ubgpsuite/lonetix/include/df/stm.h

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2021-06-07 16:55:13 +02:00
// SPDX-License-Identifier: LGPL-3.0-or-later
/**
* \file stm.h
*
* General stream I/O definitions and utilities.
*
* \copyright The DoubleFourteen Code Forge (C) All Rights Reserved
* \author Lorenzo Cogotti
*/
#ifndef DF_STM_H_
#define DF_STM_H_
#include "sys/fsdef.h" // Fildes and SeekMode definitions
/**
* \brief I/O stream operations interface.
*
* Defines an interface to work with an abstract I/O stream.
*/
typedef struct {
/**
* \brief Read bytes from the stream.
*
* Function pointer may be `NULL` on write-only streams.
*
* \param streamp Stream handle
* \param buf Destination buffer
* \param nbytes_ Bytes count to be read from `streamp` to `buf`
*
* \return Number of bytes actually read from the stream,
* which may be less than the requested number of bytes.
* If no bytes are available (`EOF`) function returns 0.
* On error `-1` is returned.
*
* \see For reference `Sys_Fread()`
*/
Sint64 (*Read)(void *streamp, void *buf, size_t nbytes);
/**
* \brief Write bytes to the stream.
*
* Function pointer may be `NULL` on read-only streams.
*
* \param streamp Stream handle
* \param buf buffer to be written, holds at least `nbytes` bytes
* \param nbytes Bytes count to be written to `hn`
*
* \return Number of bytes actually written to `streamp`, which
* may be less than `nbytes`, -1 on error.
*
* \see For reference `Sys_Fwrite()`
*/
Sint64 (*Write)(void *streamp, const void *buf, size_t nbytes);
/**
* \brief Seek inside the stream.
*
* Function pointer may be `NULL` on non-seekable streams.
*
* \param streamp Stream handle
* \param off Seek offset in bytes
* \param whence Seek mode
*
* \return The final cursor position on success, -1 on error.
*
* \see For reference [Sys_Fseek()](@ref Sys_Fseek)
*/
Sint64 (*Seek)(void *streamp, Sint64 off, SeekMode whence);
/**
* \brief Retrieve current position inside stream.
*
* Function pointer may be `NULL` on non-seekable streams.
*
* \param streamp Stream handle
*
* \return Current cursor position inside `streamp`, -1 on error.
*
* \see For reference `Sys_Ftell()`
*/
Sint64 (*Tell)(void *streamp);
/**
* \brief Finalizes writes to stream.
*
* Function pointer may be `NULL` in read-only streams or when such
* operation is unavailable or meaningless.
*
* \param streamp Stream handle
*
* \return`OK` on success`NG` otherwise.
*/
Judgement (*Finish)(void *streamp);
/**
* \brief Closes the stream and free its resources.
*
* Function pointer may be `NULL` if such operation is not necessary.
*
* \param streamp Stream handle to be closed
*
* \see For reference `Sys_Fclose()`
*/
void (*Close)(void *streamp);
} StmOps;
/**
* \brief Implementation of `StmOps` over `Fildes`.
*
* May be used to enable any function accepting `StmOps` to
* work with `Fildes`.
* Complete ownership is provided by `Stm_FildesOps`, non-closing
* access is provided by `Stm_NcFildesOps`.
* `Finish()` function performs a full file sync to disk
* (as in: `Sys_Fsync()` with a `TRUE` `fullSync` flag).
*
* @{
* \var Stm_FildesOps
* \var Stm_NcFildesOps
* @}
*/
extern const StmOps *const Stm_FildesOps;
extern const StmOps *const Stm_NcFildesOps;
/**
* \brief Obtain a stream pointer from a file descriptor.
*
* \param [in] fd File descriptor
*
* \return Pointer suitable to be used as the `streamp` parameter for
* a `StmOps` interface.
*
* \see `Stm_FildesOps`, `Stm_NcFildesOps`
*
* \note Returned pointer may very well be `NULL`.
*/
FORCE_INLINE void *STM_FILDES(Fildes fd)
{
STATIC_ASSERT(sizeof(fd) <= sizeof(Sintptr), "STM_FILDES() ill formed on this platform");
return ((void *) ((Sintptr) fd));
}
#endif