/src/git/pack-bitmap.c

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#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "commit.h"
#include "gettext.h"
#include "hex.h"
#include "strbuf.h"
#include "tag.h"
#include "diff.h"
#include "revision.h"
#include "progress.h"
#include "list-objects.h"
#include "pack.h"
#include "pack-bitmap.h"
#include "pack-revindex.h"
#include "pack-objects.h"
#include "packfile.h"
#include "repository.h"
#include "trace2.h"
#include "object-file.h"
#include "object-store-ll.h"
#include "list-objects-filter-options.h"
#include "midx.h"
#include "config.h"
#include "pseudo-merge.h"

/*
 * An entry on the bitmap index, representing the bitmap for a given
 * commit.
 */
struct stored_bitmap {
  struct object_id oid;
  struct ewah_bitmap *root;
  struct stored_bitmap *xor;
  int flags;
};

/*
 * The active bitmap index for a repository. By design, repositories only have
 * a single bitmap index available (the index for the biggest packfile in
 * the repository), since bitmap indexes need full closure.
 *
 * If there is more than one bitmap index available (e.g. because of alternates),
 * the active bitmap index is the largest one.
 */
struct bitmap_index {
  /*
   * The pack or multi-pack index (MIDX) that this bitmap index belongs
   * to.
   *
   * Exactly one of these must be non-NULL; this specifies the object
   * order used to interpret this bitmap.
   */
  struct packed_git *pack;
  struct multi_pack_index *midx;

  /* mmapped buffer of the whole bitmap index */
  unsigned char *map;
  size_t map_size; /* size of the mmaped buffer */
  size_t map_pos; /* current position when loading the index */

  /*
   * Type indexes.
   *
   * Each bitmap marks which objects in the packfile  are of the given
   * type. This provides type information when yielding the objects from
   * the packfile during a walk, which allows for better delta bases.
   */
  struct ewah_bitmap *commits;
  struct ewah_bitmap *trees;
  struct ewah_bitmap *blobs;
  struct ewah_bitmap *tags;

  /* Map from object ID -> `stored_bitmap` for all the bitmapped commits */
  kh_oid_map_t *bitmaps;

  /* Number of bitmapped commits */
  uint32_t entry_count;

  /* If not NULL, this is a name-hash cache pointing into map. */
  uint32_t *hashes;

  /* The checksum of the packfile or MIDX; points into map. */
  const unsigned char *checksum;

  /*
   * If not NULL, this point into the commit table extension
   * (within the memory mapped region `map`).
   */
  unsigned char *table_lookup;

  /* This contains the pseudo-merge cache within 'map' (if found). */
  struct pseudo_merge_map pseudo_merges;

  /*
   * Extended index.
   *
   * When trying to perform bitmap operations with objects that are not
   * packed in `pack`, these objects are added to this "fake index" and
   * are assumed to appear at the end of the packfile for all operations
   */
  struct eindex {
    struct object **objects;
    uint32_t *hashes;
    uint32_t count, alloc;
    kh_oid_pos_t *positions;
  } ext_index;

  /* Bitmap result of the last performed walk */
  struct bitmap *result;

  /* "have" bitmap from the last performed walk */
  struct bitmap *haves;

  /* Version of the bitmap index */
  unsigned int version;
};

static int pseudo_merges_satisfied_nr;
static int pseudo_merges_cascades_nr;
static int existing_bitmaps_hits_nr;
static int existing_bitmaps_misses_nr;
static int roots_with_bitmaps_nr;
static int roots_without_bitmaps_nr;

static struct ewah_bitmap *lookup_stored_bitmap(struct stored_bitmap *st)
{
  struct ewah_bitmap *parent;
  struct ewah_bitmap *composed;

  if (!st->xor)
    return st->root;

  composed = ewah_pool_new();
  parent = lookup_stored_bitmap(st->xor);
  ewah_xor(st->root, parent, composed);

  ewah_pool_free(st->root);
  st->root = composed;
  st->xor = NULL;

  return composed;
}

struct ewah_bitmap *read_bitmap(const unsigned char *map,
        size_t map_size, size_t *map_pos)
{
  struct ewah_bitmap *b = ewah_pool_new();

  ssize_t bitmap_size = ewah_read_mmap(b, map + *map_pos,
               map_size - *map_pos);

  if (bitmap_size < 0) {
    error(_("failed to load bitmap index (corrupted?)"));
    ewah_pool_free(b);
    return NULL;
  }

