plugins/fts-squat/squat-trie.c

	squat-trie.c revision ed4bd0ef77522f567c493d3ca5c71c78f20b7320
905N/A/* Copyright (c) 2007-2017 Dovecot authors, see the included COPYING file */
905N/A
905N/A#include "lib.h"
905N/A#include "array.h"
905N/A#include "str.h"
905N/A#include "read-full.h"
905N/A#include "istream.h"
905N/A#include "ostream.h"
905N/A#include "unichar.h"
905N/A#include "nfs-workarounds.h"
905N/A#include "file-cache.h"
905N/A#include "seq-range-array.h"
905N/A#include "squat-uidlist.h"
905N/A#include "squat-trie-private.h"
905N/A
905N/A#include <stdio.h>
905N/A#include <unistd.h>
905N/A#include <sys/mman.h>
905N/A
905N/A#define DEFAULT_NORMALIZE_MAP_CHARS \
3996N/A    "EOTIRSACDNLMVUGPHBFWYXKJQZ0123456789@.-+#$%_&"
905N/A#define DEFAULT_PARTIAL_LEN 4
905N/A#define DEFAULT_FULL_LEN 4
905N/A
905N/A#define MAX_FAST_LEVEL 3
4448N/A#define SEQUENTIAL_COUNT 46
905N/A
905N/A#define TRIE_BYTES_LEFT(n) \
905N/A    ((n) * SQUAT_PACK_MAX_SIZE)
4448N/A#define TRIE_READAHEAD_SIZE \
905N/A    I_MAX(4096, 1 + 256 + TRIE_BYTES_LEFT(256))
4448N/A
4448N/Astruct squat_trie_build_context {
3661N/A    struct squat_trie *trie;
3996N/A    struct ostream *output;
3996N/A    struct squat_uidlist_build_context *uidlist_build_ctx;
3996N/A
905N/A    struct file_lock *file_lock;
905N/A    struct dotlock *dotlock;
905N/A
905N/A    uint32_t first_uid;
905N/A    bool compress_nodes:1;
905N/A};
905N/A
4448N/Astruct squat_trie_iterate_node {
4448N/A    struct squat_node *node;
905N/A    ARRAY_TYPE(seq_range) shifts;
4448N/A    unsigned int idx;
4448N/A};
905N/A
905N/Astruct squat_trie_iterate_context {
905N/A    struct squat_trie *trie;
905N/A    struct squat_trie_iterate_node cur;
4448N/A    ARRAY(struct squat_trie_iterate_node) parents;
4448N/A    bool failed;
905N/A};
4448N/A
905N/Astatic int squat_trie_map(struct squat_trie *trie, bool building);
3996N/A
3996N/Avoid squat_trie_delete(struct squat_trie *trie)
4448N/A{
    i_unlink_if_exists(trie->path);
    squat_uidlist_delete(trie->uidlist);
}

static void squat_trie_set_corrupted(struct squat_trie *trie)
{
    trie->corrupted = TRUE;
    i_error("Corrupted file %s", trie->path);
    squat_trie_delete(trie);
}

static void squat_trie_normalize_map_build(struct squat_trie *trie)
{
    static unsigned char valid_chars[] =
        DEFAULT_NORMALIZE_MAP_CHARS;
    unsigned int i, j;

    memset(trie->default_normalize_map, 0,
           sizeof(trie->default_normalize_map));

#if 1
    for (i = 0, j = 1; i < sizeof(valid_chars)-1; i++) {
        unsigned char chr = valid_chars[i];

        if (chr >= 'A' && chr <= 'Z')
            trie->default_normalize_map[chr-'A'+'a'] = j;
        trie->default_normalize_map[chr] = j++;
    }
    i_assert(j <= SEQUENTIAL_COUNT);

    for (i = 128; i < 256; i++)
        trie->default_normalize_map[i] = j++;
#else
    for (i = 0; i < sizeof(valid_chars)-1; i++) {
        unsigned char chr = valid_chars[i];

        if (chr >= 'A' && chr <= 'Z')
            trie->default_normalize_map[chr-'A'+'a'] = chr;
        trie->default_normalize_map[chr] = chr;
    }
    for (i = 128; i < 256; i++)
        trie->default_normalize_map[i] = i_toupper(i);
#endif
}

static void node_free(struct squat_trie *trie, struct squat_node *node)
{
    struct squat_node *children;
    unsigned int i;

    if (node->leaf_string_length > 0) {
        if (NODE_IS_DYNAMIC_LEAF(node))
            i_free(node->children.leaf_string);
    } else if (!node->children_not_mapped) {
        children = NODE_CHILDREN_NODES(node);

        trie->node_alloc_size -=
            NODE_CHILDREN_ALLOC_SIZE(node->child_count);
        for (i = 0; i < node->child_count; i++)
            node_free(trie, &children[i]);

        i_free(node->children.data);
    }
}

struct squat_trie *
squat_trie_init(const char *path, uint32_t uidvalidity,
        enum file_lock_method lock_method, enum squat_index_flags flags,
        mode_t mode, gid_t gid)
{
    struct squat_trie *trie;

    trie = i_new(struct squat_trie, 1);
    trie->path = i_strdup(path);
    trie->uidlist = squat_uidlist_init(trie);
    trie->fd = -1;
    trie->lock_method = lock_method;
    trie->uidvalidity = uidvalidity;
    trie->flags = flags;
    trie->create_mode = mode;
    trie->create_gid = gid;
    squat_trie_normalize_map_build(trie);

    trie->dotlock_set.use_excl_lock =
        (flags & SQUAT_INDEX_FLAG_DOTLOCK_USE_EXCL) != 0;
    trie->dotlock_set.nfs_flush = (flags & SQUAT_INDEX_FLAG_NFS_FLUSH) != 0;
    trie->dotlock_set.timeout = SQUAT_TRIE_LOCK_TIMEOUT;
    trie->dotlock_set.stale_timeout = SQUAT_TRIE_DOTLOCK_STALE_TIMEOUT;
    trie->default_partial_len = DEFAULT_PARTIAL_LEN;
    trie->default_full_len = DEFAULT_FULL_LEN;
    return trie;
}

static void squat_trie_close_fd(struct squat_trie *trie)
{
    trie->data = NULL;
    trie->data_size = 0;

    if (trie->mmap_size != 0) {
        if (munmap(trie->mmap_base, trie->mmap_size) < 0)
            i_error("munmap(%s) failed: %m", trie->path);
        trie->mmap_base = NULL;
        trie->mmap_size = 0;
    }
    i_close_fd_path(&trie->fd, trie->path);
}

static void squat_trie_close(struct squat_trie *trie)
{
    trie->corrupted = FALSE;
    node_free(trie, &trie->root);
    i_zero(&trie->root);
    i_zero(&trie->hdr);

    squat_trie_close_fd(trie);
    if (trie->file_cache != NULL)
        file_cache_free(&trie->file_cache);
    trie->locked_file_size = 0;
}

void squat_trie_deinit(struct squat_trie **_trie)
{
    struct squat_trie *trie = *_trie;

    *_trie = NULL;
    squat_trie_close(trie);
    squat_uidlist_deinit(trie->uidlist);
    i_free(trie->path);
    i_free(trie);
}

void squat_trie_set_partial_len(struct squat_trie *trie, unsigned int len)
{
    trie->default_partial_len = len;
}

void squat_trie_set_full_len(struct squat_trie *trie, unsigned int len)
{
    trie->default_full_len = len;
}

static void squat_trie_header_init(struct squat_trie *trie)
{
    i_zero(&trie->hdr);
    trie->hdr.version = SQUAT_TRIE_VERSION;
    trie->hdr.indexid = time(NULL);
    trie->hdr.uidvalidity = trie->uidvalidity;
    trie->hdr.partial_len = trie->default_partial_len;
    trie->hdr.full_len = trie->default_full_len;

    i_assert(sizeof(trie->hdr.normalize_map) ==
         sizeof(trie->default_normalize_map));
    memcpy(trie->hdr.normalize_map, trie->default_normalize_map,
           sizeof(trie->hdr.normalize_map));
}

static int squat_trie_open_fd(struct squat_trie *trie)
{
    trie->fd = open(trie->path, O_RDWR);
    if (trie->fd == -1) {
        if (errno == ENOENT) {
            squat_trie_header_init(trie);
            return 0;
        }
        i_error("open(%s) failed: %m", trie->path);
        return -1;
    }
    if (trie->file_cache != NULL)
        file_cache_set_fd(trie->file_cache, trie->fd);
    return 0;
}

