ClickHouse/dbms/src/IO/tests/parse_int_perf2.cpp

#include <iostream>
#include <iomanip>

#include <DB/IO/ReadHelpers.h>
#include <DB/IO/ReadBufferFromFileDescriptor.h>

#include <DB/Common/Stopwatch.h>


namespace test
{
	template <typename T>
	void readIntText(T & x, DB::ReadBuffer & buf)
	{
		bool negative = false;
		x = 0;

		if (unlikely(buf.eof()))
			DB::throwReadAfterEOF();

		if (std::is_signed<T>::value && *buf.position() == '-')
		{
			++buf.position();
			negative = true;
		}

		if (*buf.position() == '0')
		{
			++buf.position();
			return;
		}

		while (!buf.eof())
		{
			if ((*buf.position() & 0xF0) == 0x30)
			{
				x *= 10;
				x += *buf.position() & 0x0F;
				++buf.position();
			}
			else
				break;
		}

		if (std::is_signed<T>::value && negative)
			x = -x;
	}
}


int main(int argc, char ** argv)
{
	try
	{
		DB::ReadBufferFromFileDescriptor in(STDIN_FILENO);
		Int64 n = 0;
		size_t nums = 0;

		Stopwatch watch;

		while (!in.eof())
		{
			DB::readIntText(n, in);
			in.ignore();

			//std::cerr << "n: " << n << std::endl;

			++nums;
		}

		watch.stop();
		std::cerr << std::fixed << std::setprecision(2)
			<< "Read " << nums << " numbers (" << in.count() / 1000000.0 << " MB) in " << watch.elapsedSeconds() << " sec., "
			<< nums / watch.elapsedSeconds() << " num/sec. (" << in.count() / watch.elapsedSeconds() / 1000000 << " MB/s.)"
			<< std::endl;
	}
	catch (const DB::Exception & e)
	{
		std::cerr << e.what() << ", " << e.displayText() << std::endl;
		return 1;
	}

	return 0;
}