ClickHouse/dbms/src/IO/MMapReadBufferFromFileDescriptor.cpp
2018-06-13 05:52:03 +03:00

91 lines
2.4 KiB
C++

#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <Common/ProfileEvents.h>
#include <Common/formatReadable.h>
#include <IO/MMapReadBufferFromFileDescriptor.h>
namespace DB
{
namespace ErrorCodes
{
extern const int CANNOT_ALLOCATE_MEMORY;
extern const int CANNOT_MUNMAP;
extern const int CANNOT_STAT;
extern const int BAD_ARGUMENTS;
extern const int LOGICAL_ERROR;
}
void MMapReadBufferFromFileDescriptor::init(int fd_, size_t offset, size_t length_)
{
fd = fd_;
length = length_;
if (length)
{
void * buf = mmap(nullptr, length, PROT_READ, MAP_PRIVATE, fd, offset);
if (MAP_FAILED == buf)
throwFromErrno("MMapReadBufferFromFileDescriptor: Cannot mmap " + formatReadableSizeWithBinarySuffix(length) + ".",
ErrorCodes::CANNOT_ALLOCATE_MEMORY);
BufferBase::set(static_cast<char *>(buf), length, 0);
}
}
void MMapReadBufferFromFileDescriptor::init(int fd_, size_t offset)
{
fd = fd_;
struct stat stat_res {};
if (0 != fstat(fd, &stat_res))
throwFromErrno("MMapReadBufferFromFileDescriptor: Cannot fstat.", ErrorCodes::CANNOT_STAT);
off_t file_size = stat_res.st_size;
if (file_size < 0)
throw Exception("MMapReadBufferFromFileDescriptor: fstat returned negative file size", ErrorCodes::LOGICAL_ERROR);
if (offset > static_cast<size_t>(file_size))
throw Exception("MMapReadBufferFromFileDescriptor: requested offset is greater than file size", ErrorCodes::BAD_ARGUMENTS);
init(fd, offset, file_size - offset);
}
MMapReadBufferFromFileDescriptor::MMapReadBufferFromFileDescriptor(int fd, size_t offset, size_t length)
: MMapReadBufferFromFileDescriptor()
{
init(fd, offset, length);
}
MMapReadBufferFromFileDescriptor::MMapReadBufferFromFileDescriptor(int fd, size_t offset)
: MMapReadBufferFromFileDescriptor()
{
init(fd, offset);
}
MMapReadBufferFromFileDescriptor::~MMapReadBufferFromFileDescriptor()
{
if (length)
finish(); /// Exceptions will lead to std::terminate and that's Ok.
}
void MMapReadBufferFromFileDescriptor::finish()
{
if (0 != munmap(internalBuffer().begin(), length))
throwFromErrno("MMapReadBufferFromFileDescriptor: Cannot munmap " + formatReadableSizeWithBinarySuffix(length) + ".",
ErrorCodes::CANNOT_MUNMAP);
length = 0;
}
}