int squat_trie_open(struct squat_trie *trie)
{
    squat_trie_close(trie);

    if (squat_trie_open_fd(trie) < 0)
        return -1;
    return squat_trie_map(trie, FALSE);
}

static int squat_trie_is_file_stale(struct squat_trie *trie)
{
    struct stat st, st2;

    if ((trie->flags & SQUAT_INDEX_FLAG_NFS_FLUSH) != 0)
        nfs_flush_file_handle_cache(trie->path);
    if (nfs_safe_stat(trie->path, &st) < 0) {
        if (errno == ENOENT)
            return 1;

        i_error("stat(%s) failed: %m", trie->path);
        return -1;
    }
    if (fstat(trie->fd, &st2) < 0) {
        if (errno == ESTALE)
            return 1;
        i_error("fstat(%s) failed: %m", trie->path);
        return -1;
    }
    trie->locked_file_size = st2.st_size;

    if (st.st_ino == st2.st_ino && CMP_DEV_T(st.st_dev, st2.st_dev)) {
        i_assert(trie->locked_file_size >= trie->data_size);
        return 0;
    }
    return 1;
}

int squat_trie_refresh(struct squat_trie *trie)
{
    int ret;

    ret = squat_trie_is_file_stale(trie);
    if (ret > 0)
        ret = squat_trie_open(trie);
    return ret;
}

static int squat_trie_lock(struct squat_trie *trie, int lock_type,
               struct file_lock **file_lock_r,
               struct dotlock **dotlock_r)
{
    int ret;

    i_assert(trie->fd != -1);

    *file_lock_r = NULL;
    *dotlock_r = NULL;

    for (;;) {
        if (trie->lock_method != FILE_LOCK_METHOD_DOTLOCK) {
            ret = file_wait_lock(trie->fd, trie->path, lock_type,
                         trie->lock_method,
                         SQUAT_TRIE_LOCK_TIMEOUT,
                         file_lock_r);
        } else {
            ret = file_dotlock_create(&trie->dotlock_set,
                          trie->path, 0, dotlock_r);
        }
        if (ret == 0) {
            i_error("squat trie %s: Locking timed out", trie->path);
            return 0;
        }
        if (ret < 0)
            return -1;

        /* if the trie has been compressed, we need to reopen the
           file and try to lock again */
        ret = squat_trie_is_file_stale(trie);
        if (ret == 0)
            break;

        if (*file_lock_r != NULL)
            file_unlock(file_lock_r);
        else
            file_dotlock_delete(dotlock_r);
        if (ret < 0)
            return -1;

        squat_trie_close(trie);
        if (squat_trie_open_fd(trie) < 0)
            return -1;
        if (trie->fd == -1)
            return 0;
    }

    if ((trie->flags & SQUAT_INDEX_FLAG_NFS_FLUSH) != 0)
        nfs_flush_read_cache_locked(trie->path, trie->fd);
    return 1;
}

static void
node_make_sequential(struct squat_trie *trie, struct squat_node *node, int level)
{
    const unsigned int alloc_size =
        NODE_CHILDREN_ALLOC_SIZE(SEQUENTIAL_COUNT);
    struct squat_node *children;
    unsigned char *chars;
    unsigned int i;

    i_assert(node->child_count == 0);

    trie->node_alloc_size += alloc_size;

    node->want_sequential = FALSE;
    node->have_sequential = TRUE;

    node->child_count = SEQUENTIAL_COUNT;
    node->children.data = i_malloc(alloc_size);

    chars = NODE_CHILDREN_CHARS(node);
    for (i = 0; i < SEQUENTIAL_COUNT; i++)
        chars[i] = i;

    if (level < MAX_FAST_LEVEL) {
        children = NODE_CHILDREN_NODES(node);
        for (i = 0; i < SEQUENTIAL_COUNT; i++)
            children[i].want_sequential = TRUE;
    }
}

static unsigned int
node_add_child(struct squat_trie *trie, struct squat_node *node,
           unsigned char chr, int level)
{
    unsigned int old_child_count = node->child_count;
    struct squat_node *children, *old_children;
    unsigned char *chars;
    size_t old_size, new_size;

    i_assert(node->leaf_string_length == 0);

    if (node->want_sequential) {
        node_make_sequential(trie, node, level);

        if (chr < SEQUENTIAL_COUNT)
            return chr;
        old_child_count = SEQUENTIAL_COUNT;
    }

    node->child_count++;
    new_size = NODE_CHILDREN_ALLOC_SIZE(node->child_count);

    if (old_child_count == 0) {
        /* first child */
        node->children.data = i_malloc(new_size);
        trie->node_alloc_size += new_size;
    } else {
        old_size = NODE_CHILDREN_ALLOC_SIZE(old_child_count);
        if (old_size != new_size) {
            trie->node_alloc_size += new_size - old_size;
            node->children.data = i_realloc(node->children.data,
                            old_size, new_size);
        }

        children = NODE_CHILDREN_NODES(node);
        old_children = (void *)(NODE_CHILDREN_CHARS(node) +
                    MEM_ALIGN(old_child_count));
        if (children != old_children) {
            memmove(children, old_children,
                old_child_count * sizeof(struct squat_node));
        }
    }

    chars = NODE_CHILDREN_CHARS(node);
    i_assert(chars != NULL);
    chars[node->child_count - 1] = chr;
    return node->child_count - 1;
}

static int
trie_file_cache_read(struct squat_trie *trie, size_t offset, size_t size)
{
    if (trie->file_cache == NULL)
        return 0;

    if (file_cache_read(trie->file_cache, offset, size) < 0) {
        i_error("read(%s) failed: %m", trie->path);
        return -1;
    }
    trie->data = file_cache_get_map(trie->file_cache, &trie->data_size);
    return 0;
}

static int
node_read_children(struct squat_trie *trie, struct squat_node *node, int level)
{
    const uint8_t *data, *end;
    const unsigned char *child_chars;
    struct squat_node *child, *children = NULL;
    uoff_t node_offset;
    unsigned int i, child_idx, child_count;
    uoff_t base_offset;
    uint32_t num;

    i_assert(node->children_not_mapped);
    i_assert(!node->have_sequential);
    i_assert(trie->unmapped_child_count > 0);
    i_assert(trie->data_size <= trie->locked_file_size);

    trie->unmapped_child_count--;
    node_offset = node->children.offset;
    node->children_not_mapped = FALSE;
    node->children.data = NULL;

    if (trie_file_cache_read(trie, node_offset, TRIE_READAHEAD_SIZE) < 0)
        return -1;
    if (unlikely(node_offset >= trie->data_size)) {
        squat_trie_set_corrupted(trie);
        return -1;
    }

    data = CONST_PTR_OFFSET(trie->data, node_offset);
    end = CONST_PTR_OFFSET(trie->data, trie->data_size);
    child_count = *data++;
    if (unlikely(node_offset + child_count >= trie->data_size)) {
        squat_trie_set_corrupted(trie);
        return -1;
    }

    if (child_count == 0)
        return 0;

    child_chars = data;
    data += child_count;

    /* get child offsets */
    base_offset = node_offset;
    for (i = 0; i < child_count; i++) {
        /* we always start with !have_sequential, so at i=0 this
           check always goes to add the first child */
        if (node->have_sequential && child_chars[i] < SEQUENTIAL_COUNT)
            child_idx = child_chars[i];
        else {
            child_idx = node_add_child(trie, node, child_chars[i],
                           level);
            children = NODE_CHILDREN_NODES(node);
        }

        i_assert(children != NULL);

        child = &children[child_idx];

        /* 1) child offset */
        num = squat_unpack_num(&data, end);
        if (num == 0) {
            /* no children */
        } else {
            if ((num & 1) != 0) {
                base_offset += num >> 1;
            } else {
                base_offset -= num >> 1;
            }
            if (base_offset >= trie->locked_file_size) {
                squat_trie_set_corrupted(trie);
                return -1;
            }
            trie->unmapped_child_count++;
            child->children_not_mapped = TRUE;
            child->children.offset = base_offset;
        }

        /* 2) uidlist */
        child->uid_list_idx = squat_unpack_num(&data, end);
        if (child->uid_list_idx == 0) {
            /* we don't write nodes with empty uidlists */
            squat_trie_set_corrupted(trie);
            return -1;
        }
        if (!UIDLIST_IS_SINGLETON(child->uid_list_idx)) {
            /* 3) next uid */
            child->next_uid = squat_unpack_num(&data, end) + 1;
        } else {
            uint32_t idx = child->uid_list_idx;

            child->next_uid = 1 +
                squat_uidlist_singleton_last_uid(idx);
        }

