path: root/camel/camel-block-file.c

/*
 * Copyright (C) 2001 Ximian Inc.
 *
 * Authors: Michael Zucchi <notzed@ximian.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program 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., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/stat.h>
#include <sys/uio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>

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

#include "e-util/e-msgport.h"

#include "camel-block-file.h"

#ifdef ENABLE_THREADS
#include <pthread.h>
#endif

#define d(x) /*(printf("%s(%d):%s: ",  __FILE__, __LINE__, __PRETTY_FUNCTION__),(x))*/

#ifdef ENABLE_THREADS

/* Locks must be obtained in the order defined */

struct _CamelBlockFilePrivate {
    /* We use the private structure to form our lru list from */
    struct _CamelBlockFilePrivate *next;
    struct _CamelBlockFilePrivate *prev;

    struct _CamelBlockFile *base;

    pthread_mutex_t root_lock; /* for modifying the root block */
    pthread_mutex_t cache_lock; /* for refcounting, flag manip, cache manip */
    pthread_mutex_t io_lock; /* for all io ops */
};

#define CAMEL_BLOCK_FILE_LOCK(kf, lock) (pthread_mutex_lock(&(kf)->priv->lock))
#define CAMEL_BLOCK_FILE_TRYLOCK(kf, lock) (pthread_mutex_trylock(&(kf)->priv->lock))
#define CAMEL_BLOCK_FILE_UNLOCK(kf, lock) (pthread_mutex_unlock(&(kf)->priv->lock))

#define LOCK(x) pthread_mutex_lock(&x)
#define UNLOCK(x) pthread_mutex_unlock(&x)

static pthread_mutex_t block_file_lock = PTHREAD_MUTEX_INITIALIZER;

#else
#define CAMEL_BLOCK_FILE_LOCK(kf, lock)
#define CAMEL_BLOCK_FILE_TRYLOCK(kf, lock)
#define CAMEL_BLOCK_FILE_UNLOCK(kf, lock)
#define LOCK(x)
#define UNLOCK(x)
#endif

/* lru cache of block files */
static EDList block_file_list = E_DLIST_INITIALISER(block_file_list);
/* list to store block files that are actually intialised */
static EDList block_file_active_list = E_DLIST_INITIALISER(block_file_active_list);
static int block_file_count = 0;
static int block_file_threshhold = 10;

#define CBF_CLASS(o) ((CamelBlockFileClass *)(((CamelObject *)o)->classfuncs))

static int sync_nolock(CamelBlockFile *bs);
static int sync_block_nolock(CamelBlockFile *bs, CamelBlock *bl);

static int
block_file_validate_root(CamelBlockFile *bs)
{
    struct stat st;
    CamelBlockRoot *br;

    br = bs->root;

    fstat(bs->fd, &st);

    d(printf("Validate root: '%s'\n", bs->path));
    d(printf("version: %.8s (%.8s)\n", bs->root->version, bs->version));
    d(printf("block size: %d (%d)%s\n", br->block_size, bs->block_size,
        br->block_size != bs->block_size ? " BAD":" OK"));
    d(printf("free: %ld (%d add size < %ld)%s\n", (long)br->free, br->free / bs->block_size * bs->block_size, (long)st.st_size,
        (br->free > st.st_size) || (br->free % bs->block_size) != 0 ? " BAD":" OK"));
    d(printf("last: %ld (%d and size: %ld)%s\n", (long)br->last, br->last / bs->block_size * bs->block_size, (long)st.st_size,
        (br->last != st.st_size) || ((br->last % bs->block_size) != 0) ? " BAD": " OK"));
    d(printf("flags: %s\n", (br->flags & CAMEL_BLOCK_FILE_SYNC)?"SYNC":"unSYNC"));

