src/lib-index/mail-cache-fields.c

	mail-cache-fields.c revision 6157a322f2ac1ea1332d9003ecb0b11466aa8fe7
c25356d5978632df6203437e1953bcb29e0c736fTimo Sirainen/* Copyright (c) 2004-2007 Dovecot authors, see the included COPYING file */
c25356d5978632df6203437e1953bcb29e0c736fTimo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen#include "lib.h"
cfdaa223525f87c9c980a25cc7bb6770a248d76aTimo Sirainen#include "ioloop.h"
cfdaa223525f87c9c980a25cc7bb6770a248d76aTimo Sirainen#include "buffer.h"
cfdaa223525f87c9c980a25cc7bb6770a248d76aTimo Sirainen#include "hash.h"
cfdaa223525f87c9c980a25cc7bb6770a248d76aTimo Sirainen#include "file-cache.h"
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen#include "read-full.h"
4f7c150ea0fb986d229379cda622cdcb2d827fd2Timo Sirainen#include "write-full.h"
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen#include "mmap-util.h"
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen#include "mail-cache-private.h"
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen#include <stddef.h>
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen#define CACHE_FIELD_IS_NEWLY_WANTED(cache, field_idx) \
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    ((cache)->field_file_map[field_idx] == (uint32_t)-1 && \
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen     (cache)->fields[field_idx].used)
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainenstatic bool field_has_fixed_size(enum mail_cache_field_type type)
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen{
3c9783956dea385b322cd7fa6bf8c98c17a907a0Timo Sirainen    switch (type) {
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_FIXED_SIZE:
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_BITMASK:
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen        return TRUE;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_VARIABLE_SIZE:
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_STRING:
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_HEADER:
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen        return FALSE;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    case MAIL_CACHE_FIELD_COUNT:
e65cc79f80577e83c706f0678c78e2c0bd91434fTimo Sirainen        break;
7d6389e4053c2dac1fb37180b5756b00785983dcTimo Sirainen    }
7d6389e4053c2dac1fb37180b5756b00785983dcTimo Sirainen
6ef7e31619edfaa17ed044b45861d106a86191efTimo Sirainen    i_unreached();
f1ddb98e6b639394ae205b305be1ddcfab102578Timo Sirainen    return FALSE;
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen}
40992309053d51192ae1b36d1dd6c057f2d37257Timo Sirainen
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainenstatic bool field_decision_is_valid(enum mail_cache_decision_type type)
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen{
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen    switch (type & ~MAIL_CACHE_DECISION_FORCED) {
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen    case MAIL_CACHE_DECISION_NO:
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen    case MAIL_CACHE_DECISION_TEMP:
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen    case MAIL_CACHE_DECISION_YES:
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen        return TRUE;
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen    default:
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen        return FALSE;
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen    }
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen}
b96dcd982888d89e6f2508258d6d9588d79c7a26Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainenstatic int field_type_verify(struct mail_cache *cache, unsigned int idx,
e82af44fe25ca9b88210f313548dc08538e4a677Timo Sirainen                 enum mail_cache_field_type type, unsigned int size)
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen{
b567e0172c73dcf7642462e86962060358dd5f28Timo Sirainen    const struct mail_cache_field *field = &cache->fields[idx].field;
b567e0172c73dcf7642462e86962060358dd5f28Timo Sirainen
f8464772990b52cb8de4553bc1135adcf72813b8Timo Sirainen    if (field->type != type) {
f4a19b0cf11cdff437571708d9d788d02a906a00Timo Sirainen        mail_cache_set_corrupted(cache,
f4a19b0cf11cdff437571708d9d788d02a906a00Timo Sirainen            "registered field %s type changed", field->name);
10c5fd417af4ee30b68c967f5e7d5a49f4f149b5Timo Sirainen        return -1;
10c5fd417af4ee30b68c967f5e7d5a49f4f149b5Timo Sirainen    }
10c5fd417af4ee30b68c967f5e7d5a49f4f149b5Timo Sirainen    if (field->field_size != size && field_has_fixed_size(type)) {
10c5fd417af4ee30b68c967f5e7d5a49f4f149b5Timo Sirainen        mail_cache_set_corrupted(cache,
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen            "registered field %s size changed", field->name);
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        return -1;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    }
473080c7c0d25ddfdf77e7dfa0ba8f73c6c669d5Timo Sirainen    return 0;
964c86de7158ccafdfe665853579d71232e2634eTimo Sirainen}
1f18053d463f0294387b5e4dd11f9010bda9a24eTimo Sirainen
