src/lib-index/mail-transaction-log-view.c

	mail-transaction-log-view.c revision 7471f28b16b81f9af413c879b3efb16eeafd2bd9
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch/* Copyright (c) 2003-2010 Dovecot authors, see the included COPYING file */
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch#include "lib.h"
66134fbce11778241ca9f8458ee2a0488a05bde0Stephan Bosch#include "array.h"
66134fbce11778241ca9f8458ee2a0488a05bde0Stephan Bosch#include "mail-index-private.h"
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch#include "mail-transaction-log-view-private.h"
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
66134fbce11778241ca9f8458ee2a0488a05bde0Stephan Boschstruct mail_transaction_log_view *
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschmail_transaction_log_view_open(struct mail_transaction_log *log)
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch{
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    struct mail_transaction_log_view *view;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view = i_new(struct mail_transaction_log_view, 1);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view->log = log;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view->broken = TRUE;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view->head = view->tail = view->log->head;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view->head->refcount++;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    i_array_init(&view->file_refs, 8);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    array_append(&view->file_refs, &view->head, 1);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    view->next = log->views;
4d955db590c3d76a631dfc5d37bcdf578a43e55aStephan Bosch    log->views = view;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    return view;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch}
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschstatic void
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschmail_transaction_log_view_unref_all(struct mail_transaction_log_view *view)
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch{
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    struct mail_transaction_log_file *const *files;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    unsigned int i, count;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    files = array_get(&view->file_refs, &count);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    for (i = 0; i < count; i++)
4d955db590c3d76a631dfc5d37bcdf578a43e55aStephan Bosch        files[i]->refcount--;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
0dffa25d211be541ee3c953b23566a1a990789dfTimo Sirainen    array_clear(&view->file_refs);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch}
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschvoid mail_transaction_log_view_close(struct mail_transaction_log_view **_view)
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch{
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch        struct mail_transaction_log_view *view = *_view;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    struct mail_transaction_log_view **p;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    *_view = NULL;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    for (p = &view->log->views; *p != NULL; p = &(*p)->next) {
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch        if (*p == view) {
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch            *p = view->next;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch            break;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch        }
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    }
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    mail_transaction_log_view_unref_all(view);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    mail_transaction_logs_clean(view->log);
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
639bb36b12b9f9bb54c8bb1be50eac623622f8a0Timo Sirainen    array_free(&view->file_refs);
dc78180b54a05d5736d0e0e444cba0332265eb62Phil Carmody    i_free(view);
639bb36b12b9f9bb54c8bb1be50eac623622f8a0Timo Sirainen}
639bb36b12b9f9bb54c8bb1be50eac623622f8a0Timo Sirainen
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschvoid mail_transaction_log_views_close(struct mail_transaction_log *log)
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch{
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    struct mail_transaction_log_view *view;
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch    for (view = log->views; view != NULL; view = view->next)
4d955db590c3d76a631dfc5d37bcdf578a43e55aStephan Bosch        view->log = NULL;
4d955db590c3d76a631dfc5d37bcdf578a43e55aStephan Bosch}
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Boschint mail_transaction_log_view_set(struct mail_transaction_log_view *view,
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch                  uint32_t min_file_seq, uoff_t min_file_offset,
6ae6496c225238a2c55a8cd96744ad976c44a726Stephan Bosch                  uint32_t max_file_seq, uoff_t max_file_offset,
                  bool *reset_r)
{
    struct mail_transaction_log_file *file, *const *files, *tail;
    uoff_t start_offset, end_offset;
    unsigned int i;
    uint32_t seq;
    int ret;

    i_assert(min_file_seq <= max_file_seq);

