date: make DATE_MODE thread-safe

[git.git] / cache-tree.c

#include "git-compat-util.h"
#include "environment.h"
#include "hex.h"
#include "lockfile.h"
#include "tree.h"
#include "tree-walk.h"
#include "cache-tree.h"
#include "bulk-checkin.h"
#include "object-file.h"
#include "object-store-ll.h"
#include "read-cache-ll.h"
#include "replace-object.h"
#include "promisor-remote.h"
#include "trace.h"
#include "trace2.h"

#ifndef DEBUG_CACHE_TREE
#define DEBUG_CACHE_TREE 0
#endif

struct cache_tree *cache_tree(void)
{
        struct cache_tree *it = xcalloc(1, sizeof(struct cache_tree));
        it->entry_count = -1;
        return it;
}

void cache_tree_free(struct cache_tree **it_p)
{
        int i;
        struct cache_tree *it = *it_p;

        if (!it)
                return;
        for (i = 0; i < it->subtree_nr; i++)
                if (it->down[i]) {
                        cache_tree_free(&it->down[i]->cache_tree);
                        free(it->down[i]);
                }
        free(it->down);
        free(it);
        *it_p = NULL;
}

static int subtree_name_cmp(const char *one, int onelen,
                            const char *two, int twolen)
{
        if (onelen < twolen)
                return -1;
        if (twolen < onelen)
                return 1;
        return memcmp(one, two, onelen);
}

int cache_tree_subtree_pos(struct cache_tree *it, const char *path, int pathlen)
{
        struct cache_tree_sub **down = it->down;
        int lo, hi;
        lo = 0;
        hi = it->subtree_nr;
        while (lo < hi) {
                int mi = lo + (hi - lo) / 2;
                struct cache_tree_sub *mdl = down[mi];
                int cmp = subtree_name_cmp(path, pathlen,
                                           mdl->name, mdl->namelen);
                if (!cmp)
                        return mi;
                if (cmp < 0)
                        hi = mi;
                else
                        lo = mi + 1;
        }
        return -lo-1;
}

static struct cache_tree_sub *find_subtree(struct cache_tree *it,
                                           const char *path,
                                           int pathlen,
                                           int create)
{
        struct cache_tree_sub *down;
        int pos = cache_tree_subtree_pos(it, path, pathlen);
        if (0 <= pos)
                return it->down[pos];
        if (!create)
                return NULL;

        pos = -pos-1;
        ALLOC_GROW(it->down, it->subtree_nr + 1, it->subtree_alloc);
        it->subtree_nr++;

        FLEX_ALLOC_MEM(down, name, path, pathlen);
        down->cache_tree = NULL;
        down->namelen = pathlen;

        if (pos < it->subtree_nr)
                MOVE_ARRAY(it->down + pos + 1, it->down + pos,
                           it->subtree_nr - pos - 1);
        it->down[pos] = down;
        return down;
}

struct cache_tree_sub *cache_tree_sub(struct cache_tree *it, const char *path)
{
        int pathlen = strlen(path);
        return find_subtree(it, path, pathlen, 1);
}

static int do_invalidate_path(struct cache_tree *it, const char *path)
{
        /* a/b/c
         * ==> invalidate self
         * ==> find "a", have it invalidate "b/c"
         * a
         * ==> invalidate self
         * ==> if "a" exists as a subtree, remove it.
         */
        const char *slash;
        int namelen;
        struct cache_tree_sub *down;

