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Do not skip or add a byte for the report ID when manipulating data.

This is not compatible to our current schema where one kernel device
is attached per report ID of every USB HID device since the drivers
already strip the data buffers.

Fix a parsing issue reported by henning@

/*	$OpenBSD: data.c,v 1.8 2014/06/04 12:13:30 mpi Exp $	*/
/*	$NetBSD: data.c,v 1.1 2001/12/28 17:45:26 augustss Exp $	*/

/*
 * Copyright (c) 1999 Lennart Augustsson <augustss@netbsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <stdlib.h>
#include "usbhid.h"

int32_t
hid_get_data(const void *p, const hid_item_t *h)
{
	const uint8_t *buf;
	uint32_t hpos;
	uint32_t hsize;
	uint32_t data;
	int i, end, offs;

	buf = p;

#if 0
	/* Skip report ID byte. */
	if (h->report_ID > 0)
		buf++;
#endif

	hpos = h->pos;			/* bit position of data */
	hsize = h->report_size;		/* bit length of data */

	/* Range check and limit */
	if (hsize == 0)
		return (0);
	if (hsize > 32)
		hsize = 32;

	offs = hpos / 8;
	end = (hpos + hsize) / 8 - offs;
	data = 0;
	for (i = 0; i <= end; i++)
		data |= buf[offs + i] << (i*8);

	/* Correctly shift down data */
	data >>= hpos % 8;
	hsize = 32 - hsize;

	/* Mask and sign extend in one */
	if ((h->logical_minimum < 0) || (h->logical_maximum < 0))
		data = (int32_t)((int32_t)data << hsize) >> hsize;
	else
		data = (uint32_t)((uint32_t)data << hsize) >> hsize;

	return (data);
}

void
hid_set_data(void *p, const hid_item_t *h, int32_t data)
{
	uint8_t *buf;
	uint32_t hpos;
	uint32_t hsize;
	uint32_t mask;
	int i;
	int end;
	int offs;

	buf = p;

#if 0
	/* Set report ID byte. */
	if (h->report_ID > 0)
		*buf++ = h->report_ID & 0xff;
#endif

	hpos = h->pos;			/* bit position of data */
	hsize = h->report_size;		/* bit length of data */

	if (hsize != 32) {
		mask = (1 << hsize) - 1;
		data &= mask;
	} else
		mask = ~0;

	data <<= (hpos % 8);
	mask <<= (hpos % 8);
	mask = ~mask;

	offs = hpos / 8;
	end = (hpos + hsize) / 8 - offs;

	for (i = 0; i <= end; i++)
		buf[offs + i] = (buf[offs + i] & (mask >> (i*8))) |
		    ((data >> (i*8)) & 0xff);
}