    *reset_r = FALSE;

    if (view->log == NULL) {
        /* transaction log is closed already. this log view shouldn't
           be used anymore. */
        return -1;
    }

    tail = view->log->files;
    if (min_file_seq == 0) {
        /* index file doesn't exist yet. this transaction log should
           start from the beginning */
        if (tail->hdr.prev_file_seq != 0) {
            /* but it doesn't */
            return 0;
        }

        min_file_seq = tail->hdr.file_seq;
        min_file_offset = 0;

        if (max_file_seq == 0) {
            max_file_seq = min_file_seq;
            max_file_offset = min_file_offset;
        }
    }

    if (min_file_seq == tail->hdr.prev_file_seq &&
        min_file_offset == tail->hdr.prev_file_offset) {
        /* we can skip this */
        min_file_seq = tail->hdr.file_seq;
        min_file_offset = 0;

        if (min_file_seq > max_file_seq) {
            /* empty view */
            max_file_seq = min_file_seq;
            max_file_offset = min_file_offset;
        }
    }

    if (min_file_seq == max_file_seq && min_file_offset > max_file_offset) {
        /* log file offset is probably corrupted in the index file. */
        mail_transaction_log_view_set_corrupted(view,
            "file_seq=%u, min_file_offset (%"PRIuUOFF_T
            ") > max_file_offset (%"PRIuUOFF_T")",
            min_file_seq, min_file_offset, max_file_offset);
        return -1;
    }

    if (min_file_offset > 0 && min_file_offset < tail->hdr.hdr_size) {
        /* log file offset is probably corrupted in the index file. */
        mail_transaction_log_view_set_corrupted(view,
            "file_seq=%u, min_file_offset (%"PRIuUOFF_T
            ") < hdr_size (%u)",
            min_file_seq, min_file_offset, tail->hdr.hdr_size);
        return -1;
    }

    view->tail = view->head = file = NULL;
    for (seq = min_file_seq; seq <= max_file_seq; seq++) {
        if (file == NULL || file->hdr.file_seq != seq) {
            /* see if we could find the missing file. if we know
               the max. file sequence, make sure NFS attribute
               cache gets flushed if necessary. */
            bool nfs_flush = max_file_seq != (uint32_t)-1;

            ret = mail_transaction_log_find_file(view->log, seq,
                                 nfs_flush, &file);
            if (ret <= 0) {
                if (ret < 0)
                    return -1;

                /* not found / corrupted */
                file = NULL;
            }
        }

        if (file == NULL || file->hdr.file_seq != seq) {
            if (file == NULL && max_file_seq == (uint32_t)-1 &&
                view->head == view->log->head) {
                /* we just wanted to sync everything */
                i_assert(max_file_offset == (uoff_t)-1);
                max_file_seq = seq-1;
                break;
            }
            /* if any of the found files reset the index,
               ignore any missing files up to it */
            file = view->tail != NULL ? view->tail :
                view->log->files;
            for (;; file = file->next) {
                if (file == NULL ||
                    file->hdr.file_seq > max_file_seq) {
                    /* missing files in the middle */
                    return 0;
                }

                if (file->hdr.file_seq >= seq &&
                    file->hdr.prev_file_seq == 0) {
                    /* we can ignore the missing file */
                    break;
                }
            }
            seq = file->hdr.file_seq;
            view->tail = NULL;
        }

        if (view->tail == NULL)
            view->tail = file;
        view->head = file;
        file = file->next;
    }
    i_assert(view->tail != NULL);

    if (min_file_offset == 0) {
        /* beginning of the file */
        min_file_offset = view->tail->hdr.hdr_size;
        if (min_file_offset > max_file_offset &&
            min_file_seq == max_file_seq) {
            /* we don't actually want to show anything */
            max_file_offset = min_file_offset;
        }
    }
    i_assert(min_file_offset >= view->tail->hdr.hdr_size);

    /* we have all of them. update refcounts. */
    mail_transaction_log_view_unref_all(view);

    /* Reference all used files. */
    for (file = view->tail;; file = file->next) {
        array_append(&view->file_refs, &file, 1);
        file->refcount++;

        if (file == view->head)
            break;
    }

    view->cur = view->tail;
    view->cur_offset = view->cur->hdr.file_seq == min_file_seq ?
        min_file_offset : view->cur->hdr.hdr_size;

    /* Map the files only after we've found them all. Otherwise if we map
       one file and then another file just happens to get rotated, we could
       include both files in the view but skip the last transactions from
       the first file.

