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#pragma once
#include "coding/reader.hpp"
#include "coding/write_to_sink.hpp"
#include "base/assert.hpp"
#include "std/string.hpp"
#include "std/utility.hpp"
template <class WriterT> class VarSerialVectorWriter
{
public:
// Actually, it is possible to refactor to accept maxPossibleSize (i.e. capacity) instead of size.
VarSerialVectorWriter(WriterT & writer, uint32_t size)
: m_writer(writer), m_size(size), m_recordNumber(0)
{
WriteToSink(m_writer, size);
m_sizesOffset = m_writer.Pos();
m_writer.Seek(GetDataStartPos());
}
~VarSerialVectorWriter()
{
CHECK_EQUAL(m_recordNumber, m_size, ());
}
void FinishRecord()
{
CHECK_LESS(m_recordNumber, m_size, ());
uint64_t const pos = m_writer.Pos();
uint64_t const recordSize64 = pos - GetDataStartPos();
uint32_t const recordSize = static_cast<uint32_t>(recordSize64);
CHECK_EQUAL(recordSize, recordSize64, ());
m_writer.Seek(m_sizesOffset + m_recordNumber * sizeof(uint32_t));
WriteToSink(m_writer, recordSize);
m_writer.Seek(pos);
++m_recordNumber;
}
private:
uint64_t GetDataStartPos() const
{
return m_sizesOffset + m_size * sizeof(uint32_t);
}
private:
WriterT & m_writer;
uint64_t m_sizesOffset;
uint32_t m_size;
uint32_t m_recordNumber;
};
template <class ReaderT>
class VarSerialVectorReader
{
public:
template <typename SourceT>
explicit VarSerialVectorReader(SourceT & source) :
/// Reading this code can blow your mind :)
/// Initialization (and declaration below) order of m_offsetsReader and m_dataReader matters!!!
/// @see ReaderSource::SubReader - it's not constant.
/// @todo Do this stuff in a better way.
m_size(ReadPrimitiveFromSource<uint32_t>(source)),
m_offsetsReader(source.SubReader(m_size * sizeof(uint32_t))),
m_dataReader(source.SubReader())
{
}
/// Used for unit tests only. Dont't do COW in production code.
string Read(uint32_t i) const
{
pair<uint32_t, uint32_t> const posAsize = GetPosAndSize(i);
string result;
result.resize(posAsize.second);
ReadFromPos(m_dataReader, posAsize.first, (void *)result.data(), posAsize.second);
return result;
}
ReaderT SubReader(uint32_t i) const
{
pair<uint32_t, uint32_t> const posAsize = GetPosAndSize(i);
return m_dataReader.SubReader(posAsize.first, posAsize.second);
}
uint64_t Size() const { return m_size; }
private:
pair<uint32_t, uint32_t> GetPosAndSize(uint32_t i) const
{
uint32_t const begin =
i == 0 ? 0 : ReadPrimitiveFromPos<uint32_t>(m_offsetsReader, (i - 1) * sizeof(uint32_t));
uint32_t const end = ReadPrimitiveFromPos<uint32_t>(m_offsetsReader, i * sizeof(uint32_t));
ASSERT_LESS_OR_EQUAL(begin, end, ());
return make_pair(begin, end - begin);
}
private:
/// @note Do NOT change declaration order.
uint64_t m_size;
ReaderT m_offsetsReader;
ReaderT m_dataReader;
};
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