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use crate::windows_native::descriptor::typedefs::{Caps, LinkCollectionNode};
use crate::windows_native::descriptor::types::{ItemNodeType, Items, MainItemNode, MainItems};
use crate::windows_native::error::{WinError, WinResult};
use crate::windows_native::utils::PeakIterExt;
pub fn encode_descriptor(
main_item_list: &[MainItemNode],
caps_list: &[Caps],
link_collection_nodes: &[LinkCollectionNode],
) -> WinResult<Vec<u8>> {
// ***********************************
// Encode the report descriptor output
// ***********************************
let mut writer = DescriptorWriter::default();
let mut last_report_id = 0;
let mut last_usage_page = 0;
let mut last_physical_min = 0; // If both, Physical Minimum and Physical Maximum are 0, the logical limits should be taken as physical limits according USB HID spec 1.11 chapter 6.2.2.7
let mut last_physical_max = 0;
let mut last_unit_exponent = 0; // If Unit Exponent is Undefined it should be considered as 0 according USB HID spec 1.11 chapter 6.2.2.7
let mut last_unit = 0; // If the first nibble is 7, or second nibble of Unit is 0, the unit is None according USB HID spec 1.11 chapter 6.2.2.7
let mut inhibit_write_of_usage = false; // Needed in case of delimited usage print, before the normal collection or cap
let mut report_count = 0;
for (current, next) in main_item_list.iter().peaking() {
let rt_idx = current.main_item_type;
let caps_idx = current.caps_index;
match current.main_item_type {
MainItems::Collection => {
if last_usage_page
!= link_collection_nodes[current.collection_index].link_usage_page
{
// Write "Usage Page" at the begin of a collection - except it refers the same table as wrote last
last_usage_page =
link_collection_nodes[current.collection_index].link_usage_page;
writer.write(Items::GlobalUsagePage, last_usage_page)?;
}
if inhibit_write_of_usage {
// Inhibit only once after DELIMITER statement
inhibit_write_of_usage = false;
} else {
// Write "Usage" of collection
writer.write(
Items::LocalUsage,
link_collection_nodes[current.collection_index].link_usage,
)?;
}
// Write begin of "Collection"
writer.write(
Items::MainCollection,
link_collection_nodes[current.collection_index].collection_type(),
)?;
}
MainItems::CollectionEnd => {
// Write "End Collection"
writer.write(Items::MainCollectionEnd, 0)?;
}
MainItems::DelimiterOpen => {
// Current.collection_index seems to always be != -1 -> removing branches compared to c
// Write "Usage Page" inside of a collection delmiter section
if last_usage_page
!= link_collection_nodes[current.collection_index].link_usage_page
{
last_usage_page =
link_collection_nodes[current.collection_index].link_usage_page;
writer.write(
Items::GlobalUsagePage,
link_collection_nodes[current.collection_index].collection_type(),
)?;
}
// Write "Delimiter Open"
writer.write(Items::LocalDelimiter, 1)?; // 1 = open set of aliased usages
}
MainItems::DelimiterUsage => {
// Current.collection_index seems to always be != -1 -> removing branches compared to c
// Write aliased collection "Usage"
writer.write(
Items::LocalUsage,
link_collection_nodes[current.collection_index].link_usage,
)?;
}
MainItems::DelimiterClose => {
// Write "Delimiter Close"
writer.write(Items::LocalDelimiter, 0)?; // 0 = close set of aliased usages
// Inhibit next usage write
inhibit_write_of_usage = true;
}
_ if current.node_type == ItemNodeType::Padding => {
// Padding
// The preparsed data doesn't contain any information about padding. Therefore all undefined gaps
// in the reports are filled with the same style of constant padding.
