root/split-index.c

DEFINITIONS

1. init_split_index
2. read_link_extension
3. write_link_extension
4. mark_base_index_entries
5. move_cache_to_base_index
6. mark_entry_for_delete
7. replace_entry
8. merge_base_index
9. prepare_to_write_split_index
10. finish_writing_split_index
11. discard_split_index
12. save_or_free_index_entry
13. replace_index_entry_in_base

#include "cache.h"
#include "split-index.h"
#include "ewah/ewok.h"

struct split_index *init_split_index(struct index_state *istate)
{
        if (!istate->split_index) {
                istate->split_index = xcalloc(1, sizeof(*istate->split_index));
                istate->split_index->refcount = 1;
        }
        return istate->split_index;
}

int read_link_extension(struct index_state *istate,
                         const void *data_, unsigned long sz)
{
        const unsigned char *data = data_;
        struct split_index *si;
        int ret;

        if (sz < 20)
                return error("corrupt link extension (too short)");
        si = init_split_index(istate);
        hashcpy(si->base_sha1, data);
        data += 20;
        sz -= 20;
        if (!sz)
                return 0;
        si->delete_bitmap = ewah_new();
        ret = ewah_read_mmap(si->delete_bitmap, data, sz);
        if (ret < 0)
                return error("corrupt delete bitmap in link extension");
        data += ret;
        sz -= ret;
        si->replace_bitmap = ewah_new();
        ret = ewah_read_mmap(si->replace_bitmap, data, sz);
        if (ret < 0)
                return error("corrupt replace bitmap in link extension");
        if (ret != sz)
                return error("garbage at the end of link extension");
        return 0;
}

int write_link_extension(struct strbuf *sb,
                         struct index_state *istate)
{
        struct split_index *si = istate->split_index;
        strbuf_add(sb, si->base_sha1, 20);
        if (!si->delete_bitmap && !si->replace_bitmap)
                return 0;
        ewah_serialize_strbuf(si->delete_bitmap, sb);
        ewah_serialize_strbuf(si->replace_bitmap, sb);
        return 0;
}

static void mark_base_index_entries(struct index_state *base)
{
        int i;
        /*
         * To keep track of the shared entries between
         * istate->base->cache[] and istate->cache[], base entry
         * position is stored in each base entry. All positions start
         * from 1 instead of 0, which is resrved to say "this is a new
         * entry".
         */
        for (i = 0; i < base->cache_nr; i++)
                base->cache[i]->index = i + 1;
}

void move_cache_to_base_index(struct index_state *istate)
{
        struct split_index *si = istate->split_index;
        int i;

        /*
         * do not delete old si->base, its index entries may be shared
         * with istate->cache[]. Accept a bit of leaking here because
         * this code is only used by short-lived update-index.
         */
        si->base = xcalloc(1, sizeof(*si->base));
        si->base->version = istate->version;
        /* zero timestamp disables racy test in ce_write_index() */
        si->base->timestamp = istate->timestamp;
        ALLOC_GROW(si->base->cache, istate->cache_nr, si->base->cache_alloc);
        si->base->cache_nr = istate->cache_nr;
        memcpy(si->base->cache, istate->cache,
               sizeof(*istate->cache) * istate->cache_nr);
        mark_base_index_entries(si->base);
        for (i = 0; i < si->base->cache_nr; i++)
                si->base->cache[i]->ce_flags &= ~CE_UPDATE_IN_BASE;
}

static void mark_entry_for_delete(size_t pos, void *data)
{
        struct index_state *istate = data;
        if (pos >= istate->cache_nr)
                die("position for delete %d exceeds base index size %d",
                    (int)pos, istate->cache_nr);
        istate->cache[pos]->ce_flags |= CE_REMOVE;
        istate->split_index->nr_deletions = 1;
}

static void replace_entry(size_t pos, void *data)
{
        struct index_state *istate = data;
        struct split_index *si = istate->split_index;
        struct cache_entry *dst, *src;

