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common/usbx_host_classes/src/ux_host_class_hid_field_decompress.c
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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** USBX Component */
/** */
/** HID Class */
/** */
/**************************************************************************/
/**************************************************************************/
/* Include necessary system files. */
#define UX_SOURCE_CODE
#include "ux_api.h"
#include "ux_host_class_hid.h"
#include "ux_host_stack.h"
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _ux_host_class_hid_field_decompress PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Chaoqiong Xiao, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function will decompress a field and return the usage/value. */
/* */
/* INPUT */
/* */
/* hid_field Pointer to HID field */
/* report_buffer Pointer to report buffer */
/* client_report Pointer to client report */
/* */
/* OUTPUT */
/* */
/* Completion Status */
/* */
/* CALLS */
/* */
/* None */
/* */
/* CALLED BY */
/* */
/* HID Class */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Chaoqiong Xiao Initial Version 6.0 */
/* 09-30-2020 Chaoqiong Xiao Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
UINT _ux_host_class_hid_field_decompress(UX_HOST_CLASS_HID_FIELD *hid_field, UCHAR *report_buffer, UX_HOST_CLASS_HID_CLIENT_REPORT *client_report)
{
ULONG field_report_count;
ULONG field_report_size;
ULONG data_offset_byte;
ULONG data_offset_bit;
ULONG data_offset_bit_in_report;
ULONG field_value;
ULONG field_value_bit_shifting;
ULONG field_usage;
ULONG report_content;
/* Calculate the address of the beginning of the field in the report. */
data_offset_byte = (hid_field -> ux_host_class_hid_field_report_offset >> 3);
/* Calculate the bit start address. Hopefully things will be on a boundary but not necessary. */
data_offset_bit = hid_field -> ux_host_class_hid_field_report_offset & 7;
/* Each report field has a report_count value. This count is used to extract values from the
incoming report and build each usage/value instance. */
for (field_report_count = 0; field_report_count < hid_field -> ux_host_class_hid_field_report_count; field_report_count++)
{
/* Get the report size in bits. */
field_report_size = hid_field -> ux_host_class_hid_field_report_size;
/* We use the bit offset for this report and not the generic field bit offset. */
data_offset_bit_in_report = data_offset_bit;
/* Reset the local value. */
field_value = 0;
/* And start with bit 0 in the target value. */
field_value_bit_shifting = 0;
/* Build the value field bit by bit. */
while (field_report_size-- != 0)
{
/* Read the content. This method is redundant if we are not changing byte but it
makes the algorithm much easier. */
report_content = (ULONG) *(report_buffer + data_offset_byte + (data_offset_bit_in_report >> 3));
/* Shift the current value content to allow space to store the new bit. */
field_value |= ((report_content >> (data_offset_bit_in_report & 7)) & 1) << field_value_bit_shifting;
/* Move to next bit in the report. */
data_offset_bit_in_report++;
/* And the next bit in the value. */
field_value_bit_shifting++;
}
/* The Usage value will depend if the data is defined as a variable or an array in the HID report. */
if (hid_field -> ux_host_class_hid_field_value & UX_HOST_CLASS_HID_ITEM_VARIABLE)
{
/* Take the usage directly from the usage array. */
field_usage = *(hid_field -> ux_host_class_hid_field_usages + field_report_count);
}
else
{
/* This is an array, so compute the usage from the min value, the report count and the
computed report value. */
field_usage = hid_field -> ux_host_class_hid_field_usage_min + (ULONG)((SLONG)field_value - hid_field -> ux_host_class_hid_field_logical_min);
/* Also add the usage page. */
field_usage |= (hid_field -> ux_host_class_hid_field_usage_page << 16);
}
/* Put the value and the usage into the caller's buffer. */
*(client_report -> ux_host_class_hid_client_report_buffer + client_report -> ux_host_class_hid_client_report_actual_length) = field_usage;
client_report -> ux_host_class_hid_client_report_actual_length++;
*(client_report -> ux_host_class_hid_client_report_buffer + client_report -> ux_host_class_hid_client_report_actual_length) = field_value;
client_report -> ux_host_class_hid_client_report_actual_length++;
/* Calculate the next address for this field. */
data_offset_bit += hid_field -> ux_host_class_hid_field_report_size;
}
/* Return successful completion. */
return(UX_SUCCESS);
}