/*
 * cifra - embedded cryptography library
 * Written in 2014 by Joseph Birr-Pixton <jpixton@gmail.com>
 *
 * To the extent possible under law, the author(s) have dedicated all
 * copyright and related and neighboring rights to this software to the
 * public domain worldwide. This software is distributed without any
 * warranty.
 *
 * You should have received a copy of the CC0 Public Domain Dedication
 * along with this software. If not, see
 * <http://creativecommons.org/publicdomain/zero/1.0/>.
 */

#ifndef BITOPS_H
#define BITOPS_H

#include <stdint.h>
#include <stddef.h>

/* Assorted bitwise and common operations used in ciphers. */

/** Circularly rotate right x by n bits.
 *  0 > n > 32. */
static inline uint32_t rotr32(uint32_t x, unsigned n)
{
  return (x >> n) | (x << (32 - n));
}

/** Read 4 bytes from buf, as a 32-bit big endian quantity. */
static inline uint32_t read32_be(const uint8_t buf[4])
{
  return (buf[0] << 24) |
         (buf[1] << 16) |
         (buf[2] << 8) |
         (buf[3]);
}

/** Encode v as a 32-bit big endian quantity into buf. */
static inline void write32_be(uint32_t v, uint8_t buf[4])
{
  *buf++ = (v >> 24) & 0xff;
  *buf++ = (v >> 16) & 0xff;
  *buf++ = (v >> 8) & 0xff;
  *buf   = v & 0xff;
}

/** Encode v as a 64-bit big endian quantity into buf. */
static inline void write64_be(uint64_t v, uint8_t buf[8])
{
  *buf++ = (v >> 56) & 0xff;
  *buf++ = (v >> 48) & 0xff;
  *buf++ = (v >> 40) & 0xff;
  *buf++ = (v >> 32) & 0xff;
  *buf++ = (v >> 24) & 0xff;
  *buf++ = (v >> 16) & 0xff;
  *buf++ = (v >> 8) & 0xff;
  *buf   = v & 0xff;
}

#endif