/*
 * Copyright 1996, 1997 Hans Reiser, see reiserfs/README for licensing and copyright details
 */
#define _GNU_SOURCE

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <asm/types.h>

#include <sys/types.h>
/*#include <linux/unistd.h>*/


#include "io.h"
#include "misc.h"



/* All buffers are in double linked cycled list. Buffers of tree are
   hashed by their block number.  If getblk found buffer with wanted
   block number in hash queue it moves buffer to the end of list */

#define BLOCK_SIZE 1024
#define MAX_NR_BUFFERS 16384
static int g_nr_buffers;

#define NR_HASH_QUEUES 4096
static struct buffer_head * g_a_hash_queues [NR_HASH_QUEUES];
static struct buffer_head * g_buffer_list_head;
static struct buffer_head * g_buffer_heads;



static void show_buffers (int dev, int size)
{
    int all = 0;
    int dirty = 0;
    int in_use = 0; /* count != 0 */
    int free = 0;
    struct buffer_head * next = g_buffer_list_head;

    for (;;) {
	if (!next)
	    die ("show_buffers: buffer list is corrupted");
	if (next->b_dev == dev && next->b_size == size) {
	    all ++;
	    if (next->b_count != 0) {
		in_use ++;
	    }
	    if (buffer_dirty (next)) {
		dirty ++;
	    }
	    if (buffer_clean (next) && next->b_count == 0) {
		free ++;
	    }
	}
	next = next->b_next;
	if (next == g_buffer_list_head)
	    break;
    }

    printf ("show_buffers (dev %d, size %d): free %d, count != 0 %d, dirty %d, all %d\n", dev, size, free, in_use, dirty, all);
}


static void insert_into_hash_queue (struct buffer_head * bh)
{
    int index = bh->b_blocknr % NR_HASH_QUEUES;

    if (bh->b_hash_prev || bh->b_hash_next)
	die ("insert_into_hash_queue: hash queue corrupted");

    if (g_a_hash_queues[index]) {
	g_a_hash_queues[index]->b_hash_prev = bh;
	bh->b_hash_next = g_a_hash_queues[index];
    }
    g_a_hash_queues[index] = bh;
}


static void remove_from_hash_queue (struct buffer_head * bh)
{
    if (bh->b_hash_next == 0 && bh->b_hash_prev == 0 && bh != g_a_hash_queues[bh->b_blocknr % NR_HASH_QUEUES])
	/* (b_dev == 0) ? */
	return;

    if (bh == g_a_hash_queues[bh->b_blocknr % NR_HASH_QUEUES]) {
	if (bh->b_hash_prev != 0)
	    die ("remove_from_hash_queue: hash queue corrupted");
	g_a_hash_queues[bh->b_blocknr % NR_HASH_QUEUES] = bh->b_hash_next;
    }
    if (bh->b_hash_next)
	bh->b_hash_next->b_hash_prev = bh->b_hash_prev;

    if (bh->b_hash_prev)
	bh->b_hash_prev->b_hash_next = bh->b_hash_next;

    bh->b_hash_prev = bh->b_hash_next = 0;
}


static void put_buffer_list_end (struct buffer_head * bh)
{
    struct buffer_head * last = 0;

    if (bh->b_prev || bh->b_next)
	die ("put_buffer_list_end: buffer list corrupted");

    if (g_buffer_list_head == 0) {
	bh->b_next = bh;
	bh->b_prev = bh;
	g_buffer_list_head = bh;
    } else {
	last = g_buffer_list_head->b_prev;
    
	bh->b_next = last->b_next;
	bh->b_prev = last;
	last->b_next->b_prev = bh;
	last->b_next = bh;
    }
}


static void remove_from_buffer_list (struct buffer_head * bh)
{
    if (bh == bh->b_next) {
	g_buffer_list_head = 0;
    } else {
	bh->b_prev->b_next = bh->b_next;
	bh->b_next->b_prev = bh->b_prev;
	if (bh == g_buffer_list_head)
	    g_buffer_list_head = bh->b_next;
    }

    bh->b_next = bh->b_prev = 0;
}


static void put_buffer_list_head (struct buffer_head * bh)
{
    put_buffer_list_end (bh);
    g_buffer_list_head = bh;
}


#define GROW_BUFFERS__NEW_BUFERS_PER_CALL 10
/* creates number of new buffers and insert them into head of buffer list 
 */
static int grow_buffers (int size)
{
    int i;
    struct buffer_head * bh, * tmp;

    if (g_nr_buffers + GROW_BUFFERS__NEW_BUFERS_PER_CALL > MAX_NR_BUFFERS)
	return 0;