    if (br->last == 0
        || memcmp(bs->root->version, bs->version, 8) != 0
        || br->block_size != bs->block_size
        || (br->free % bs->block_size) != 0
        || (br->last % bs->block_size) != 0
        || fstat(bs->fd, &st) == -1
        || st.st_size != br->last
        || br->free > st.st_size
        || (br->flags & CAMEL_BLOCK_FILE_SYNC) == 0) {
        g_warning("Invalid root: '%s'", bs->path);
        g_warning("version: %.8s (%.8s)", bs->root->version, bs->version);
        g_warning("block size: %d (%d)%s", br->block_size, bs->block_size,
              br->block_size != bs->block_size ? " BAD":" OK");
        g_warning("free: %ld (%d add size < %ld)%s", (long)br->free, br->free / bs->block_size * bs->block_size, (long)st.st_size,
              (br->free > st.st_size) || (br->free % bs->block_size) != 0 ? " BAD":" OK");
        g_warning("last: %ld (%d and size: %ld)%s", (long)br->last, br->last / bs->block_size * bs->block_size, (long)st.st_size,
              (br->last != st.st_size) || ((br->last % bs->block_size) != 0) ? " BAD": " OK");
        g_warning("flags: %s", (br->flags & CAMEL_BLOCK_FILE_SYNC)?"SYNC":"unSYNC");
        return -1;
    }

    return 0;
}

static int
block_file_init_root(CamelBlockFile *bs)
{
    CamelBlockRoot *br = bs->root;

    memset(br, 0, bs->block_size);
    memcpy(br->version, bs->version, 8);
    br->last = bs->block_size;
    br->flags = CAMEL_BLOCK_FILE_SYNC;
    br->free = 0;
    br->block_size = bs->block_size;

    return 0;
}

static void
camel_block_file_class_init(CamelBlockFileClass *klass)
{
    klass->validate_root = block_file_validate_root;
    klass->init_root = block_file_init_root;
}

static guint
block_hash_func(const void *v)
{
    return ((camel_block_t)v) >> CAMEL_BLOCK_SIZE_BITS;
}

static void
camel_block_file_init(CamelBlockFile *bs)
{
    struct _CamelBlockFilePrivate *p;

    bs->fd = -1;
    bs->block_size = CAMEL_BLOCK_SIZE;
    e_dlist_init(&bs->block_cache);
    bs->blocks = g_hash_table_new((GHashFunc)block_hash_func, NULL);
    /* this cache size and the text index size have been tuned for about the best
       with moderate memory usage.  Doubling the memory usage barely affects performance. */
    bs->block_cache_limit = 256;

    p = bs->priv = g_malloc0(sizeof(*bs->priv));
    p->base = bs;

#ifdef ENABLE_THREADS
    pthread_mutex_init(&p->root_lock, NULL);
    pthread_mutex_init(&p->cache_lock, NULL);
    pthread_mutex_init(&p->io_lock, NULL);
#endif

    /* link into lru list */
    LOCK(block_file_lock);
    e_dlist_addhead(&block_file_list, (EDListNode *)p);

#if 0
    {
        printf("dumping block list\n");
        printf(" head = %p p = %p\n", block_file_list.head, p);
        p = block_file_list.head;
        while (p->next) {
            printf(" '%s'\n", p->base->path);
            p = p->next;
        }
    }
#endif

    UNLOCK(block_file_lock);
}

static void
camel_block_file_finalise(CamelBlockFile *bs)
{
    CamelBlock *bl, *bn;
    struct _CamelBlockFilePrivate *p;

    p = bs->priv;

    if (bs->root_block)
        camel_block_file_sync(bs);

    /* remove from lru list */
    LOCK(block_file_lock);
    if (bs->fd != -1)
        block_file_count--;
    e_dlist_remove((EDListNode *)p);
    UNLOCK(block_file_lock);

    bl = (CamelBlock *)bs->block_cache.head;
    bn = bl->next;
    while (bn) {
        if (bl->refcount != 0)
            g_warning("Block '%d' still referenced", bl->id);
        g_free(bl);
        bl = bn;
        bn = bn->next;
    }

    if (bs->root_block)
        camel_block_file_unref_block(bs, bs->root_block);
    g_free(bs->path);
    close(bs->fd);

#ifdef ENABLE_THREADS
    pthread_mutex_destroy(&p->io_lock);
    pthread_mutex_destroy(&p->cache_lock);
    pthread_mutex_destroy(&p->root_lock);
#endif
    g_free(p);
}

