doc: fix the max number of branches shown by "show-branch"

[alt-git.git] / delta-islands.c

#include "cache.h"
#include "attr.h"
#include "object.h"
#include "blob.h"
#include "commit.h"
#include "tag.h"
#include "tree.h"
#include "delta.h"
#include "pack.h"
#include "tree-walk.h"
#include "diff.h"
#include "revision.h"
#include "list-objects.h"
#include "progress.h"
#include "refs.h"
#include "khash.h"
#include "pack-bitmap.h"
#include "pack-objects.h"
#include "delta-islands.h"
#include "oid-array.h"
#include "config.h"

KHASH_INIT(str, const char *, void *, 1, kh_str_hash_func, kh_str_hash_equal)

static kh_oid_map_t *island_marks;
static unsigned island_counter;
static unsigned island_counter_core;

struct remote_island {
        uint64_t hash;
        struct oid_array oids;
};

struct island_bitmap {
        uint32_t refcount;
        uint32_t bits[FLEX_ARRAY];
};

static uint32_t island_bitmap_size;

/*
 * Allocate a new bitmap; if "old" is not NULL, the new bitmap will be a copy
 * of "old". Otherwise, the new bitmap is empty.
 */
static struct island_bitmap *island_bitmap_new(const struct island_bitmap *old)
{
        size_t size = sizeof(struct island_bitmap) + (island_bitmap_size * 4);
        struct island_bitmap *b = xcalloc(1, size);

        if (old)
                memcpy(b, old, size);

        b->refcount = 1;
        return b;
}

static void island_bitmap_or(struct island_bitmap *a, const struct island_bitmap *b)
{
        uint32_t i;

        for (i = 0; i < island_bitmap_size; ++i)
                a->bits[i] |= b->bits[i];
}

static int island_bitmap_is_subset(struct island_bitmap *self,
                struct island_bitmap *super)
{
        uint32_t i;

        if (self == super)
                return 1;

        for (i = 0; i < island_bitmap_size; ++i) {
                if ((self->bits[i] & super->bits[i]) != self->bits[i])
                        return 0;
        }

        return 1;
}

#define ISLAND_BITMAP_BLOCK(x) (x / 32)
#define ISLAND_BITMAP_MASK(x) (1 << (x % 32))

static void island_bitmap_set(struct island_bitmap *self, uint32_t i)
{
        self->bits[ISLAND_BITMAP_BLOCK(i)] |= ISLAND_BITMAP_MASK(i);
}

static int island_bitmap_get(struct island_bitmap *self, uint32_t i)
{
        return (self->bits[ISLAND_BITMAP_BLOCK(i)] & ISLAND_BITMAP_MASK(i)) != 0;
}

int in_same_island(const struct object_id *trg_oid, const struct object_id *src_oid)
{
        khiter_t trg_pos, src_pos;

        /* If we aren't using islands, assume everything goes together. */
        if (!island_marks)
                return 1;

        /*
         * If we don't have a bitmap for the target, we can delta it
         * against anything -- it's not an important object
         */
        trg_pos = kh_get_oid_map(island_marks, *trg_oid);
        if (trg_pos >= kh_end(island_marks))
                return 1;

        /*
         * if the source (our delta base) doesn't have a bitmap,
         * we don't want to base any deltas on it!
         */
        src_pos = kh_get_oid_map(island_marks, *src_oid);
        if (src_pos >= kh_end(island_marks))
                return 0;

        return island_bitmap_is_subset(kh_value(island_marks, trg_pos),
                                kh_value(island_marks, src_pos));
}

int island_delta_cmp(const struct object_id *a, const struct object_id *b)
{
        khiter_t a_pos, b_pos;
        struct island_bitmap *a_bitmap = NULL, *b_bitmap = NULL;

        if (!island_marks)
                return 0;

        a_pos = kh_get_oid_map(island_marks, *a);
        if (a_pos < kh_end(island_marks))
                a_bitmap = kh_value(island_marks, a_pos);