#if DEBUG_CACHE_TREE
        fprintf(stderr, "cache-tree invalidate <%s>\n", path);
#endif

        if (!it)
                return 0;
        slash = strchrnul(path, '/');
        namelen = slash - path;
        it->entry_count = -1;
        if (!*slash) {
                int pos;
                pos = cache_tree_subtree_pos(it, path, namelen);
                if (0 <= pos) {
                        cache_tree_free(&it->down[pos]->cache_tree);
                        free(it->down[pos]);
                        /* 0 1 2 3 4 5
                         *       ^     ^subtree_nr = 6
                         *       pos
                         * move 4 and 5 up one place (2 entries)
                         * 2 = 6 - 3 - 1 = subtree_nr - pos - 1
                         */
                        MOVE_ARRAY(it->down + pos, it->down + pos + 1,
                                   it->subtree_nr - pos - 1);
                        it->subtree_nr--;
                }
                return 1;
        }
        down = find_subtree(it, path, namelen, 0);
        if (down)
                do_invalidate_path(down->cache_tree, slash + 1);
        return 1;
}

void cache_tree_invalidate_path(struct index_state *istate, const char *path)
{
        if (do_invalidate_path(istate->cache_tree, path))
                istate->cache_changed |= CACHE_TREE_CHANGED;
}

static int verify_cache(struct index_state *istate, int flags)
{
        unsigned i, funny;
        int silent = flags & WRITE_TREE_SILENT;

        /* Verify that the tree is merged */
        funny = 0;
        for (i = 0; i < istate->cache_nr; i++) {
                const struct cache_entry *ce = istate->cache[i];
                if (ce_stage(ce)) {
                        if (silent)
                                return -1;
                        if (10 < ++funny) {
                                fprintf(stderr, "...\n");
                                break;
                        }
                        fprintf(stderr, "%s: unmerged (%s)\n",
                                ce->name, oid_to_hex(&ce->oid));
                }
        }
        if (funny)
                return -1;

        /* Also verify that the cache does not have path and path/file
         * at the same time.  At this point we know the cache has only
         * stage 0 entries.
         */
        funny = 0;
        for (i = 0; i + 1 < istate->cache_nr; i++) {
                /* path/file always comes after path because of the way
                 * the cache is sorted.  Also path can appear only once,
                 * which means conflicting one would immediately follow.
                 */
                const struct cache_entry *this_ce = istate->cache[i];
                const struct cache_entry *next_ce = istate->cache[i + 1];
                const char *this_name = this_ce->name;
                const char *next_name = next_ce->name;
                int this_len = ce_namelen(this_ce);
                if (this_len < ce_namelen(next_ce) &&
                    next_name[this_len] == '/' &&
                    strncmp(this_name, next_name, this_len) == 0) {
                        if (10 < ++funny) {
                                fprintf(stderr, "...\n");
                                break;
                        }
                        fprintf(stderr, "You have both %s and %s\n",
                                this_name, next_name);
                }
        }
        if (funny)
                return -1;
        return 0;
}

static void discard_unused_subtrees(struct cache_tree *it)
{
        struct cache_tree_sub **down = it->down;
        int nr = it->subtree_nr;
        int dst, src;
        for (dst = src = 0; src < nr; src++) {
                struct cache_tree_sub *s = down[src];
                if (s->used)
                        down[dst++] = s;
                else {
                        cache_tree_free(&s->cache_tree);
                        free(s);
                        it->subtree_nr--;
                }
        }
}

int cache_tree_fully_valid(struct cache_tree *it)
{
        int i;
        if (!it)
                return 0;
        if (it->entry_count < 0 || !repo_has_object_file(the_repository, &it->oid))
                return 0;
        for (i = 0; i < it->subtree_nr; i++) {
                if (!cache_tree_fully_valid(it->down[i]->cache_tree))
                        return 0;
        }
        return 1;
}

static int must_check_existence(const struct cache_entry *ce)
{
        return !(repo_has_promisor_remote(the_repository) && ce_skip_worktree(ce));
}

static int update_one(struct cache_tree *it,
                      struct cache_entry **cache,
                      int entries,
                      const char *base,
                      int baselen,
                      int *skip_count,
                      int flags)
{
        struct strbuf buffer;
        int missing_ok = flags & WRITE_TREE_MISSING_OK;
        int dryrun = flags & WRITE_TREE_DRY_RUN;
        int repair = flags & WRITE_TREE_REPAIR;
        int to_invalidate = 0;
        int i;

        assert(!(dryrun && repair));

