drdwr.c

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/* This file is part of the Zebra server.
   Copyright (C) Index Data
 
   Zebra is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 2, or (at your option) any later
   version.
 
   Zebra is distributed in the hope that it will be useful, but WITHOUT ANY
   WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
*/
 
 
 
#if HAVE_CONFIG_H
#include <config.h>
#endif
#include <sys/types.h>
#include <fcntl.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
 
#include "dict-p.h"
 
void dict_pr_lru(Dict_BFile bf)
{
    struct Dict_file_block *p;
    for (p=bf->lru_back; p; p = p->lru_next)
    {
        printf(" %d", p->no);
    }
    printf("\n");
    fflush(stdout);
}
 
static struct Dict_file_block *find_block(Dict_BFile bf, int no)
{
    struct Dict_file_block *p;
 
    for (p=bf->hash_array[no% bf->hash_size]; p; p=p->h_next)
        if (p->no == no)
            break;
    return p;
}
 
static void release_block(Dict_BFile bf, struct Dict_file_block *p)
{
    assert(p);
 
    /* remove from lru queue */
    if (p->lru_prev)
        p->lru_prev->lru_next = p->lru_next;
    else
        bf->lru_back = p->lru_next;
    if (p->lru_next)
        p->lru_next->lru_prev = p->lru_prev;
    else
        bf->lru_front = p->lru_prev;
 
    /* remove from hash chain */
    *p->h_prev = p->h_next;
    if (p->h_next)
        p->h_next->h_prev = p->h_prev;
 
    /* move to list of free blocks */
    p->h_next = bf->free_list;
    bf->free_list = p;
}
 
void dict_bf_flush_blocks(Dict_BFile bf, int no_to_flush)
{
    struct Dict_file_block *p;
    int i;
    for (i=0; i != no_to_flush && bf->lru_back; i++)
    {
        p = bf->lru_back;
        if (p->dirty)
        {
            if (!bf->compact_flag)
                bf_write(bf->bf, p->no, 0, 0, p->data);
            else
            {
                int effective_block = p->no / bf->block_size;
                int effective_offset = p->no -
                    effective_block * bf->block_size;
                int remain = bf->block_size - effective_offset;
 
                if (remain >= p->nbytes)
                {
                    bf_write(bf->bf, effective_block, effective_offset,
                             p->nbytes, p->data);
#if 0
                    yaz_log(YLOG_LOG, "bf_write no=%d offset=%d size=%d",
                            effective_block, effective_offset,
                            p->nbytes);
#endif
 
                }
                else
                {
#if 0
                    yaz_log(YLOG_LOG, "bf_write1 no=%d offset=%d size=%d",
                            effective_block, effective_offset,
                            remain);
#endif
                    bf_write(bf->bf, effective_block, effective_offset,
                             remain, p->data);
#if 0
                    yaz_log(YLOG_LOG, "bf_write2 no=%d offset=%d size=%d",
                            effective_block+1, 0, p->nbytes - remain);
#endif
                    bf_write(bf->bf, effective_block+1, 0,
                             p->nbytes - remain, (char*)p->data + remain);
                }
            }
        }
        release_block(bf, p);
    }
}
 
static struct Dict_file_block *alloc_block(Dict_BFile bf, int no)
{
    struct Dict_file_block *p, **pp;
 
    if (!bf->free_list)
        dict_bf_flush_blocks(bf, 1);
    assert(bf->free_list);
    p = bf->free_list;
    bf->free_list = p->h_next;
    p->dirty = 0;
    p->no = no;
 
    /* insert at front in lru chain */
    p->lru_next = NULL;
    p->lru_prev = bf->lru_front;
    if (bf->lru_front)
        bf->lru_front->lru_next = p;
    else
        bf->lru_back = p;
    bf->lru_front = p;
 
    /* insert in hash chain */
    pp = bf->hash_array + (no % bf->hash_size);
    p->h_next = *pp;
    p->h_prev = pp;
    if (*pp)
        (*pp)->h_prev = &p->h_next;
    *pp = p;
 
    return p;
}
 
static void move_to_front(Dict_BFile bf, struct Dict_file_block *p)
{
    /* Already at front? */
    if (!p->lru_next)
        return ;
 
    /* Remove */
    if (p->lru_prev)
        p->lru_prev->lru_next = p->lru_next;
    else
        bf->lru_back = p->lru_next;
    p->lru_next->lru_prev = p->lru_prev;
 
    /* Insert at front */
    p->lru_next = NULL;
    p->lru_prev = bf->lru_front;
    if (bf->lru_front)
        bf->lru_front->lru_next = p;
    else
        bf->lru_back = p;
    bf->lru_front = p;
}
 
int dict_bf_readp(Dict_BFile bf, int no, void **bufp)
{
    struct Dict_file_block *p;
    int i;
    if ((p = find_block(bf, no)))
    {
        *bufp = p->data;
        move_to_front(bf, p);
        bf->hits++;
        return 1;
    }
    bf->misses++;
    p = alloc_block(bf, no);
 
    if (!bf->compact_flag)
        i = bf_read(bf->bf, no, 0, 0, p->data);
    else
    {
        int effective_block = no / bf->block_size;
        int effective_offset = no - effective_block * bf->block_size;
 
        i = bf_read(bf->bf, effective_block, effective_offset,
                    bf->block_size - effective_offset, p->data);
        if (i > 0 && effective_offset > 0)
            i = bf_read(bf->bf, effective_block+1, 0, effective_offset,
                        (char*) p->data + bf->block_size - effective_offset);
        i = 1;
    }
    if (i > 0)
    {
        *bufp = p->data;
        return i;
    }
    release_block(bf, p);
    *bufp = NULL;
    return i;
}
 
int dict_bf_newp(Dict_BFile dbf, int no, void **bufp, int nbytes)
{
    struct Dict_file_block *p;
    if (!(p = find_block(dbf, no)))
        p = alloc_block(dbf, no);
    else
        move_to_front(dbf, p);
    *bufp = p->data;
    memset(p->data, 0, dbf->block_size);
    p->dirty = 1;
    p->nbytes = nbytes;
#if 0
    printf("bf_newp of %d:", no);
    dict_pr_lru(dbf);
#endif
    return 1;
}
 
int dict_bf_touch(Dict_BFile dbf, int no)
{
    struct Dict_file_block *p;
    if ((p = find_block(dbf, no)))
    {
        p->dirty = 1;
        return 0;
    }
    return -1;
}
 
/*
 * Local variables:
 * c-basic-offset: 4
 * c-file-style: "Stroustrup"
 * indent-tabs-mode: nil
 * End:
 * vim: shiftwidth=4 tabstop=8 expandtab
 */