        if (pos >= istate->cache_nr)
                die("position for replacement %d exceeds base index size %d",
                    (int)pos, istate->cache_nr);
        if (si->nr_replacements >= si->saved_cache_nr)
                die("too many replacements (%d vs %d)",
                    si->nr_replacements, si->saved_cache_nr);
        dst = istate->cache[pos];
        if (dst->ce_flags & CE_REMOVE)
                die("entry %d is marked as both replaced and deleted",
                    (int)pos);
        src = si->saved_cache[si->nr_replacements];
        if (ce_namelen(src))
                die("corrupt link extension, entry %d should have "
                    "zero length name", (int)pos);
        src->index = pos + 1;
        src->ce_flags |= CE_UPDATE_IN_BASE;
        src->ce_namelen = dst->ce_namelen;
        copy_cache_entry(dst, src);
        free(src);
        si->nr_replacements++;
}

void merge_base_index(struct index_state *istate)
{
        struct split_index *si = istate->split_index;
        unsigned int i;

        mark_base_index_entries(si->base);

        si->saved_cache     = istate->cache;
        si->saved_cache_nr  = istate->cache_nr;
        istate->cache_nr    = si->base->cache_nr;
        istate->cache       = NULL;
        istate->cache_alloc = 0;
        ALLOC_GROW(istate->cache, istate->cache_nr, istate->cache_alloc);
        memcpy(istate->cache, si->base->cache,
               sizeof(*istate->cache) * istate->cache_nr);

        si->nr_deletions = 0;
        si->nr_replacements = 0;
        ewah_each_bit(si->replace_bitmap, replace_entry, istate);
        ewah_each_bit(si->delete_bitmap, mark_entry_for_delete, istate);
        if (si->nr_deletions)
                remove_marked_cache_entries(istate);

        for (i = si->nr_replacements; i < si->saved_cache_nr; i++) {
                if (!ce_namelen(si->saved_cache[i]))
                        die("corrupt link extension, entry %d should "
                            "have non-zero length name", i);
                add_index_entry(istate, si->saved_cache[i],
                                ADD_CACHE_OK_TO_ADD |
                                ADD_CACHE_KEEP_CACHE_TREE |
                                /*
                                 * we may have to replay what
                                 * merge-recursive.c:update_stages()
                                 * does, which has this flag on
                                 */
                                ADD_CACHE_SKIP_DFCHECK);
                si->saved_cache[i] = NULL;
        }

        ewah_free(si->delete_bitmap);
        ewah_free(si->replace_bitmap);
        free(si->saved_cache);
        si->delete_bitmap  = NULL;
        si->replace_bitmap = NULL;
        si->saved_cache    = NULL;
        si->saved_cache_nr = 0;
}

void prepare_to_write_split_index(struct index_state *istate)
{
        struct split_index *si = init_split_index(istate);
        struct cache_entry **entries = NULL, *ce;
        int i, nr_entries = 0, nr_alloc = 0;

        si->delete_bitmap = ewah_new();
        si->replace_bitmap = ewah_new();

