thin-provisioning-tools/block-cache/io_engine.h

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#ifndef BLOCK_CACHE_IO_ENGINE_H
#define BLOCK_CACHE_IO_ENGINE_H
#include "base/unique_handle.h"
#include <boost/optional.hpp>
#include <ctype.h>
#include <set>
#include <string>
#include <libaio.h>
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//----------------------------------------------------------------
namespace bcache {
using sector_t = uint64_t;
unsigned const SECTOR_SHIFT = 9;
unsigned const PAGE_SIZE = 4096;
// Virtual base class to aid unit testing
class io_engine {
public:
enum mode {
M_READ_ONLY,
M_READ_WRITE
};
enum dir {
D_READ,
D_WRITE
};
enum sharing {
EXCLUSIVE,
SHARED
};
io_engine() {}
virtual ~io_engine() {}
using handle = unsigned;
virtual handle open_file(std::string const &path, mode m, sharing s = EXCLUSIVE) = 0;
virtual void close_file(handle h) = 0;
// returns false if there are insufficient resources to
// queue the IO
virtual bool issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsigned context) = 0;
// returns (success, context)
using wait_result = std::pair<bool, unsigned>;
virtual boost::optional<wait_result> wait() = 0;
virtual boost::optional<wait_result> wait(unsigned &microsec) = 0;
private:
io_engine(io_engine const &) = delete;
io_engine &operator =(io_engine const &) = delete;
};
//--------------------------------
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class control_block_set {
public:
control_block_set(unsigned nr);
iocb *alloc(unsigned context);
void free(iocb *);
unsigned context(iocb *) const;
private:
struct cblock {
unsigned context;
struct iocb cb;
};
std::set<unsigned> free_cbs_;
std::vector<cblock> cbs_;
};
//----------------
class aio_engine : public io_engine {
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public:
// max_io is the maximum nr of concurrent ios expected
aio_engine(unsigned max_io);
~aio_engine();
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using handle = unsigned;
virtual handle open_file(std::string const &path, mode m, sharing s = EXCLUSIVE);
virtual void close_file(handle h);
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// Returns false if queueing the io failed
virtual bool issue_io(handle h, dir d, sector_t b, sector_t e, void *data, unsigned context);
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virtual boost::optional<wait_result> wait();
virtual boost::optional<wait_result> wait(unsigned &microsec);
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private:
static struct timespec micro_to_ts(unsigned micro);
static unsigned ts_to_micro(timespec const &ts);
boost::optional<io_engine::wait_result> wait_(timespec *ts);
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std::list<base::unique_fd> descriptors_;
io_context_t aio_context_;
control_block_set cbs_;
aio_engine(io_engine const &) = delete;
aio_engine &operator =(io_engine const &) = delete;
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};
}
//----------------------------------------------------------------
#endif