device/hid/hid_report_descriptor_item.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "device/hid/hid_report_descriptor_item.h"
   6
   7 #include <stdlib.h>
   8
   9 #include "base/logging.h"
  10 #include "device/hid/hid_usage_and_page.h"
  11
  12 namespace device {
  13
  14 namespace {
  15
  16 struct Header {
  17   uint8_t size : 2;
  18   uint8_t type : 2;
  19   uint8_t tag : 4;
  20 };
  21
  22 }  // namespace
  23
  24 HidReportDescriptorItem::HidReportDescriptorItem(
  25     const uint8_t* bytes,
  26     HidReportDescriptorItem* previous)
  27     : previous_(previous), next_(NULL), parent_(NULL), shortData_(0) {
  28   Header* header = (Header*)&bytes[0];
  29   tag_ = (Tag)(header->tag << 2 | header->type);
  30
  31   if (IsLong()) {
  32     // In a long item, payload size is the second byte.
  33     payload_size_ = bytes[1];
  34   } else {
  35     payload_size_ = header->size;
  36     DCHECK(payload_size_ <= sizeof(shortData_));
  37     memcpy(&shortData_, &bytes[GetHeaderSize()], payload_size());
  38   }
  39
  40   if (previous) {
  41     DCHECK(!previous->next_);
  42     previous->next_ = this;
  43     switch (previous->tag()) {
  44       case kTagCollection:
  45         parent_ = previous;
  46         break;
  47       default:
  48         break;
  49     }
  50     if (!parent_) {
  51       switch (tag()) {
  52         case kTagEndCollection:
  53           if (previous->parent()) {
  54             parent_ = previous->parent()->parent();
  55           }
  56           break;
  57         default:
  58           parent_ = previous->parent();
  59           break;
  60       }
  61     }
  62   }
  63 }
  64
  65 size_t HidReportDescriptorItem::GetDepth() const {
  66   HidReportDescriptorItem* parent_item = parent();
  67   if (parent_item)
  68     return parent_item->GetDepth() + 1;
  69   return 0;
  70 }
  71
  72 bool HidReportDescriptorItem::IsLong() const { return tag() == kTagLong; }
  73
  74 size_t HidReportDescriptorItem::GetHeaderSize() const {
  75   return IsLong() ? 3 : 1;
  76 }
  77
  78 size_t HidReportDescriptorItem::GetSize() const {
  79   return GetHeaderSize() + payload_size();
  80 }
  81
  82 uint32_t HidReportDescriptorItem::GetShortData() const {
  83   DCHECK(!IsLong());
  84   return shortData_;
  85 }
  86
  87 HidReportDescriptorItem::CollectionType
  88 HidReportDescriptorItem::GetCollectionTypeFromValue(uint32_t value) {
  89   switch (value) {
  90     case 0x00:
  91       return kCollectionTypePhysical;
  92     case 0x01:
  93       return kCollectionTypeApplication;
  94     case 0x02:
  95       return kCollectionTypeLogical;
  96     case 0x03:
  97       return kCollectionTypeReport;
  98     case 0x04:
  99       return kCollectionTypeNamedArray;
 100     case 0x05:
 101       return kCollectionTypeUsageSwitch;
 102     case 0x06:
 103       return kCollectionTypeUsageModifier;
 104     default:
 105       break;
 106   }
 107   if (0x80 < value && value < 0xFF)
 108     return kCollectionTypeVendor;
 109   return kCollectionTypeReserved;
 110 }
 111
 112 }  // namespace device