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Inside Macintosh: Files /

Chapter 2 - File Manager / File Manager Reference

Low-Level File Access Routines

Allocating File Blocks

The File Manager provides two low-level functions, PBAllocate and PBAllocContig, that allow you to allocate additional blocks to a file. The File Manager automatically allocates file blocks if you move the logical end-of-file past the physical end-of-file, and it automatically deallocates unneeded blocks from a file if you move the logical end-of-file to a position more than one allocation block before the current physical end-of-file. Consequently, you do not in general need to be concerned with allocating or deallocating file blocks. However, you can improve file block contiguity if you use the PBAllocate or PBAllocContig function to preallocate file blocks. This is most useful if you know in advance how big a file is likely to become.

PBAllocate and PBAllocContig are not supported by AppleShare volumes. Instead, use SetEOF or PBSetEOF to extend a file by setting the end-of-file.

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Subtopics

PBAllocate

PBAllocContig