iokit/Families/IOHIDSystem/IOHIDDescriptorParser/HIDNextItem.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:           HIDNextItem.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                 (DF)    David Ferguson
  42                 (JRH)   Rhoads Hollowell
  43                 (BWS)   Brent Schorsch
  44
  45         Change History (most recent first):
  46
  47           <USB4>         11/3/99        DF              And now I get to add the code to actually fix the checkin below.
  48           <USB3>         11/1/99        BWS             Fix long item calc error, fix by Dave Ferguson
  49           <USB2>          6/1/99        JRH             Get rid of an uninitialized variable warning. It turns out that
  50                                                                         with the code flow it was never being used before being
  51                                                                         initialized, but the compiler was complaining.
  52           <USB1>          3/5/99        BWS             first checked in
  53 */
  54
  55 #include "HIDLib.h"
  56
  57 /*
  58  *-----------------------------------------------------------------------------
  59  *
  60  * HIDNextItem - Get the Next Item
  61  *
  62  *       Input:
  63  *                        ptDescriptor                  - Descriptor Structure
  64  *       Output:
  65  *                        ptItem                                - Caller-provided Item Structure
  66  *       Returns:
  67  *                        kHIDSuccess             - Success
  68  *                        kHIDEndOfDescriptorErr - End of the HID Report Descriptor
  69  *
  70  *-----------------------------------------------------------------------------
  71 */
  72 OSStatus HIDNextItem(HIDReportDescriptor *ptDescriptor)
  73 {
  74         HIDItem *ptItem;
  75         unsigned char iHeader;
  76         unsigned char *psD;
  77         int i;
  78         int iLength;
  79         UInt32 *piX;
  80         int iSize;
  81         int iByte = 0;
  82 /*
  83  *      Disallow Null Pointers
  84 */
  85         if (ptDescriptor==NULL)
  86                 return kHIDNullPointerErr;
  87 /*
  88  *      Use local pointers
  89 */
  90         ptItem = &ptDescriptor->item;
  91         psD = ptDescriptor->descriptor;
  92         piX = &ptDescriptor->index;
  93         iLength = ptDescriptor->descriptorLength;
  94 /*
  95  *      Don't go past the end of the buffer
  96 */
  97         if (*piX >= iLength)
  98                 return kHIDEndOfDescriptorErr;
  99 /*
 100  *      Get the header byte
 101 */
 102         iHeader = psD[(*piX)++];
 103 /*
 104  *      Don't go past the end of the buffer
 105 */
 106         if (*piX > iLength)
 107                 return kHIDEndOfDescriptorErr;
 108         ptItem->itemType = iHeader;
 109         ptItem->itemType &= kHIDItemTypeMask;
 110         ptItem->itemType >>= kHIDItemTypeShift;
 111 /*
 112  *      Long Item Header
 113  *      Skip Long Items!
 114 */
 115         if (iHeader==kHIDLongItemHeader)
 116         {
 117                 iSize = psD[(*piX)++];
 118                 ptItem->tag = *piX++;
 119         }
 120 /*
 121  *      Short Item Header
 122 */
 123         else
 124         {
 125                 iSize = iHeader;
 126                 iSize &= kHIDItemSizeMask;
 127                 if (iSize==3)
 128                         iSize = 4;
 129                 ptItem->byteCount = iSize;
 130                 ptItem->tag = iHeader;
 131                 ptItem->tag &= kHIDItemTagMask;
 132                 ptItem->tag >>= kHIDItemTagShift;
 133         }
 134 /*
 135  *      Don't go past the end of the buffer
 136 */
 137         if ((*piX + iSize) > iLength)
 138                 return kHIDEndOfDescriptorErr;
 139 /*
 140  *      Pick up the data
 141 */
 142         ptItem->unsignedValue = 0;
 143         if (iSize==0)
 144         {
 145                 ptItem->signedValue = 0;
 146                 return kHIDSuccess;
 147         }
 148 /*
 149  *      Get the data bytes
 150 */
 151         for (i = 0; i < iSize; i++)
 152         {
 153                 iByte = psD[(*piX)++];
 154                 ptItem->unsignedValue |= (iByte << (i*8));
 155         }
 156 /*
 157  *      Keep one value unsigned
 158 */
 159         ptItem->signedValue = ptItem->unsignedValue;
 160 /*
 161  *      Sign extend one value
 162 */
 163         if ((iByte & 0x80) != 0)
 164         {
 165                 while (i < sizeof(int))
 166                         ptItem->signedValue |= (0xFF << ((i++)*8));
 167         }
 168         return kHIDSuccess;
 169 }