6ef7e31619edfaa17ed044b45861d106a86191efTimo Sirainenvoid mail_cache_register_fields(struct mail_cache *cache,
e82af44fe25ca9b88210f313548dc08538e4a677Timo Sirainen                struct mail_cache_field *fields,
e714eed72515794c46c6712a611e5ab924d903daTimo Sirainen                unsigned int fields_count)
e714eed72515794c46c6712a611e5ab924d903daTimo Sirainen{
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    void *orig_key, *orig_value;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    char *name;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    unsigned int new_idx;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    unsigned int i, j;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    new_idx = cache->fields_count;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    for (i = 0; i < fields_count; i++) {
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        if (hash_lookup_full(cache->field_name_hash, fields[i].name,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                     &orig_key, &orig_value)) {
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            i_assert(fields[i].type < MAIL_CACHE_FIELD_COUNT);
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            fields[i].idx =
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                POINTER_CAST_TO(orig_value, unsigned int);
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            (void)field_type_verify(cache, fields[i].idx,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                        fields[i].type,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                        fields[i].field_size);
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            continue;
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        }
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        /* check if the same header is being registered in the
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen           same field array */
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        for (j = 0; j < i; j++) {
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen            if (strcasecmp(fields[i].name, fields[j].name) == 0) {
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                fields[i].idx = fields[j].idx;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                break;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            }
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        }
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        if (j == i)
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            fields[i].idx = new_idx++;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    }
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    if (new_idx == cache->fields_count)
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        return;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    /* @UNSAFE */
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    cache->fields = i_realloc(cache->fields,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                  cache->fields_count * sizeof(*cache->fields),
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                  new_idx * sizeof(*cache->fields));
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    cache->field_file_map =
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        i_realloc(cache->field_file_map,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen              cache->fields_count * sizeof(*cache->field_file_map),
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen              new_idx * sizeof(*cache->field_file_map));
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    for (i = 0; i < fields_count; i++) {
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        unsigned int idx = fields[i].idx;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        if (idx < cache->fields_count)
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen            continue;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        /* new index - save it */
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        name = p_strdup(cache->field_pool, fields[i].name);
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        cache->fields[idx].field = fields[i];
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        cache->fields[idx].field.name = name;
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        cache->field_file_map[idx] = (uint32_t)-1;
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        if (!field_has_fixed_size(cache->fields[idx].field.type))
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen            cache->fields[idx].field.field_size = (unsigned int)-1;
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        hash_insert(cache->field_name_hash, name, POINTER_CAST(idx));
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    }
