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#ifndef IO_URING_ENGINE_H
#define IO_URING_ENGINE_H 1
#include <functional>
#include <queue>
#include <stddef.h>
#include <string_view>
#include <sys/socket.h>
#include <sys/types.h>
#include <linux/stat.h>
struct io_uring_sqe;
#ifndef WITHOUT_URING
#include <liburing.h>
#endif
class IOUringEngine {
public:
IOUringEngine(size_t slop_bytes);
void submit_read(int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
// NOTE: We just do the stat() to get the data into the dentry cache for fast access,
// or to check whether the file exists. Thus, the callback has only an OK/not OK boolean.
void submit_stat(const char *path, std::function<void(bool ok)> cb);
bool get_supports_stat() { return supports_stat; }
void finish();
size_t get_waiting_reads() const { return pending_reads + queued_reads.size(); }
private:
#ifndef WITHOUT_URING
void submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, std::function<void(std::string_view)> cb);
void submit_stat_internal(io_uring_sqe *sqe, char *path, std::function<void(bool)> cb);
io_uring ring;
#endif
size_t pending_reads = 0; // Number of requests we have going in the ring.
bool using_uring, supports_stat = false;
const size_t slop_bytes;
struct QueuedRead {
int fd;
size_t len;
off_t offset;
std::function<void(std::string_view)> cb;
};
std::queue<QueuedRead> queued_reads;
struct QueuedStat {
char *pathname; // Owned by us.
std::function<void(bool)> cb;
};
std::queue<QueuedStat> queued_stats;
enum Op { OP_READ,
OP_STAT };
struct PendingRead {
Op op;
std::function<void(std::string_view)> read_cb;
std::function<void(bool)> stat_cb;
union {
struct {
void *buf;
size_t len;
// For re-submission.
int fd;
off_t offset;
iovec iov;
} read;
struct {
char *pathname;
struct statx *buf;
} stat;
};
};
// 256 simultaneous requests should be ample, for slow and fast media alike.
static constexpr size_t queue_depth = 256;
};
#endif // !defined(IO_URING_ENGINE_H)
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