8. Function specifications-2

8.2 File operations

List

Title Function specifications

Function Open file

Function Name GFS_Open

No 2.1

Form

GfsHn GFS_Open (Sint32 fid)

input

fid: file identifier

output

none

Function value

File handle. Returns NULL in case of error.

function

Opens the specified file and returns a file handle.

List

Title Function specifications

Function File close

Function Name GFS_Close

No 2.2

Form

void GFS_Close (GfsHn gfs)

input

gfs: file handle

output

none

Function value

none

function

Closes the specified file handle.

List

Title Function specifications

Function Move access pointer

Function Name GFS_Seek

No 2.3

Form

Sint32 GFS_Seek (GfsHn gfs, Sint32 off, Sint32 org)

input

gfs	: File handle
off	: Access pointer movement amount (sector unit)
org	: Movement criteria (seek mode: GFS_SEEK_ ~)

output

none

Function value

The position of the access pointer after the move. Negative error code if there is an error.

function

Move the access pointer off sector away from org.
You cannot specify an access pointer outside the range of the file.

List

Title Function specifications

Function Get access pointer

Function Name GFS_Tell

No 2.4

Form

Sint32 GFS_Tell (GfsHn gfs)

input

gfs: file handle

output

none

Function value

The position of the access pointer. Negative error code in case of error.

function

Gets the position of the access pointer.

List

Title Function specifications

Function Checking the end of the file

Function Name GFS_IsEof

No 2.5

Form

Bool GFS_IsEof (GfsHn gfs)

input

gfs: file handle

output

none

Function value

End-of-file flag.

function

Checks if the access pointer has reached the end of the file. Function values have the following meanings:

TRUE	: The end of the file has been reached.
FALSE	: The end of the file has not been reached.

If an invalid file handle is entered, it is considered that the end of the file has been reached.

List

Title Function specifications

Function Conversion from byte size to sector length

Function Name GFS_ByteToSct

No 2.6

Form

Sint32 GFS_ByteToSct (GfsHn gfs, Sint32 nbyte)

input

gfs	: File handle
nbyte	: Number of bytes

output

none

Function value

Number of sectors. Negative error code in case of error.

function

Converts units from bytes to sectors (nsct). The sector length nsct is calculated by the following formula.

nsct = (nbyte + file sector length-1) / file sector length;

If the sector length is indefinite (a mixture of Form1 and Form2), 0 is the function value.

List

Title Function specifications

Function Get file size

Function Name GFS_GetFileSize

No 2.7 2.7

Form

void GFS_GetFileSize (GfsHn gfs, Sint32 * sctsize, Sint32 * nsct, Sint32 * lastsize)

input

gfs: File handle

output

sctsize	: Sector length
nsct	: Number of sectors (including last sector)
lastsize	: Number of bytes occupied by file data in the last sector

Function value

none

function

Gets the information to determine the size of the file. You can suppress the output of that information by specifying NULL for sctsize, nsct, and lastsize. The file size (fsize) is calculated by the following formula.
fsize ＝ sctsize ＊ (nsct-1) ＋ lastsize;

remarks

In a file in which Form1 and Form2 are mixed, both sctsize and lastsize will be 0.

List

Title Function specifications

Function Get file information

Function Name GFS_GetFileInfo

No 2.8

Form

void GFS_GetFileInfo (GfsHn gfs, Sint32 * fid, Sint32 * fn, Sint32 * fsize, Sint32 * atr)

input

gfs: File handle

output

fid	: File identifier
fn	: File number
fsize	: File size (unit: bytes)
atr	: File attributes

Function value

none

function

Get file information. You can suppress the output of that information by specifying NULL for fid, fn, fsize, and atr. Since the file size is the value recorded in the directory information, the size of one sector is calculated as 2048 bytes.

List

Title Function specifications

Function Get the number of sectors in the CD buffer partition

Function Name GFS_GetNumCdbuf

No 2.9

Form

Sint32 GFS_GetNumCdbuf (GfsHn gfs)

input

gfs: file handle

output

none

Function value

Number of sectors in the CD buffer partition

function

Gets the number of sectors existing in the CD buffer partition.