        /* 4) unused uids + leaf string flag */
        num = squat_unpack_num(&data, end);
        child->unused_uids = num >> 1;
        if ((num & 1) != 0) {
            /* leaf string */
            unsigned int len;
            unsigned char *dest;

            /* 5) leaf string length */
            len = child->leaf_string_length =
                squat_unpack_num(&data, end) + 1;
            if (!NODE_IS_DYNAMIC_LEAF(child))
                dest = child->children.static_leaf_string;
            else {
                dest = child->children.leaf_string =
                    i_malloc(len);
            }

            if (trie->file_cache != NULL) {
                /* the string may be long -
                   recalculate the end pos */
                size_t offset, size;

                offset = (const char *)data -
                    (const char *)trie->data;
                size = len + TRIE_BYTES_LEFT(child_count - i);

                if (trie_file_cache_read(trie, offset,
                             size) < 0)
                    return -1;
                data = CONST_PTR_OFFSET(trie->data, offset);
                end = CONST_PTR_OFFSET(trie->data,
                               trie->data_size);
                child_chars = CONST_PTR_OFFSET(trie->data,
                                   node_offset + 1);
            }

            if ((size_t)(end - data) < len) {
                squat_trie_set_corrupted(trie);
                return -1;
            }
            memcpy(dest, data, len);
            data += len;
        }
    }
    if (unlikely(data == end)) {
        /* we should never get this far */
        squat_trie_set_corrupted(trie);
        return -1;
    }
    return 0;
}

static void
node_write_children(struct squat_trie_build_context *ctx,
            struct squat_node *node, const uoff_t *node_offsets)
{
    struct squat_node *children;
    const unsigned char *chars;
    uint8_t child_count, buf[SQUAT_PACK_MAX_SIZE * 5], *bufp;
    uoff_t base_offset;
    unsigned int i;

    chars = NODE_CHILDREN_CHARS(node);
    children = NODE_CHILDREN_NODES(node);

    base_offset = ctx->output->offset;
    child_count = node->child_count;
    o_stream_nsend(ctx->output, &child_count, 1);
    o_stream_nsend(ctx->output, chars, child_count);

    for (i = 0; i < child_count; i++) {
        bufp = buf;
        /* 1) child offset */
        if (node_offsets[i] == 0)
            *bufp++ = 0;
        else if (node_offsets[i] >= base_offset) {
            squat_pack_num(&bufp,
                ((node_offsets[i] - base_offset) << 1) | 1);
            base_offset = node_offsets[i];
        } else {
            squat_pack_num(&bufp,
                       (base_offset - node_offsets[i]) << 1);
            base_offset = node_offsets[i];
        }

        /* 2) uidlist */
        squat_pack_num(&bufp, children[i].uid_list_idx);
        if (!UIDLIST_IS_SINGLETON(children[i].uid_list_idx)) {
            /* 3) next uid */
            squat_pack_num(&bufp, children[i].next_uid - 1);
        }

        if (children[i].leaf_string_length == 0) {
            /* 4a) unused uids */
            squat_pack_num(&bufp, children[i].unused_uids << 1);
            o_stream_nsend(ctx->output, buf, bufp - buf);
        } else {
            i_assert(node_offsets[i] == 0);
            /* 4b) unused uids + flag */
            squat_pack_num(&bufp, (children[i].unused_uids << 1) | 1);
            /* 5) leaf string length */
            squat_pack_num(&bufp, children[i].leaf_string_length - 1);
            o_stream_nsend(ctx->output, buf, bufp - buf);
            o_stream_nsend(ctx->output,
                       NODE_LEAF_STRING(&children[i]),
                       children[i].leaf_string_length);
        }
    }
}

static inline void
node_add_uid(struct squat_trie_build_context *ctx, uint32_t uid,
         struct squat_node *node)
{
    if (uid < node->next_uid) {
        /* duplicate */
        return;
    }
    node->unused_uids += uid - node->next_uid;
    node->next_uid = uid + 1;

    node->uid_list_idx =
        squat_uidlist_build_add_uid(ctx->uidlist_build_ctx,
                        node->uid_list_idx, uid);
}

static void
node_split_string(struct squat_trie_build_context *ctx, struct squat_node *node)
{
    struct squat_node *child;
    unsigned char *str;
    unsigned int uid, idx, leafstr_len = node->leaf_string_length;

    i_assert(leafstr_len > 0);

    /* make a copy of the leaf string and convert to normal node by
       removing it. */
    str = t_malloc_no0(leafstr_len);
    if (!NODE_IS_DYNAMIC_LEAF(node))
        memcpy(str, node->children.static_leaf_string, leafstr_len);
    else {
        memcpy(str, node->children.leaf_string, leafstr_len);
        i_free(node->children.leaf_string);
    }
    node->leaf_string_length = 0;

    /* create a new child node for the rest of the string */
    idx = node_add_child(ctx->trie, node, str[0], MAX_FAST_LEVEL);
    child = NODE_CHILDREN_NODES(node) + idx;

    /* update uidlist to contain all of parent's UIDs */
    child->next_uid =  node->next_uid - node->unused_uids;
    for (uid = 0; uid < child->next_uid; uid++) {
        child->uid_list_idx =
            squat_uidlist_build_add_uid(ctx->uidlist_build_ctx,
                            child->uid_list_idx, uid);
    }

    i_assert(!child->have_sequential && child->children.data == NULL);
    if (leafstr_len > 1) {
        /* make the child a leaf string */
        leafstr_len--;
        child->leaf_string_length = leafstr_len;
        if (!NODE_IS_DYNAMIC_LEAF(child)) {
            memcpy(child->children.static_leaf_string,
                   str + 1, leafstr_len);
        } else {
            child->children.leaf_string = i_malloc(leafstr_len);
            memcpy(child->children.leaf_string,
                   str + 1, leafstr_len);
        }
    }
}

static bool
node_leaf_string_add_or_split(struct squat_trie_build_context *ctx,
                  struct squat_node *node,
                  const unsigned char *data, unsigned int data_len)
{
    const unsigned char *str = NODE_LEAF_STRING(node);
    const unsigned int leafstr_len = node->leaf_string_length;
    unsigned int i;

    if (data_len != leafstr_len) {
        /* different lengths, can't match */
        T_BEGIN {
            node_split_string(ctx, node);
        } T_END;
        return FALSE;
    }

    for (i = 0; i < data_len; i++) {
        if (data[i] != str[i]) {
            /* non-match */
            T_BEGIN {
                node_split_string(ctx, node);
            } T_END;
            return FALSE;
        }
    }
    return TRUE;
}

static int squat_build_add(struct squat_trie_build_context *ctx, uint32_t uid,
               const unsigned char *data, unsigned int size)
{
    struct squat_trie *trie = ctx->trie;
    struct squat_node *node = &trie->root;
    const unsigned char *end = data + size;
    unsigned char *chars;
    unsigned int idx;
    int level = 0;

    for (;;) {
        if (node->children_not_mapped) {
            if (unlikely(node_read_children(trie, node, level) < 0))
                return -1;
        }

        if (node->leaf_string_length != 0) {
            /* the whole string must match or we need to split
               the node */
            if (node_leaf_string_add_or_split(ctx, node, data,
                              end - data)) {
                node_add_uid(ctx, uid, node);
                return 0;
            }
        }

        node_add_uid(ctx, uid, node);

        if (unlikely(uid < node->unused_uids)) {
            squat_trie_set_corrupted(trie);
            return -1;
        }
        /* child node's UIDs are relative to ours. so for example if
           we're adding UID 4 and this node now has [2,4] UIDs,
           unused_uids=3 and so the child node will be adding
           UID 4-3 = 1. */
        uid -= node->unused_uids;

        if (data == end)
            return 0;
        level++;

        if (node->have_sequential) {
            i_assert(node->child_count >= SEQUENTIAL_COUNT);
            if (*data < SEQUENTIAL_COUNT) {
                idx = *data;
                goto found;
            }
            idx = SEQUENTIAL_COUNT;
        } else {
            idx = 0;
        }
        chars = NODE_CHILDREN_CHARS(node);
        for (; idx < node->child_count; idx++) {
            if (chars[idx] == *data)
                goto found;
        }
        break;
    found:
        data++;
        node = NODE_CHILDREN_NODES(node) + idx;
    }

