Replace mmap with io_uring.

[plocate] / io_uring_engine.h

diff --git a/io_uring_engine.h b/io_uring_engine.h
new file mode 100644 (file)
index 0000000..93e7a0d
--- /dev/null
+++ b/io_uring_engine.h
@@ -0,0 +1,51 @@
+#ifndef IO_URING_ENGINE_H
+#define IO_URING_ENGINE_H 1
+
+#include <functional>
+#include <queue>
+#include <string>
+#include <stdint.h>
+#include <liburing.h>
+
+class IOUringEngine {
+public:
+       IOUringEngine();
+       void submit_read(int fd, size_t len, off_t offset, std::function<void(std::string)> cb);
+       void finish();
+       size_t get_waiting_reads() const { return pending_reads + queued_reads.size(); }
+
+private:
+       void submit_read_internal(io_uring_sqe *sqe, int fd, size_t len, off_t offset, std::function<void(std::string)> cb);
+
+       io_uring ring;
+       size_t pending_reads = 0;  // Number of requests we have going in the ring.
+       bool using_uring;
+
+       struct QueuedRead {
+               int fd;
+               size_t len;
+               off_t offset;
+               std::function<void(std::string)> cb;
+       };
+       std::queue<QueuedRead> queued_reads;
+
+       struct PendingRead {
+               void *buf;
+               size_t len;
+               std::function<void(std::string)> cb;
+
+               // For re-submission.
+               int fd;
+               off_t offset;
+               iovec iov;
+       };
+
+       // 256 simultaneous requests should be ample, for slow and fast media alike.
+       static constexpr size_t queue_depth = 256;
+};
+
+// A wrapper around pread() that returns an incomplete read.
+// Always synchronous (no io_uring).
+void complete_pread(int fd, void *ptr, size_t len, off_t offset);
+
+#endif  // !defined(IO_URING_ENGINE_H)