        *skip_count = 0;

        /*
         * If the first entry of this region is a sparse directory
         * entry corresponding exactly to 'base', then this cache_tree
         * struct is a "leaf" in the data structure, pointing to the
         * tree OID specified in the entry.
         */
        if (entries > 0) {
                const struct cache_entry *ce = cache[0];

                if (S_ISSPARSEDIR(ce->ce_mode) &&
                    ce->ce_namelen == baselen &&
                    !strncmp(ce->name, base, baselen)) {
                        it->entry_count = 1;
                        oidcpy(&it->oid, &ce->oid);
                        return 1;
                }
        }

        if (0 <= it->entry_count && repo_has_object_file(the_repository, &it->oid))
                return it->entry_count;

        /*
         * We first scan for subtrees and update them; we start by
         * marking existing subtrees -- the ones that are unmarked
         * should not be in the result.
         */
        for (i = 0; i < it->subtree_nr; i++)
                it->down[i]->used = 0;

        /*
         * Find the subtrees and update them.
         */
        i = 0;
        while (i < entries) {
                const struct cache_entry *ce = cache[i];
                struct cache_tree_sub *sub;
                const char *path, *slash;
                int pathlen, sublen, subcnt, subskip;

                path = ce->name;
                pathlen = ce_namelen(ce);
                if (pathlen <= baselen || memcmp(base, path, baselen))
                        break; /* at the end of this level */

                slash = strchr(path + baselen, '/');
                if (!slash) {
                        i++;
                        continue;
                }
                /*
                 * a/bbb/c (base = a/, slash = /c)
                 * ==>
                 * path+baselen = bbb/c, sublen = 3
                 */
                sublen = slash - (path + baselen);
                sub = find_subtree(it, path + baselen, sublen, 1);
                if (!sub->cache_tree)
                        sub->cache_tree = cache_tree();
                subcnt = update_one(sub->cache_tree,
                                    cache + i, entries - i,
                                    path,
                                    baselen + sublen + 1,
                                    &subskip,
                                    flags);
                if (subcnt < 0)
                        return subcnt;
                if (!subcnt)
                        die("index cache-tree records empty sub-tree");
                i += subcnt;
                sub->count = subcnt; /* to be used in the next loop */
                *skip_count += subskip;
                sub->used = 1;
        }

        discard_unused_subtrees(it);

        /*
         * Then write out the tree object for this level.
         */
        strbuf_init(&buffer, 8192);

        i = 0;
        while (i < entries) {
                const struct cache_entry *ce = cache[i];
                struct cache_tree_sub *sub = NULL;
                const char *path, *slash;
                int pathlen, entlen;
                const struct object_id *oid;
                unsigned mode;
                int expected_missing = 0;
                int contains_ita = 0;
                int ce_missing_ok;

                path = ce->name;
                pathlen = ce_namelen(ce);
                if (pathlen <= baselen || memcmp(base, path, baselen))
                        break; /* at the end of this level */

                slash = strchr(path + baselen, '/');
                if (slash) {
                        entlen = slash - (path + baselen);
                        sub = find_subtree(it, path + baselen, entlen, 0);
                        if (!sub)
                                die("cache-tree.c: '%.*s' in '%s' not found",
                                    entlen, path + baselen, path);
                        i += sub->count;
                        oid = &sub->cache_tree->oid;
                        mode = S_IFDIR;
                        contains_ita = sub->cache_tree->entry_count < 0;
                        if (contains_ita) {
                                to_invalidate = 1;
                                expected_missing = 1;
                        }
                }
                else {
                        oid = &ce->oid;
                        mode = ce->ce_mode;
                        entlen = pathlen - baselen;
                        i++;
                }

                ce_missing_ok = mode == S_IFGITLINK || missing_ok ||
                        !must_check_existence(ce);
                if (is_null_oid(oid) ||
                    (!ce_missing_ok && !repo_has_object_file(the_repository, oid))) {
                        strbuf_release(&buffer);
                        if (expected_missing)
                                return -1;
                        return error("invalid object %06o %s for '%.*s'",
                                mode, oid_to_hex(oid), entlen+baselen, path);
                }