    /* create new children */
    i_assert(node->leaf_string_length == 0);

    for (;;) {
        idx = node_add_child(trie, node, *data,
                     size - (end - data) + 1);
        node = NODE_CHILDREN_NODES(node) + idx;

        node_add_uid(ctx, uid, node);
        uid = 0;

        if (++data == end)
            break;

        if (!node->have_sequential) {
            /* convert the node into a leaf string */
            unsigned int len = end - data;

            i_assert(node->children.data == NULL);
            node->leaf_string_length = len;
            if (!NODE_IS_DYNAMIC_LEAF(node)) {
                memcpy(node->children.static_leaf_string,
                       data, len);
            } else {
                node->children.leaf_string = i_malloc(len);
                memcpy(node->children.leaf_string, data, len);
            }
            break;
        }
    }
    return 0;
}

static int
squat_build_word_bytes(struct squat_trie_build_context *ctx, uint32_t uid,
               const unsigned char *data, unsigned int size)
{
    struct squat_trie *trie = ctx->trie;
    unsigned int i;

    if (trie->hdr.full_len <= trie->hdr.partial_len)
        i = 0;
    else {
        /* the first word is longer than others */
        if (squat_build_add(ctx, uid, data,
                    I_MIN(size, trie->hdr.full_len)) < 0)
            return -1;
        i = 1;
    }

    for (; i < size; i++) {
        if (squat_build_add(ctx, uid, data + i,
                    I_MIN(trie->hdr.partial_len, size-i)) < 0)
            return -1;
    }
    return 0;
}

static int
squat_build_word(struct squat_trie_build_context *ctx, uint32_t uid,
         const unsigned char *data, const uint8_t *char_lengths,
         unsigned int size)
{
    struct squat_trie *trie = ctx->trie;
    unsigned int i, j, bytelen;

    if (char_lengths == NULL) {
        /* optimization path: all characters are bytes */
        return squat_build_word_bytes(ctx, uid, data, size);
    }

    if (trie->hdr.full_len <= trie->hdr.partial_len)
        i = 0;
    else {
        /* the first word is longer than others */
        bytelen = 0;
        for (j = 0; j < trie->hdr.full_len && bytelen < size; j++)
            bytelen += char_lengths[bytelen];
        i_assert(bytelen <= size);

        if (squat_build_add(ctx, uid, data, bytelen) < 0)
            return -1;
        i = char_lengths[0];
    }

    for (; i < size; i += char_lengths[i]) {
        bytelen = 0;
        for (j = 0; j < trie->hdr.partial_len && i+bytelen < size; j++)
            bytelen += char_lengths[i + bytelen];
        i_assert(i + bytelen <= size);

        if (squat_build_add(ctx, uid, data + i, bytelen) < 0)
            return -1;
    }
    return 0;
}

static unsigned char *
squat_data_normalize(struct squat_trie *trie, const unsigned char *data,
             unsigned int size)
{
    static const unsigned char replacement_utf8[] = { 0xef, 0xbf, 0xbd };
    unsigned char *dest;
    unsigned int i;

    dest = t_malloc_no0(size);
    for (i = 0; i < size; i++) {
        if (data[i] == replacement_utf8[0] && i + 2 < size &&
            data[i+1] == replacement_utf8[1] &&
            data[i+2] == replacement_utf8[2]) {
            /* Don't index replacement character */
            dest[i++] = 0;
            dest[i++] = 0;
            dest[i] = 0;
        } else {
            dest[i] = trie->hdr.normalize_map[data[i]];
        }
    }
    return dest;
}

static int
squat_trie_build_more_real(struct squat_trie_build_context *ctx,
               uint32_t uid, enum squat_index_type type,
               const unsigned char *input, unsigned int size)
{
    struct squat_trie *trie = ctx->trie;
    const unsigned char *data;
    uint8_t *char_lengths;
    unsigned int i, start = 0;
    bool multibyte_chars = FALSE;
    int ret = 0;

    uid = uid * 2 + (type == SQUAT_INDEX_TYPE_HEADER ? 1 : 0);

    char_lengths = t_malloc_no0(size);
    data = squat_data_normalize(trie, input, size);
    for (i = 0; i < size; i++) {
        char_lengths[i] = uni_utf8_char_bytes(input[i]);
        if (char_lengths[i] != 1)
            multibyte_chars = TRUE;
        if (data[i] != '\0')
            continue;

        while (start < i && data[start] == '\0')
            start++;
        if (i != start) {
            if (squat_build_word(ctx, uid, data + start,
                         !multibyte_chars ? NULL :
                         char_lengths + start,
                         i - start) < 0) {
                ret = -1;
                start = i;
                break;
            }
        }
        start = i + 1;
    }
    while (start < i && data[start] == '\0')
        start++;
    if (i != start) {
        if (squat_build_word(ctx, uid, data + start,
                     !multibyte_chars ? NULL :
                     char_lengths + start, i - start) < 0)
            ret = -1;
    }
    return ret;
}

int squat_trie_build_more(struct squat_trie_build_context *ctx,
              uint32_t uid, enum squat_index_type type,
              const unsigned char *input, unsigned int size)
{
    int ret = 0;

    if (size != 0) T_BEGIN {
        ret = squat_trie_build_more_real(ctx, uid, type, input, size);
    } T_END;
    return ret;
}

static void
node_drop_unused_children(struct squat_trie *trie, struct squat_node *node)
{
    unsigned char *chars;
    struct squat_node *children_src, *children_dest;
    unsigned int i, j, orig_child_count = node->child_count;

    chars = NODE_CHILDREN_CHARS(node);
    children_src = NODE_CHILDREN_NODES(node);

    /* move chars */
    for (i = j = 0; i < orig_child_count; i++) {
        if (children_src[i].next_uid != 0)
            chars[j++] = chars[i];
    }
    node->child_count = j;

    /* move children. note that children_dest may point to different
       location than children_src, although they both point to the
       same node. */
    children_dest = NODE_CHILDREN_NODES(node);
    for (i = j = 0; i < orig_child_count; i++) {
        if (children_src[i].next_uid != 0)
            children_dest[j++] = children_src[i];
        else
            node_free(trie, &children_src[i]);
    }
}

static int
squat_write_node(struct squat_trie_build_context *ctx, struct squat_node *node,
         uoff_t *node_offset_r, int level)
{
    struct squat_trie *trie = ctx->trie;
    struct squat_node *children;
    unsigned int i;
    uoff_t *node_offsets;
    uint8_t child_count;
    int ret;

    i_assert(node->next_uid != 0);

    if (node->children_not_mapped && ctx->compress_nodes) {
        if (node_read_children(trie, node, MAX_FAST_LEVEL) < 0)
            return -1;
    }

    node->have_sequential = FALSE;
    node_drop_unused_children(trie, node);

    child_count = node->child_count;
    if (child_count == 0) {
        i_assert(!node->children_not_mapped ||
             node->leaf_string_length == 0);
        *node_offset_r = !node->children_not_mapped ? 0 :
            node->children.offset;
        return 0;
    }
    i_assert(!node->children_not_mapped);

    trie->hdr.node_count++;

    children = NODE_CHILDREN_NODES(node);
    node_offsets = t_new(uoff_t, child_count);
    for (i = 0; i < child_count; i++) {
        T_BEGIN {
            ret = squat_write_node(ctx, &children[i],
                           &node_offsets[i], level + 1);
        } T_END;
        if (ret < 0)
            return -1;
    }

    *node_offset_r = ctx->output->offset;
    node_write_children(ctx, node, node_offsets);
    return 0;
}

static int squat_write_nodes(struct squat_trie_build_context *ctx)
{
    struct squat_trie *trie = ctx->trie;
    uoff_t node_offset;
    int ret;

    if (ctx->trie->root.next_uid == 0)
        return 0;