c4457e497e01b57565d24da624968699b166e02aTimo Sirainen    cache->fields_count = new_idx;
c4457e497e01b57565d24da624968699b166e02aTimo Sirainen}
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainenunsigned int
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainenmail_cache_register_lookup(struct mail_cache *cache, const char *name)
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen{
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    void *orig_key, *orig_value;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    if (hash_lookup_full(cache->field_name_hash, name,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                 &orig_key, &orig_value))
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        return POINTER_CAST_TO(orig_value, unsigned int);
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    else
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        return (unsigned int)-1;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen}
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainenconst struct mail_cache_field *
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainenmail_cache_register_get_list(struct mail_cache *cache, pool_t pool,
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen                 unsigned int *count_r)
63cde222abaaa2a9bdaa9a143698dbc8b23bd742Timo Sirainen{
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        struct mail_cache_field *list;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    unsigned int i;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
e023e3c2677ab66d7a7445eae9caf3d739e199cbTimo Sirainen    if (!cache->opened)
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen        (void)mail_cache_open_and_verify(cache);
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    list = p_new(pool, struct mail_cache_field, cache->fields_count);
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen    for (i = 0; i < cache->fields_count; i++) {
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen        list[i] = cache->fields[i].field;
964c86de7158ccafdfe665853579d71232e2634eTimo Sirainen        list[i].name = p_strdup(pool, list[i].name);
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen    }
a399486f2d8d5bed51bc6344baba61a7f2b0dcdbTimo Sirainen
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    *count_r = cache->fields_count;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen    return list;
fc4ff2356fee6389d4cf2b3f12f4098a436f0502Timo Sirainen}
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen
9f431ccfb6932746db56245c8a3d3415717ef545Timo Sirainenstatic int mail_cache_header_fields_get_offset(struct mail_cache *cache,
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen                           uint32_t *offset_r, bool map)
16133a719ce8b6a5b8cedd721340cc1607c43433Timo Sirainen{
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    const struct mail_cache_header_fields *field_hdr;
964c86de7158ccafdfe665853579d71232e2634eTimo Sirainen    struct mail_cache_header_fields tmp_field_hdr;
d5cebe7f98e63d4e2822863ef2faa4971e8b3a5dTimo Sirainen    uint32_t offset = 0, next_offset;
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen    unsigned int next_count = 0;
964c86de7158ccafdfe665853579d71232e2634eTimo Sirainen    int ret;
16133a719ce8b6a5b8cedd721340cc1607c43433Timo Sirainen
08aea01ef9a9d20703e0fcf8618e6195c0037a44Timo Sirainen    if (MAIL_CACHE_IS_UNUSABLE(cache)) {
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        *offset_r = 0;
43d3ea2780b5f8557ede7b4c039e8f56cb8d357dTimo Sirainen        return 0;
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen    }
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen    /* find the latest header */
3c9783956dea385b322cd7fa6bf8c98c17a907a0Timo Sirainen    offset = 0;
3c9783956dea385b322cd7fa6bf8c98c17a907a0Timo Sirainen    next_offset = cache->last_field_header_offset != 0 ?
ebfcfd258acc89633c47d9c3b0b40a1a3f75cdcbTimo Sirainen        cache->last_field_header_offset :
d1f0acc7fc722e13e8296228703adfe8a884d59eTimo Sirainen        mail_index_offset_to_uint32(cache->hdr->field_header_offset);
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen    while (next_offset != 0) {
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen        if (next_offset == offset) {
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen            mail_cache_set_corrupted(cache,
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen                "next_offset in field header loops");
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen            return -1;
3dadeec1ce7a5bf72fbd850658df1db3cedd4416Timo Sirainen        }
3dadeec1ce7a5bf72fbd850658df1db3cedd4416Timo Sirainen        offset = next_offset;
0a8926b91a84abf462afdc1ed95def229377d7ffTimo Sirainen
4261a8b43792dc4db4b39e6910319835b7450e84Timo Sirainen        if (cache->mmap_base != NULL) {
965ed6ea3fc8f7637bd0d159d2fdb283a191ce34Timo Sirainen            if (mail_cache_map(cache, offset,
                       sizeof(*field_hdr)) < 0)
                return -1;