       We're mapping the files in reverse order so that _log_file_map()
       can verify that prev_file_offset matches how far it actually managed
       to sync the file. */
    files = array_idx(&view->file_refs, 0);
    for (i = array_count(&view->file_refs); i > 0; i--) {
        file = files[i-1];
        start_offset = file->hdr.file_seq == min_file_seq ?
            min_file_offset : file->hdr.hdr_size;
        end_offset = file->hdr.file_seq == max_file_seq ?
            max_file_offset : (uoff_t)-1;
        ret = mail_transaction_log_file_map(file, start_offset,
                            end_offset);
        if (ret <= 0)
            return ret;

        if (file->hdr.prev_file_seq == 0) {
            /* this file resets the index.
               don't bother reading the others. */
            if (view->cur != file ||
                view->cur_offset == file->hdr.hdr_size) {
                view->cur = file;
                view->cur_offset = file->hdr.hdr_size;
                *reset_r = TRUE;
                break;
            }
            i_assert(i == 1);
        }
    }

    if (min_file_seq == view->head->hdr.file_seq &&
        min_file_offset > view->head->sync_offset) {
        /* log file offset is probably corrupted in the index file. */
        mail_transaction_log_view_set_corrupted(view,
            "file_seq=%u, min_file_offset (%"PRIuUOFF_T
            ") > sync_offset (%"PRIuUOFF_T")", min_file_seq,
            min_file_offset, view->head->sync_offset);
        return -1;
    }

    i_assert(max_file_seq == (uint32_t)-1 ||
         max_file_seq == view->head->hdr.file_seq);
    i_assert(max_file_offset == (uoff_t)-1 ||
         max_file_offset <= view->head->sync_offset);
    i_assert(min_file_seq != max_file_seq ||
         max_file_seq != view->head->hdr.file_seq ||
         max_file_offset != (uoff_t)-1 ||
         min_file_offset <= view->head->sync_offset);

    view->prev_file_seq = view->cur->hdr.file_seq;
    view->prev_file_offset = view->cur_offset;

    view->min_file_seq = min_file_seq;
    view->min_file_offset = min_file_offset;
    view->max_file_seq = max_file_seq;
    view->max_file_offset = I_MIN(max_file_offset, view->head->sync_offset);
    view->broken = FALSE;

    if (mail_transaction_log_file_get_highest_modseq_at(view->cur,
                view->cur_offset, &view->prev_modseq) < 0)
        return -1;

    i_assert(view->cur_offset <= view->cur->sync_offset);
    return 1;
}

void mail_transaction_log_view_clear(struct mail_transaction_log_view *view,
                     uint32_t oldest_file_seq)
{
    struct mail_transaction_log_file *file;

    mail_transaction_log_view_unref_all(view);
    if (mail_transaction_log_find_file(view->log, oldest_file_seq, FALSE,
                       &file) > 0) {
        for (; file != NULL; file = file->next) {
            array_append(&view->file_refs, &file, 1);
            file->refcount++;
        }
    }

    view->cur = view->head = view->tail = NULL;

    view->mark_file = NULL;
    view->mark_offset = 0;
    view->mark_modseq = 0;

    view->min_file_seq = view->max_file_seq = 0;
    view->min_file_offset = view->max_file_offset = 0;
    view->cur_offset = 0;

    view->prev_file_seq = 0;
    view->prev_file_offset = 0;
    view->prev_modseq = 0;
}

void
mail_transaction_log_view_get_prev_pos(struct mail_transaction_log_view *view,
                       uint32_t *file_seq_r,
                       uoff_t *file_offset_r)
{
    *file_seq_r = view->prev_file_seq;
    *file_offset_r = view->prev_file_offset;
}

uint64_t
mail_transaction_log_view_get_prev_modseq(struct mail_transaction_log_view *view)
{
    return view->prev_modseq;
}

