Low Level I/O
[C Runtime Library.]

Collaboration diagram for Low Level I/O:

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Detailed Description

Low level input and output operations.

 #include <io.h> 

Standard C runtime file interface to Nut/OS devices.

Defines
#define	_O_RDONLY   0x0000
#define	_O_WRONLY   0x0001
#define	_O_RDWR   0x0002
#define	_O_APPEND   0x0008
#define	_O_CREAT   0x0100
#define	_O_TRUNC   0x0200
#define	_O_EXCL   0x0400
#define	_O_TEXT   0x4000
#define	_O_BINARY   0x8000
#define	IOCTL_GETSTATUS   0x0001
#define	IOCTL_SETSTATUS   0x0002
#define	IOCTL_SETBUFFERMODE   0x0003
#define	IOCTL_GETBUFFERMODE   0x0004
#define	IOCTL_GETOUTBUFSIZE   0x0005
#define	IOCTL_SETOUTBUFSIZE   0x0006
#define	IOCTL_GETINBUFSIZE   0x0007
#define	IOCTL_SETINBUFSIZE   0x0008
#define	IOCTL_FLUSHOUTBUF   0x0009
	Flush the output buffer.
#define	IOCTL_GETFILESIZE   0x000A
	Return the number of bytes currently available in the input buffer.
#define	IOCTL_GETOUTBUFCOUNT   0x000B
	Return the number of bytes currently available in the input buffer.
#define	IOCTL_GETINBUFCOUNT   0x000C
	Return the number of bytes currently available in the output buffer.
Functions
int	_close (int fd)
	Close a file, device or socket.
long	_filelength (int fd)
	Return the length of a file.
int	_ioctl (int fd, int cmd, void *data)
	Perform device specific control functions.
int	_open (CONST char *name, int mode)
	Open a file.
int	_read (int fd, void *buffer, unsigned int count)
	Read data from a file, device or socket.
int	_seek (int fd, long offset, int origin)
	Move read/write position of a file.
long	_tell (int fd)
	Return the read/write position of a stream.
int	_write (int fd, CONST void *data, unsigned int count)
	Write data to a file, device or socket.
int	_write_P (int fd, PGM_P data, unsigned int count)
	Writes data from program space to a file, device or socket.

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Define Documentation

#define _O_RDONLY   0x0000

Read only.

#define _O_WRONLY   0x0001

Write only.

#define _O_RDWR   0x0002

Read and write.

#define _O_APPEND   0x0008

Start writing at the end.

#define _O_CREAT   0x0100

Create file if it does not exist.

#define _O_TRUNC   0x0200

Truncate file if it exists.

#define _O_EXCL   0x0400

Open only if it does not exist.

#define _O_TEXT   0x4000

EOL translation.

#define _O_BINARY   0x8000

Raw mode.

#define IOCTL_FLUSHOUTBUF   0x0009

Flush the output buffer. Currently not provided by any known device.

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Function Documentation

int _close (  int  fd  )

Close a file, device or socket. The calling thread may be suspended until all buffered output data has been written. Parameters: fd  Descriptor of a previously opened file, device or connected socket. Returns: 0 if the file was successfully closed or -1 to indicate an error.

long _filelength (  int  fd  )

Return the length of a file. Parameters: fd  Descriptor of a previously opened file, device or connected socket. Returns: Filelength in bytes or -1 in case of an error.

int _ioctl (  int  fd, int  cmd, void *  data )

Perform device specific control functions. Check the specific device driver for a list of supported control functions. Parameters: fd  Descriptor of a previously opened device or connected socket. cmd  Requested control function. data  Points to a buffer that contains any data required for the given control function or receives data from that function.

int _open (  CONST char *  name, int  mode )

Open a file. Parameters: name  The name of a registered device, optionally followed by a colon and a filename. mode  Operation mode. May be any of the following: _O_APPEND Always write at the end. _O_BINARY Raw mode. _O_CREAT Create file if it does not exist. _O_EXCL Open only if it does not exist. _O_RDONLY Read only. _O_RDWR Read and write. _O_TEXT End of line translation. _O_TRUNC Truncate file if it exists. _O_WRONLY Write only. Returns: File descriptor for the opened file or -1 to indicate an error.

int _read (  int  fd, void *  buffer, unsigned int  count )

Read data from a file, device or socket. Parameters: fd  Descriptor of a previously opened file, device or connected socket. buffer  Pointer to the buffer that receives the data. count  Maximum number of bytes to read. Returns: The number of bytes read, which may be less than the number of bytes specified. A return value of -1 indicates an error. Examples: playmp3/playmp3.c, and uart/uart.c.

int _seek (  int  fd, long  offset, int  origin )

Move read/write position of a file. Parameters: fd  Descriptor of a previously opened file, device or connected socket. offset  Number of bytes from initial position. origin  Initial position to seek from. Returns: 0 if no error occured -1 on error. errno is set

long _tell (  int  fd  )

Return the read/write position of a stream. Parameters: fd  Descriptor of a previously opened file, device or connected socket. Returns: The current position or -1 on error.

int _write (  int  fd, CONST void *  data, unsigned int  count )

Write data to a file, device or socket. Parameters: fd  Descriptor of a previously opened file, device or connected socket. data  Pointer to data in program space to be written. count  Number of bytes to write. Returns: The number of bytes written, which may be less than the number of bytes specified. A return value of -1 indicates an error. Note: The write implementation of the underlying driver does not need to be thread-safe. Parallel writes using device usartavr will lead to intermixed data (if data doesn't fit into ringbuffer on the first try ) Examples: uart/uart.c.

int _write_P (  int  fd, PGM_P  data, unsigned int  count )

Writes data from program space to a file, device or socket. Similar to _write() except that the data is located in program memory. Parameters: fd  Descriptor of a previously opened file, device or connected socket. data  Pointer to data in program space to be written. count  Number of bytes to write. Returns: The number of bytes written, which may be less than the number of bytes specified. A return value of -1 indicates an error. Note: The write implementation of the underlying driver does not need to be thread-safe. Parallel writes using device usartavr will lead to intermixed data (if data doesn't fit into ringbuffer on the first try ) Examples: uart/uart.c.

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