    T_BEGIN {
        ret = squat_write_node(ctx, &ctx->trie->root, &node_offset, 0);
    } T_END;
    if (ret < 0)
        return -1;

    trie->hdr.root_offset = node_offset;
    trie->hdr.root_unused_uids = trie->root.unused_uids;
    trie->hdr.root_next_uid = trie->root.next_uid;
    trie->hdr.root_uidlist_idx = trie->root.uid_list_idx;
    return 0;
}

static struct squat_trie_iterate_context *
squat_trie_iterate_init(struct squat_trie *trie)
{
    struct squat_trie_iterate_context *ctx;

    ctx = i_new(struct squat_trie_iterate_context, 1);
    ctx->trie = trie;
    ctx->cur.node = &trie->root;
    i_array_init(&ctx->parents, trie->hdr.partial_len*2);
    return ctx;
}

static int
squat_trie_iterate_deinit(struct squat_trie_iterate_context *ctx)
{
    struct squat_trie_iterate_node *node;
    int ret = ctx->failed ? -1 : 0;

    if (array_is_created(&ctx->cur.shifts)) {
        array_foreach_modifiable(&ctx->parents, node)
            array_free(&node->shifts);
        array_free(&ctx->cur.shifts);
    }
    array_free(&ctx->parents);
    i_free(ctx);
    return ret;
}

static struct squat_node *
squat_trie_iterate_first(struct squat_trie_iterate_context *ctx)
{
    if (ctx->cur.node->children_not_mapped) {
        if (node_read_children(ctx->trie, ctx->cur.node, 1) < 0) {
            ctx->failed = TRUE;
            return NULL;
        }
    }
    return ctx->cur.node;
}

static struct squat_node *
squat_trie_iterate_next(struct squat_trie_iterate_context *ctx,
            ARRAY_TYPE(seq_range) *shifts_r)
{
    struct squat_trie_iterate_node *iter_nodes;
    struct squat_node *children;
    unsigned int count, shift_count = 0;

    while (ctx->cur.idx == ctx->cur.node->child_count ||
           ctx->cur.node->uid_list_idx == 0)
    {
        iter_nodes = array_get_modifiable(&ctx->parents, &count);
        if (count == 0)
            return NULL;

        if (array_is_created(&ctx->cur.shifts))
            array_free(&ctx->cur.shifts);
        ctx->cur = iter_nodes[count-1];
        array_delete(&ctx->parents, count-1, 1);
    }

    *shifts_r = ctx->cur.shifts;
    if (array_is_created(&ctx->cur.shifts))
        shift_count = array_count(&ctx->cur.shifts);

    children = NODE_CHILDREN_NODES(ctx->cur.node);
    while (children[ctx->cur.idx++].uid_list_idx == 0) {
        if (ctx->cur.idx == ctx->cur.node->child_count) {
            /* no more non-empty children in this node */
            return squat_trie_iterate_next(ctx, shifts_r);
        }
    }
    array_append(&ctx->parents, &ctx->cur, 1);
    ctx->cur.node = &children[ctx->cur.idx-1];
    ctx->cur.idx = 0;
    if (shift_count != 0)
        i_array_init(&ctx->cur.shifts, shift_count);
    else
        i_zero(&ctx->cur.shifts);
    return squat_trie_iterate_first(ctx);
}

static void
squat_uidlist_update_expunged_uids(const ARRAY_TYPE(seq_range) *shifts_arr,
                   ARRAY_TYPE(seq_range) *child_shifts,
                   ARRAY_TYPE(seq_range) *uids_arr,
                   struct squat_trie *trie,
                   struct squat_node *node, bool do_shifts)
{
    const struct seq_range *shifts;
    struct seq_range *uids, shift;
    unsigned int i, uid_idx, uid_count, shift_count;
    uint32_t child_shift_seq1, child_shift_count, seq_high;
    unsigned int shift_sum = 0, child_sum = 0;

    if (!array_is_created(shifts_arr)) {
        i_assert(node->uid_list_idx != 0 || node->child_count == 0);
        return;
    }

    /* we'll recalculate this */
    node->unused_uids = 0;

    uids = array_get_modifiable(uids_arr, &uid_count);
    shifts = array_get(shifts_arr, &shift_count);
    for (i = 0, uid_idx = 0, seq_high = 0;; ) {
        /* skip UID ranges until we skip/overlap shifts */
        while (uid_idx < uid_count &&
               (i == shift_count ||
            I_MAX(shifts[i].seq1, seq_high) > uids[uid_idx].seq2))
        {
            i_assert(uids[uid_idx].seq1 >= shift_sum);
            uids[uid_idx].seq1 -= shift_sum;
            uids[uid_idx].seq2 -= shift_sum;
            child_sum += uids[uid_idx].seq2 -
                uids[uid_idx].seq1 + 1;

            if (uid_idx > 0 &&
                uids[uid_idx-1].seq2 >= uids[uid_idx].seq1 - 1) {
                /* we can merge this and the previous range */
                i_assert(uids[uid_idx-1].seq2 ==
                     uids[uid_idx].seq1 - 1);
                uids[uid_idx-1].seq2 = uids[uid_idx].seq2;
                array_delete(uids_arr, uid_idx, 1);
                uids = array_get_modifiable(uids_arr,
                                &uid_count);
            } else {
                if (uid_idx == 0)
                    node->unused_uids += uids[0].seq1;
                else {
                    node->unused_uids +=
                        uids[uid_idx].seq1 -
                        uids[uid_idx-1].seq2 - 1;
                }
                uid_idx++;
            }
        }
        if (uid_idx == uid_count)
            break;

        shift.seq1 = I_MAX(shifts[i].seq1, seq_high);
        shift.seq2 = shifts[i].seq2;
        if (shift.seq2 < uids[uid_idx].seq1) {
            /* shift is entirely before UID range */
            shift_sum += shift.seq2 - shift.seq1 + 1;
            i++;
        } else {
            /* handle shifts before UID range */
            if (shift.seq1 < uids[uid_idx].seq1) {
                shift_sum += uids[uid_idx].seq1 - shift.seq1;
                shift.seq1 = uids[uid_idx].seq1;
            }
            /* update child shifts */
            child_shift_seq1 = child_sum +
                shift.seq1 - uids[uid_idx].seq1;
            child_shift_count =
                I_MIN(shift.seq2, uids[uid_idx].seq2) -
                shift.seq1 + 1;
            seq_range_array_add_range(child_shifts,
                          child_shift_seq1,
                          child_shift_seq1 +
                          child_shift_count - 1);
            child_sum += child_shift_count;

            /* if the shifts continue after the UID range,
               treat it in the next loop iteration */
            if (shift.seq2 <= uids[uid_idx].seq2)
                i++;
            else
                seq_high = uids[uid_idx].seq2 + 1;

            /* update UIDs - no matter where within the UID range
               the shifts happened, the result is the same:
               shift number of UIDs are removed, and the rest
               are decreased by shift_sum.

                  123     uids child_shifts
               a) s    -> 12   1
               b)  s   -> 12   2
               c)   s  -> 12   3
            */
            if (uids[uid_idx].seq1 +
                child_shift_count > uids[uid_idx].seq2) {
                /* removed completely */
                array_delete(uids_arr, uid_idx, 1);
                uids = array_get_modifiable(uids_arr,
                                &uid_count);
            } else if (do_shifts) {
                /* the next loop iteration fixes the UIDs */
                uids[uid_idx].seq1 += child_shift_count;
            } else {
                seq_range_array_remove_range(uids_arr,
                    shift.seq1,
                    I_MIN(shift.seq2, uids[uid_idx].seq2));
                uids = array_get_modifiable(uids_arr,
                                &uid_count);
            }
            shift_sum += child_shift_count;
        }
        if (!do_shifts) {
            /* root node - UIDs are only removed, not shifted */
            shift_sum = 0;
        }
    }

    if (uid_count == 0) {
        /* no UIDs left, delete the node's children and mark it
           unused */
        if (!NODE_IS_DYNAMIC_LEAF(node))
            node_free(trie, node);

        node->child_count = 0;
        node->have_sequential = FALSE;
        node->next_uid = 0;
    } else {
        if (do_shifts)
            node->next_uid = uids[uid_count-1].seq2 + 1;
        else {
            node->unused_uids += (node->next_uid - 1) -
                uids[uid_count-1].seq2;
        }
    }
}

static int
squat_trie_expunge_uidlists(struct squat_trie_build_context *ctx,
                struct squat_uidlist_rebuild_context *rebuild_ctx,
                struct squat_trie_iterate_context *iter,
                const ARRAY_TYPE(seq_range) *expunged_uids)
{
    struct squat_node *node;
    ARRAY_TYPE(seq_range) uid_range, root_shifts, shifts;
    bool shift = FALSE;
    int ret = 0;

    node = squat_trie_iterate_first(iter);
    if (node->uid_list_idx == 0)
        return 0;

    i_array_init(&uid_range, 1024);
    i_array_init(&root_shifts, array_count(expunged_uids));
    array_append_array(&root_shifts, expunged_uids);

    if (array_count(expunged_uids) > 0)
        i_array_init(&iter->cur.shifts, array_count(expunged_uids));

