path: root/libibex/block.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*-
 *
 * Copyright (C) 2000 Helix Code, Inc.
 *
 * Authors: Michael Zucchi <notzed@helixcode.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public License
 * as published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 * 
 * This library 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
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with the Gnome Library; see the file COPYING.LIB.  If not,
 * write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
  block file/cache/utility functions
*/

#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

#include <glib.h>

#include "block.h"

#define d(x)
/*#define DEBUG*/


#ifdef IBEX_STATS
static void
init_stats(struct _memcache *index)
{
    index->stats = g_hash_table_new(g_direct_hash, g_direct_equal);
}

static void
dump_1_stat(int id, struct _stat_info *info, struct _memcache *index)
{
    printf("%d %d %d %d %d\n", id, info->read, info->write, info->cache_hit, info->cache_miss);
}

static void
dump_stats(struct _memcache *index)
{
    printf("Block reads writes hits misses\n");
    g_hash_table_foreach(index->stats, dump_1_stat, index);
}

static void
add_read(struct _memcache *index, int id)
{
    struct _stat_info *info;

    info = g_hash_table_lookup(index->stats, (void *)id);
    if (info == NULL) {
        info = g_malloc0(sizeof(*info));
        g_hash_table_insert(index->stats, (void *)id, info);
    }
    info->read++;
}

static void
add_write(struct _memcache *index, int id)
{
    struct _stat_info *info;

    info = g_hash_table_lookup(index->stats, (void *)id);
    if (info == NULL) {
        info = g_malloc0(sizeof(*info));
        g_hash_table_insert(index->stats, (void *)id, info);
    }
    info->write++;
}

static void
add_hit(struct _memcache *index, int id)
{
    struct _stat_info *info;

    info = g_hash_table_lookup(index->stats, (void *)id);
    if (info == NULL) {
        info = g_malloc0(sizeof(*info));
        g_hash_table_insert(index->stats, (void *)id, info);
    }
    info->cache_hit++;
}

static void
add_miss(struct _memcache *index, int id)
{
    struct _stat_info *info;

    info = g_hash_table_lookup(index->stats, (void *)id);
    if (info == NULL) {
        info = g_malloc0(sizeof(*info));
        g_hash_table_insert(index->stats, (void *)id, info);
    }
    info->cache_miss++;
}
#endif /* IBEX_STATS */


/* simple list routines (for simplified memory management of cache/lists) */

/**
 * ibex_list_new:
 * @v: 
 * 
 * Initialise a list header.  A list header must always be initialised
 * before use.
 **/
void ibex_list_new(struct _list *v)
{
    v->head = (struct _listnode *)&v->tail;
    v->tail = 0;
    v->tailpred = (struct _listnode *)&v->head;
}

/**
 * ibex_list_addhead:
 * @l: List.
 * @n: Node to append.
 * 
 * Prepend a listnode to the head of the list @l.
 * 
 * Return value: Always @n.
 **/
struct _listnode *ibex_list_addhead(struct _list *l, struct _listnode *n)
{
    n->next = l->head;
    n->prev = (struct _listnode *)&l->head;
    l->head->prev = n;
    l->head = n;
    return n;
}

/**
 * ibex_list_addtail:
 * @l: 
 * @n: 
 * 
 * Append a listnode to the end of the list @l.
 * 
 * Return value: Always the same as @n.
 **/
struct _listnode *ibex_list_addtail(struct _list *l, struct _listnode *n)
{
    n->next = (struct _listnode *)&l->tail;
    n->prev = l->tailpred;
    l->tailpred->next = n;
    l->tailpred = n;
    return n;
}

/**
 * ibex_list_remove:
 * @n: The node to remove.
 * 
 * Remove a listnode from a list.
 * 
 * Return value: Always the same as @n.
 **/
struct _listnode *ibex_list_remove(struct _listnode *n)
{
    n->next->prev = n->prev;
    n->prev->next = n->next;
    return n;
}

static struct _memblock *
memblock_addr(struct _block *block)
{
    return (struct _memblock *)(((char *)block) - G_STRUCT_OFFSET(struct _memblock, data));
}

