Fix incorrect multiple-count report field sizing #30
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schmidtsamuelw
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- Add `HIDInputReportItem::get_total_size()`, the item's size times its count - Use `HIDInputReportItem::get_total_size()` to calculate the correct item offset in `HIDInputReport::push_back` Offsets for `HIDInputReportItem` instances within a report are calculated using the size of the field, but the message will contain N fields of the given size. As a result, multiple-count fields give every following `HIDInputReportItem` an incorrect offset when parsing HID reports. In addition, the report's calculated total size is incorrect, which would cause issues with any code that might rely on its size in the future. Introducing a member to provide the correct total size allows correct calculation of a report's size.
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When enumerating a device's report fields, the resulting
HIDInputReportItemis instantiated with a count and the size of an individual field. The total size of the item is the field size times the number of fields associated with this item, butHIDInputReport::push_back(), which is used to give instantiated report items their offset in the report's buffer, uses only the individual field's size.The effect of this is that the offset for every
HIDInputReportItemis incorrect (too low) after the first item that has a count greater than one. This PR is a simple fix to giveHIDInputReportItema public member to provide its total size toHIDInputReportso that correct offsets can be calculated.