CamelType
camel_block_file_get_type(void)
{
    static CamelType type = CAMEL_INVALID_TYPE;
    
    if (type == CAMEL_INVALID_TYPE) {
        type = camel_type_register(camel_object_get_type(), "CamelBlockFile",
                       sizeof (CamelBlockFile),
                       sizeof (CamelBlockFileClass),
                       (CamelObjectClassInitFunc) camel_block_file_class_init,
                       NULL,
                       (CamelObjectInitFunc) camel_block_file_init,
                       (CamelObjectFinalizeFunc) camel_block_file_finalise);
    }
    
    return type;
}

/* 'use' a block file for io */
static int
block_file_use(CamelBlockFile *bs)
{
    struct _CamelBlockFilePrivate *nw, *nn, *p = bs->priv;
    CamelBlockFile *bf;
    int err;

    /* We want to:
        remove file from active list
        lock it

       Then when done:
        unlock it
        add it back to end of active list
    */

    CAMEL_BLOCK_FILE_LOCK(bs, io_lock);

    if (bs->fd != -1)
        return 0;
    else
        d(printf("Turning block file online: %s\n", bs->path));

    if ((bs->fd = open(bs->path, bs->flags, 0600)) == -1) {
        err = errno;
        CAMEL_BLOCK_FILE_UNLOCK(bs, io_lock);
        errno = err;
        return -1;
    }

    LOCK(block_file_lock);
    e_dlist_remove((EDListNode *)p);
    e_dlist_addtail(&block_file_active_list, (EDListNode *)p);

    block_file_count++;

    nw = (struct _CamelBlockFilePrivate *)block_file_list.head;
    nn = nw->next;
    while (block_file_count > block_file_threshhold && nn) {
        /* We never hit the current blockfile here, as its removed from the list first */
        bf = nw->base;
        if (bf->fd != -1) {
            /* Need to trylock, as any of these lock levels might be trying
               to lock the block_file_lock, so we need to check and abort if so */
            if (CAMEL_BLOCK_FILE_TRYLOCK(bf, root_lock) == 0) {
                if (CAMEL_BLOCK_FILE_TRYLOCK(bf, cache_lock) == 0) {
                    if (CAMEL_BLOCK_FILE_TRYLOCK(bf, io_lock) == 0) {
                        d(printf("[%d] Turning block file offline: %s\n", block_file_count-1, bf->path));
                        sync_nolock(bf);
                        close(bf->fd);
                        bf->fd = -1;
                        block_file_count--;
                        CAMEL_BLOCK_FILE_UNLOCK(bf, io_lock);
                    }
                    CAMEL_BLOCK_FILE_UNLOCK(bf, cache_lock);
                }
                CAMEL_BLOCK_FILE_UNLOCK(bf, root_lock);
            }
        }
        nw = nn;
        nn = nw->next;
    }

    UNLOCK(block_file_lock);

    return 0;
}

static void
block_file_unuse(CamelBlockFile *bs)
{
    LOCK(block_file_lock);
    e_dlist_remove((EDListNode *)bs->priv);
    e_dlist_addtail(&block_file_list, (EDListNode *)bs->priv);
    UNLOCK(block_file_lock);

    CAMEL_BLOCK_FILE_UNLOCK(bs, io_lock);
}

/*
o = camel_cache_get(c, key);
camel_cache_unref(c, key);
camel_cache_add(c, key, o);
camel_cache_remove(c, key);
*/

/**
 * camel_block_file_new:
 * @path: 
 * @: 
 * @block_size: 
 * 
 * Allocate a new block file, stored at @path.  @version contains an 8 character
 * version string which must match the head of the file, or the file will be
 * intitialised.
 * 
 * @block_size is currently ignored and is set to CAMEL_BLOCK_SIZE.
 *
 * Return value: The new block file, or NULL if it could not be created.
 **/
CamelBlockFile *camel_block_file_new(const char *path, int flags, const char version[8], size_t block_size)
{
    CamelBlockFile *bs;

    bs = (CamelBlockFile *)camel_object_new(camel_block_file_get_type());
    memcpy(bs->version, version, 8);
    bs->path = g_strdup(path);
    bs->flags = flags;

    bs->root_block = camel_block_file_get_block(bs, 0);
    if (bs->root_block == NULL) {
        camel_object_unref((CamelObject *)bs);
        return NULL;
    }
    camel_block_file_detach_block(bs, bs->root_block);
    bs->root = (CamelBlockRoot *)&bs->root_block->data;

    /* we only need these flags on first open */
    bs->flags &= ~(O_CREAT|O_EXCL|O_TRUNC);

