view miscutil/bitmanip.c @ 146:0fa0cd251a31

gsmefr-dec-parse: use factored-out ETSI bit reader
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 14 Dec 2022 08:05:08 +0000
parents 41f1ae68d253
children
line wrap: on
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/*
 * This module provides two utility functions that serve as building blocks
 * for frame bit reordering operations.
 */

#include <stdint.h>

msb_get_bit(buf, bn)
	uint8_t *buf;
{
	int pos_byte = bn >> 3;
	int pos_bit  = 7 - (bn & 7);

	return (buf[pos_byte] >> pos_bit) & 1;
}

msb_set_bit(buf, bn, bit)
	uint8_t *buf;
{
	int pos_byte = bn >> 3;
	int pos_bit  = 7 - (bn & 7);

	if (bit)
		buf[pos_byte] |= (1 << pos_bit);
	else
		buf[pos_byte] &= ~(1 << pos_bit);
}