PBAllocateSync
PBAllocate Increase file allocation; logical EOF un changed
#include <Files.h> File Manager (PBxxx)
OSErr PBAllocate(pb, async ); Boolean async ; 0=await completion; 1=immediate return PBAllocate increases the physical size of an open file, adding one or more
allocation blocks to the end of the file. The file must be opened with a
read/write permission level.
pb is the address of a 50-byte IOParam structure. The relevant fields are as follows:
Out-In Name Type Size Offset Description
-> ioCompletion ProcPtr 4 12 Completion routine address (if async =TRUE) -> ioRefNum short 2 24 File reference number
-> ioReqCount long 4 36 Desired disk space to add to the file, in bytes
<- ioResult OSErr 2 16 Error Code (0=no error, 1=not done yet) <- ioActCount long 4 40 Actual amount of space added, in bytes
async is a Boolean value. Use FALSE for normal (synchronous) operation or TRUE to enqueue the request and resume control immediately. See Async I/O.
noErr (0) No error
fLckdErr (-45) File is locked
fnOpnErr (-38) File not open
ioErr (-36) I/O error
rfNumErr (-51) Bad ioRefNum
vLckdErr (-46) Volume is locked
wPrErr (-44) Diskette is write-protected
wrPermErr (-61) Write permissions error
Notes: PBAllocate expects the reference number of an open file in ioRefNum (it
must be unlocked, opened with write permission, and it must exist on an
unlocked volume).
ioReqCount bytes are added to the current physical EOF and the result is
rounded up to the next higher allocation block size. For instance, if
ioReqCount=1, the physical EOF will increase by 512 bytes and ioActCount
will return containing 512.
If there isn't enough room on the disk to satisfy the request, then all
available storage is added to the file and dskFulErr is returned. Compare
this to PBAllocContig and PBSetEOF (which do NOT perform such
absurd partial allocations).
The PBAllocContig function may be preferable. It attempts to find a contiguous block of disk space of the requested size (contiguous blocks make
for faster file access).