        b_pos = kh_get_oid_map(island_marks, *b);
        if (b_pos < kh_end(island_marks))
                b_bitmap = kh_value(island_marks, b_pos);

        if (a_bitmap) {
                if (!b_bitmap || !island_bitmap_is_subset(a_bitmap, b_bitmap))
                        return -1;
        }
        if (b_bitmap) {
                if (!a_bitmap || !island_bitmap_is_subset(b_bitmap, a_bitmap))
                        return 1;
        }

        return 0;
}

static struct island_bitmap *create_or_get_island_marks(struct object *obj)
{
        khiter_t pos;
        int hash_ret;

        pos = kh_put_oid_map(island_marks, obj->oid, &hash_ret);
        if (hash_ret)
                kh_value(island_marks, pos) = island_bitmap_new(NULL);

        return kh_value(island_marks, pos);
}

static void set_island_marks(struct object *obj, struct island_bitmap *marks)
{
        struct island_bitmap *b;
        khiter_t pos;
        int hash_ret;

        pos = kh_put_oid_map(island_marks, obj->oid, &hash_ret);
        if (hash_ret) {
                /*
                 * We don't have one yet; make a copy-on-write of the
                 * parent.
                 */
                marks->refcount++;
                kh_value(island_marks, pos) = marks;
                return;
        }

        /*
         * We do have it. Make sure we split any copy-on-write before
         * updating.
         */
        b = kh_value(island_marks, pos);
        if (b->refcount > 1) {
                b->refcount--;
                b = kh_value(island_marks, pos) = island_bitmap_new(b);
        }
        island_bitmap_or(b, marks);
}

static void mark_remote_island_1(struct repository *r,
                                 struct remote_island *rl,
                                 int is_core_island)
{
        uint32_t i;

        for (i = 0; i < rl->oids.nr; ++i) {
                struct island_bitmap *marks;
                struct object *obj = parse_object(r, &rl->oids.oid[i]);

                if (!obj)
                        continue;

                marks = create_or_get_island_marks(obj);
                island_bitmap_set(marks, island_counter);

                if (is_core_island && obj->type == OBJ_COMMIT)
                        obj->flags |= NEEDS_BITMAP;

                /* If it was a tag, also make sure we hit the underlying object. */
                while (obj && obj->type == OBJ_TAG) {
                        obj = ((struct tag *)obj)->tagged;
                        if (obj) {
                                parse_object(r, &obj->oid);
                                marks = create_or_get_island_marks(obj);
                                island_bitmap_set(marks, island_counter);
                        }
                }
        }

        if (is_core_island)
                island_counter_core = island_counter;

        island_counter++;
}

struct tree_islands_todo {
        struct object_entry *entry;
        unsigned int depth;
};

static int tree_depth_compare(const void *a, const void *b)
{
        const struct tree_islands_todo *todo_a = a;
        const struct tree_islands_todo *todo_b = b;

        return todo_a->depth - todo_b->depth;
}

void resolve_tree_islands(struct repository *r,
                          int progress,
                          struct packing_data *to_pack)
{
        struct progress *progress_state = NULL;
        struct tree_islands_todo *todo;
        int nr = 0;
        int i;

        if (!island_marks)
                return;

        /*
         * We process only trees, as commits and tags have already been handled
         * (and passed their marks on to root trees, as well. We must make sure
         * to process them in descending tree-depth order so that marks
         * propagate down the tree properly, even if a sub-tree is found in
         * multiple parent trees.
         */
        ALLOC_ARRAY(todo, to_pack->nr_objects);
        for (i = 0; i < to_pack->nr_objects; i++) {
                if (oe_type(&to_pack->objects[i]) == OBJ_TREE) {
                        todo[nr].entry = &to_pack->objects[i];
                        todo[nr].depth = oe_tree_depth(to_pack, &to_pack->objects[i]);
                        nr++;
                }
        }
        QSORT(todo, nr, tree_depth_compare);

        if (progress)
                progress_state = start_progress(_("Propagating island marks"), nr);

