Asynchronous input output library

The library provides functions to issue asynchronous input output operations through native kernel aio api. The library offers a convenient api for nonblocking (non-sleep) implementation of a file read/write/sync.

Prerequisites

• A linux kernel with AIO enabled (CONFIG_AIO = y).
• Libaio kernel aio wrapper.
• File should be open with O_DIRECT flag
• IO operation should by 512 bytes aligned by position and size
• Memory buffers should be 512 bytes aligned

API

int io_ctx_create(struct io_ctx *io_ctx, int capacity, int (*wait_cb)(int wait_fd));

Create an AIO context.

Parameters:

• io_ctx - pointer to a context structure
• capacity - AIO queue capacity
• wait_cb - a callback to wait for a completions eventfd

Return:

• 0 for success
• a negative errno

int io_ctx_process(struct io_ctx *io_ctx);

Process completed aio requests. Retrieve all completed requests and call corresponding completion callbacks.

Parameters:

• io_ctx - pointer to a context structure

Return:

• count of competed ios
• negative errno

void io_ctx_destroy(struct io_ctx *io_ctx);

Wait until all active ios are done and destroy AIO context.

Parameters:

• io_ctx - pointer to a context structure

int io_ctx_write(struct io_ctx *io_ctx, int fd, void *data, size_t count, long long offset, void (*complete_cb)(int result, void *data), void *data_cb);

Send a write request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• data - source to write
• count - count of byte to write
• offset - write position
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_pwrite(struct io_ctx *io_ctx, int fd, const struct iovec *iov, int iovcnt, long long offset, void (*complete_cb)(int result, void *data), void *data_cb);

Send a vector write request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• iov - source to write
• iovcnt - length of a source vector
• offset - write position
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_read(struct io_ctx *io_ctx, int fd, void *data, size_t len, long long offset, void (*complete_cb)(int result, void *data), void *data_cb);

Send a read request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• data - destination to read
• count - count of byte to read
• offset - read position
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_pread(struct io_ctx *io_ctx, int fd, const struct iovec *iov, int iovcnt, long long offset, void (*complete_cb)(int result, void *data), void *data_cb);

Send a vector read request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• iov - destination to read
• iovcnt - length of a destination vector
• offset - read position
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_fsync(struct io_ctx *io_ctx, int fd, void (*sync_cb)(int result, void *data), void *data_cb);

Send a file sync request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_fdsync(struct io_ctx *io_ctx, int fd, void (*sync_cb)(int result, void *data), void *data_cb);

Send a file data sync request.

Parameters:

• io_ctx - pointer to a context structure
• fd - file handle
• complete_cb - completion callback
• data_cb - completion callback data

Return:

• request key
• negative errno

int io_ctx_cancel(struct io_ctx *io_ctx, int key);

Cancel an aio file request.

Parameters:

• io_ctx - pointer to a context structure
• key - key of a previous issued io

Return:

• 0 for success
• negative errno