  *map_pos += bitmap_size;

  return b;
}

/*
 * Read a bitmap from the current read position on the mmaped
 * index, and increase the read position accordingly
 */
static struct ewah_bitmap *read_bitmap_1(struct bitmap_index *index)
{
  return read_bitmap(index->map, index->map_size, &index->map_pos);
}

static uint32_t bitmap_num_objects(struct bitmap_index *index)
{
  if (index->midx)
    return index->midx->num_objects;
  return index->pack->num_objects;
}

static int load_bitmap_header(struct bitmap_index *index)
{
  struct bitmap_disk_header *header = (void *)index->map;
  size_t header_size = sizeof(*header) - GIT_MAX_RAWSZ + the_hash_algo->rawsz;

  if (index->map_size < header_size + the_hash_algo->rawsz)
    return error(_("corrupted bitmap index (too small)"));

  if (memcmp(header->magic, BITMAP_IDX_SIGNATURE, sizeof(BITMAP_IDX_SIGNATURE)) != 0)
    return error(_("corrupted bitmap index file (wrong header)"));

  index->version = ntohs(header->version);
  if (index->version != 1)
    return error(_("unsupported version '%d' for bitmap index file"), index->version);

  /* Parse known bitmap format options */
  {
    uint32_t flags = ntohs(header->options);
    size_t cache_size = st_mult(bitmap_num_objects(index), sizeof(uint32_t));
    unsigned char *index_end = index->map + index->map_size - the_hash_algo->rawsz;

    if ((flags & BITMAP_OPT_FULL_DAG) == 0)
      BUG("unsupported options for bitmap index file "
        "(Git requires BITMAP_OPT_FULL_DAG)");

    if (flags & BITMAP_OPT_HASH_CACHE) {
      if (cache_size > index_end - index->map - header_size)
        return error(_("corrupted bitmap index file (too short to fit hash cache)"));
      index->hashes = (void *)(index_end - cache_size);
      index_end -= cache_size;
    }

    if (flags & BITMAP_OPT_LOOKUP_TABLE) {
      size_t table_size = st_mult(ntohl(header->entry_count),
                BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH);
      if (table_size > index_end - index->map - header_size)
        return error(_("corrupted bitmap index file (too short to fit lookup table)"));
      if (git_env_bool("GIT_TEST_READ_COMMIT_TABLE", 1))
        index->table_lookup = (void *)(index_end - table_size);
      index_end -= table_size;
    }

    if (flags & BITMAP_OPT_PSEUDO_MERGES) {
      unsigned char *pseudo_merge_ofs;
      size_t table_size;
      uint32_t i;

      if (sizeof(table_size) > index_end - index->map - header_size)
        return error(_("corrupted bitmap index file (too short to fit pseudo-merge table header)"));

      table_size = get_be64(index_end - 8);
      if (table_size > index_end - index->map - header_size)
        return error(_("corrupted bitmap index file (too short to fit pseudo-merge table)"));

      if (git_env_bool("GIT_TEST_USE_PSEUDO_MERGES", 1)) {
        const unsigned char *ext = (index_end - table_size);

        index->pseudo_merges.map = index->map;
        index->pseudo_merges.map_size = index->map_size;
        index->pseudo_merges.commits = ext + get_be64(index_end - 16);
        index->pseudo_merges.commits_nr = get_be32(index_end - 20);
        index->pseudo_merges.nr = get_be32(index_end - 24);

        if (st_add(st_mult(index->pseudo_merges.nr,
               sizeof(uint64_t)),
             24) > table_size)
          return error(_("corrupted bitmap index file, pseudo-merge table too short"));