    shifts = root_shifts;
    do {
        i_assert(node->uid_list_idx != 0);
        array_clear(&uid_range);
        if (squat_uidlist_get_seqrange(ctx->trie->uidlist,
                           node->uid_list_idx,
                           &uid_range) < 0) {
            ret = -1;
            break;
        }
        squat_uidlist_update_expunged_uids(&shifts, &iter->cur.shifts,
                           &uid_range, ctx->trie, node,
                           shift);
        node->uid_list_idx =
            squat_uidlist_rebuild_nextu(rebuild_ctx, &uid_range);
        i_assert(node->uid_list_idx != 0 || node->next_uid == 0);

        node = squat_trie_iterate_next(iter, &shifts);
        shift = TRUE;
    } while (node != NULL);
    array_free(&uid_range);
    array_free(&root_shifts);
    return ret;
}

static int
squat_trie_renumber_uidlists2(struct squat_trie_build_context *ctx,
                  struct squat_uidlist_rebuild_context *rebuild_ctx,
                  struct squat_trie_iterate_context *iter)
{
    struct squat_node *node;
    ARRAY_TYPE(seq_range) shifts;
    ARRAY_TYPE(uint32_t) uids;
    int ret = 0;

    node = squat_trie_iterate_first(iter);
    if (node->uid_list_idx == 0)
        return 0;

    i_array_init(&uids, 1024);
    while (node != NULL) {
        i_assert(node->uid_list_idx != 0);
        if (!UIDLIST_IS_SINGLETON(node->uid_list_idx)) {
            /* rebuild the uidlist */
            array_clear(&uids);
            if (squat_uidlist_get(ctx->trie->uidlist,
                          node->uid_list_idx, &uids) < 0) {
                ret = -1;
                break;
            }
            node->uid_list_idx =
                squat_uidlist_rebuild_next(rebuild_ctx, &uids);
        }
        node = squat_trie_iterate_next(iter, &shifts);
    }
    array_free(&uids);
    return ret;
}

static int
squat_trie_renumber_uidlists(struct squat_trie_build_context *ctx,
                 const ARRAY_TYPE(seq_range) *expunged_uids,
                 bool compress)
{
    struct squat_trie_iterate_context *iter;
    struct squat_uidlist_rebuild_context *rebuild_ctx;
    time_t now;
    int ret = 0;

    if ((ret = squat_uidlist_rebuild_init(ctx->uidlist_build_ctx,
                          compress, &rebuild_ctx)) <= 0)
        return ret;

    now = time(NULL);
    ctx->trie->hdr.indexid =
        I_MAX((unsigned int)now, ctx->trie->hdr.indexid + 1);

    iter = squat_trie_iterate_init(ctx->trie);
    if (expunged_uids != NULL) {
        ret = squat_trie_expunge_uidlists(ctx, rebuild_ctx, iter,
                          expunged_uids);
    } else {
        ret = squat_trie_renumber_uidlists2(ctx, rebuild_ctx, iter);
    }
    if (squat_trie_iterate_deinit(iter) < 0)
        ret = -1;

    /* lock the trie before we rename uidlist */
    i_assert(ctx->file_lock == NULL && ctx->dotlock == NULL);
    if (squat_trie_lock(ctx->trie, F_WRLCK,
                &ctx->file_lock, &ctx->dotlock) <= 0)
        ret = -1;
    return squat_uidlist_rebuild_finish(rebuild_ctx, ret < 0);
}

static bool squat_trie_check_header(struct squat_trie *trie)
{
    if (trie->hdr.version != SQUAT_TRIE_VERSION ||
        trie->hdr.uidvalidity != trie->uidvalidity)
        return FALSE;

    if (trie->hdr.partial_len > trie->hdr.full_len) {
        i_error("Corrupted %s: partial len > full len", trie->path);
        return FALSE;
    }
    if (trie->hdr.full_len == 0) {
        i_error("Corrupted %s: full len=0", trie->path);
        return FALSE;
    }
    return TRUE;
}

static int squat_trie_map_header(struct squat_trie *trie)
{
    int ret;

    if (trie->locked_file_size == 0) {
        /* newly created file */
        squat_trie_header_init(trie);
        return 1;
    }
    i_assert(trie->fd != -1);

    if ((trie->flags & SQUAT_INDEX_FLAG_MMAP_DISABLE) != 0) {
        ret = pread_full(trie->fd, &trie->hdr, sizeof(trie->hdr), 0);
        if (ret <= 0) {
            if (ret < 0) {
                i_error("pread(%s) failed: %m", trie->path);
                return -1;
            }
            i_error("Corrupted %s: File too small", trie->path);
            return 0;
        }
        trie->data = NULL;
        trie->data_size = 0;
    } else {
        if (trie->locked_file_size < sizeof(trie->hdr)) {
            i_error("Corrupted %s: File too small", trie->path);
            return 0;
        }
        if (trie->mmap_size != 0) {
            if (munmap(trie->mmap_base, trie->mmap_size) < 0)
                i_error("munmap(%s) failed: %m", trie->path);
        }

        trie->mmap_size = trie->locked_file_size;
        trie->mmap_base = mmap(NULL, trie->mmap_size,
                       PROT_READ | PROT_WRITE,
                       MAP_SHARED, trie->fd, 0);
        if (trie->mmap_base == MAP_FAILED) {
            trie->data = trie->mmap_base = NULL;
            trie->data_size = trie->mmap_size = 0;
            i_error("mmap(%s) failed: %m", trie->path);
            return -1;
        }
        memcpy(&trie->hdr, trie->mmap_base, sizeof(trie->hdr));
        trie->data = trie->mmap_base;
        trie->data_size = trie->mmap_size;
    }

    return squat_trie_check_header(trie) ? 1 : 0;
}

static int squat_trie_map(struct squat_trie *trie, bool building)
{
    struct file_lock *file_lock = NULL;
    struct dotlock *dotlock = NULL;
    bool changed;
    int ret;

    if (trie->fd != -1) {
        if (squat_trie_lock(trie, F_RDLCK, &file_lock, &dotlock) <= 0)
            return -1;
        if ((trie->flags & SQUAT_INDEX_FLAG_MMAP_DISABLE) != 0 &&
            trie->file_cache == NULL)
            trie->file_cache = file_cache_new_path(trie->fd, trie->path);
    }

    ret = squat_trie_map_header(trie);
    if (ret == 0) {
        if (file_lock != NULL)
            file_unlock(&file_lock);
        else
            file_dotlock_delete(&dotlock);
        squat_trie_delete(trie);
        squat_trie_close(trie);
        squat_trie_header_init(trie);
    }
    changed = trie->root.children.offset != trie->hdr.root_offset;

    if (changed || trie->hdr.root_offset == 0) {
        node_free(trie, &trie->root);
        i_zero(&trie->root);
        trie->root.want_sequential = TRUE;
        trie->root.unused_uids = trie->hdr.root_unused_uids;
        trie->root.next_uid = trie->hdr.root_next_uid;
        trie->root.uid_list_idx = trie->hdr.root_uidlist_idx;
        trie->root.children.offset = trie->hdr.root_offset;

        if (trie->hdr.root_offset == 0) {
            trie->unmapped_child_count = 0;
            trie->root.children_not_mapped = FALSE;
        } else {
            trie->unmapped_child_count = 1;
            trie->root.children_not_mapped = TRUE;
        }
    }

    if (ret >= 0 && !building) {
        /* do this while we're still locked */
        ret = squat_uidlist_refresh(trie->uidlist);
    }

    if (file_lock != NULL)
        file_unlock(&file_lock);
    if (dotlock != NULL)
        file_dotlock_delete(&dotlock);
    if (ret < 0)
        return -1;

    return trie->hdr.root_offset == 0 || !changed ? 0 :
        node_read_children(trie, &trie->root, 1);
}

int squat_trie_create_fd(struct squat_trie *trie, const char *path, int flags)
{
    mode_t old_mask;
    int fd;

    old_mask = umask(0);
    fd = open(path, O_RDWR | O_CREAT | flags, trie->create_mode);
    umask(old_mask);
    if (fd == -1) {
        i_error("creat(%s) failed: %m", path);
        return -1;
    }
    if (trie->create_gid != (gid_t)-1) {
        if (fchown(fd, (uid_t)-1, trie->create_gid) < 0) {
            i_error("fchown(%s, -1, %ld) failed: %m",
                path, (long)trie->create_gid);
            i_close_fd(&fd);
            return -1;
        }
    }
    return fd;
}

int squat_trie_build_init(struct squat_trie *trie,
              struct squat_trie_build_context **ctx_r)
{
    struct squat_trie_build_context *ctx;
    struct squat_uidlist_build_context *uidlist_build_ctx;

    if (trie->fd == -1) {
        trie->fd = squat_trie_create_fd(trie, trie->path, 0);
        if (trie->fd == -1)
            return -1;

        if (trie->file_cache != NULL)
            file_cache_set_fd(trie->file_cache, trie->fd);
        i_assert(trie->locked_file_size == 0);
    }

