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https://github.com/zephyrproject-rtos/zephyr
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The table allows to wrap read/write (i.e. POSIX-compatible) semantics of any I/O object in POSIX-compatible fd (file descriptor) handling. Intended I/O objects include files, sockets, special devices, etc. The table table itself consists of (underlying obj*, function table*) pairs, where function table provides entries for read(), write, and generalized ioctl(), where generalized ioctl handles all other operations, up to and including closing of the underlying I/O object. Fixes: #7405 Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
111 lines
3.3 KiB
C
111 lines
3.3 KiB
C
/*
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* Copyright (c) 2018 Linaro Limited
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef ZEPHYR_INCLUDE_POSIX_POSIX__FDTABLE_H_
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#define ZEPHYR_INCLUDE_POSIX_POSIX__FDTABLE_H_
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#include <sys/types.h>
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/* FIXME: For native_posix ssize_t, off_t. */
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#include <fs.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* File descriptor virtual method table.
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* All operations beyond read/write go thru ioctl method.
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*/
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struct fd_op_vtable {
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ssize_t (*read)(void *obj, void *buf, size_t sz);
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ssize_t (*write)(void *obj, const void *buf, size_t sz);
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int (*ioctl)(void *obj, unsigned int request, ...);
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};
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/**
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* @brief Reserve file descriptor.
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*
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* This function allows to reserve a space for file descriptor entry in
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* the underlying table, and thus allows caller to fail fast if no free
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* descriptor is available. If this function succeeds, z_finalize_fd()
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* or z_free_fd() must be called mandatorily.
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*
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* @return Allocated file descriptor, or -1 in case of error (errno is set)
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*/
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int z_reserve_fd(void);
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/**
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* @brief Finalize creation of file descriptor.
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*
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* This function should be called exactly once after z_reserve_fd(), and
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* should not be called in any other case.
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*
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* @param fd File descriptor previously returned by z_reserve_fd()
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* @param obj pointer to I/O object structure
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* @param vtable pointer to I/O operation implementations for the object
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*/
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void z_finalize_fd(int fd, void *obj, const struct fd_op_vtable *vtable);
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/**
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* @brief Allocate file descriptor for underlying I/O object.
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*
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* This function combines operations of z_reserve_fd() and z_finalize_fd()
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* in one step, and provided for convenience.
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*
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* @param obj pointer to I/O object structure
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* @param vtable pointer to I/O operation implementations for the object
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*
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* @return Allocated file descriptor, or -1 in case of error (errno is set)
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*/
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int z_alloc_fd(void *obj, const struct fd_op_vtable *vtable);
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/**
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* @brief Release reserved file descriptor.
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*
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* This function may be called once after z_reserve_fd(), and should
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* not be called in any other case.
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*
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* @param fd File descriptor previously returned by z_reserve_fd()
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*/
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void z_free_fd(int fd);
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/**
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* @brief Get underlying object pointer from file descriptor.
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*
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* This function is useful for functions other than read/write/ioctl
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* to look up underlying I/O object by fd, optionally checking its
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* type (using vtable reference). If fd refers to invalid entry,
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* NULL will be returned with errno set to EBADF. If fd is valid,
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* but vtable param is not NULL and doesn't match object's vtable,
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* NULL is returned and errno set to err param.
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*
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* @param fd File descriptor previously returned by z_reserve_fd()
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* @param vtable Expected object vtable or NULL
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* @param err errno value to set if object vtable doesn't match
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*
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* @return Object pointer or NULL, with errno set
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*/
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void *z_get_fd_obj(int fd, const struct fd_op_vtable *vtable, int err);
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/**
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* Request codes for fd_op_vtable.ioctl().
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*
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* Note that these codes are internal Zephyr numbers, for internal
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* Zephyr operation (and subject to change without notice, not part
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* of "stable ABI"). These are however expected to co-exist with
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* "well-known" POSIX/Linux ioctl numbers, and not clash with them.
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*/
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enum {
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ZFD_IOCTL_CLOSE = 1,
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ZFD_IOCTL_FSYNC,
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ZFD_IOCTL_LSEEK,
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};
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#ifdef __cplusplus
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}
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#endif
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#endif /* ZEPHYR_INCLUDE_POSIX_POSIX__FDTABLE_H_ */
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