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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines / Allocating File Blocks

PBAllocate

You can use the PBAllocate function to allocate additional blocks to an open file.

FUNCTION PBAllocate (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.
-->	ioReqCount	LongInt	The number of bytes requested.
<--	ioActCount	LongInt	The number of bytes actually allocated, rounded up to the nearest multiple of the allocation block size.

DESCRIPTION

The PBAllocate function adds ioReqCount bytes to the specified file and sets the physical end-of-file to 1 byte beyond the last block allocated. If there isn't enough empty space on the volume to satisfy the allocation request, PBAllocate allocates the rest of the space on the volume and returns dskFulErr as its function result.

Note

If the total number of requested bytes is unavailable, PBAllocate allocates whatever space, contiguous or not, is available. To force the allocation of the entire requested space as a contiguous piece, call PBAllocContig instead.

ASSEMBLY-LANGUAGE INFORMATION

The trap macro for PBAllocate is _Allocate.

RESULT CODES

noErr	0	No error
dskFulErr	-34	Disk full
ioErr	-36	I/O error
fnOpnErr	-38	File not open
wPrErr	-44	Hardware volume lock
fLckdErr	-45	File is locked
vLckdErr	-46	Software volume lock
rfNumErr	-51	Bad reference number
wrPermErr	-61	Read/write permission doesn't allow writing