                /*
                 * CE_REMOVE entries are removed before the index is
                 * written to disk. Skip them to remain consistent
                 * with the future on-disk index.
                 */
                if (ce->ce_flags & CE_REMOVE) {
                        *skip_count = *skip_count + 1;
                        continue;
                }

                /*
                 * CE_INTENT_TO_ADD entries exist in on-disk index but
                 * they are not part of generated trees. Invalidate up
                 * to root to force cache-tree users to read elsewhere.
                 */
                if (!sub && ce_intent_to_add(ce)) {
                        to_invalidate = 1;
                        continue;
                }

                /*
                 * "sub" can be an empty tree if all subentries are i-t-a.
                 */
                if (contains_ita && is_empty_tree_oid(oid))
                        continue;

                strbuf_grow(&buffer, entlen + 100);
                strbuf_addf(&buffer, "%o %.*s%c", mode, entlen, path + baselen, '\0');
                strbuf_add(&buffer, oid->hash, the_hash_algo->rawsz);

#if DEBUG_CACHE_TREE
                fprintf(stderr, "cache-tree update-one %o %.*s\n",
                        mode, entlen, path + baselen);
#endif
        }

        if (repair) {
                struct object_id oid;
                hash_object_file(the_hash_algo, buffer.buf, buffer.len,
                                 OBJ_TREE, &oid);
                if (repo_has_object_file_with_flags(the_repository, &oid, OBJECT_INFO_SKIP_FETCH_OBJECT))
                        oidcpy(&it->oid, &oid);
                else
                        to_invalidate = 1;
        } else if (dryrun) {
                hash_object_file(the_hash_algo, buffer.buf, buffer.len,
                                 OBJ_TREE, &it->oid);
        } else if (write_object_file_flags(buffer.buf, buffer.len, OBJ_TREE,
                                           &it->oid, flags & WRITE_TREE_SILENT
                                           ? HASH_SILENT : 0)) {
                strbuf_release(&buffer);
                return -1;
        }

        strbuf_release(&buffer);
        it->entry_count = to_invalidate ? -1 : i - *skip_count;
#if DEBUG_CACHE_TREE
        fprintf(stderr, "cache-tree update-one (%d ent, %d subtree) %s\n",
                it->entry_count, it->subtree_nr,
                oid_to_hex(&it->oid));
#endif
        return i;
}

int cache_tree_update(struct index_state *istate, int flags)
{
        int skip, i;

        i = verify_cache(istate, flags);

        if (i)
                return i;

        if (!istate->cache_tree)
                istate->cache_tree = cache_tree();

        if (!(flags & WRITE_TREE_MISSING_OK) && repo_has_promisor_remote(the_repository))
                prefetch_cache_entries(istate, must_check_existence);

        trace_performance_enter();
        trace2_region_enter("cache_tree", "update", the_repository);
        begin_odb_transaction();
        i = update_one(istate->cache_tree, istate->cache, istate->cache_nr,
                       "", 0, &skip, flags);
        end_odb_transaction();
        trace2_region_leave("cache_tree", "update", the_repository);
        trace_performance_leave("cache_tree_update");
        if (i < 0)
                return i;
        istate->cache_changed |= CACHE_TREE_CHANGED;
        return 0;
}

static void write_one(struct strbuf *buffer, struct cache_tree *it,
                      const char *path, int pathlen)
{
        int i;