    /* Do we need to init the root block? */
    if (CBF_CLASS(bs)->validate_root(bs) == -1) {
        d(printf("Initialise root block: %.8s\n", version));

        CBF_CLASS(bs)->init_root(bs);
        camel_block_file_touch_block(bs, bs->root_block);
        if (block_file_use(bs) == -1) {
            camel_object_unref((CamelObject *)bs);
            return NULL;
        }
        if (sync_block_nolock(bs, bs->root_block) == -1
            || ftruncate(bs->fd, bs->root->last) == -1) {
            block_file_unuse(bs);
            camel_object_unref((CamelObject *)bs);
            return NULL;
        }
        block_file_unuse(bs);
    }

    return bs;
}

int
camel_block_file_rename(CamelBlockFile *bs, const char *path)
{
    int ret;
    struct stat st;
    int err;

    CAMEL_BLOCK_FILE_LOCK(bs, io_lock);

    ret = rename(bs->path, path);
    if (ret == -1) {
        /* Maybe the rename actually worked */
        err = errno;
        if (stat(path, &st) == 0
            && stat(bs->path, &st) == -1
            && errno == ENOENT)
            ret = 0;
        errno = err;
    }

    if (ret != -1) {
        g_free(bs->path);
        bs->path = g_strdup(path);
    }

    CAMEL_BLOCK_FILE_UNLOCK(bs, io_lock);

    return ret;
}

/**
 * camel_block_file_new_block:
 * @bs: 
 * 
 * Allocate a new block, return a pointer to it.  Old blocks
 * may be flushed to disk during this call.
 * 
 * Return value: The block, or NULL if an error occured.
 **/
CamelBlock *camel_block_file_new_block(CamelBlockFile *bs)
{
    CamelBlock *bl;

    CAMEL_BLOCK_FILE_LOCK(bs, root_lock);

    if (bs->root->free) {
        bl = camel_block_file_get_block(bs, bs->root->free);
        if (bl == NULL)
            goto fail;
        bs->root->free = ((camel_block_t *)bl->data)[0];
    } else {
        bl = camel_block_file_get_block(bs, bs->root->last);
        if (bl == NULL)
            goto fail;
        bs->root->last += CAMEL_BLOCK_SIZE;
    }

    bs->root_block->flags |= CAMEL_BLOCK_DIRTY;

    bl->flags |= CAMEL_BLOCK_DIRTY;
    memset(bl->data, 0, CAMEL_BLOCK_SIZE);
fail:
    CAMEL_BLOCK_FILE_UNLOCK(bs, root_lock);

    return bl;
}

/**
 * camel_block_file_free_block:
 * @bs: 
 * @id: 
 * 
 * 
 **/
int camel_block_file_free_block(CamelBlockFile *bs, camel_block_t id)
{
    CamelBlock *bl;

    bl = camel_block_file_get_block(bs, id);
    if (bl == NULL)
        return -1;

    CAMEL_BLOCK_FILE_LOCK(bs, root_lock);

    ((camel_block_t *)bl->data)[0] = bs->root->free;
    bs->root->free = bl->id;
    bs->root_block->flags |= CAMEL_BLOCK_DIRTY;
    bl->flags |= CAMEL_BLOCK_DIRTY;
    camel_block_file_unref_block(bs, bl);

    CAMEL_BLOCK_FILE_UNLOCK(bs, root_lock);

    return 0;
}

/**
 * camel_block_file_get_block:
 * @bs: 
 * @id: 
 * 
 * Retreive a block @id.
 * 
 * Return value: The block, or NULL if blockid is invalid or a file error
 * occured.
 **/
CamelBlock *camel_block_file_get_block(CamelBlockFile *bs, camel_block_t id)
{
    CamelBlock *bl, *flush, *prev;

    /* Sanity check: Dont allow reading of root block (except before its been read)
       or blocks with invalid block id's */
    if ((bs->root == NULL && id != 0)
        || (bs->root != NULL && (id > bs->root->last || id == 0))
        || (id % bs->block_size) != 0) {
        errno = EINVAL;
        return NULL;
    }

