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#include <IO/MMapReadBufferFromFileWithCache.h>
namespace DB
{
namespace ErrorCodes
{
extern const int ARGUMENT_OUT_OF_BOUND;
extern const int CANNOT_SEEK_THROUGH_FILE;
}
void MMapReadBufferFromFileWithCache::init()
{
size_t length = mapped->getLength();
BufferBase::set(mapped->getData(), length, 0);
size_t page_size = static_cast<size_t>(::getPageSize());
ReadBuffer::padded = (length % page_size) > 0 && (length % page_size) <= (page_size - (PADDING_FOR_SIMD - 1));
ReadBufferFromFileBase::file_size = length;
}
MMapReadBufferFromFileWithCache::MMapReadBufferFromFileWithCache(
MMappedFileCache & cache, const std::string & file_name, size_t offset, size_t length)
{
mapped = cache.getOrSet(cache.hash(file_name, offset, length), [&]
{
return std::make_shared<MMappedFile>(file_name, offset, length);
});
init();
}
MMapReadBufferFromFileWithCache::MMapReadBufferFromFileWithCache(
MMappedFileCache & cache, const std::string & file_name, size_t offset)
{
mapped = cache.getOrSet(cache.hash(file_name, offset, -1), [&]
{
return std::make_shared<MMappedFile>(file_name, offset);
});
init();
}
std::string MMapReadBufferFromFileWithCache::getFileName() const
{
return mapped->getFileName();
}
off_t MMapReadBufferFromFileWithCache::getPosition()
{
return count();
}
off_t MMapReadBufferFromFileWithCache::seek(off_t offset, int whence)
{
off_t new_pos;
if (whence == SEEK_SET)
new_pos = offset;
else if (whence == SEEK_CUR)
new_pos = count() + offset;
else
throw Exception(ErrorCodes::ARGUMENT_OUT_OF_BOUND, "MMapReadBufferFromFileWithCache::seek expects SEEK_SET or SEEK_CUR as whence");
working_buffer = internal_buffer;
if (new_pos < 0 || new_pos > off_t(working_buffer.size()))
throw Exception(ErrorCodes::CANNOT_SEEK_THROUGH_FILE,
"Cannot seek through file {} because seek position ({}) is out of bounds [0, {}]",
getFileName(), new_pos, working_buffer.size());
position() = working_buffer.begin() + new_pos;
return new_pos;
}
}
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