aboutsummaryrefslogtreecommitdiffstats
path: root/camel/camel-block-file.c
blob: be30ad6f179d69bf053ca0c9eaf61c6cd66e896b (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
/*
 * 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;
}