    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    bl = g_hash_table_lookup(bs->blocks, (void *)id);

    d(printf("Get  block %08x: %s\n", id, bl?"cached":"must read"));

    if (bl == NULL) {
        /* LOCK io_lock */
        if (block_file_use(bs) == -1) {
            CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
            return NULL;
        }

        bl = g_malloc0(sizeof(*bl));
        bl->id = id;
        if (lseek(bs->fd, id, SEEK_SET) == -1
            || read(bs->fd, bl->data, CAMEL_BLOCK_SIZE) == -1) {
            block_file_unuse(bs);
            CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
            g_free(bl);
            return NULL;
        }

        bs->block_cache_count++;
        g_hash_table_insert(bs->blocks, (void *)bl->id, bl);

        /* flush old blocks */
        flush = (CamelBlock *)bs->block_cache.tailpred;
        prev = flush->prev;
        while (bs->block_cache_count > bs->block_cache_limit && prev) {
            if (flush->refcount == 0) {
                if (sync_block_nolock(bs, flush) != -1) {
                    g_hash_table_remove(bs->blocks, (void *)flush->id);
                    e_dlist_remove((EDListNode *)flush);
                    g_free(flush);
                    bs->block_cache_count--;
                }
            }
            flush = prev;
            prev = prev->prev;
        }
        /* UNLOCK io_lock */
        block_file_unuse(bs);
    } else {
        e_dlist_remove((EDListNode *)bl);
    }

    e_dlist_addhead(&bs->block_cache, (EDListNode *)bl);
    bl->refcount++;

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);

    d(printf("Got  block %08x\n", id));

    return bl;
}

/**
 * camel_block_file_detach_block:
 * @bs: 
 * @bl: 
 * 
 * Detatch a block from the block file's cache.  The block should
 * be unref'd or attached when finished with.  The block file will
 * perform no writes of this block or flushing of it if the cache
 * fills.
 **/
void camel_block_file_detach_block(CamelBlockFile *bs, CamelBlock *bl)
{
    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    g_hash_table_remove(bs->blocks, (void *)bl->id);
    e_dlist_remove((EDListNode *)bl);
    bl->flags |= CAMEL_BLOCK_DETACHED;

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
}

/**
 * camel_block_file_attach_block:
 * @bs: 
 * @bl: 
 * 
 * Reattach a block that has been detached.
 **/
void camel_block_file_attach_block(CamelBlockFile *bs, CamelBlock *bl)
{
    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    g_hash_table_insert(bs->blocks, (void *)bl->id, bl);
    e_dlist_addtail(&bs->block_cache, (EDListNode *)bl);
    bl->flags &= ~CAMEL_BLOCK_DETACHED;

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
}

/**
 * camel_block_file_touch_block:
 * @bs: 
 * @bl: 
 * 
 * Mark a block as dirty.  The block will be written to disk if
 * it ever expires from the cache.
 **/
void camel_block_file_touch_block(CamelBlockFile *bs, CamelBlock *bl)
{
    CAMEL_BLOCK_FILE_LOCK(bs, root_lock);
    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    bl->flags |= CAMEL_BLOCK_DIRTY;

    if ((bs->root->flags & CAMEL_BLOCK_FILE_SYNC) && bl != bs->root_block) {
        d(printf("turning off sync flag\n"));
        bs->root->flags &= ~CAMEL_BLOCK_FILE_SYNC;
        bs->root_block->flags |= CAMEL_BLOCK_DIRTY;
        camel_block_file_sync_block(bs, bs->root_block);
    }

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
    CAMEL_BLOCK_FILE_UNLOCK(bs, root_lock);
}

/**
 * camel_block_file_unref_block:
 * @bs: 
 * @bl: 
 * 
 * Mark a block as unused.  If a block is used it will not be
 * written to disk, or flushed from memory.
 *
 * If a block is detatched and this is the last reference, the
 * block will be freed.
 **/
void camel_block_file_unref_block(CamelBlockFile *bs, CamelBlock *bl)
{
    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    if (bl->refcount == 1 && (bl->flags & CAMEL_BLOCK_DETACHED))
        g_free(bl);
    else
        bl->refcount--;