        CALLOC_ARRAY(index->pseudo_merges.v,
               index->pseudo_merges.nr);

        pseudo_merge_ofs = index_end - 24 -
          (index->pseudo_merges.nr * sizeof(uint64_t));
        for (i = 0; i < index->pseudo_merges.nr; i++) {
          index->pseudo_merges.v[i].at = get_be64(pseudo_merge_ofs);
          pseudo_merge_ofs += sizeof(uint64_t);
        }
      }

      index_end -= table_size;
    }
  }

  index->entry_count = ntohl(header->entry_count);
  index->checksum = header->checksum;
  index->map_pos += header_size;
  return 0;
}

static struct stored_bitmap *store_bitmap(struct bitmap_index *index,
            struct ewah_bitmap *root,
            const struct object_id *oid,
            struct stored_bitmap *xor_with,
            int flags)
{
  struct stored_bitmap *stored;
  khiter_t hash_pos;
  int ret;

  stored = xmalloc(sizeof(struct stored_bitmap));
  stored->root = root;
  stored->xor = xor_with;
  stored->flags = flags;
  oidcpy(&stored->oid, oid);

  hash_pos = kh_put_oid_map(index->bitmaps, stored->oid, &ret);

  /*
   * A 0 return code means the insertion succeeded with no changes,
   * because the SHA1 already existed on the map. This is bad, there
   * shouldn't be duplicated commits in the index.
   */
  if (ret == 0) {
    error(_("duplicate entry in bitmap index: '%s'"), oid_to_hex(oid));
    return NULL;
  }

  kh_value(index->bitmaps, hash_pos) = stored;
  return stored;
}

static inline uint32_t read_be32(const unsigned char *buffer, size_t *pos)
{
  uint32_t result = get_be32(buffer + *pos);
  (*pos) += sizeof(result);
  return result;
}

static inline uint8_t read_u8(const unsigned char *buffer, size_t *pos)
{
  return buffer[(*pos)++];
}

#define MAX_XOR_OFFSET 160

static int nth_bitmap_object_oid(struct bitmap_index *index,
         struct object_id *oid,
         uint32_t n)
{
  if (index->midx)
    return nth_midxed_object_oid(oid, index->midx, n) ? 0 : -1;
  return nth_packed_object_id(oid, index->pack, n);
}

static int load_bitmap_entries_v1(struct bitmap_index *index)
{
  uint32_t i;
  struct stored_bitmap *recent_bitmaps[MAX_XOR_OFFSET] = { NULL };

  for (i = 0; i < index->entry_count; ++i) {
    int xor_offset, flags;
    struct ewah_bitmap *bitmap = NULL;
    struct stored_bitmap *xor_bitmap = NULL;
    uint32_t commit_idx_pos;
    struct object_id oid;

    if (index->map_size - index->map_pos < 6)
      return error(_("corrupt ewah bitmap: truncated header for entry %d"), i);

    commit_idx_pos = read_be32(index->map, &index->map_pos);
    xor_offset = read_u8(index->map, &index->map_pos);
    flags = read_u8(index->map, &index->map_pos);

    if (nth_bitmap_object_oid(index, &oid, commit_idx_pos) < 0)
      return error(_("corrupt ewah bitmap: commit index %u out of range"),
             (unsigned)commit_idx_pos);

    bitmap = read_bitmap_1(index);
    if (!bitmap)
      return -1;

    if (xor_offset > MAX_XOR_OFFSET || xor_offset > i)
      return error(_("corrupted bitmap pack index"));

    if (xor_offset > 0) {
      xor_bitmap = recent_bitmaps[(i - xor_offset) % MAX_XOR_OFFSET];

      if (!xor_bitmap)
        return error(_("invalid XOR offset in bitmap pack index"));
    }

    recent_bitmaps[i % MAX_XOR_OFFSET] = store_bitmap(
      index, bitmap, &oid, xor_bitmap, flags);
  }