/**
 * ibex_block_dirty:
 * @block: 
 * 
 * Dirty a block.  This will cause it to be written to disk on
 * a cache sync, or when the block is flushed from the cache.
 **/
void
ibex_block_dirty(struct _block *block)
{
    memblock_addr(block)->flags |= BLOCK_DIRTY;
}

static void
sync_block(struct _memcache *block_cache, struct _memblock *memblock)
{
    lseek(block_cache->fd, memblock->block, SEEK_SET);
    if (write(block_cache->fd, &memblock->data, sizeof(memblock->data)) != -1) {
        memblock->flags &= ~BLOCK_DIRTY;
    }
#ifdef IBEX_STATS
    add_write(block_cache, memblock->block);
#endif
}

/**
 * ibex_block_cache_sync:
 * @block_cache: 
 * 
 * Ensure the block cache is fully synced to disk.
 **/
void
ibex_block_cache_sync(struct _memcache *block_cache)
{
    struct _memblock *memblock;

    memblock = (struct _memblock *)block_cache->nodes.head;
    while (memblock->next) {
        if (memblock->flags & BLOCK_DIRTY) {
            sync_block(block_cache, memblock);
        }
        memblock = memblock->next;
    }
    fsync(block_cache->fd);

#ifdef IBEX_STATS
    dump_stats(block_cache);
#endif

}

/**
 * ibex_block_cache_flush:
 * @block_cache: 
 * 
 * Ensure the block cache is fully synced to disk, and then flush
 * its contents from memory.
 **/
void
ibex_block_cache_flush(struct _memcache *block_cache)
{
    struct _memblock *mw, *mn;

    ibex_block_cache_sync(block_cache);

    mw = (struct _memblock *)block_cache->nodes.head;
    mn = mw->next;
    while (mn) {
        g_hash_table_remove(block_cache->index, (void *)mw->block);
        g_free(mw);
        mw = mn;
        mn = mn->next;
    }
    ibex_list_new(&block_cache->nodes);
}


/**
 * ibex_block_read:
 * @block_cache: 
 * @blockid: 
 * 
 * Read the data of a block by blockid.  The data contents is backed by
 * the block cache, and should be considered static.
 *
 * TODO; should this return a NULL block on error?
 *
 * Return value: The address of the block data (which may be cached).
 **/
struct _block *
ibex_block_read(struct _memcache *block_cache, blockid_t blockid)
{
    struct _memblock *memblock;

    {
        /* assert blockid<roof */
        if (blockid > 0) {
            struct _root *root = (struct _root *)ibex_block_read(block_cache, 0);
            g_assert(blockid < root->roof);
        }
    }

    memblock = g_hash_table_lookup(block_cache->index, (void *)blockid);
    if (memblock) {
        d(printf("foudn blockid in cache %d = %p\n", blockid, &memblock->data));
        /* 'access' page */
        ibex_list_remove((struct _listnode *)memblock);
        ibex_list_addtail(&block_cache->nodes, (struct _listnode *)memblock);
#ifdef IBEX_STATS
        add_hit(block_cache, memblock->block);
#endif
        return &memblock->data;
    }
#ifdef IBEX_STATS
    add_miss(block_cache, blockid);
    add_read(block_cache, blockid);
#endif
    d(printf("loading blockid from disk %d\n", blockid));
    memblock = g_malloc(sizeof(*memblock));
    memblock->block = blockid;
    memblock->flags = 0;
    lseek(block_cache->fd, blockid, SEEK_SET);
    memset(&memblock->data, 0, sizeof(memblock->data));
    read(block_cache->fd, &memblock->data, sizeof(memblock->data));
    ibex_list_addtail(&block_cache->nodes, (struct _listnode *)memblock);
    g_hash_table_insert(block_cache->index, (void *)blockid, memblock);
    if (block_cache->count >= CACHE_SIZE) {
        struct _memblock *old = (struct _memblock *)block_cache->nodes.head;
        d(printf("discaring cache block %d\n", old->block));
        g_hash_table_remove(block_cache->index, (void *)old->block);
        ibex_list_remove((struct _listnode *)old);
        if (old->flags & BLOCK_DIRTY) {
            sync_block(block_cache, old);
        }
        g_free(old);
    } else {
        block_cache->count++;
    }

    d(printf("  --- cached blocks : %d\n", block_cache->count));

    return &memblock->data;
}

/**
 * ibex_block_cache_open:
 * @name: 
 * @flags: Flags as to open(2), should use O_RDWR and optionally O_CREAT.
 * @mode: Mose as to open(2)
 * 
 * Open a block file.
 * 
 * FIXME; this currently also initialises the word and name indexes
 * because their pointers are stored in the root block.  Should be
 * upto the caller to manage these pointers/data.
 *
 * Return value: NULL if the backing file could not be opened.
 **/
struct _memcache *
ibex_block_cache_open(const char *name, int flags, int mode)
{
    struct _root *root;
    struct _memcache *block_cache = g_malloc0(sizeof(*block_cache));

    d(printf("opening ibex file: %s", name));