        /* One "cache-tree" entry consists of the following:
         * path (NUL terminated)
         * entry_count, subtree_nr ("%d %d\n")
         * tree-sha1 (missing if invalid)
         * subtree_nr "cache-tree" entries for subtrees.
         */
        strbuf_grow(buffer, pathlen + 100);
        strbuf_add(buffer, path, pathlen);
        strbuf_addf(buffer, "%c%d %d\n", 0, it->entry_count, it->subtree_nr);

#if DEBUG_CACHE_TREE
        if (0 <= it->entry_count)
                fprintf(stderr, "cache-tree <%.*s> (%d ent, %d subtree) %s\n",
                        pathlen, path, it->entry_count, it->subtree_nr,
                        oid_to_hex(&it->oid));
        else
                fprintf(stderr, "cache-tree <%.*s> (%d subtree) invalid\n",
                        pathlen, path, it->subtree_nr);
#endif

        if (0 <= it->entry_count) {
                strbuf_add(buffer, it->oid.hash, the_hash_algo->rawsz);
        }
        for (i = 0; i < it->subtree_nr; i++) {
                struct cache_tree_sub *down = it->down[i];
                if (i) {
                        struct cache_tree_sub *prev = it->down[i-1];
                        if (subtree_name_cmp(down->name, down->namelen,
                                             prev->name, prev->namelen) <= 0)
                                die("fatal - unsorted cache subtree");
                }
                write_one(buffer, down->cache_tree, down->name, down->namelen);
        }
}

void cache_tree_write(struct strbuf *sb, struct cache_tree *root)
{
        trace2_region_enter("cache_tree", "write", the_repository);
        write_one(sb, root, "", 0);
        trace2_region_leave("cache_tree", "write", the_repository);
}

static struct cache_tree *read_one(const char **buffer, unsigned long *size_p)
{
        const char *buf = *buffer;
        unsigned long size = *size_p;
        const char *cp;
        char *ep;
        struct cache_tree *it;
        int i, subtree_nr;
        const unsigned rawsz = the_hash_algo->rawsz;

        it = NULL;
        /* skip name, but make sure name exists */
        while (size && *buf) {
                size--;
                buf++;
        }
        if (!size)
                goto free_return;
        buf++; size--;
        it = cache_tree();

        cp = buf;
        it->entry_count = strtol(cp, &ep, 10);
        if (cp == ep)
                goto free_return;
        cp = ep;
        subtree_nr = strtol(cp, &ep, 10);
        if (cp == ep)
                goto free_return;
        while (size && *buf && *buf != '\n') {
                size--;
                buf++;
        }
        if (!size)
                goto free_return;
        buf++; size--;
        if (0 <= it->entry_count) {
                if (size < rawsz)
                        goto free_return;
                oidread(&it->oid, (const unsigned char *)buf);
                buf += rawsz;
                size -= rawsz;
        }

#if DEBUG_CACHE_TREE
        if (0 <= it->entry_count)
                fprintf(stderr, "cache-tree <%s> (%d ent, %d subtree) %s\n",
                        *buffer, it->entry_count, subtree_nr,
                        oid_to_hex(&it->oid));
        else
                fprintf(stderr, "cache-tree <%s> (%d subtrees) invalid\n",
                        *buffer, subtree_nr);
#endif

        /*
         * Just a heuristic -- we do not add directories that often but
         * we do not want to have to extend it immediately when we do,
         * hence +2.
         */
        it->subtree_alloc = subtree_nr + 2;
        CALLOC_ARRAY(it->down, it->subtree_alloc);
        for (i = 0; i < subtree_nr; i++) {
                /* read each subtree */
                struct cache_tree *sub;
                struct cache_tree_sub *subtree;
                const char *name = buf;

                sub = read_one(&buf, &size);
                if (!sub)
                        goto free_return;
                subtree = cache_tree_sub(it, name);
                subtree->cache_tree = sub;
        }
        if (subtree_nr != it->subtree_nr)
                die("cache-tree: internal error");
        *buffer = buf;
        *size_p = size;
        return it;