// Write "Report Size" with number of padding bits
writer.write(
Items::GlobalReportSize,
current.last_bit - current.first_bit + 1,
)?;
// Write "Report Count" for padding always as 1
writer.write(Items::GlobalReportCount, 1)?;
if rt_idx == MainItems::Input {
// Write "Input" main item - We know it's Constant - We can only guess the other bits, but they don't matter in case of const
writer.write(Items::MainInput, 0x03)?; // Const / Abs
} else if rt_idx == MainItems::Output {
// Write "Output" main item - We know it's Constant - We can only guess the other bits, but they don't matter in case of const
writer.write(Items::MainOutput, 0x03)?; // Const / Abs
} else if rt_idx == MainItems::Feature {
// Write "Feature" main item - We know it's Constant - We can only guess the other bits, but they don't matter in case of const
writer.write(Items::MainFeature, 0x03)?; // Const / Abs
}
report_count = 0;
}
_ if caps_list[caps_idx as usize].is_button_cap() => {
let caps = caps_list[caps_idx as usize];
// Button
// (The preparsed data contain different data for 1 bit Button caps, than for parametric Value caps)
if last_report_id != caps.report_id {
// Write "Report ID" if changed
last_report_id = caps.report_id;
writer.write(Items::GlobalReportId, last_report_id)?;
}
// Write "Usage Page" when changed
if caps.usage_page != last_usage_page {
last_usage_page = caps.usage_page;
writer.write(Items::GlobalUsagePage, last_usage_page)?;
}
// Write only local report items for each cap, if ReportCount > 1
if caps.is_range() {
report_count += caps.range().data_index_max - caps.range().data_index_min;
}
if inhibit_write_of_usage {
// Inhibit only once after Delimiter - Reset flag
inhibit_write_of_usage = false;
} else if caps.is_range() {
// Write range from "Usage Minimum" to "Usage Maximum"
writer.write(Items::LocalUsageMinimum, caps.range().usage_min)?;
writer.write(Items::LocalUsageMaximum, caps.range().usage_max)?;
} else {
// Write single "Usage"
writer.write(Items::LocalUsage, caps.not_range().usage)?;
}
if caps.is_designator_range() {
// Write physical descriptor indices range from "Designator Minimum" to "Designator Maximum"
writer.write(Items::LocalDesignatorMinimum, caps.range().designator_min)?;
writer.write(Items::LocalDesignatorMaximum, caps.range().designator_max)?;
} else if caps.not_range().designator_index != 0 {
// Designator set 0 is a special descriptor set (of the HID Physical Descriptor),
// that specifies the number of additional descriptor sets.
// Therefore Designator Index 0 can never be a useful reference for a control and we can inhibit it.
// Write single "Designator Index"
writer.write(
Items::LocalDesignatorIndex,
caps.not_range().designator_index,
)?;
}
if caps.is_string_range() {
// Write range of indices of the USB string descriptor, from "String Minimum" to "String Maximum"
writer.write(Items::LocalStringMinimum, caps.range().string_min)?;
writer.write(Items::LocalStringMaximum, caps.range().string_max)?;
} else if caps.not_range().string_index != 0 {
// String Index 0 is a special entry of the USB string descriptor, that contains a list of supported languages,
// therefore Designator Index 0 can never be a useful reference for a control and we can inhibit it.
// Write single "String Index"
writer.write(Items::LocalString, caps.not_range().string_index)?;
}
if next.is_some_and(|next| {
next.main_item_type == rt_idx &&
next.node_type == ItemNodeType::Cap &&
!caps.is_range() && // This node in list is no array
!caps_list[next.caps_index as usize].is_range() && // Next node in list is no array
caps_list[next.caps_index as usize].is_button_cap() &&
caps_list[next.caps_index as usize].usage_page == caps.usage_page &&
caps_list[next.caps_index as usize].report_id == caps.report_id &&
caps_list[next.caps_index as usize].bit_field == caps.bit_field
}) {
if next.unwrap().first_bit != current.first_bit {
// In case of IsMultipleItemsForArray for multiple dedicated usages for a multi-button array, the report count should be incremented
// Skip global items until any of them changes, than use ReportCount item to write the count of identical report fields
report_count += 1;
}
} else {