static bool
mail_transaction_log_view_get_last(struct mail_transaction_log_view *view,
                   struct mail_transaction_log_file **last_r,
                   uoff_t *last_offset_r)
{
    struct mail_transaction_log_file *cur = view->cur;
    uoff_t cur_offset = view->cur_offset;
    bool last = FALSE;

    if (cur == NULL) {
        *last_r = NULL;
        return TRUE;
    }

    for (;;) {
        if (cur->hdr.file_seq == view->max_file_seq) {
            /* last file */
            if (cur_offset == view->max_file_offset ||
                cur_offset == cur->sync_offset) {
                /* we're all finished */
                last = TRUE;
            }
        } else if (cur_offset == cur->sync_offset) {
            /* end of file, go to next one */
            if (cur->next == NULL) {
                last = TRUE;
            } else {
                cur = cur->next;
                cur_offset = cur->hdr.hdr_size;
                continue;
            }
        }

        /* not EOF */
        break;
    }

    *last_r = cur;
    *last_offset_r = cur_offset;
    return last;
}

bool mail_transaction_log_view_is_last(struct mail_transaction_log_view *view)
{
    struct mail_transaction_log_file *cur;
    uoff_t cur_offset;

    return mail_transaction_log_view_get_last(view, &cur, &cur_offset);
}

void
mail_transaction_log_view_set_corrupted(struct mail_transaction_log_view *view,
                    const char *fmt, ...)
{
    va_list va;

    view->broken = TRUE;

    va_start(va, fmt);
    T_BEGIN {
        mail_transaction_log_file_set_corrupted(view->log->head, "%s",
            t_strdup_vprintf(fmt, va));
    } T_END;
    va_end(va);
}

bool
mail_transaction_log_view_is_corrupted(struct mail_transaction_log_view *view)
{
    return view->broken;
}

static bool
log_view_is_uid_range_valid(struct mail_transaction_log_file *file,
                enum mail_transaction_type rec_type,
                const ARRAY_TYPE(seq_range) *uids)
{
    const struct seq_range *rec, *prev = NULL;
    unsigned int i, count = array_count(uids);

    if ((uids->arr.buffer->used % uids->arr.element_size) != 0) {
        mail_transaction_log_file_set_corrupted(file,
            "Invalid record size (type=0x%x)", rec_type);
        return FALSE;
    } else if (count == 0) {
        mail_transaction_log_file_set_corrupted(file,
            "No UID ranges (type=0x%x)", rec_type);
        return FALSE;
    }

    for (i = 0; i < count; i++, prev = rec) {
        rec = array_idx(uids, i);
        if (rec->seq1 > rec->seq2 || rec->seq1 == 0) {
            mail_transaction_log_file_set_corrupted(file,
                "Invalid UID range (%u .. %u, type=0x%x)",
                rec->seq1, rec->seq2, rec_type);
            return FALSE;
        }
        if (prev != NULL && rec->seq1 <= prev->seq2) {
            mail_transaction_log_file_set_corrupted(file,
                "Non-sorted UID ranges (type=0x%x)", rec_type);
            return FALSE;
        }
    }
    return TRUE;
}

static bool
log_view_is_record_valid(struct mail_transaction_log_file *file,
             const struct mail_transaction_header *hdr,
             const void *data)
{
    enum mail_transaction_type rec_type;
    ARRAY_TYPE(seq_range) uids = ARRAY_INIT;
    buffer_t uid_buf;
    uint32_t rec_size;

    rec_type = hdr->type & MAIL_TRANSACTION_TYPE_MASK;
    rec_size = mail_index_offset_to_uint32(hdr->size) - sizeof(*hdr);