 free_return:
        cache_tree_free(&it);
        return NULL;
}

struct cache_tree *cache_tree_read(const char *buffer, unsigned long size)
{
        struct cache_tree *result;

        if (buffer[0])
                return NULL; /* not the whole tree */

        trace2_region_enter("cache_tree", "read", the_repository);
        result = read_one(&buffer, &size);
        trace2_region_leave("cache_tree", "read", the_repository);

        return result;
}

static struct cache_tree *cache_tree_find(struct cache_tree *it, const char *path)
{
        if (!it)
                return NULL;
        while (*path) {
                const char *slash;
                struct cache_tree_sub *sub;

                slash = strchrnul(path, '/');
                /*
                 * Between path and slash is the name of the subtree
                 * to look for.
                 */
                sub = find_subtree(it, path, slash - path, 0);
                if (!sub)
                        return NULL;
                it = sub->cache_tree;

                path = slash;
                while (*path == '/')
                        path++;
        }
        return it;
}

static int write_index_as_tree_internal(struct object_id *oid,
                                        struct index_state *index_state,
                                        int cache_tree_valid,
                                        int flags,
                                        const char *prefix)
{
        if (flags & WRITE_TREE_IGNORE_CACHE_TREE) {
                cache_tree_free(&index_state->cache_tree);
                cache_tree_valid = 0;
        }

        if (!cache_tree_valid && cache_tree_update(index_state, flags) < 0)
                return WRITE_TREE_UNMERGED_INDEX;

        if (prefix) {
                struct cache_tree *subtree;
                subtree = cache_tree_find(index_state->cache_tree, prefix);
                if (!subtree)
                        return WRITE_TREE_PREFIX_ERROR;
                oidcpy(oid, &subtree->oid);
        }
        else
                oidcpy(oid, &index_state->cache_tree->oid);

        return 0;
}

struct tree* write_in_core_index_as_tree(struct repository *repo) {
        struct object_id o;
        int was_valid, ret;

        struct index_state *index_state = repo->index;
        was_valid = index_state->cache_tree &&
                    cache_tree_fully_valid(index_state->cache_tree);

        ret = write_index_as_tree_internal(&o, index_state, was_valid, 0, NULL);
        if (ret == WRITE_TREE_UNMERGED_INDEX) {
                int i;
                bug("there are unmerged index entries:");
                for (i = 0; i < index_state->cache_nr; i++) {
                        const struct cache_entry *ce = index_state->cache[i];
                        if (ce_stage(ce))
                                bug("%d %.*s", ce_stage(ce),
                                    (int)ce_namelen(ce), ce->name);
                }
                BUG("unmerged index entries when writing in-core index");
        }

        return lookup_tree(repo, &index_state->cache_tree->oid);
}


int write_index_as_tree(struct object_id *oid, struct index_state *index_state, const char *index_path, int flags, const char *prefix)
{
        int entries, was_valid;
        struct lock_file lock_file = LOCK_INIT;
        int ret;

        hold_lock_file_for_update(&lock_file, index_path, LOCK_DIE_ON_ERROR);

        entries = read_index_from(index_state, index_path, get_git_dir());
        if (entries < 0) {
                ret = WRITE_TREE_UNREADABLE_INDEX;
                goto out;
        }

        was_valid = !(flags & WRITE_TREE_IGNORE_CACHE_TREE) &&
                    index_state->cache_tree &&
                    cache_tree_fully_valid(index_state->cache_tree);

        ret = write_index_as_tree_internal(oid, index_state, was_valid, flags,
                                           prefix);
        if (!ret && !was_valid) {
                write_locked_index(index_state, &lock_file, COMMIT_LOCK);
                /* Not being able to write is fine -- we are only interested
                 * in updating the cache-tree part, and if the next caller
                 * ends up using the old index with unupdated cache-tree part
                 * it misses the work we did here, but that is just a
                 * performance penalty and not a big deal.
                 */
        }