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
}

static int
sync_block_nolock(CamelBlockFile *bs, CamelBlock *bl)
{
    d(printf("Sync block %08x: %s\n", bl->id, (bl->flags & CAMEL_BLOCK_DIRTY)?"dirty":"clean"));

    if (bl->flags & CAMEL_BLOCK_DIRTY) {
        if (lseek(bs->fd, bl->id, SEEK_SET) == -1
            || write(bs->fd, bl->data, CAMEL_BLOCK_SIZE) != CAMEL_BLOCK_SIZE) {
            return -1;
        }
        bl->flags &= ~CAMEL_BLOCK_DIRTY;
    }

    return 0;
}

static int
sync_nolock(CamelBlockFile *bs)
{
    CamelBlock *bl, *bn;
    int work = FALSE;

    bl = (CamelBlock *)bs->block_cache.head;
    bn = bl->next;
    while (bn) {
        if (bl->flags & CAMEL_BLOCK_DIRTY) {
            work = TRUE;
            if (sync_block_nolock(bs, bl) == -1)
                return -1;
        }
        bl = bn;
        bn = bn->next;
    }

    if (!work
        && (bs->root_block->flags & CAMEL_BLOCK_DIRTY) == 0
        && (bs->root->flags & CAMEL_BLOCK_FILE_SYNC) != 0)
        return 0;

    d(printf("turning on sync flag\n"));

    bs->root->flags |= CAMEL_BLOCK_FILE_SYNC;

    return sync_block_nolock(bs, bs->root_block);
}

/**
 * camel_block_file_sync_block:
 * @bs: 
 * @bl: 
 * 
 * Flush a block to disk immediately.  The block will only
 * be flushed to disk if it is marked as dirty (touched).
 * 
 * Return value: -1 on io error.
 **/
int camel_block_file_sync_block(CamelBlockFile *bs, CamelBlock *bl)
{
    int ret;

    /* LOCK io_lock */
    if (block_file_use(bs) == -1)
        return -1;

    ret = sync_block_nolock(bs, bl);

    block_file_unuse(bs);

    return ret;
}

/**
 * camel_block_file_sync:
 * @bs: 
 * 
 * Sync all dirty blocks to disk, including the root block.
 * 
 * Return value: -1 on io error.
 **/
int camel_block_file_sync(CamelBlockFile *bs)
{
    int ret;

    CAMEL_BLOCK_FILE_LOCK(bs, root_lock);
    CAMEL_BLOCK_FILE_LOCK(bs, cache_lock);

    /* LOCK io_lock */
    if (block_file_use(bs) == -1)
        ret = -1;
    else {
        ret = sync_nolock(bs);
        block_file_unuse(bs);
    }

    CAMEL_BLOCK_FILE_UNLOCK(bs, cache_lock);
    CAMEL_BLOCK_FILE_UNLOCK(bs, root_lock);

    return ret;
}

/* ********************************************************************** */

struct _CamelKeyFilePrivate {
    struct _CamelKeyFilePrivate *next;
    struct _CamelKeyFilePrivate *prev;

    struct _CamelKeyFile *base;

#ifdef ENABLE_THREADS
    pthread_mutex_t lock;
#endif
};

#ifdef ENABLE_THREADS
#define CAMEL_KEY_FILE_LOCK(kf, lock) (pthread_mutex_lock(&(kf)->priv->lock))
#define CAMEL_KEY_FILE_TRYLOCK(kf, lock) (pthread_mutex_trylock(&(kf)->priv->lock))
#define CAMEL_KEY_FILE_UNLOCK(kf, lock) (pthread_mutex_unlock(&(kf)->priv->lock))

static pthread_mutex_t key_file_lock = PTHREAD_MUTEX_INITIALIZER;

#else
#define CAMEL_KEY_FILE_LOCK(kf, lock)
#define CAMEL_KEY_FILE_TRYLOCK(kf, lock)
#define CAMEL_KEY_FILE_UNLOCK(kf, lock)
#endif

/* lru cache of block files */
static EDList key_file_list = E_DLIST_INITIALISER(key_file_list);
static EDList key_file_active_list = E_DLIST_INITIALISER(key_file_active_list);
static int key_file_count = 0;
static int key_file_threshhold = 10;

static void
camel_key_file_class_init(CamelKeyFileClass *klass)
{
}

static void
camel_key_file_init(CamelKeyFile *bs)
{
    struct _CamelKeyFilePrivate *p;

    p = bs->priv = g_malloc0(sizeof(*bs->priv));
    p->base = bs;