            field_hdr = CONST_PTR_OFFSET(cache->data, offset);
        } else {
            /* if we need to follow multiple offsets to get to
               the last one, it's faster to just pread() the file
               instead of going through cache */
            ret = pread_full(cache->fd, &tmp_field_hdr,
                     sizeof(tmp_field_hdr), offset);
            if (ret < 0) {
                mail_cache_set_syscall_error(cache, "pread()");
                return -1;
            }
            if (ret == 0) {
                mail_cache_set_corrupted(cache,
                    "next_offset points outside file");
                return -1;
            }
            field_hdr = &tmp_field_hdr;
        }

        next_offset =
            mail_index_offset_to_uint32(field_hdr->next_offset);
        next_count++;
    }

    if (offset == 0) {
        mail_cache_set_corrupted(cache, "missing header fields");
        return -1;
    }
    cache->last_field_header_offset = offset;

    if (next_count > MAIL_CACHE_HEADER_FIELD_CONTINUE_COUNT)
        cache->need_compress_file_seq = cache->hdr->file_seq;

    if (map) {
        if (cache->file_cache != NULL) {
            /* we can't trust that the cached data is valid */
            file_cache_invalidate(cache->file_cache, offset,
                          field_hdr->size);
        }
        if (mail_cache_map(cache, offset, field_hdr->size) < 0)
            return -1;
    }

    *offset_r = offset;
    return 0;
}

int mail_cache_header_fields_read(struct mail_cache *cache)
{
    const struct mail_cache_header_fields *field_hdr = NULL;
    struct mail_cache_field field;
    const uint32_t *last_used, *sizes;
    const uint8_t *types, *decisions;
    const char *p, *names, *end;
    void *orig_key, *orig_value;
    unsigned int new_fields_count;
    time_t max_drop_time;
    uint32_t offset, i;

    if (mail_cache_header_fields_get_offset(cache, &offset, TRUE) < 0)
        return -1;

    if (offset == 0) {
        /* no fields - the file is empty */
        return 0;
    }

    field_hdr = CONST_PTR_OFFSET(cache->data, offset);
    if (offset + field_hdr->size > cache->mmap_length) {
        mail_cache_set_corrupted(cache,
                     "field header points outside file");
        return -1;
    }

    /* check the fixed size of the header. name[] has to be checked
       separately */
    if (field_hdr->size < sizeof(*field_hdr) +
        field_hdr->fields_count * (sizeof(uint32_t)*2 + 1 + 2)) {
        mail_cache_set_corrupted(cache, "invalid field header size");
        return -1;
    }

    field_hdr = CONST_PTR_OFFSET(cache->data, offset);
    new_fields_count = field_hdr->fields_count;

    if (new_fields_count != 0) {
        cache->file_field_map =
            i_realloc(cache->file_field_map,
                  cache->file_fields_count *
                  sizeof(unsigned int),
                  new_fields_count * sizeof(unsigned int));
    } else {
        i_free_and_null(cache->file_field_map);
    }
    cache->file_fields_count = new_fields_count;

    last_used = CONST_PTR_OFFSET(field_hdr, MAIL_CACHE_FIELD_LAST_USED());
    sizes = CONST_PTR_OFFSET(field_hdr,
        MAIL_CACHE_FIELD_SIZE(field_hdr->fields_count));
    types = CONST_PTR_OFFSET(field_hdr,
        MAIL_CACHE_FIELD_TYPE(field_hdr->fields_count));
    decisions = CONST_PTR_OFFSET(field_hdr,
        MAIL_CACHE_FIELD_DECISION(field_hdr->fields_count));
    names = CONST_PTR_OFFSET(field_hdr,
        MAIL_CACHE_FIELD_NAMES(field_hdr->fields_count));
    end = CONST_PTR_OFFSET(field_hdr, field_hdr->size);

    /* clear the old mapping */
    for (i = 0; i < cache->fields_count; i++)
        cache->field_file_map[i] = (uint32_t)-1;

    max_drop_time = cache->index->map->hdr.day_stamp -
        MAIL_CACHE_FIELD_DROP_SECS;

    memset(&field, 0, sizeof(field));
    for (i = 0; i < field_hdr->fields_count; i++) {
        for (p = names; p != end && *p != '\0'; p++) ;
        if (p == end || *names == '\0') {
            mail_cache_set_corrupted(cache,
                "field header names corrupted");
            return -1;
        }