        if (si->base) {
                /* Go through istate->cache[] and mark CE_MATCHED to
                 * entry with positive index. We'll go through
                 * base->cache[] later to delete all entries in base
                 * that are not marked eith either CE_MATCHED or
                 * CE_UPDATE_IN_BASE. If istate->cache[i] is a
                 * duplicate, deduplicate it.
                 */
                for (i = 0; i < istate->cache_nr; i++) {
                        struct cache_entry *base;
                        /* namelen is checked separately */
                        const unsigned int ondisk_flags =
                                CE_STAGEMASK | CE_VALID | CE_EXTENDED_FLAGS;
                        unsigned int ce_flags, base_flags, ret;
                        ce = istate->cache[i];
                        if (!ce->index)
                                continue;
                        if (ce->index > si->base->cache_nr) {
                                ce->index = 0;
                                continue;
                        }
                        ce->ce_flags |= CE_MATCHED; /* or "shared" */
                        base = si->base->cache[ce->index - 1];
                        if (ce == base)
                                continue;
                        if (ce->ce_namelen != base->ce_namelen ||
                            strcmp(ce->name, base->name)) {
                                ce->index = 0;
                                continue;
                        }
                        ce_flags = ce->ce_flags;
                        base_flags = base->ce_flags;
                        /* only on-disk flags matter */
                        ce->ce_flags   &= ondisk_flags;
                        base->ce_flags &= ondisk_flags;
                        ret = memcmp(&ce->ce_stat_data, &base->ce_stat_data,
                                     offsetof(struct cache_entry, name) -
                                     offsetof(struct cache_entry, ce_stat_data));
                        ce->ce_flags = ce_flags;
                        base->ce_flags = base_flags;
                        if (ret)
                                ce->ce_flags |= CE_UPDATE_IN_BASE;
                        free(base);
                        si->base->cache[ce->index - 1] = ce;
                }
                for (i = 0; i < si->base->cache_nr; i++) {
                        ce = si->base->cache[i];
                        if ((ce->ce_flags & CE_REMOVE) ||
                            !(ce->ce_flags & CE_MATCHED))
                                ewah_set(si->delete_bitmap, i);
                        else if (ce->ce_flags & CE_UPDATE_IN_BASE) {
                                ewah_set(si->replace_bitmap, i);
                                ce->ce_flags |= CE_STRIP_NAME;
                                ALLOC_GROW(entries, nr_entries+1, nr_alloc);
                                entries[nr_entries++] = ce;
                        }
                }
        }

        for (i = 0; i < istate->cache_nr; i++) {
                ce = istate->cache[i];
                if ((!si->base || !ce->index) && !(ce->ce_flags & CE_REMOVE)) {
                        assert(!(ce->ce_flags & CE_STRIP_NAME));
                        ALLOC_GROW(entries, nr_entries+1, nr_alloc);
                        entries[nr_entries++] = ce;
                }
                ce->ce_flags &= ~CE_MATCHED;
        }

        /*
         * take cache[] out temporarily, put entries[] in its place
         * for writing
         */
        si->saved_cache = istate->cache;
        si->saved_cache_nr = istate->cache_nr;
        istate->cache = entries;
        istate->cache_nr = nr_entries;
}

void finish_writing_split_index(struct index_state *istate)
{
        struct split_index *si = init_split_index(istate);

        ewah_free(si->delete_bitmap);
        ewah_free(si->replace_bitmap);
        si->delete_bitmap = NULL;
        si->replace_bitmap = NULL;
        free(istate->cache);
        istate->cache = si->saved_cache;
        istate->cache_nr = si->saved_cache_nr;
}

void discard_split_index(struct index_state *istate)
{
        struct split_index *si = istate->split_index;
        if (!si)
                return;
        istate->split_index = NULL;
        si->refcount--;
        if (si->refcount)
                return;
        if (si->base) {
                discard_index(si->base);
                free(si->base);
        }
        free(si);
}

void save_or_free_index_entry(struct index_state *istate, struct cache_entry *ce)
{
        if (ce->index &&
            istate->split_index &&
            istate->split_index->base &&
            ce->index <= istate->split_index->base->cache_nr &&
            ce == istate->split_index->base->cache[ce->index - 1])
                ce->ce_flags |= CE_REMOVE;
        else
                free(ce);
}

void replace_index_entry_in_base(struct index_state *istate,
                                 struct cache_entry *old,
                                 struct cache_entry *new)
{
        if (old->index &&
            istate->split_index &&
            istate->split_index->base &&
            old->index <= istate->split_index->base->cache_nr) {
                new->index = old->index;
                if (old != istate->split_index->base->cache[new->index - 1])
                        free(istate->split_index->base->cache[new->index - 1]);
                istate->split_index->base->cache[new->index - 1] = new;
        }
}