out:
        rollback_lock_file(&lock_file);
        return ret;
}

static void prime_cache_tree_sparse_dir(struct cache_tree *it,
                                        struct tree *tree)
{

        oidcpy(&it->oid, &tree->object.oid);
        it->entry_count = 1;
}

static void prime_cache_tree_rec(struct repository *r,
                                 struct cache_tree *it,
                                 struct tree *tree,
                                 struct strbuf *tree_path)
{
        struct tree_desc desc;
        struct name_entry entry;
        int cnt;
        size_t base_path_len = tree_path->len;

        oidcpy(&it->oid, &tree->object.oid);

        init_tree_desc(&desc, tree->buffer, tree->size);
        cnt = 0;
        while (tree_entry(&desc, &entry)) {
                if (!S_ISDIR(entry.mode))
                        cnt++;
                else {
                        struct cache_tree_sub *sub;
                        struct tree *subtree = lookup_tree(r, &entry.oid);

                        if (parse_tree(subtree) < 0)
                                exit(128);
                        sub = cache_tree_sub(it, entry.path);
                        sub->cache_tree = cache_tree();

                        /*
                         * Recursively-constructed subtree path is only needed when working
                         * in a sparse index (where it's used to determine whether the
                         * subtree is a sparse directory in the index).
                         */
                        if (r->index->sparse_index) {
                                strbuf_setlen(tree_path, base_path_len);
                                strbuf_add(tree_path, entry.path, entry.pathlen);
                                strbuf_addch(tree_path, '/');
                        }

                        /*
                         * If a sparse index is in use, the directory being processed may be
                         * sparse. To confirm that, we can check whether an entry with that
                         * exact name exists in the index. If it does, the created subtree
                         * should be sparse. Otherwise, cache tree expansion should continue
                         * as normal.
                         */
                        if (r->index->sparse_index &&
                            index_entry_exists(r->index, tree_path->buf, tree_path->len))
                                prime_cache_tree_sparse_dir(sub->cache_tree, subtree);
                        else
                                prime_cache_tree_rec(r, sub->cache_tree, subtree, tree_path);
                        cnt += sub->cache_tree->entry_count;
                }
        }

        it->entry_count = cnt;
}

void prime_cache_tree(struct repository *r,
                      struct index_state *istate,
                      struct tree *tree)
{
        struct strbuf tree_path = STRBUF_INIT;

        trace2_region_enter("cache-tree", "prime_cache_tree", r);
        cache_tree_free(&istate->cache_tree);
        istate->cache_tree = cache_tree();

        prime_cache_tree_rec(r, istate->cache_tree, tree, &tree_path);
        strbuf_release(&tree_path);
        istate->cache_changed |= CACHE_TREE_CHANGED;
        trace2_region_leave("cache-tree", "prime_cache_tree", r);
}

/*
 * find the cache_tree that corresponds to the current level without
 * exploding the full path into textual form.  The root of the
 * cache tree is given as "root", and our current level is "info".
 * (1) When at root level, info->prev is NULL, so it is "root" itself.
 * (2) Otherwise, find the cache_tree that corresponds to one level
 *     above us, and find ourselves in there.
 */
static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
                                                         struct traverse_info *info)
{
        struct cache_tree *our_parent;

        if (!info->prev)
                return root;
        our_parent = find_cache_tree_from_traversal(root, info->prev);
        return cache_tree_find(our_parent, info->name);
}

int cache_tree_matches_traversal(struct cache_tree *root,
                                 struct name_entry *ent,
                                 struct traverse_info *info)
{
        struct cache_tree *it;

        it = find_cache_tree_from_traversal(root, info);
        it = cache_tree_find(it, ent->path);
        if (it && it->entry_count > 0 && oideq(&ent->oid, &it->oid))
                return it->entry_count;
        return 0;
}

static void verify_one_sparse(struct index_state *istate,
                              struct strbuf *path,
                              int pos)
{
        struct cache_entry *ce = istate->cache[pos];

        if (!S_ISSPARSEDIR(ce->ce_mode))
                BUG("directory '%s' is present in index, but not sparse",
                    path->buf);
}

