public HID.UsagePage GetUsagePage(int index, ref HIDItemStateLocal localItemState)
{
if (!usagePage.HasValue)
{
var usage = localItemState.GetUsage(index);
return((HID.UsagePage)(usage >> 16));
}
return((HID.UsagePage)usagePage.Value);
}
// Wipe state but preserve usageList allocation.
public static void Reset(ref HIDItemStateLocal state)
{
var usageList = state.usageList;
state = new HIDItemStateLocal();
if (usageList != null)
{
usageList.Clear();
state.usageList = usageList;
}
}
public unsafe static bool ParseReportDescriptor(byte *bufferPtr, int bufferLength, ref HID.HIDDeviceDescriptor deviceDescriptor)
{
// Item state.
var localItemState = new HIDItemStateLocal();
var globalItemState = new HIDItemStateGlobal();
// Lists where we accumulate the data from the HID items.
var reports = new List <HIDReportData>();
var elements = new List <HID.HIDElementDescriptor>();
var collections = new List <HID.HIDCollectionDescriptor>();
var currentCollection = -1;
// Parse the linear list of items.
var endPtr = bufferPtr + bufferLength;
var currentPtr = bufferPtr;
while (currentPtr < endPtr)
{
var firstByte = *currentPtr;
////TODO
if (firstByte == 0xFE)
{
throw new NotImplementedException("long item support");
}
// Read item header.
var itemSize = (byte)(firstByte & 0x3);
var itemTypeAndTag = (byte)(firstByte & 0xFC);
++currentPtr;
// Process item.
switch (itemTypeAndTag)
{
// ------------ Global Items --------------
// These set item state permanently until it is reset.
// Usage Page
case (int)HIDItemTypeAndTag.UsagePage:
globalItemState.usagePage = ReadData(itemSize, currentPtr, endPtr);
break;
// Report Count
case (int)HIDItemTypeAndTag.ReportCount:
globalItemState.reportCount = ReadData(itemSize, currentPtr, endPtr);
break;
// Report Size
case (int)HIDItemTypeAndTag.ReportSize:
globalItemState.reportSize = ReadData(itemSize, currentPtr, endPtr);
break;
// Report ID
case (int)HIDItemTypeAndTag.ReportID:
globalItemState.reportId = ReadData(itemSize, currentPtr, endPtr);
break;
// Logical Minimum
case (int)HIDItemTypeAndTag.LogicalMinimum:
globalItemState.logicalMinimum = ReadData(itemSize, currentPtr, endPtr);
break;
// Logical Maximum
case (int)HIDItemTypeAndTag.LogicalMaximum:
globalItemState.logicalMaximum = ReadData(itemSize, currentPtr, endPtr);
break;
// Physical Minimum
case (int)HIDItemTypeAndTag.PhysicalMinimum:
globalItemState.physicalMinimum = ReadData(itemSize, currentPtr, endPtr);
break;
// Physical Maximum
case (int)HIDItemTypeAndTag.PhysicalMaximum:
globalItemState.physicalMaximum = ReadData(itemSize, currentPtr, endPtr);
break;
// Unit Exponent
case (int)HIDItemTypeAndTag.UnitExponent:
globalItemState.unitExponent = ReadData(itemSize, currentPtr, endPtr);
break;
// Unit
case (int)HIDItemTypeAndTag.Unit:
globalItemState.unit = ReadData(itemSize, currentPtr, endPtr);
break;
// ------------ Local Items --------------
// These set the state for the very next elements to be generated.
// Usage
case (int)HIDItemTypeAndTag.Usage:
localItemState.SetUsage(ReadData(itemSize, currentPtr, endPtr));
break;
// Usage Minimum
case (int)HIDItemTypeAndTag.UsageMinimum:
localItemState.usageMinimum = ReadData(itemSize, currentPtr, endPtr);
break;
// Usage Maximum
case (int)HIDItemTypeAndTag.UsageMaximum:
localItemState.usageMaximum = ReadData(itemSize, currentPtr, endPtr);
break;
// ------------ Main Items --------------
// These emit things into the descriptor based on the local and global item state.