    /* uidlist locks building */
    if (squat_uidlist_build_init(trie->uidlist, &uidlist_build_ctx) < 0)
        return -1;

    if (squat_trie_map(trie, TRUE) < 0) {
        squat_uidlist_build_deinit(&uidlist_build_ctx);
        return -1;
    }

    ctx = i_new(struct squat_trie_build_context, 1);
    ctx->trie = trie;
    ctx->uidlist_build_ctx = uidlist_build_ctx;
    ctx->first_uid = trie->root.next_uid;

    *ctx_r = ctx;
    return 0;
}

static int squat_trie_write_lock(struct squat_trie_build_context *ctx)
{
    if (ctx->file_lock != NULL || ctx->dotlock != NULL)
        return 0;

    if (squat_trie_lock(ctx->trie, F_WRLCK,
                &ctx->file_lock, &ctx->dotlock) <= 0)
        return -1;
    return 0;
}

static int squat_trie_write(struct squat_trie_build_context *ctx)
{
    struct squat_trie *trie = ctx->trie;
    struct file_lock *file_lock = NULL;
    struct ostream *output;
    const char *path;
    int fd = -1, ret = 0;

    if ((trie->hdr.used_file_size > sizeof(trie->hdr) &&
        trie->unmapped_child_count < trie->hdr.node_count/4) || 1) {
        /* we might as well recreate the file */
        ctx->compress_nodes = TRUE;

        path = t_strconcat(trie->path, ".tmp", NULL);
        fd = squat_trie_create_fd(trie, path, O_TRUNC);
        if (fd == -1)
            return -1;

        if (trie->lock_method != FILE_LOCK_METHOD_DOTLOCK) {
            ret = file_wait_lock(fd, path, F_WRLCK,
                         trie->lock_method,
                         SQUAT_TRIE_LOCK_TIMEOUT,
                         &file_lock);
            if (ret <= 0) {
                if (ret == 0) {
                    i_error("file_wait_lock(%s) failed: %m",
                        path);
                }
                i_close_fd(&fd);
                return -1;
            }
        }

        output = o_stream_create_fd(fd, 0);
        o_stream_cork(output);
        o_stream_nsend(output, &trie->hdr, sizeof(trie->hdr));
    } else {
        /* we need to lock only while header is being written */
        path = trie->path;
        ctx->compress_nodes =
            trie->hdr.used_file_size == sizeof(trie->hdr);

        if (trie->hdr.used_file_size == 0) {
            /* lock before opening the file, in case we reopen it */
            if (squat_trie_write_lock(ctx) < 0)
                return -1;
        }
        output = o_stream_create_fd(trie->fd, 0);
        o_stream_cork(output);

        if (trie->hdr.used_file_size != 0)
            (void)o_stream_seek(output, trie->hdr.used_file_size);
        else
            o_stream_nsend(output, &trie->hdr, sizeof(trie->hdr));
    }

    ctx->output = output;
    ret = squat_write_nodes(ctx);
    ctx->output = NULL;

    /* write 1 byte guard at the end of file, so that we can verify broken
       squat_unpack_num() input by checking if data==end */
    o_stream_nsend(output, "", 1);

    if (trie->corrupted)
        ret = -1;
    if (ret == 0)
        ret = squat_trie_write_lock(ctx);
    if (ret == 0) {
        trie->hdr.used_file_size = output->offset;
        (void)o_stream_seek(output, 0);
        o_stream_nsend(output, &trie->hdr, sizeof(trie->hdr));
    }
    if (o_stream_finish(output) < 0) {
        i_error("write(%s) failed: %s", path,
            o_stream_get_error(output));
        ret = -1;
    }
    o_stream_destroy(&output);

    if (fd == -1) {
        /* appended to the existing file */
        i_assert(file_lock == NULL);
        return ret;
    }

    /* recreating the trie file */
    if (ret < 0) {
        if (close(fd) < 0)
            i_error("close(%s) failed: %m", path);
        fd = -1;
    } else if (rename(path, trie->path) < 0) {
        i_error("rename(%s, %s) failed: %m", path, trie->path);
        ret = -1;
    }

    if (ret < 0) {
        i_unlink_if_exists(path);
        if (file_lock != NULL)
            file_lock_free(&file_lock);
    } else {
        squat_trie_close_fd(trie);
        trie->fd = fd;
        trie->locked_file_size = trie->hdr.used_file_size;
        if (trie->file_cache != NULL)
            file_cache_set_fd(trie->file_cache, trie->fd);

        if (ctx->file_lock != NULL)
            file_lock_free(&ctx->file_lock);
        ctx->file_lock = file_lock;
    }
    return ret;
}

int squat_trie_build_deinit(struct squat_trie_build_context **_ctx,
                const ARRAY_TYPE(seq_range) *expunged_uids)
{
    struct squat_trie_build_context *ctx = *_ctx;
    bool compress, unlock = TRUE;
    int ret;

    *_ctx = NULL;

    compress = (ctx->trie->root.next_uid - ctx->first_uid) > 10;

    /* keep trie locked while header is being written and when files are
       being renamed, so that while trie is read locked, uidlist can't
       change under. */
    squat_uidlist_build_flush(ctx->uidlist_build_ctx);
    ret = squat_trie_renumber_uidlists(ctx, expunged_uids, compress);
    if (ret == 0) {
        ret = squat_trie_write(ctx);
        if (ret < 0)
            unlock = FALSE;
    }

    if (ret == 0)
        ret = squat_uidlist_build_finish(ctx->uidlist_build_ctx);
    if (ctx->file_lock != NULL) {
        if (unlock)
            file_unlock(&ctx->file_lock);
        else
            file_lock_free(&ctx->file_lock);
    }
    if (ctx->dotlock != NULL)
        file_dotlock_delete(&ctx->dotlock);
    squat_uidlist_build_deinit(&ctx->uidlist_build_ctx);

    i_free(ctx);
    return ret;
}

int squat_trie_get_last_uid(struct squat_trie *trie, uint32_t *last_uid_r)
{
    if (trie->fd == -1) {
        if (squat_trie_open(trie) < 0)
            return -1;
    }

    *last_uid_r = I_MAX((trie->root.next_uid+1)/2, 1) - 1;
    return 0;
}

static int
squat_trie_lookup_data(struct squat_trie *trie, const unsigned char *data,
               unsigned int size, ARRAY_TYPE(seq_range) *uids)
{
    struct squat_node *node = &trie->root;
    unsigned char *chars;
    unsigned int idx;
    int level = 0;

    array_clear(uids);

    for (;;) {
        if (node->children_not_mapped) {
            if (node_read_children(trie, node, level) < 0)
                return -1;
        }
        if (node->leaf_string_length != 0) {
            unsigned int len = node->leaf_string_length;
            const unsigned char *str;

            if (len > sizeof(node->children.static_leaf_string))
                str = node->children.leaf_string;
            else
                str = node->children.static_leaf_string;

            if (size > len || memcmp(data, str, size) != 0)
                return 0;