        if (types[i] > MAIL_CACHE_FIELD_COUNT) {
            mail_cache_set_corrupted(cache, "field type corrupted");
            return -1;
        }
        if (!field_decision_is_valid(decisions[i])) {
            mail_cache_set_corrupted(cache,
                "field decision type corrupted");
            return -1;
        }

        if (hash_lookup_full(cache->field_name_hash, names,
                     &orig_key, &orig_value)) {
            /* already exists, see if decision can be updated */
            field.idx = POINTER_CAST_TO(orig_value, unsigned int);
            if (!cache->fields[field.idx].decision_dirty) {
                cache->fields[field.idx].field.decision =
                    decisions[i];
            }
            if (field_type_verify(cache, field.idx,
                          types[i], sizes[i]) < 0)
                return -1;
        } else {
            field.name = names;
            field.type = types[i];
            field.field_size = sizes[i];
            field.decision = decisions[i];
            mail_cache_register_fields(cache, &field, 1);
        }
        if (cache->field_file_map[field.idx] != (uint32_t)-1) {
            mail_cache_set_corrupted(cache,
                "Duplicated field in header: %s", names);
            return -1;
        }
        cache->fields[field.idx].used = TRUE;

        cache->field_file_map[field.idx] = i;
        cache->file_field_map[i] = field.idx;

        /* update last_used if it's newer than ours */
        if (last_used[i] > cache->fields[field.idx].last_used)
            cache->fields[field.idx].last_used = last_used[i];

        if (cache->fields[field.idx].last_used < max_drop_time &&
            cache->fields[field.idx].last_used != 0) {
            /* time to drop this field. don't bother dropping
               fields that have never been used. */
            cache->need_compress_file_seq = cache->hdr->file_seq;
        }

                names = p + 1;
    }
    return 0;
}

static void copy_to_buf(struct mail_cache *cache, buffer_t *dest, bool add_new,
            size_t offset, size_t size)
{
    const void *data;
    unsigned int i, field;

    /* copy the existing fields */
    for (i = 0; i < cache->file_fields_count; i++) {
        field = cache->file_field_map[i];
                data = CONST_PTR_OFFSET(&cache->fields[field], offset);
        buffer_append(dest, data, size);
    }
    if (!add_new)
        return;

    /* copy newly wanted fields */
    for (i = 0; i < cache->fields_count; i++) {
        if (CACHE_FIELD_IS_NEWLY_WANTED(cache, i)) {
            data = CONST_PTR_OFFSET(&cache->fields[i], offset);
            buffer_append(dest, data, size);
        }
    }
}

static void copy_to_buf_byte(struct mail_cache *cache, buffer_t *dest,
                 bool add_new, size_t offset)
{
    const int *data;
    unsigned int i, field;
    uint8_t byte;

    /* copy the existing fields */
    for (i = 0; i < cache->file_fields_count; i++) {
        field = cache->file_field_map[i];
                data = CONST_PTR_OFFSET(&cache->fields[field], offset);
        byte = (uint8_t)*data;
        buffer_append(dest, &byte, 1);
    }
    if (!add_new)
        return;

    /* copy newly wanted fields */
    for (i = 0; i < cache->fields_count; i++) {
        if (CACHE_FIELD_IS_NEWLY_WANTED(cache, i)) {
            data = CONST_PTR_OFFSET(&cache->fields[i], offset);
            byte = (uint8_t)*data;
            buffer_append(dest, &byte, 1);
        }
    }
}

static int mail_cache_header_fields_update_locked(struct mail_cache *cache)
{
    buffer_t *buffer;
    uint32_t i, offset, dec_offset;
    int ret = 0;

    if (mail_cache_header_fields_read(cache) < 0 ||
        mail_cache_header_fields_get_offset(cache, &offset, FALSE) < 0)
        return -1;

    t_push();
    buffer = buffer_create_dynamic(pool_datastack_create(), 256);

