==== FS_WRITE ====

**Purpose**

Write the specified number of bytes to a file from a buffer location.   

**Calling Sequence**

<code c>
int far pascal FS_WRITE(psffsi, psffsd, pDat, pLen, IOflag)

struct sffsi far * psffsi;
struct sffsd far * psffsd;
char far * pData;
unsigned short far * pLen;
unsigned short IOflag;
</code>

**Where**

//psffsi// is a pointer to the file-system-independent portion of an open file instance.   

//sfi_position// is the location within the file where the data is to be written to. The FSD should update the //sfi_position// and sfi_size fields.   

//psffsd// is a pointer to the file-system-dependent portion of an open file instance.   

//pData// is the address of the application data area.   

Addressing of this data area is not validated by the kernel (see //FSH_PROBEBUF//).   

//pLen// is a pointer to the length of the application data area.   

On input, this is the number of bytes that are to be written. On output, this is the number of bytes successfully written. If the application data area is smaller than the length, no transfer is to take place. The FSD does not need to verify this pointer.   

//IOflag// indicates information about the operation on the handle.   

|//IOflag// == 0x0010 |indicates write-through |
|//IOflag// == 0x0020 |indicates no-cache |

**Remarks**

If write is successful and is a file, the FSD should set //ST_SWRITE// and //ST_PWRITE// to make the kernel time stamp the last modification time in the SFT.   

The FSD should return an error if an attempt is made to write beyond the end with a direct access device handle.   

Of the information passed in //IOflag//, the write-through bit is a mandatory bit in that any data written to the block device must be put out on the medium before the device driver returns. The no-cache bit, on the other hand, is an advisory bit that says whether the data being transferred is worth caching or not.