Repo created

libs/coding/value_opt_string.hpp

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+#pragma once
+
+#include "coding/varint.hpp"
+
+#include "base/assert.hpp"
+#include "base/string_utils.hpp"
+
+#include <limits>
+#include <string>
+
+class StringNumericOptimal
+{
+public:
+  bool operator==(StringNumericOptimal const & rhs) const { return m_s == rhs.m_s; }
+
+  void Set(std::string const & s)
+  {
+    CHECK(!s.empty(), ());
+    m_s = s;
+  }
+
+  void Clear() { m_s.clear(); }
+  bool IsEmpty() const { return m_s.empty(); }
+  std::string const & Get() const { return m_s; }
+
+  /// First uint64_t value is:
+  /// - a number if low control bit is 1;
+  /// - a string size-1 if low control bit is 0;
+  template <typename Sink>
+  void Write(Sink & sink) const
+  {
+    uint64_t n;
+    if (ToInt(n) && (m_s.size() == 1 || m_s.front() != '0'))
+      WriteVarUint(sink, ((n << 1) | 1));
+    else
+    {
+      size_t const sz = m_s.size();
+      ASSERT_GREATER(sz, 0, ());
+
+      WriteVarUint(sink, static_cast<uint32_t>((sz - 1) << 1));
+      sink.Write(m_s.c_str(), sz);
+    }
+  }
+
+  template <typename Source>
+  void Read(Source & src)
+  {
+    uint64_t sz = ReadVarUint<uint64_t>(src);
+
+    if ((sz & 1) != 0)
+      m_s = strings::to_string(sz >> 1);
+    else
+    {
+      sz = (sz >> 1) + 1;
+      ASSERT_LESS_OR_EQUAL(sz, std::numeric_limits<size_t>::max(), ("sz is out of platform's range."));
+      m_s.resize(static_cast<size_t>(sz));
+      src.Read(&m_s[0], static_cast<size_t>(sz));
+    }
+  }
+
+private:
+  bool ToInt(uint64_t & n) const
+  {
+    // If string is a number and we have space for control bit
+    return (strings::to_uint64(m_s, n) && ((n << 1) >> 1) == n);
+  }
+
+  std::string m_s;
+};
+
+inline std::string DebugPrint(StringNumericOptimal const & s)
+{
+  return s.Get();
+}