    /* get memory for array of buffer heads */
    bh = (struct buffer_head *)getmem (GROW_BUFFERS__NEW_BUFERS_PER_CALL * sizeof (struct buffer_head) + sizeof (struct buffer_head *));
    if (g_buffer_heads == 0)
	g_buffer_heads = bh;
    else {
	/* link new array to the end of array list */
	tmp = g_buffer_heads;
	while (*(struct buffer_head **)(tmp + GROW_BUFFERS__NEW_BUFERS_PER_CALL) != 0)
	    tmp = *(struct buffer_head **)(tmp + GROW_BUFFERS__NEW_BUFERS_PER_CALL);
	*(struct buffer_head **)(tmp + GROW_BUFFERS__NEW_BUFERS_PER_CALL) = bh;
    }

    for (i = 0; i < GROW_BUFFERS__NEW_BUFERS_PER_CALL; i ++) {

	tmp = bh + i;
	memset (tmp, 0, sizeof (struct buffer_head));
	tmp->b_data = getmem (size);
	if (tmp->b_data == 0)
	    die ("grow_buffers: no memory for new buffer data");
	tmp->b_dev = 0;
	tmp->b_size = size;
	put_buffer_list_head (tmp);

	g_nr_buffers ++;
    }
    return GROW_BUFFERS__NEW_BUFERS_PER_CALL;
}


struct buffer_head * find_buffer (int dev, int block, int size)
{		
    struct buffer_head * next;

    next = g_a_hash_queues[block % NR_HASH_QUEUES];
    for (;;) {
	struct buffer_head *tmp = next;
	if (!next)
	    break;
	next = tmp->b_hash_next;
	if (tmp->b_blocknr != block || tmp->b_size != size || tmp->b_dev != dev)
	    continue;
	next = tmp;
	break;
    }
    return next;
}

void __wait_on_buffer (struct buffer_head * bh)
{
}

struct buffer_head * get_hash_table(dev_t dev, int block, int size)
{
    struct buffer_head * bh;

    bh = find_buffer (dev, block, size);
    if (bh) {
	bh->b_count ++;
    }
    return bh;
}


static struct buffer_head * get_free_buffer (int size)
{
    struct buffer_head * next = g_buffer_list_head;

    if (!next)
	return 0;
    for (;;) {
	if (!next)
	    die ("get_free_buffer: buffer list is corrupted");
	if (next->b_count == 0 && buffer_clean (next) && next->b_size == size) {
	    remove_from_hash_queue (next);
	    remove_from_buffer_list (next);
	    put_buffer_list_end (next);
	    return next;
	}
	next = next->b_next;
	if (next == g_buffer_list_head)
	    break;
    }
    return 0;
}


static void sync_buffers (int size, int to_write)
{
    struct buffer_head * next = g_buffer_list_head;
    int written = 0;

    for (;;) {
	if (!next)
	    die ("flush_buffer: buffer list is corrupted");
    
	if ((!size || next->b_size == size) && buffer_dirty (next) && buffer_uptodate (next)) {
	    written ++;
	    bwrite (next);
	    if (written == to_write)
		return;
	}
    
	next = next->b_next;
	if (next == g_buffer_list_head)
	    break;
    }
}

void flush_buffers (void)
{
    sync_buffers (0, 0);
}


struct buffer_head * getblk (int dev, int block, int size)
{
    struct buffer_head * bh;

    bh = find_buffer (dev, block, size);
    if (bh) {
	if (0 && !buffer_uptodate (bh))
	    die ("getblk: buffer must be uptodate");
	// move the buffer to the end of list

	/*checkmem (bh->b_data, bh->b_size);*/

	remove_from_buffer_list (bh);
	put_buffer_list_end (bh);
	bh->b_count ++;
	return bh;
    }

    bh = get_free_buffer (size);
    if (bh == 0) {
	if (grow_buffers (size) == 0) {
	    sync_buffers (size, 10);
	}
	bh = get_free_buffer (size);
	if (bh == 0) {
	    show_buffers (dev, size);
	    die ("getblk: no free buffers after grow_buffers and refill (%d)", g_nr_buffers);
	}
    }

    bh->b_count = 1;
    bh->b_dev = dev;
    bh->b_size = size;
    bh->b_blocknr = block;
    bh->b_end_io = NULL ;
    memset (bh->b_data, 0, size);
    clear_bit(BH_Dirty, &bh->b_state);
    clear_bit(BH_Uptodate, &bh->b_state);

    insert_into_hash_queue (bh);
    /*checkmem (bh->b_data, bh->b_size);*/

    return bh;
}

struct buffer_head * reiserfs_getblk (int dev, int block, int size, int *repeat)
{
    return getblk (dev, block, size);
}


void brelse (struct buffer_head * bh)
{
    if (bh == 0)
	return;
    if (bh->b_count == 0) {
	die ("brelse: can not free a free buffer %lu", bh->b_blocknr);
    }
    /*checkmem (bh->b_data, bh->b_size);*/
    bh->b_count --;
}


void bforget (struct buffer_head * bh)
{
    if (bh) {
	brelse (bh);
	remove_from_hash_queue (bh);
	remove_from_buffer_list (bh);
	put_buffer_list_head (bh);
    }
}