#ifdef ENABLE_THREADS
    pthread_mutex_init(&p->lock, NULL);
#endif

    LOCK(key_file_lock);
    e_dlist_addhead(&key_file_list, (EDListNode *)p);
    UNLOCK(key_file_lock);
}

static void
camel_key_file_finalise(CamelKeyFile *bs)
{
    struct _CamelKeyFilePrivate *p = bs->priv;

    LOCK(key_file_lock);
    e_dlist_remove((EDListNode *)p);
    UNLOCK(key_file_lock);

    if (bs->fp)
        fclose(bs->fp);
    g_free(bs->path);

#ifdef ENABLE_THREADS
    pthread_mutex_destroy(&p->lock);
#endif

    g_free(p);
}

CamelType
camel_key_file_get_type(void)
{
    static CamelType type = CAMEL_INVALID_TYPE;
    
    if (type == CAMEL_INVALID_TYPE) {
        type = camel_type_register(camel_object_get_type(), "CamelKeyFile",
                       sizeof (CamelKeyFile),
                       sizeof (CamelKeyFileClass),
                       (CamelObjectClassInitFunc) camel_key_file_class_init,
                       NULL,
                       (CamelObjectInitFunc) camel_key_file_init,
                       (CamelObjectFinalizeFunc) camel_key_file_finalise);
    }
    
    return type;
}

/* 'use' a key file for io */
static int
key_file_use(CamelKeyFile *bs)
{
    struct _CamelKeyFilePrivate *nw, *nn, *p = bs->priv;
    CamelKeyFile *bf;
    int err, fd;
    char *flag;

    /* We want to:
        remove file from active list
        lock it

       Then when done:
        unlock it
        add it back to end of active list
    */

    /* TODO: Check header on reset? */

    CAMEL_KEY_FILE_LOCK(bs, lock);

    if (bs->fp != NULL)
        return 0;
    else
        d(printf("Turning key file online: '%s'\n", bs->path));

    if ((bs->flags & O_ACCMODE) == O_RDONLY)
        flag = "r";
    else
        flag = "a+";

    if ((fd = open(bs->path, bs->flags, 0600)) == -1
        || (bs->fp = fdopen(fd, flag)) == NULL) {
        err = errno;
        close(fd);
        CAMEL_KEY_FILE_UNLOCK(bs, lock);
        errno = err;
        return -1;
    }

    LOCK(key_file_lock);
    e_dlist_remove((EDListNode *)p);
    e_dlist_addtail(&key_file_active_list, (EDListNode *)p);

    key_file_count++;

    nw = (struct _CamelKeyFilePrivate *)key_file_list.head;
    nn = nw->next;
    while (key_file_count > key_file_threshhold && nn) {
        /* We never hit the current keyfile here, as its removed from the list first */
        bf = nw->base;
        if (bf->fp != NULL) {
            /* Need to trylock, as any of these lock levels might be trying
               to lock the key_file_lock, so we need to check and abort if so */
            if (CAMEL_BLOCK_FILE_TRYLOCK(bf, lock) == 0) {
                d(printf("Turning key file offline: %s\n", bf->path));
                fclose(bf->fp);
                bf->fp = NULL;
                key_file_count--;
                CAMEL_BLOCK_FILE_UNLOCK(bf, lock);
            }
        }
        nw = nn;
        nn = nw->next;
    }

    UNLOCK(key_file_lock);

    return 0;
}

static void
key_file_unuse(CamelKeyFile *bs)
{
    LOCK(key_file_lock);
    e_dlist_remove((EDListNode *)bs->priv);
    e_dlist_addtail(&key_file_list, (EDListNode *)bs->priv);
    UNLOCK(key_file_lock);

    CAMEL_KEY_FILE_UNLOCK(bs, lock);
}

/**
 * camel_key_file_new:
 * @path: 
 * @flags: open flags
 * @version[]: Version string (header) of file.  Currently
 * written but not checked.
 * 
 * Create a new key file.  A linked list of record blocks.
 * 
 * Return value: A new key file, or NULL if the file could not
 * be opened/created/initialised.
 **/
CamelKeyFile *
camel_key_file_new(const char *path, int flags, const char version[8])
{
    CamelKeyFile *kf;
    off_t last;
    int err;

    d(printf("New key file '%s'\n", path));

    kf = (CamelKeyFile *)camel_object_new(camel_key_file_get_type());
    kf->path = g_strdup(path);
    kf->fp = NULL;
    kf->flags = flags;
    kf->last = 8;

    if (key_file_use(kf) == -1) {
        camel_object_unref((CamelObject *)kf);
        kf = NULL;
    } else {
        fseek(kf->fp, 0, SEEK_END);
        last = ftell(kf->fp);
        if (last == 0) {
            fwrite(version, 8, 1, kf->fp);
            last += 8;
        }
        kf->last = last;

        err = ferror(kf->fp);
        key_file_unuse(kf);

