xref: /src/lib/libusbhid/data.c

/*	$NetBSD: data.c,v 1.9 2020/04/04 21:21:35 fox Exp $	*/

/*
 * Copyright (c) 1999 Lennart Augustsson <augustss (at) 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 <sys/cdefs.h>
__RCSID("$NetBSD: data.c,v 1.9 2020/04/04 21:21:35 fox Exp $");

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

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

	_DIAGASSERT(p != NULL);
	_DIAGASSERT(h != NULL);

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

	if (hsize == 0)
		return (0);
	offs = hpos / 8;
	end = (hpos + hsize + 7) / 8 - offs;
	data = 0;
	for (i = 0; i < end; i++)
		data |= ((uint32_t)buf[offs + i]) << (i*8);
	data >>= hpos % 8;
	if (hsize < 32) {
		data &= (1 << hsize) - 1;
		if (h->logical_minimum < 0 && (data & (1<<(hsize-1)))) {
			/* Need to sign extend */
			data |= 0xffffffff & ~((1<<hsize)-1);
		}
	}
	return (int)(data);
}

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

	_DIAGASSERT(p != NULL);
	_DIAGASSERT(h != NULL);

	buf = p;
	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 = ((uint32_t)data) << (hpos % 8);
	mask = ((uint32_t)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] & ((uint32_t)mask >> (i*8))) |
			(((uint32_t)data >> (i*8)) & 0xff);
}