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HParmBlkPtr

HParamBlockRec union

#include <Files.h>

typedef union HParamBlockRec { Size Description

HIOParam ioParam; 50 Generally used in I/O for open files

HFileParam fileParam; 80 Used for unopened files

HVolumeParam volumeParam; 122 Used in volume-specific functions

AccessParam accessParam; 48 Used in shared environment calls

ObjParam objParam; 44 Used in shared environment calls

CopyParam copyParam; 52 Used in shared environment calls

WDParam wdParam; 52 Used in shared environment calls

FIDParam fidParam; 58 Used in calls which manipulate File

ID's

CSParam csParam; 76 Used by PBCatSearch

ForeignPrivParam foreignPrivParam; 68 Used for communication with foreign

file systems

} HParamBlockRec; 122 (size of aggregate - largest struct in

union structure)

typedef HParamBlockRec *HParmBlkPtr; Note Parm / Param spelling

convention

Notes: All ten structures on this union share the same names for the first eight

fields (the first 24 bytes). These fields are also the same in the flat file

system version ParamBlockRec. These common fields are defined in a

macro as the ParamBlockHeader.

This is the HFS variation of the ParamBlockRec. It should be used in

HFS-specific calls (PBHxxx). A typical technique for using parameter

blocks is to allocate the HParamBlockRec union and create pointers that

refer to the relevant structure data types:

HParamBlockRec hpb; /* allocate a union */

HIOParam *hipb=(HIOParam *)&hpb; /* and struc ptrs */

HFileParam *hfpb=(HFileParam *)&hpb; /* all point same addr */

HVolumeParam *hvpb=(HVolumeParam *)&hpb;

AccessParam *hapb=(AccessParam *)&hpb;

ObjParam *hopb=(ObjParam *)&hpb;

CopyParam *hcpb=(CopyParam *)&hpb;

WDParam *hwpb=(WDParam *)&hpb;

hpb.ioParam.ioVRefNum = 2; /* as a union member */

hpb. fileParam.ioFlFndrInfo.fdType = 'TEXT';

hpb. volumeParam.ioVolIndex = 0;

hpb. accessParam.ioDenyModes = 0;

hpb.objParam.ioObjType = 2;

hpb.copyParam.ioDstVRefNum = 1;

hpb.wdParam.ioWDIndex = 1;

hipb->ioVRefNum = 2; /* or as a structure field */

hfpb->ioFlFndrInfo.fdType = 'TEXT';

hvpb->ioVolIndex = 0;

hapb->ioDenyModes = 0;

hopb->ioObjType = 2;

hcpb->ioDstVRefNum = 1;

hwpb->ioWDIndex = 1;

You can also use ad hoc type coercion:

unsigned char pb[80]; /* big enough to hold FileParam or IOParam */

short theVRef;

theVRef = ((HIOParam *)pb)-> ioVRefNum; /* fetch a field */

((HFileParam *)pb)->ioFlLgLen = 1000L; /* store a field */

printf("File type is '%c%c%c%c'\n", pb[32], pb[33], pb[34],pb[35]);

Referenced by (45):