    copy_to_buf(cache, buffer, FALSE,
            offsetof(struct mail_cache_field_private, last_used),
            sizeof(uint32_t));
    ret = mail_cache_write(cache, buffer->data, buffer->used,
                   offset + MAIL_CACHE_FIELD_LAST_USED());
    if (ret == 0) {
        buffer_set_used_size(buffer, 0);
        copy_to_buf_byte(cache, buffer, FALSE,
                 offsetof(struct mail_cache_field, decision));

        dec_offset = offset +
            MAIL_CACHE_FIELD_DECISION(cache->file_fields_count);
        ret = mail_cache_write(cache, buffer->data, buffer->used,
                       dec_offset);
        if (ret == 0) {
            for (i = 0; i < cache->file_fields_count; i++)
                cache->fields[i].decision_dirty = FALSE;
        }
    }
    t_pop();

    if (ret == 0)
        cache->field_header_write_pending = FALSE;

    return ret;
}

int mail_cache_header_fields_update(struct mail_cache *cache)
{
    int ret;

    if (cache->locked)
        return mail_cache_header_fields_update_locked(cache);

    if (mail_cache_lock(cache, NULL) <= 0)
        return -1;

    ret = mail_cache_header_fields_update_locked(cache);
    if (mail_cache_unlock(cache) < 0)
        ret = -1;
    return ret;
}

void mail_cache_header_fields_get(struct mail_cache *cache, buffer_t *dest)
{
    struct mail_cache_header_fields hdr;
    unsigned int field;
    const char *name;
    uint32_t i;

    memset(&hdr, 0, sizeof(hdr));
    hdr.fields_count = cache->file_fields_count;
    for (i = 0; i < cache->fields_count; i++) {
        if (cache->fields[i].last_used == 0) {
            /* return newly added fields' last_used as
               the current time */
            cache->fields[i].last_used = ioloop_time;
        }
        if (CACHE_FIELD_IS_NEWLY_WANTED(cache, i))
            hdr.fields_count++;
    }
    buffer_append(dest, &hdr, sizeof(hdr));

    /* we have to keep the field order for the existing fields. */
    copy_to_buf(cache, dest, TRUE,
            offsetof(struct mail_cache_field_private, last_used),
            sizeof(uint32_t));
    copy_to_buf(cache, dest, TRUE,
            offsetof(struct mail_cache_field, field_size),
            sizeof(uint32_t));
    copy_to_buf_byte(cache, dest, TRUE,
             offsetof(struct mail_cache_field, type));
    copy_to_buf_byte(cache, dest, TRUE,
             offsetof(struct mail_cache_field, decision));

    i_assert(dest->used == sizeof(hdr) +
         (sizeof(uint32_t)*2 + 2) * hdr.fields_count);

    /* add existing fields' names */
    for (i = 0; i < cache->file_fields_count; i++) {
        field = cache->file_field_map[i];
        name = cache->fields[field].field.name;
        buffer_append(dest, name, strlen(name)+1);
    }
    /* add newly wanted fields' names */
    for (i = 0; i < cache->fields_count; i++) {
        if (CACHE_FIELD_IS_NEWLY_WANTED(cache, i)) {
            name = cache->fields[i].field.name;
            buffer_append(dest, name, strlen(name)+1);
        }
    }

    hdr.size = dest->used;
    buffer_write(dest, 0, &hdr, sizeof(hdr));

    if ((hdr.size & 3) != 0)
        buffer_append_zero(dest, 4 - (hdr.size & 3));
}

int mail_cache_header_fields_get_next_offset(struct mail_cache *cache,
                         uint32_t *offset_r)
{
    if (mail_cache_header_fields_get_offset(cache, offset_r, FALSE) < 0)
        return -1;

    if (*offset_r == 0) {
        *offset_r = offsetof(struct mail_cache_header,
                     field_header_offset);
    } else {
        *offset_r += offsetof(struct mail_cache_header_fields,
                      next_offset);
    }
    return 0;
}