            /* match */
            break;
        }

        if (size == 0)
            break;
        level++;

        if (node->have_sequential) {
            if (*data < SEQUENTIAL_COUNT) {
                idx = *data;
                goto found;
            }
            idx = SEQUENTIAL_COUNT;
        } else {
            idx = 0;
        }
        chars = NODE_CHILDREN_CHARS(node);
        for (; idx < node->child_count; idx++) {
            if (chars[idx] == *data)
                goto found;
        }
        return 0;
    found:
        /* follow to children */
        if (level == 1) {
            /* root level, add all UIDs */
            if (squat_uidlist_get_seqrange(trie->uidlist,
                               node->uid_list_idx,
                               uids) < 0)
                return -1;
        } else {
            if (squat_uidlist_filter(trie->uidlist,
                         node->uid_list_idx, uids) < 0)
                return -1;
        }
        data++;
        size--;
        node = NODE_CHILDREN_NODES(node) + idx;
    }

    if (squat_uidlist_filter(trie->uidlist, node->uid_list_idx, uids) < 0)
        return -1;
    return 1;
}

static void
squat_trie_filter_type(enum squat_index_type type,
               const ARRAY_TYPE(seq_range) *src,
               ARRAY_TYPE(seq_range) *dest)
{
    const struct seq_range *src_range;
    struct seq_range new_range;
    unsigned int i, count, mask;
    uint32_t next_seq, uid;

    array_clear(dest);
    src_range = array_get(src, &count);
    if (count == 0)
        return;

    if ((type & SQUAT_INDEX_TYPE_HEADER) != 0 &&
        (type & SQUAT_INDEX_TYPE_BODY) != 0) {
        /* everything is fine, just fix the UIDs */
        new_range.seq1 = src_range[0].seq1 / 2;
        new_range.seq2 = src_range[0].seq2 / 2;
        for (i = 1; i < count; i++) {
            next_seq = src_range[i].seq1 / 2;
            if (next_seq == new_range.seq2 + 1) {
                /* we can continue the previous range */
            } else {
                array_append(dest, &new_range, 1);
                new_range.seq1 = src_range[i].seq1 / 2;
            }
            new_range.seq2 = src_range[i].seq2 / 2;
        }
        array_append(dest, &new_range, 1);
        return;
    }

    /* we'll have to drop either header or body UIDs */
    mask = (type & SQUAT_INDEX_TYPE_HEADER) != 0 ? 1 : 0;
    for (i = 0; i < count; i++) {
        for (uid = src_range[i].seq1; uid <= src_range[i].seq2; uid++) {
            if ((uid & 1) == mask)
                seq_range_array_add(dest, uid/2);
        }
    }
}

struct squat_trie_lookup_context {
    struct squat_trie *trie;
    enum squat_index_type type;

    ARRAY_TYPE(seq_range) *definite_uids, *maybe_uids;
    ARRAY_TYPE(seq_range) tmp_uids, tmp_uids2;
    bool first;
};

static int
squat_trie_lookup_partial(struct squat_trie_lookup_context *ctx,
              const unsigned char *data, uint8_t *char_lengths,
              unsigned int size)
{
    const unsigned int partial_len = ctx->trie->hdr.partial_len;
    unsigned int char_idx, max_chars, i, j, bytelen;
    int ret;

    for (i = 0, max_chars = 0; i < size; max_chars++)
        i += char_lengths[i];
    i_assert(max_chars > 0);

    i = 0; char_idx = 0;
    do {
        bytelen = 0;
        for (j = 0; j < partial_len && i+bytelen < size; j++)
            bytelen += char_lengths[i + bytelen];

        ret = squat_trie_lookup_data(ctx->trie, data + i, bytelen,
                         &ctx->tmp_uids);
        if (ret <= 0) {
            array_clear(ctx->maybe_uids);
            return ret;
        }

        if (ctx->first) {
            squat_trie_filter_type(ctx->type, &ctx->tmp_uids,
                           ctx->maybe_uids);
            ctx->first = FALSE;
        } else {
            squat_trie_filter_type(ctx->type, &ctx->tmp_uids,
                           &ctx->tmp_uids2);
            seq_range_array_intersect(ctx->maybe_uids,
                          &ctx->tmp_uids2);
        }
        i += char_lengths[i];
        char_idx++;
    } while (max_chars - char_idx >= partial_len);
    return 1;
}

static void squat_trie_add_unknown(struct squat_trie *trie,
                   ARRAY_TYPE(seq_range) *maybe_uids)
{
    struct seq_range *range, new_range;
    unsigned int count;
    uint32_t last_uid;

    last_uid = I_MAX((trie->root.next_uid+1)/2, 1) - 1;

    range = array_get_modifiable(maybe_uids, &count);
    if (count > 0 && range[count-1].seq2 == last_uid) {
        /* increase the range */
        range[count-1].seq2 = (uint32_t)-1;
    } else {
        new_range.seq1 = last_uid + 1;
        new_range.seq2 = (uint32_t)-1;
        array_append(maybe_uids, &new_range, 1);
    }
}

static int
squat_trie_lookup_real(struct squat_trie *trie, const char *str,
               enum squat_index_type type,
               ARRAY_TYPE(seq_range) *definite_uids,
               ARRAY_TYPE(seq_range) *maybe_uids)
{
    struct squat_trie_lookup_context ctx;
    unsigned char *data;
    uint8_t *char_lengths;
    unsigned int i, start, bytes, str_bytelen, str_charlen;
    bool searched = FALSE;
    int ret = 0;

    array_clear(definite_uids);
    array_clear(maybe_uids);

    i_zero(&ctx);
    ctx.trie = trie;
    ctx.type = type;
    ctx.definite_uids = definite_uids;
    ctx.maybe_uids = maybe_uids;
    i_array_init(&ctx.tmp_uids, 128);
    i_array_init(&ctx.tmp_uids2, 128);
    ctx.first = TRUE;

    str_bytelen = strlen(str);
    char_lengths = str_bytelen == 0 ? NULL : t_malloc0(str_bytelen);
    for (i = 0, str_charlen = 0; i < str_bytelen; str_charlen++) {
        bytes = uni_utf8_char_bytes(str[i]);
        char_lengths[i] = bytes;
        i += bytes;
    }
    data = squat_data_normalize(trie, (const unsigned char *)str,
                    str_bytelen);

    for (i = start = 0; i < str_bytelen && ret >= 0; i += char_lengths[i]) {
        if (data[i] != '\0')
            continue;

        /* string has nonindexed characters.
           search it in parts. */
        if (i != start) {
            ret = squat_trie_lookup_partial(&ctx, data + start,
                            char_lengths + start,
                            i - start);
            searched = TRUE;
        }
        start = i + char_lengths[i];
    }

    if (start == 0) {
        if (str_charlen <= trie->hdr.partial_len ||
            trie->hdr.full_len > trie->hdr.partial_len) {
            ret = squat_trie_lookup_data(trie, data, str_bytelen,
                             &ctx.tmp_uids);
            if (ret > 0) {
                squat_trie_filter_type(type, &ctx.tmp_uids,
                               definite_uids);
            }
        } else {
            array_clear(definite_uids);
        }

        if (str_charlen <= trie->hdr.partial_len ||
            trie->hdr.partial_len == 0) {
            /* we have the result */
            array_clear(maybe_uids);
        } else {
            ret = squat_trie_lookup_partial(&ctx, data + start,
                            char_lengths + start,
                            i - start);
        }
    } else if (str_bytelen > 0) {
        /* string has nonindexed characters. finish the search. */
        array_clear(definite_uids);
        if (i != start && ret >= 0) {
            ret = squat_trie_lookup_partial(&ctx, data + start,
                            char_lengths + start,
                            i - start);
        } else if (!searched) {
            /* string has only nonindexed chars,
               list all root UIDs as maybes */
            ret = squat_uidlist_get_seqrange(trie->uidlist,
                            trie->root.uid_list_idx,
                            &ctx.tmp_uids);
            squat_trie_filter_type(type, &ctx.tmp_uids,
                           maybe_uids);
        }
    } else {
        /* zero string length - list all root UIDs as definite
           answers */
#if 0 /* FIXME: this code is never actually reached now. */
        ret = squat_uidlist_get_seqrange(trie->uidlist,
                         trie->root.uid_list_idx,
                         &ctx.tmp_uids);
        squat_trie_filter_type(type, &ctx.tmp_uids,
                       definite_uids);
#else
        i_unreached();
#endif
    }
    seq_range_array_remove_seq_range(maybe_uids, definite_uids);
    squat_trie_add_unknown(trie, maybe_uids);
    array_free(&ctx.tmp_uids);
    array_free(&ctx.tmp_uids2);
    return ret < 0 ? -1 : 0;
}

int squat_trie_lookup(struct squat_trie *trie, const char *str,
              enum squat_index_type type,
              ARRAY_TYPE(seq_range) *definite_uids,
              ARRAY_TYPE(seq_range) *maybe_uids)
{
    int ret;

    T_BEGIN {
        ret = squat_trie_lookup_real(trie, str, type,
                         definite_uids, maybe_uids);
    } T_END;
    return ret;
}

struct squat_uidlist *squat_trie_get_uidlist(struct squat_trie *trie)
{
    return trie->uidlist;
}

size_t squat_trie_mem_used(struct squat_trie *trie, unsigned int *count_r)
{
    *count_r = trie->hdr.node_count;
    return trie->node_alloc_size;
}