    /* we want to be extra careful with expunges */
    if ((hdr->type & MAIL_TRANSACTION_EXPUNGE) != 0) {
        if (rec_type != (MAIL_TRANSACTION_EXPUNGE |
                 MAIL_TRANSACTION_EXPUNGE_PROT)) {
            mail_transaction_log_file_set_corrupted(file,
                "expunge record missing protection mask");
            return FALSE;
        }
        rec_type &= ~MAIL_TRANSACTION_EXPUNGE_PROT;
    }
    if ((hdr->type & MAIL_TRANSACTION_EXPUNGE_GUID) != 0) {
        if (rec_type != (MAIL_TRANSACTION_EXPUNGE_GUID |
                 MAIL_TRANSACTION_EXPUNGE_PROT)) {
            mail_transaction_log_file_set_corrupted(file,
                "expunge guid record missing protection mask");
            return FALSE;
        }
        rec_type &= ~MAIL_TRANSACTION_EXPUNGE_PROT;
    }

    if (rec_size == 0) {
        mail_transaction_log_file_set_corrupted(file,
            "Empty record contents (type=0x%x)", rec_type);
        return FALSE;
    }

    /* records that are exported by syncing and view syncing will be
       checked here so that we don't have to implement the same validation
       multiple times. other records are checked internally by
       mail_index_sync_record(). */
    switch (rec_type) {
    case MAIL_TRANSACTION_APPEND:
        if ((rec_size % sizeof(struct mail_index_record)) != 0) {
            mail_transaction_log_file_set_corrupted(file,
                "Invalid append record size");
            return FALSE;
        }
        break;
    case MAIL_TRANSACTION_EXPUNGE:
        buffer_create_const_data(&uid_buf, data, rec_size);
        array_create_from_buffer(&uids, &uid_buf,
            sizeof(struct mail_transaction_expunge));
        break;
    case MAIL_TRANSACTION_EXPUNGE_GUID:
        if ((rec_size % sizeof(struct mail_transaction_expunge_guid)) != 0) {
            mail_transaction_log_file_set_corrupted(file,
                "Invalid expunge guid record size");
            return FALSE;
        }
        break;
    case MAIL_TRANSACTION_FLAG_UPDATE:
        buffer_create_const_data(&uid_buf, data, rec_size);
        array_create_from_buffer(&uids, &uid_buf,
            sizeof(struct mail_transaction_flag_update));
        break;
    case MAIL_TRANSACTION_KEYWORD_UPDATE: {
        const struct mail_transaction_keyword_update *rec = data;
        unsigned int seqset_offset;

        seqset_offset = sizeof(*rec) + rec->name_size;
        if ((seqset_offset % 4) != 0)
            seqset_offset += 4 - (seqset_offset % 4);

        if (seqset_offset > rec_size) {
            mail_transaction_log_file_set_corrupted(file,
                "Invalid keyword update record size");
            return FALSE;
        }

        buffer_create_const_data(&uid_buf,
                     CONST_PTR_OFFSET(data, seqset_offset),
                     rec_size - seqset_offset);
        array_create_from_buffer(&uids, &uid_buf,
                     sizeof(uint32_t)*2);
        break;
    }
    case MAIL_TRANSACTION_KEYWORD_RESET:
        buffer_create_const_data(&uid_buf, data, rec_size);
        array_create_from_buffer(&uids, &uid_buf,
            sizeof(struct mail_transaction_keyword_reset));
        break;
    default:
        break;
    }

    if (array_is_created(&uids)) {
        if (!log_view_is_uid_range_valid(file, rec_type, &uids))
            return FALSE;
    }
    return TRUE;
}

static int
log_view_get_next(struct mail_transaction_log_view *view,
          const struct mail_transaction_header **hdr_r,
          const void **data_r)
{
    const struct mail_transaction_header *hdr;
    struct mail_transaction_log_file *file;
    const void *data;
    enum mail_transaction_type rec_type;
    uint32_t full_size;
    size_t file_size;
    int ret;

    if (view->cur == NULL)
        return 0;