/*
 * Returns:
 *  0 - Verification completed.
 *  1 - Restart verification - a call to ensure_full_index() freed the cache
 *      tree that is being verified and verification needs to be restarted from
 *      the new toplevel cache tree.
 */
static int verify_one(struct repository *r,
                      struct index_state *istate,
                      struct cache_tree *it,
                      struct strbuf *path)
{
        int i, pos, len = path->len;
        struct strbuf tree_buf = STRBUF_INIT;
        struct object_id new_oid;

        for (i = 0; i < it->subtree_nr; i++) {
                strbuf_addf(path, "%s/", it->down[i]->name);
                if (verify_one(r, istate, it->down[i]->cache_tree, path))
                        return 1;
                strbuf_setlen(path, len);
        }

        if (it->entry_count < 0 ||
            /* no verification on tests (t7003) that replace trees */
            lookup_replace_object(r, &it->oid) != &it->oid)
                return 0;

        if (path->len) {
                /*
                 * If the index is sparse and the cache tree is not
                 * index_name_pos() may trigger ensure_full_index() which will
                 * free the tree that is being verified.
                 */
                int is_sparse = istate->sparse_index;
                pos = index_name_pos(istate, path->buf, path->len);
                if (is_sparse && !istate->sparse_index)
                        return 1;

                if (pos >= 0) {
                        verify_one_sparse(istate, path, pos);
                        return 0;
                }

                pos = -pos - 1;
        } else {
                pos = 0;
        }

        i = 0;
        while (i < it->entry_count) {
                struct cache_entry *ce = istate->cache[pos + i];
                const char *slash;
                struct cache_tree_sub *sub = NULL;
                const struct object_id *oid;
                const char *name;
                unsigned mode;
                int entlen;

                if (ce->ce_flags & (CE_STAGEMASK | CE_INTENT_TO_ADD | CE_REMOVE))
                        BUG("%s with flags 0x%x should not be in cache-tree",
                            ce->name, ce->ce_flags);
                name = ce->name + path->len;
                slash = strchr(name, '/');
                if (slash) {
                        entlen = slash - name;
                        sub = find_subtree(it, ce->name + path->len, entlen, 0);
                        if (!sub || sub->cache_tree->entry_count < 0)
                                BUG("bad subtree '%.*s'", entlen, name);
                        oid = &sub->cache_tree->oid;
                        mode = S_IFDIR;
                        i += sub->cache_tree->entry_count;
                } else {
                        oid = &ce->oid;
                        mode = ce->ce_mode;
                        entlen = ce_namelen(ce) - path->len;
                        i++;
                }
                strbuf_addf(&tree_buf, "%o %.*s%c", mode, entlen, name, '\0');
                strbuf_add(&tree_buf, oid->hash, r->hash_algo->rawsz);
        }
        hash_object_file(r->hash_algo, tree_buf.buf, tree_buf.len, OBJ_TREE,
                         &new_oid);
        if (!oideq(&new_oid, &it->oid))
                BUG("cache-tree for path %.*s does not match. "
                    "Expected %s got %s", len, path->buf,
                    oid_to_hex(&new_oid), oid_to_hex(&it->oid));
        strbuf_setlen(path, len);
        strbuf_release(&tree_buf);
        return 0;
}

void cache_tree_verify(struct repository *r, struct index_state *istate)
{
        struct strbuf path = STRBUF_INIT;

        if (!istate->cache_tree)
                return;
        if (verify_one(r, istate, istate->cache_tree, &path)) {
                strbuf_reset(&path);
                if (verify_one(r, istate, istate->cache_tree, &path))
                        BUG("ensure_full_index() called twice while verifying cache tree");
        }
        strbuf_release(&path);
}