        /* we only need these flags on first open */
        kf->flags &= ~(O_CREAT|O_EXCL|O_TRUNC);

        if (err) {
            camel_object_unref((CamelObject *)kf);
            kf = NULL;
        }
    }

    return kf;
}

int
camel_key_file_rename(CamelKeyFile *kf, const char *path)
{
    int ret;
    struct stat st;
    int err;

    CAMEL_KEY_FILE_LOCK(kf, lock);

    ret = rename(kf->path, path);
    if (ret == -1) {
        /* Maybe the rename actually worked */
        err = errno;
        if (stat(path, &st) == 0
            && stat(kf->path, &st) == -1
            && errno == ENOENT)
            ret = 0;
        errno = err;
    }

    if (ret != -1) {
        g_free(kf->path);
        kf->path = g_strdup(path);
    }

    CAMEL_KEY_FILE_UNLOCK(kf, lock);

    return ret;
}

/**
 * camel_key_file_write:
 * @kf: 
 * @parent: 
 * @len: 
 * @records: 
 * 
 * Write a new list of records to the key file.
 * 
 * Return value: -1 on io error.  The key file will remain unchanged.
 **/
int
camel_key_file_write(CamelKeyFile *kf, camel_block_t *parent, size_t len, camel_key_t *records)
{
    camel_block_t next;
    guint32 size;
    int ret = -1;

    d(printf("write key %08x len = %d\n", *parent, len));

    if (len == 0) {
        d(printf(" new parent = %08x\n", *parent));
        return 0;
    }

    /* LOCK */
    if (key_file_use(kf) == -1)
        return -1;

    size = len;

    /* FIXME: Use io util functions? */
    next = kf->last;
    fseek(kf->fp, kf->last, SEEK_SET);
    fwrite(parent, sizeof(*parent), 1, kf->fp);
    fwrite(&size, sizeof(size), 1, kf->fp);
    fwrite(records, sizeof(records[0]), len, kf->fp);

    if (ferror(kf->fp)) {
        clearerr(kf->fp);
    } else {
        kf->last = ftell(kf->fp);
        *parent = next;
        ret = len;
    }

    /* UNLOCK */
    key_file_unuse(kf);

    d(printf(" new parent = %08x\n", *parent));

    return ret;
}

/**
 * camel_key_file_read:
 * @kf: 
 * @start: The record pointer.  This will be set to the next record pointer on success.
 * @len: Number of records read, if != NULL.
 * @records: Records, allocated, must be freed with g_free, if != NULL.
 * 
 * Read the next block of data from the key file.  Returns the number of
 * records.
 * 
 * Return value: -1 on io error.
 **/
int
camel_key_file_read(CamelKeyFile *kf, camel_block_t *start, size_t *len, camel_key_t **records)
{
    guint32 size;
    long pos = *start;
    camel_block_t next;
    int ret = -1;

    if (pos == 0)
        return 0;

    /* LOCK */
    if (key_file_use(kf) == -1)
        return -1;

    if (fseek(kf->fp, pos, SEEK_SET) == -1
        || fread(&next, sizeof(next), 1, kf->fp) != 1
        || fread(&size, sizeof(size), 1, kf->fp) != 1
        || size > 1024) {
        clearerr(kf->fp);
        goto fail;
    }

    if (len)
        *len = size;

    if (records) {
        camel_key_t *keys = g_malloc(size * sizeof(camel_key_t));

        if (fread(keys, sizeof(camel_key_t), size, kf->fp) != size) {
            g_free(keys);
            goto fail;
        }
        *records = keys;
    }

    *start = next;

    ret = 0;
fail:
    /* UNLOCK */
    key_file_unuse(kf);

    return ret;
}