if caps.button().logical_min == 0 && caps.button().logical_max == 0 {
// While a HID report descriptor must always contain LogicalMinimum and LogicalMaximum,
// the preparsed data contain both fields set to zero, for the case of simple buttons
// Write "Logical Minimum" set to 0 and "Logical Maximum" set to 1
writer.write(Items::GlobalLogicalMinimum, 0)?;
writer.write(Items::GlobalLogicalMaximum, 1)?;
} else {
// Write logical range from "Logical Minimum" to "Logical Maximum"
writer.write(Items::GlobalLogicalMinimum, caps.button().logical_min)?;
writer.write(Items::GlobalLogicalMaximum, caps.button().logical_max)?;
}
// Write "Report Size"
writer.write(Items::GlobalReportSize, caps.report_size)?;
// Write "Report Count"
if !caps.is_range() {
// Variable bit field with one bit per button
// In case of multiple usages with the same items, only "Usage" is written per cap, and "Report Count" is incremented
writer.write(Items::GlobalReportCount, caps.report_count + report_count)?;
} else {
// Button array of "Report Size" x "Report Count
writer.write(Items::GlobalReportCount, caps.report_count)?;
}
// Buttons have only 1 bit and therefore no physical limits/units -> Set to undefined state
if last_physical_min != 0 {
// Write "Physical Minimum", but only if changed
last_physical_min = 0;
writer.write(Items::GlobalPhysicalMinimum, last_physical_min)?;
}
if last_physical_max != 0 {
// Write "Physical Maximum", but only if changed
last_physical_max = 0;
writer.write(Items::GlobalPhysicalMaximum, last_physical_max)?;
}
if last_unit_exponent != 0 {
// Write "Unit Exponent", but only if changed
last_unit_exponent = 0;
writer.write(Items::GlobalUnitExponent, last_unit_exponent)?;
}
if last_unit != 0 {
// Write "Unit",but only if changed
last_unit = 0;
writer.write(Items::GlobalUnit, last_unit)?;
}
// Write "Input" main item
if rt_idx == MainItems::Input {
writer.write(Items::MainInput, caps.bit_field)?;
}
// Write "Output" main item
else if rt_idx == MainItems::Output {
writer.write(Items::MainOutput, caps.bit_field)?;
}
// Write "Feature" main item
else if rt_idx == MainItems::Feature {
writer.write(Items::MainFeature, caps.bit_field)?;
}
report_count = 0;
}
}
_ => {
let mut caps = caps_list[caps_idx as usize];
if last_report_id != caps.report_id {
// Write "Report ID" if changed
last_report_id = caps.report_id;
writer.write(Items::GlobalReportId, last_report_id)?;
}
// Write "Usage Page" if changed
if caps.usage_page != last_usage_page {
last_usage_page = caps.usage_page;
writer.write(Items::GlobalUsagePage, last_usage_page)?;
}
if inhibit_write_of_usage {
// Inhibit only once after Delimiter - Reset flag
inhibit_write_of_usage = false;
} else if caps.is_range() {
// Write usage range from "Usage Minimum" to "Usage Maximum"
writer.write(Items::LocalUsageMinimum, caps.range().usage_min)?;
writer.write(Items::LocalUsageMaximum, caps.range().usage_max)?;
} else {
// Write single "Usage"
writer.write(Items::LocalUsage, caps.not_range().usage)?;
}
if caps.is_designator_range() {
// Write physical descriptor indices range from "Designator Minimum" to "Designator Maximum"
writer.write(Items::LocalDesignatorMinimum, caps.range().designator_min)?;
writer.write(Items::LocalDesignatorMaximum, caps.range().designator_max)?;
} else if caps.not_range().designator_index != 0 {
// Designator set 0 is a special descriptor set (of the HID Physical Descriptor),
// that specifies the number of additional descriptor sets.
// Therefore Designator Index 0 can never be a useful reference for a control and we can inhibit it.
// Write single "Designator Index"
writer.write(
Items::LocalDesignatorIndex,
caps.not_range().designator_index,
)?;
}
if caps.is_string_range() {
// Write range of indices of the USB string descriptor, from "String Minimum" to "String Maximum"
writer.write(Items::LocalStringMinimum, caps.range().string_min)?;
writer.write(Items::LocalStringMaximum, caps.range().string_max)?;
} else if caps.not_range().string_index != 0 {
// String Index 0 is a special entry of the USB string descriptor, that contains a list of supported languages,
// therefore Designator Index 0 can never be a useful reference for a control and we can inhibit it.