#if 0
#if ! ( defined __USE_LARGEFILE64 || defined __USE_FILE_OFFSET64 )
_syscall5 (int,  _llseek,  uint,  fd, ulong, hi, ulong, lo,
           loff_t *, res, uint, wh);
#endif

loff_t reiserfs_llseek (unsigned int fd, loff_t offset, unsigned int origin)
{
#if defined __USE_FILE_OFFSET64
    return lseek(fd, offset, origin);
#elif defined __USE_LARGEFILE64
    return lseek64(fd, offset, origin);
#else
    loff_t retval, result;
    retval = _llseek (fd, ((unsigned long long) offset) >> 32,
		      ((unsigned long long) offset) & 0xffffffff,
		      &result, origin);
    return (retval != 0 ? (loff_t)-1 : result);
#endif
}
#endif

static int f_read(struct buffer_head * bh)
{
    loff_t offset;
    ssize_t bytes;

    offset = (loff_t)bh->b_size * (loff_t)bh->b_blocknr;
    /*if (reiserfs_llseek (bh->b_dev, offset, SEEK_SET) == (loff_t)-1)*/
    if (lseek64 (bh->b_dev, offset, SEEK_SET) == (loff_t)-1)
        return 0;

    bytes = read (bh->b_dev, bh->b_data, bh->b_size);
    if (bytes != (ssize_t)bh->b_size)
        return 0;

    return 1;
}

struct buffer_head * bread (int dev, unsigned long block, size_t size)
{
    struct buffer_head * bh;

    /*
    if ((size == 32768 && (block == 16 || 1026)) ||
	(size == 4096 && (block == 128 || block == 8211))) {
	size = 10;
	return 0;
    }
    */

    bh = getblk (dev, block, size);
    if (buffer_uptodate (bh))
	return bh;

    if (f_read(bh) == 0)
    {
        brelse(bh);
        return 0;
    }

    mark_buffer_uptodate (bh, 0);
    return bh;
}


int valid_offset( int fd, loff_t offset)
{
    char ch;
    loff_t res;

    /*res = reiserfs_llseek (fd, offset, 0);*/
    res = lseek64 (fd, offset, 0);
    if (res < 0)
	return 0;

    if (read (fd, &ch, 1) < 1)
	return 0;

    return 1;
}


struct buffer_head * reiserfs_bread (int dev, int block, int size, int *repeat)
{
    return bread (dev, block, size);
}


int bwrite (struct buffer_head * bh)
{
    loff_t offset;
    ssize_t bytes;
    size_t size;

    if (!buffer_dirty (bh) || !buffer_uptodate (bh))
	return 0;

    size = bh->b_size;
    offset = (loff_t)size * (loff_t)bh->b_blocknr;

    if (lseek64 (bh->b_dev, offset, SEEK_SET) == (loff_t)-1){
	fprintf (stderr, "bwrite: lseek to position %Ld (block=%lu, dev=%d): %s\n",
		 offset, bh->b_blocknr, bh->b_dev, strerror (errno));
	exit (4); /* File system errors left uncorrected */
    }

    bytes = write (bh->b_dev, bh->b_data, size);
    if (bytes != (ssize_t)size) {
	fprintf (stderr, "bwrite: write %d bytes returned %d (block=%ld, dev=%d): %s\n",
		size, bytes, bh->b_blocknr, bh->b_dev, strerror (errno));
	exit (4);
    }

    mark_buffer_clean (bh);
    if (bh->b_end_io) {
	bh->b_end_io(bh, 1) ;
    }
    return 0;
}


void check_and_free_buffer_mem (void)
{
    int i = 0;
    struct buffer_head * next = g_buffer_list_head;

    //sync_buffers (0, 0);
    for (;;) {
	if (!next)
	    die ("check_and_free_buffer_mem: buffer list is corrupted");
	if (next->b_count != 0)
	    fprintf (stderr, "check_and_free_buffer_mem: not free buffer (%ld, %ld, %d)",
		     next->b_blocknr, next->b_size, next->b_count);

	if (buffer_dirty (next) && buffer_uptodate (next))
	    fprintf (stderr, "check_and_free_buffer_mem: dirty buffer %lu found\n",
		    next->b_blocknr);

	freemem (next->b_data);
	i ++;
	next = next->b_next;
	if (next == g_buffer_list_head)
	    break;
    }
    if (i != g_nr_buffers)
	die ("check_and_free_buffer_mem: found %d buffers, must be %d", i, g_nr_buffers);

    /* free buffer heads */
    while ((next = g_buffer_heads)) {
	g_buffer_heads = *(struct buffer_head **)(next + GROW_BUFFERS__NEW_BUFERS_PER_CALL);
	freemem (next);
    }
  
    return;
}


/* */
void free_buffers (void)
{
    check_and_free_buffer_mem ();
}