        for (i = 0; i < nr; i++) {
                struct object_entry *ent = todo[i].entry;
                struct island_bitmap *root_marks;
                struct tree *tree;
                struct tree_desc desc;
                struct name_entry entry;
                khiter_t pos;

                pos = kh_get_oid_map(island_marks, ent->idx.oid);
                if (pos >= kh_end(island_marks))
                        continue;

                root_marks = kh_value(island_marks, pos);

                tree = lookup_tree(r, &ent->idx.oid);
                if (!tree || parse_tree(tree) < 0)
                        die(_("bad tree object %s"), oid_to_hex(&ent->idx.oid));

                init_tree_desc(&desc, tree->buffer, tree->size);
                while (tree_entry(&desc, &entry)) {
                        struct object *obj;

                        if (S_ISGITLINK(entry.mode))
                                continue;

                        obj = lookup_object(r, &entry.oid);
                        if (!obj)
                                continue;

                        set_island_marks(obj, root_marks);
                }

                free_tree_buffer(tree);

                display_progress(progress_state, i+1);
        }

        stop_progress(&progress_state);
        free(todo);
}

struct island_load_data {
        kh_str_t *remote_islands;
        regex_t *rx;
        size_t nr;
        size_t alloc;
};
static const char *core_island_name;

static void free_config_regexes(struct island_load_data *ild)
{
        for (size_t i = 0; i < ild->nr; i++)
                regfree(&ild->rx[i]);
        free(ild->rx);
}

static void free_remote_islands(kh_str_t *remote_islands)
{
        const char *island_name;
        struct remote_island *rl;

        kh_foreach(remote_islands, island_name, rl, {
                free((void *)island_name);
                oid_array_clear(&rl->oids);
                free(rl);
        });
        kh_destroy_str(remote_islands);
}

static int island_config_callback(const char *k, const char *v, void *cb)
{
        struct island_load_data *ild = cb;

        if (!strcmp(k, "pack.island")) {
                struct strbuf re = STRBUF_INIT;

                if (!v)
                        return config_error_nonbool(k);

                ALLOC_GROW(ild->rx, ild->nr + 1, ild->alloc);

                if (*v != '^')
                        strbuf_addch(&re, '^');
                strbuf_addstr(&re, v);

                if (regcomp(&ild->rx[ild->nr], re.buf, REG_EXTENDED))
                        die(_("failed to load island regex for '%s': %s"), k, re.buf);

                strbuf_release(&re);
                ild->nr++;
                return 0;
        }

        if (!strcmp(k, "pack.islandcore"))
                return git_config_string(&core_island_name, k, v);

        return 0;
}

static void add_ref_to_island(kh_str_t *remote_islands, const char *island_name,
                                const struct object_id *oid)
{
        uint64_t sha_core;
        struct remote_island *rl = NULL;

        int hash_ret;
        khiter_t pos = kh_put_str(remote_islands, island_name, &hash_ret);

        if (hash_ret) {
                kh_key(remote_islands, pos) = xstrdup(island_name);
                kh_value(remote_islands, pos) = xcalloc(1, sizeof(struct remote_island));
        }

        rl = kh_value(remote_islands, pos);
        oid_array_append(&rl->oids, oid);

        memcpy(&sha_core, oid->hash, sizeof(uint64_t));
        rl->hash += sha_core;
}

static int find_island_for_ref(const char *refname, const struct object_id *oid,
                               int flags UNUSED, void *cb)
{
        struct island_load_data *ild = cb;

        /*
         * We should advertise 'ARRAY_SIZE(matches) - 2' as the max,
         * so we can diagnose below a config with more capture groups
         * than we support.
         */
        regmatch_t matches[16];
        int i, m;
        struct strbuf island_name = STRBUF_INIT;