// Collection
case (int)HIDItemTypeAndTag.Collection:
// Start new collection.
var parentCollection = currentCollection;
currentCollection = collections.Count;
collections.Add(new HID.HIDCollectionDescriptor
{
type = (HID.HIDCollectionType)ReadData(itemSize, currentPtr, endPtr),
parent = parentCollection,
usagePage = globalItemState.GetUsagePage(0, ref localItemState),
usage = localItemState.GetUsage(0),
firstChild = elements.Count
});
HIDItemStateLocal.Reset(ref localItemState);
break;
// EndCollection
case (int)HIDItemTypeAndTag.EndCollection:
if (currentCollection == -1)
{
return(false);
}
// Close collection.
var collection = collections[currentCollection];
collection.childCount = elements.Count - collection.firstChild;
collections[currentCollection] = collection;
// Switch back to parent collection (if any).
currentCollection = collection.parent;
HIDItemStateLocal.Reset(ref localItemState);
break;
// Input/Output/Feature
case (int)HIDItemTypeAndTag.Input:
case (int)HIDItemTypeAndTag.Output:
case (int)HIDItemTypeAndTag.Feature:
// Determine report type.
var reportType = itemTypeAndTag == (int)HIDItemTypeAndTag.Input
? HID.HIDReportType.Input
: itemTypeAndTag == (int)HIDItemTypeAndTag.Output
? HID.HIDReportType.Output
: HID.HIDReportType.Feature;
// Find report.
var reportIndex = HIDReportData.FindOrAddReport(globalItemState.reportId, reportType, reports);
var report = reports[reportIndex];
// If we have a report ID, then reports start with an 8 byte report ID.
// Shift our offsets accordingly.
if (report.currentBitOffset == 0 && globalItemState.reportId.HasValue)
{
report.currentBitOffset = 8;
}
// Add elements to report.
var reportCount = globalItemState.reportCount.GetValueOrDefault(1);
var flags = ReadData(itemSize, currentPtr, endPtr);
for (var i = 0; i < reportCount; ++i)
{
var element = new HID.HIDElementDescriptor
{
usage = localItemState.GetUsage(i) & 0xFFFF, // Mask off usage page, if set.
usagePage = globalItemState.GetUsagePage(i, ref localItemState),
reportType = reportType,
reportSizeInBits = globalItemState.reportSize.GetValueOrDefault(8),
reportOffsetInBits = report.currentBitOffset,
reportId = globalItemState.reportId.GetValueOrDefault(1),
flags = (HID.HIDElementFlags)flags,
logicalMin = globalItemState.logicalMinimum.GetValueOrDefault(0),
logicalMax = globalItemState.logicalMaximum.GetValueOrDefault(0),
physicalMin = globalItemState.GetPhysicalMin(),
physicalMax = globalItemState.GetPhysicalMax(),
unitExponent = globalItemState.unitExponent.GetValueOrDefault(0),
unit = globalItemState.unit.GetValueOrDefault(0),
};
report.currentBitOffset += element.reportSizeInBits;
elements.Add(element);
}
reports[reportIndex] = report;
HIDItemStateLocal.Reset(ref localItemState);
break;
}
if (itemSize == 3)
{
currentPtr += 4;
}
else
{
currentPtr += itemSize;
}
}
deviceDescriptor.elements = elements.ToArray();
deviceDescriptor.collections = collections.ToArray();
// Set usage and usage page on device descriptor to what's
// on the toplevel application collection.
foreach (var collection in collections)
{
if (collection.parent == -1 && collection.type == HID.HIDCollectionType.Application)
{
deviceDescriptor.usage = collection.usage;
deviceDescriptor.usagePage = collection.usagePage;
break;
}
}
return(true);
}