/* SPDX-License-Identifier: GPL-2.0 */

#include <sys/wait.h>
#include <stdio.h>
#include <inttypes.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <string.h>
#include <assert.h>
#include <sys/stat.h>
#include <stddef.h>
#include <limits.h>
#include <sys/param.h>
#include <stdbool.h>

#include "gcc-compat.h"
#include "str.h"
#include "log.h"
#include "gcc-compat.h"
#include "err.h"
#include "ipc.h"

#if (defined(__GNUC__) && defined(__i386__))
#define get16bits(d) (*((const uint16_t *) (d)))
#else
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
		+(uint32_t)(((const uint8_t *)(d))[0]) )
#endif

/*
 * SuperFastHash, by Paul Hsieh.
 * http://www.azillionmonkeys.com/qed/hash.html
 */
uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash)
{
	uint32_t tmp;
	int rem = len & 3;

	len >>= 2;

	for (;len > 0; len--) {
		hash  += get16bits (data);
		tmp    = (get16bits (data+2) << 11) ^ hash;
		hash   = (hash << 16) ^ tmp;
		data  += 2*sizeof (uint16_t);
		hash  += hash >> 11;
	}

	/* Handle end cases */
	switch (rem) {
	case 3:
		hash += get16bits (data);
		hash ^= hash << 16;
		hash ^= data[sizeof (uint16_t)] << 18;
		hash += hash >> 11;
		break;
	case 2:
		hash += get16bits (data);
		hash ^= hash << 11;
		hash += hash >> 17;
		break;
	case 1:
		hash += *data;
		hash ^= hash << 10;
		hash += hash >> 1;
	}
	/* Force "avalanching" of final 127 bits */
	hash ^= hash << 3;
	hash += hash >> 5;
	hash ^= hash << 4;
	hash += hash >> 17;
	hash ^= hash << 25;
	hash += hash >> 6;
	return hash;
}

static int mutex_get(key_t key, int flags)
{
	int ret;

	DSS_DEBUG_LOG("getting semaphore 0x%lx\n", (long)key);
	ret = semget(key, 2, flags);
	if (ret < 0)
		return -ERRNO_TO_DSS_ERROR(errno);
	return ret;
}

static int do_semop(int id, struct sembuf *sops, int num)
{
	int ret;

	DSS_DEBUG_LOG("calling semop\n");
	do {
		ret = semop(id, sops, num);
		if (ret >= 0)
			return 1;
	} while (errno == EINTR);
	return -ERRNO_TO_DSS_ERROR(errno);
}

static bool mutex_is_locked(int id)
{
	struct sembuf sops;
	int ret;

	DSS_DEBUG_LOG("trying to lock\n");

	sops.sem_num = 0;
	sops.sem_op = 0;
	sops.sem_flg = SEM_UNDO | IPC_NOWAIT;

	ret = do_semop(id, &sops, 1);
	if (ret < 0)
		return true;
	return false;
}

int lock_dss(uint32_t key)
{
	int ret, id;
	struct sembuf sops[4];

	ret = mutex_get(key, IPC_CREAT | 0600);
	if (ret < 0)
		return ret;
	id = ret;

	sops[0].sem_num = 0;
	sops[0].sem_op = 0;
	sops[0].sem_flg = SEM_UNDO | IPC_NOWAIT;

	sops[1].sem_num = 0;
	sops[1].sem_op = 1;
	sops[1].sem_flg = SEM_UNDO | IPC_NOWAIT;

	sops[2].sem_num = 1;
	sops[2].sem_op = 0;
	sops[2].sem_flg = SEM_UNDO | IPC_NOWAIT;

	sops[3].sem_num = 1;
	sops[3].sem_op = 1;
	sops[3].sem_flg = SEM_UNDO | IPC_NOWAIT;

	return do_semop(id, sops, 4);
}

int get_dss_pid(uint32_t key, pid_t *pid)
{
	int ret, semid;

	if (pid)
		*pid = 0;
	ret = mutex_get(key, 0);
	if (ret < 0)
		return ret == -ERRNO_TO_DSS_ERROR(ENOENT)? -E_NOT_RUNNING : ret;
	semid = ret;
	ret = semctl(semid, 1, GETPID);
	if (ret < 0)
		return -E_NOT_RUNNING;
	if (pid)
		*pid = ret;
	return mutex_is_locked(semid)? 1 : -E_NOT_RUNNING;
}