        /* walk backwards to get last-one-wins ordering */
        for (i = ild->nr - 1; i >= 0; i--) {
                if (!regexec(&ild->rx[i], refname,
                             ARRAY_SIZE(matches), matches, 0))
                        break;
        }

        if (i < 0)
                return 0;

        if (matches[ARRAY_SIZE(matches) - 1].rm_so != -1)
                warning(_("island regex from config has "
                          "too many capture groups (max=%d)"),
                        (int)ARRAY_SIZE(matches) - 2);

        for (m = 1; m < ARRAY_SIZE(matches); m++) {
                regmatch_t *match = &matches[m];

                if (match->rm_so == -1)
                        continue;

                if (island_name.len)
                        strbuf_addch(&island_name, '-');

                strbuf_add(&island_name, refname + match->rm_so, match->rm_eo - match->rm_so);
        }

        add_ref_to_island(ild->remote_islands, island_name.buf, oid);
        strbuf_release(&island_name);
        return 0;
}

static struct remote_island *get_core_island(kh_str_t *remote_islands)
{
        if (core_island_name) {
                khiter_t pos = kh_get_str(remote_islands, core_island_name);
                if (pos < kh_end(remote_islands))
                        return kh_value(remote_islands, pos);
        }

        return NULL;
}

static void deduplicate_islands(kh_str_t *remote_islands, struct repository *r)
{
        struct remote_island *island, *core = NULL, **list;
        unsigned int island_count, dst, src, ref, i = 0;

        island_count = kh_size(remote_islands);
        ALLOC_ARRAY(list, island_count);

        kh_foreach_value(remote_islands, island, {
                list[i++] = island;
        });

        for (ref = 0; ref + 1 < island_count; ref++) {
                for (src = ref + 1, dst = src; src < island_count; src++) {
                        if (list[ref]->hash == list[src]->hash)
                                continue;

                        if (src != dst)
                                list[dst] = list[src];

                        dst++;
                }
                island_count = dst;
        }

        island_bitmap_size = (island_count / 32) + 1;
        core = get_core_island(remote_islands);

        for (i = 0; i < island_count; ++i) {
                mark_remote_island_1(r, list[i], core && list[i]->hash == core->hash);
        }

        free(list);
}

void load_delta_islands(struct repository *r, int progress)
{
        struct island_load_data ild = { 0 };

        island_marks = kh_init_oid_map();

        git_config(island_config_callback, &ild);
        ild.remote_islands = kh_init_str();
        for_each_ref(find_island_for_ref, &ild);
        free_config_regexes(&ild);
        deduplicate_islands(ild.remote_islands, r);
        free_remote_islands(ild.remote_islands);

        if (progress)
                fprintf(stderr, _("Marked %d islands, done.\n"), island_counter);
}

void propagate_island_marks(struct commit *commit)
{
        khiter_t pos = kh_get_oid_map(island_marks, commit->object.oid);

        if (pos < kh_end(island_marks)) {
                struct commit_list *p;
                struct island_bitmap *root_marks = kh_value(island_marks, pos);

                parse_commit(commit);
                set_island_marks(&get_commit_tree(commit)->object, root_marks);
                for (p = commit->parents; p; p = p->next)
                        set_island_marks(&p->item->object, root_marks);
        }
}

void free_island_marks(void)
{
        struct island_bitmap *bitmap;

        if (island_marks) {
                kh_foreach_value(island_marks, bitmap, {
                        if (!--bitmap->refcount)
                                free(bitmap);
                });
                kh_destroy_oid_map(island_marks);
        }

        /* detect use-after-free with a an address which is never valid: */
        island_marks = (void *)-1;
}

int compute_pack_layers(struct packing_data *to_pack)
{
        uint32_t i;

        if (!core_island_name || !island_marks)
                return 1;

        for (i = 0; i < to_pack->nr_objects; ++i) {
                struct object_entry *entry = &to_pack->objects[i];
                khiter_t pos = kh_get_oid_map(island_marks, entry->idx.oid);

                oe_set_layer(to_pack, entry, 1);

                if (pos < kh_end(island_marks)) {
                        struct island_bitmap *bitmap = kh_value(island_marks, pos);

                        if (island_bitmap_get(bitmap, island_counter_core))
                                oe_set_layer(to_pack, entry, 0);
                }
        }

        return 2;
}