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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines / Reading, Writing, and Closing Files

PBWrite

You can use the PBWrite function to write any number of bytes to an open file.

FUNCTION PBWrite (paramBlock: ParmBlkPtr; async: Boolean): OSErr;

paramBlock

A pointer to a basic File Manager parameter block.

async

A Boolean value that specifies asynchronous (TRUE) or synchronous (FALSE) execution.

-->	ioCompletion	ProcPtr	A pointer to a completion routine.
<--	ioResult	OSErr	The result code of the function.
-->	ioRefNum	Integer	A file reference number.
-->	ioBuffer	Ptr	A pointer to a data buffer.
-->	ioReqCount	LongInt	The number of bytes requested.
<--	ioActCount	LongInt	The number of bytes actually written.
-->	ioPosMode	Integer	The positioning mode.
<->	ioPosOffset	LongInt	The positioning offset.

DESCRIPTION

The PBWrite function takes ioReqCount bytes from the buffer pointed to by ioBuffer and attempts to write them to the open file whose access path is specified by ioRefNum. The position of the mark is specified by ioPosMode and ioPosOffset. If the write operation completes successfully, PBWrite moves the file mark to the byte following the last byte written and returns noErr. After the write operation is completed, the mark is returned in ioPosOffset and the number of bytes actually written is returned in ioActCount.

If you try to write past the logical end-of-file, PBWrite moves the logical end-of-file. If you try to write past the physical end-of-file, PBWrite adds one or more clumps to the file and moves the physical end-of-file accordingly.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for PBWrite is _Write.

RESULT CODES

noErr	0	No error
dskFulErr	-34	Disk full
ioErr	-36	I/O error
fnOpnErr	-38	File not open
posErr	-40	Attempt to position mark before start of file
wPrErr	-44	Hardware volume lock
fLckdErr	-45	File is locked
vLckdErr	-46	Software volume lock
paramErr	-50	Negative ioReqCount
rfNumErr	-51	Bad reference number
wrPermErr	-61	Read/write permission doesn't allow writing