    /* setup cache */
    ibex_list_new(&block_cache->nodes);
    block_cache->count = 0;
    block_cache->index = g_hash_table_new(g_direct_hash, g_direct_equal);
    block_cache->fd = open(name, flags, mode);

    if (block_cache->fd == -1) {
        g_hash_table_destroy(block_cache->index);
        g_free(block_cache);
        return NULL;
    }

    root = (struct _root *)ibex_block_read(block_cache, 0);
    if (root->roof == 0 || memcmp(root->version, "ibx3", 4)) {
        d(printf("Initialising superblock\n"));
        /* reset root data */
        memcpy(root->version, "ibx3", 4);
        root->roof = 1024;
        root->free = 0;
        root->words = 0;
        root->names = 0;
        root->tail = 0; /* list of tail blocks */
        ibex_block_dirty((struct _block *)root);
    } else {
        d(printf("superblock already initialised:\n"
             " roof = %d\n free = %d\n words = %d\n names = %d\n",
             root->roof, root->free, root->words, root->names));
    }
    /* this should be moved higher up */
    {
        struct _IBEXWord *ibex_create_word_index(struct _memcache *bc, blockid_t *wordroot, blockid_t *nameroot);

        block_cache->words = ibex_create_word_index(block_cache, &root->words, &root->names);
    }

#ifdef IBEX_STATS
    init_stats(block_cache);
#endif

    return block_cache;
}

/**
 * ibex_block_cache_close:
 * @block_cache: 
 * 
 * Close the block file, sync any remaining cached data
 * to disk, and free all resources.
 **/
void
ibex_block_cache_close(struct _memcache *block_cache)
{
    struct _memblock *mw, *mn;

    ibex_block_cache_sync(block_cache);
    close(block_cache->fd);

    mw = (struct _memblock *)block_cache->nodes.head;
    mn = mw->next;
    while (mn) {
        g_free(mw);
        mw = mn;
        mn = mw->next;
    }

    g_hash_table_destroy(block_cache->index);

    g_free(block_cache);
}

/**
 * ibex_block_free:
 * @block_cache: 
 * @blockid: 
 * 
 * Return a block to the free pool.
 **/
void
ibex_block_free(struct _memcache *block_cache, blockid_t blockid)
{
    struct _root *root = (struct _root *)ibex_block_read(block_cache, 0);
    struct _block *block = ibex_block_read(block_cache, blockid);

    block->next = root->free;
    root->free = blockid;
    ibex_block_dirty((struct _block *)root);
    ibex_block_dirty((struct _block *)block);
}

/**
 * ibex_block_get:
 * @block_cache: 
 * 
 * Allocate a new block, or access a previously freed block and return
 * its block id.  The block will have zeroed contents.
 * 
 * Return value: 0 if there are no blocks left (disk full/read only
 * file, etc).
 **/
blockid_t
ibex_block_get(struct _memcache *block_cache)
{
    struct _root *root = (struct _root *)ibex_block_read(block_cache, 0);
    struct _block *block;
    blockid_t head;

    if (root->free) {
        head = root->free;
        block = ibex_block_read(block_cache, head);
        root->free = block_location(block->next);
    } else {
        /* TODO: check the block will fit first */
        /* TODO: no need to read this block, can allocate it manually (saves a syscall/read) */
        head = root->roof;
        root->roof += BLOCK_SIZE;
        block = ibex_block_read(block_cache, head);
    }

    g_assert(head != 0);

    d(printf("new block = %d\n", head));
    block->next = 0;
    block->used = 0;
    ibex_block_dirty(block);
    ibex_block_dirty((struct _block *)root);
    return head;
}