Repo created

libs/indexer/string_slice.hpp

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+#pragma once
+
+#include "base/string_utils.hpp"
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace search
+{
+class StringSliceBase
+{
+public:
+  using String = strings::UniString;
+
+  virtual ~StringSliceBase() = default;
+
+  virtual String const & Get(size_t i) const = 0;
+  virtual size_t Size() const = 0;
+};
+
+class StringSlice : public StringSliceBase
+{
+public:
+  StringSlice(std::vector<String> const & strings) : m_strings(strings) {}
+
+  virtual String const & Get(size_t i) const override { return m_strings[i]; }
+  virtual size_t Size() const override { return m_strings.size(); }
+
+private:
+  std::vector<String> const & m_strings;
+};
+
+// Allows to iterate over space-separated strings in StringSliceBase.
+class JoinIterator
+{
+public:
+  using difference_type = ptrdiff_t;
+  using value_type = strings::UniChar;
+  using pointer = strings::UniChar *;
+  using reference = strings::UniChar &;
+  using iterator_category = std::forward_iterator_tag;
+
+  static JoinIterator Begin(StringSliceBase const & slice);
+  static JoinIterator End(StringSliceBase const & slice);
+
+  bool operator==(JoinIterator const & rhs) const
+  {
+    return &m_slice == &rhs.m_slice && m_string == rhs.m_string && m_offset == rhs.m_offset;
+  }
+
+  bool operator!=(JoinIterator const & rhs) const { return !(*this == rhs); }
+
+  value_type operator*() const { return GetChar(m_string, m_offset); }
+
+  JoinIterator & operator++();
+
+private:
+  enum class Position
+  {
+    Begin,
+    End
+  };
+
+  JoinIterator(StringSliceBase const & slice, Position position);
+
+  // Normalizes current position, i.e. moves to the next valid
+  // character if current position is invalid, or to the end of the
+  // whole sequence if there are no valid positions.
+  void Normalize();
+
+  size_t GetSize(size_t string) const;
+
+  size_t GetMaxSize() const { return m_slice.Size() == 0 ? 0 : m_slice.Size() * 2 - 1; }
+
+  value_type GetChar(size_t string, size_t offset) const;
+
+  StringSliceBase const & m_slice;
+
+  // Denotes the current string the iterator points to.  Even values
+  // of |m_string| divided by two correspond to indices in
+  // |m_slice|. Odd values correspond to intermediate space
+  // characters.
+  size_t m_string;
+
+  // An index of the current character in the current string.
+  size_t m_offset;
+};
+}  // namespace search