// Write single "String Index"
writer.write(Items::LocalString, caps.not_range().string_index)?;
}
if (caps.bit_field & 0x02) != 0x02 {
// In case of an value array overwrite "Report Count"
caps.report_count =
caps.range().data_index_max - caps.range().data_index_min + 1;
}
#[allow(clippy::blocks_in_if_conditions)]
if next.is_some_and(|next| {
let next_caps = caps_list
.get(next.caps_index as usize)
.copied()
.unwrap_or_else(|| unsafe { std::mem::zeroed() });
next.main_item_type == rt_idx
&& next.node_type == ItemNodeType::Cap
&& !next_caps.is_button_cap()
&& !caps.is_range()
&& !next_caps.is_range()
&& next_caps.usage_page == caps.usage_page
&& next_caps.not_button().logical_min == caps.not_button().logical_min
&& next_caps.not_button().logical_max == caps.not_button().logical_max
&& next_caps.not_button().physical_min == caps.not_button().physical_min
&& next_caps.not_button().physical_max == caps.not_button().physical_max
&& next_caps.units_exp == caps.units_exp
&& next_caps.units == caps.units
&& next_caps.report_size == caps.report_size
&& next_caps.report_id == caps.report_id
&& next_caps.bit_field == caps.bit_field
&& next_caps.report_count == 1
&& caps.report_count == 1
}) {
// Skip global items until any of them changes, than use ReportCount item to write the count of identical report fields
report_count += 1;
} else {
// Value
// Write logical range from "Logical Minimum" to "Logical Maximum"
writer.write(Items::GlobalLogicalMinimum, caps.not_button().logical_min)?;
writer.write(Items::GlobalLogicalMaximum, caps.not_button().logical_max)?;
if (last_physical_min != caps.not_button().physical_min)
|| (last_physical_max != caps.not_button().physical_max)
{
// Write range from "Physical Minimum" to " Physical Maximum", but only if one of them changed
last_physical_min = caps.not_button().physical_min;
last_physical_max = caps.not_button().physical_max;
writer.write(Items::GlobalPhysicalMinimum, last_physical_min)?;
writer.write(Items::GlobalPhysicalMaximum, last_physical_max)?;
}
if last_unit_exponent != caps.units_exp {
// Write "Unit Exponent", but only if changed
last_unit_exponent = caps.units_exp;
writer.write(Items::GlobalUnitExponent, last_unit_exponent)?;
}
if last_unit != caps.units {
// Write physical "Unit", but only if changed
last_unit = caps.units;
writer.write(Items::GlobalUnit, last_unit)?;
}
// Write "Report Size"
writer.write(Items::GlobalReportSize, caps.report_size)?;
// Write "Report Count"
writer.write(Items::GlobalReportCount, caps.report_count + report_count)?;
if rt_idx == MainItems::Input {
// Write "Input" main item
writer.write(Items::MainInput, caps.bit_field)?;
} else if rt_idx == MainItems::Output {
// Write "Output" main item
writer.write(Items::MainOutput, caps.bit_field)?;
} else if rt_idx == MainItems::Feature {
// Write "Feature" main item
writer.write(Items::MainFeature, caps.bit_field)?;
}
report_count = 0;
}
}
}
}
Ok(writer.finish())
}
#[derive(Default)]
struct DescriptorWriter(Vec<u8>);
impl DescriptorWriter {
// Writes a short report descriptor item according USB HID spec 1.11 chapter 6.2.2.2
fn write(&mut self, item: Items, data: impl Into<i64>) -> WinResult<()> {
let data = data.into();
match item {
Items::MainCollectionEnd => {
self.0.push(item as u8);
}
Items::GlobalLogicalMinimum
| Items::GlobalLogicalMaximum
| Items::GlobalPhysicalMinimum
| Items::GlobalPhysicalMaximum => {
if let Ok(data) = i8::try_from(data) {
self.0.push((item as u8) + 0x01);
self.0.extend(data.to_le_bytes())
} else if let Ok(data) = i16::try_from(data) {
self.0.push((item as u8) + 0x02);
self.0.extend(data.to_le_bytes())
} else if let Ok(data) = i32::try_from(data) {
self.0.push((item as u8) + 0x03);
self.0.extend(data.to_le_bytes())
} else {
return Err(WinError::InvalidPreparsedData);
}
}
_ => {
if let Ok(data) = u8::try_from(data) {
self.0.push((item as u8) + 0x01);
self.0.extend(data.to_le_bytes())
} else if let Ok(data) = u16::try_from(data) {
self.0.push((item as u8) + 0x02);
self.0.extend(data.to_le_bytes())
} else if let Ok(data) = u32::try_from(data) {
self.0.push((item as u8) + 0x03);
self.0.extend(data.to_le_bytes())
} else {
return Err(WinError::InvalidPreparsedData);
}
}
}
Ok(())
}
fn finish(self) -> Vec<u8> {
self.0
}
}