kZeroDigit);
-
-  // Perform the operation (start + end) / 2 left-to-right by
-  // maintaining a "forward carry" which is either 0 or
-  // kMidDigitValue.  AddDigitValue() is in general O(n), but this
-  // operation is still O(n) despite that; calls to AddDigitValue()
-  // will overflow at most to the last position where AddDigitValue()
-  // last overflowed.
-  int forward_carry = 0;
-  for (size_t i = 0; i < max_size; ++i) {
-    const int sum_value = GetDigitValue(start, i) + GetDigitValue(end, i);
-    const int digit_value = sum_value / 2 + forward_carry;
-    // AddDigitValue returning a non-zero carry would imply that
-    // midpoint[0] >= kMaxDigit, which one can show is impossible.
-    CHECK_EQ(AddDigitValue(&midpoint, i, digit_value), 0);
-    forward_carry = (sum_value % 2 == 1) ? kMidDigitValue : 0;
-  }
-  DCHECK_EQ(forward_carry, 0);
-
-  return midpoint;
-}
-
-template <typename Traits>
-Ordinal<Traits> Ordinal<Traits>::CreateOrdinalBetween(
-    const Ordinal<Traits>& start,
-    const Ordinal<Traits>& end) {
-  CHECK(start.IsValid());
-  CHECK(end.IsValid());
-  CHECK(start.LessThan(end));
-  const std::string& start_bytes = start.ToInternalValue();
-  const std::string& end_bytes = end.ToInternalValue();
-  DCHECK_LT(start_bytes, end_bytes);
-
-  std::string midpoint = ComputeMidpoint(start_bytes, end_bytes);
-  const size_t proper_length = GetProperLength(start_bytes, midpoint);
-  midpoint.resize(proper_length, kZeroDigit);
-
-  DCHECK_GT(midpoint, start_bytes);
-  DCHECK_LT(midpoint, end_bytes);
-
-  Ordinal<Traits> midpoint_ordinal(midpoint);
-  DCHECK(midpoint_ordinal.IsValid());
-  return midpoint_ordinal;
-}
-
-}  // namespace syncer
-
-#endif  // SYNC_INTERNAL_API_PUBLIC_BASE_ORDINAL_H_