    /* prev_file_offset should point to beginning of previous log record.
       when we reach EOF, it should be left there, not to beginning of the
       next file that's not included inside the view. */
    if (mail_transaction_log_view_get_last(view, &view->cur,
                           &view->cur_offset)) {
        /* if the last file was the beginning of a file, we want to
           move prev pointers there */
        view->prev_file_seq = view->cur->hdr.file_seq;
        view->prev_file_offset = view->cur_offset;
        view->cur = NULL;
        return 0;
    }

    view->prev_file_seq = view->cur->hdr.file_seq;
    view->prev_file_offset = view->cur_offset;

    file = view->cur;

    data = buffer_get_data(file->buffer, &file_size);
    file_size += file->buffer_offset;

    if (view->cur_offset + sizeof(*hdr) > file_size) {
        mail_transaction_log_file_set_corrupted(file,
            "offset points outside file "
            "(%"PRIuUOFF_T" + %"PRIuSIZE_T" > %"PRIuSIZE_T")",
            view->cur_offset, sizeof(*hdr), file_size);
        return -1;
    }

    i_assert(view->cur_offset >= file->buffer_offset);
    hdr = CONST_PTR_OFFSET(data, view->cur_offset - file->buffer_offset);
    data = CONST_PTR_OFFSET(hdr, sizeof(*hdr));

    rec_type = hdr->type & MAIL_TRANSACTION_TYPE_MASK;
    full_size = mail_index_offset_to_uint32(hdr->size);
    if (full_size < sizeof(*hdr)) {
        mail_transaction_log_file_set_corrupted(file,
            "record size too small (type=0x%x, "
            "offset=%"PRIuUOFF_T", size=%u)",
            rec_type, view->cur_offset, full_size);
        return -1;
    }

    if (file_size - view->cur_offset < full_size) {
        mail_transaction_log_file_set_corrupted(file,
            "record size too large (type=0x%x, "
            "offset=%"PRIuUOFF_T", size=%u, end=%"PRIuSIZE_T")",
            rec_type, view->cur_offset, full_size, file_size);
        return -1;
    }

    T_BEGIN {
        ret = log_view_is_record_valid(file, hdr, data) ? 1 : -1;
    } T_END;
    if (ret > 0) {
        mail_transaction_update_modseq(hdr, data, &view->prev_modseq);
        *hdr_r = hdr;
        *data_r = data;
        view->cur_offset += full_size;
    }
    return ret;
}

int mail_transaction_log_view_next(struct mail_transaction_log_view *view,
                   const struct mail_transaction_header **hdr_r,
                   const void **data_r)
{
    const struct mail_transaction_header *hdr;
    const void *data;
    int ret = 0;

    if (view->broken)
        return -1;

    ret = log_view_get_next(view, &hdr, &data);
    if (ret <= 0) {
        if (ret < 0)
            view->cur_offset = view->cur->sync_offset;
        return ret;
    }

    /* drop expunge protection */
    if ((hdr->type & MAIL_TRANSACTION_TYPE_MASK) ==
        (MAIL_TRANSACTION_EXPUNGE | MAIL_TRANSACTION_EXPUNGE_PROT) ||
        (hdr->type & MAIL_TRANSACTION_TYPE_MASK) ==
        (MAIL_TRANSACTION_EXPUNGE_GUID | MAIL_TRANSACTION_EXPUNGE_PROT))
        view->tmp_hdr.type = hdr->type & ~MAIL_TRANSACTION_EXPUNGE_PROT;
    else
        view->tmp_hdr.type = hdr->type;

    /* return record's size */
    view->tmp_hdr.size = mail_index_offset_to_uint32(hdr->size);
    i_assert(view->tmp_hdr.size > sizeof(*hdr));
    view->tmp_hdr.size -= sizeof(*hdr);

    *hdr_r = &view->tmp_hdr;
    *data_r = data;
    return 1;
}

void mail_transaction_log_view_mark(struct mail_transaction_log_view *view)
{
    i_assert(view->cur->hdr.file_seq == view->prev_file_seq);

    view->mark_file = view->cur;
    view->mark_offset = view->prev_file_offset;
    view->mark_next_offset = view->cur_offset;
    view->mark_modseq = view->prev_modseq;
}

void mail_transaction_log_view_rewind(struct mail_transaction_log_view *view)
{
    i_assert(view->mark_file != NULL);

    view->cur = view->mark_file;
    view->cur_offset = view->mark_next_offset;
    view->prev_file_seq = view->cur->hdr.file_seq;
    view->prev_file_offset = view->mark_offset;
    view->prev_modseq = view->mark_modseq;
}