iokit/Families/IOHIDSystem/IOHIDDescriptorParser/HIDMaxUsageListLength.c

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23         File:           HIDMaxUsageListLength.c
  24
  25         Contains:       xxx put contents here xxx
  26
  27         Version:        xxx put version here xxx
  28
  29         Copyright:      © 1999 by Apple Computer, Inc., all rights reserved.
  30
  31         File Ownership:
  32
  33                 DRI:                            xxx put dri here xxx
  34
  35                 Other Contact:          xxx put other contact here xxx
  36
  37                 Technology:                     xxx put technology here xxx
  38
  39         Writers:
  40
  41                 (BWS)   Brent Schorsch
  42
  43         Change History (most recent first):
  44
  45           <USB3>         11/1/99        BWS             [2405720]  We need a better check for 'bit padding' items,
  46                                                                         rather than just is constant. We will check to make sure the
  47                                                                         item is constant, and has no usage, or zero usage. This means we
  48                                                                         need to pass an additional parameter to some internal functions
  49           <USB2>          3/6/99        BWS             Eliminate warning
  50           <USB1>          3/5/99        BWS             first checked in
  51 */
  52
  53 #include "HIDLib.h"
  54
  55 /*
  56  *------------------------------------------------------------------------------
  57  *
  58  * HIDMaxUsageListLength
  59  *
  60  *       Input:
  61  *                        reportType               - HIDP_Input, HIDP_Output, HIDP_Feature
  62  *                        usagePage                        - Page Criteria or zero
  63  *                        ptPreparsedData               - Pre-Parsed Data
  64  *       Output:
  65  *       Returns: length of list
  66  *
  67  *------------------------------------------------------------------------------
  68 */
  69 UInt32
  70 HIDMaxUsageListLength      (HIDReportType reportType,
  71                                                         HIDUsage usagePage,
  72                                                         HIDPreparsedDataRef preparsedDataRef)
  73 {
  74 #pragma unused(usagePage)       // not used, see comment below
  75
  76         HIDPreparsedDataPtr ptPreparsedData = (HIDPreparsedDataPtr) preparsedDataRef;
  77         HIDReportItem *ptReportItem;
  78         int iButtons;
  79         int i;
  80
  81
  82 /*
  83  *      Disallow Null Pointers
  84 */
  85         if (ptPreparsedData == NULL)
  86                 return 0;
  87         if (ptPreparsedData->hidTypeIfValid != kHIDOSType)
  88                 return kHIDInvalidPreparsedDataErr;
  89 /*
  90  *      Go through the ReportItems
  91  *      Filter on ReportType
  92  *      Sum the button counts
  93  *
  94  * NOTE: A more precise value for the maximum list length
  95  *               may be obtained by filtering out the usages that
  96  *               are not on the specified usage page.  Most of
  97  *               the time the number returned below is the same
  98  *               as that returned by filtering usages.  It is
  99  *               never smaller.  The tradeoff is sometimes wasting
 100  *               a few words of RAM in exchange for speed.
 101 */
 102         iButtons = 0;
 103         for (i=0; i<ptPreparsedData->reportItemCount; i++)
 104         {
 105                 ptReportItem = &ptPreparsedData->reportItems[i];
 106                 if ((ptReportItem->reportType == reportType)
 107                  && HIDIsButton(ptReportItem, preparsedDataRef))
 108                         iButtons += ptReportItem->globals.reportCount;
 109         }
 110         return iButtons;
 111 }