ClickHouse/src/IO/tests/o_direct_and_dirty_pages.cpp

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#include <string>
#include <iostream>
#include <Core/Types.h>
#include <IO/WriteHelpers.h>
#include <IO/ReadHelpers.h>
#include <IO/WriteBufferFromFile.h>
#include <IO/ReadBufferFromFile.h>
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int main(int, char **)
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{
using namespace DB;
try
{
static const size_t N = 100000;
static const size_t BUF_SIZE = 1048576;
ReadBufferFromFile rand_in("/dev/urandom");
unsigned rand = 0;
readBinary(rand, rand_in);
String test = "Hello, world! " + toString(rand);
/// Write to file as usual, read with O_DIRECT.
{
WriteBufferFromFile wb("test1", BUF_SIZE);
for (size_t i = 0; i < N; ++i)
writeStringBinary(test, wb);
wb.next();
}
{
ReadBufferFromFile rb("test1", BUF_SIZE, O_RDONLY | O_DIRECT, nullptr, 4096);
String res;
for (size_t i = 0; i < N; ++i)
readStringBinary(res, rb);
std::cerr << "test: " << test << ", res: " << res << ", bytes: " << rb.count() << std::endl;
}
/// Write to file with O_DIRECT, read as usual.
{
WriteBufferFromFile wb("test2", BUF_SIZE, O_WRONLY | O_CREAT | O_TRUNC | O_DIRECT, 0666, nullptr, 4096);
for (size_t i = 0; i < N; ++i)
writeStringBinary(test, wb);
if (wb.offset() % 4096 != 0)
{
size_t pad = 4096 - wb.offset() % 4096;
memset(wb.position(), 0, pad);
wb.position() += pad;
}
wb.next();
}
{
ReadBufferFromFile rb("test2", BUF_SIZE);
String res;
for (size_t i = 0; i < N; ++i)
readStringBinary(res, rb);
std::cerr << "test: " << test << ", res: " << res << ", bytes: " << rb.count() << std::endl;
}
}
catch (const Exception & e)
{
std::cerr << e.what() << ", " << e.displayText() << std::endl;
return 1;
}
return 0;
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}