  return 0;
}

char *midx_bitmap_filename(struct multi_pack_index *midx)
{
  struct strbuf buf = STRBUF_INIT;
  get_midx_filename_ext(&buf, midx->object_dir, get_midx_checksum(midx),
            MIDX_EXT_BITMAP);

  return strbuf_detach(&buf, NULL);
}

char *pack_bitmap_filename(struct packed_git *p)
{
  size_t len;

  if (!strip_suffix(p->pack_name, ".pack", &len))
    BUG("pack_name does not end in .pack");
  return xstrfmt("%.*s.bitmap", (int)len, p->pack_name);
}

static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
            struct multi_pack_index *midx)
{
  struct stat st;
  char *bitmap_name = midx_bitmap_filename(midx);
  int fd = git_open(bitmap_name);
  uint32_t i, preferred_pack;
  struct packed_git *preferred;

  if (fd < 0) {
    if (errno != ENOENT)
      warning_errno("cannot open '%s'", bitmap_name);
    free(bitmap_name);
    return -1;
  }
  free(bitmap_name);

  if (fstat(fd, &st)) {
    error_errno(_("cannot fstat bitmap file"));
    close(fd);
    return -1;
  }

  if (bitmap_git->pack || bitmap_git->midx) {
    struct strbuf buf = STRBUF_INIT;
    get_midx_filename(&buf, midx->object_dir);
    trace2_data_string("bitmap", the_repository,
           "ignoring extra midx bitmap file", buf.buf);
    close(fd);
    strbuf_release(&buf);
    return -1;
  }

  bitmap_git->midx = midx;
  bitmap_git->map_size = xsize_t(st.st_size);
  bitmap_git->map_pos = 0;
  bitmap_git->map = xmmap(NULL, bitmap_git->map_size, PROT_READ,
        MAP_PRIVATE, fd, 0);
  close(fd);

  if (load_bitmap_header(bitmap_git) < 0)
    goto cleanup;

  if (!hasheq(get_midx_checksum(bitmap_git->midx), bitmap_git->checksum,
        the_repository->hash_algo)) {
    error(_("checksum doesn't match in MIDX and bitmap"));
    goto cleanup;
  }

  if (load_midx_revindex(bitmap_git->midx)) {
    warning(_("multi-pack bitmap is missing required reverse index"));
    goto cleanup;
  }

  for (i = 0; i < bitmap_git->midx->num_packs; i++) {
    if (prepare_midx_pack(the_repository, bitmap_git->midx, i)) {
      warning(_("could not open pack %s"),
        bitmap_git->midx->pack_names[i]);
      goto cleanup;
    }
  }

  if (midx_preferred_pack(bitmap_git->midx, &preferred_pack) < 0) {
    warning(_("could not determine MIDX preferred pack"));
    goto cleanup;
  }

  preferred = bitmap_git->midx->packs[preferred_pack];
  if (!is_pack_valid(preferred)) {
    warning(_("preferred pack (%s) is invalid"),
      preferred->pack_name);
    goto cleanup;
  }

  return 0;

cleanup:
  munmap(bitmap_git->map, bitmap_git->map_size);
  bitmap_git->map_size = 0;
  bitmap_git->map_pos = 0;
  bitmap_git->map = NULL;
  bitmap_git->midx = NULL;
  return -1;
}

static int open_pack_bitmap_1(struct bitmap_index *bitmap_git, struct packed_git *packfile)
{
  int fd;
  struct stat st;
  char *bitmap_name;

  bitmap_name = pack_bitmap_filename(packfile);
  fd = git_open(bitmap_name);

  if (fd < 0) {
    if (errno != ENOENT)
      warning_errno("cannot open '%s'", bitmap_name);
    free(bitmap_name);
    return -1;
  }
  free(bitmap_name);

  if (fstat(fd, &st)) {
    error_errno(_("cannot fstat bitmap file"));
    close(fd);
    return -1;
  }

  if (bitmap_git->pack || bitmap_git->midx) {
    trace2_data_string("bitmap", the_repository,
           "ignoring extra bitmap file", packfile->pack_name);
    close(fd);
    return -1;
  }

  if (!is_pack_valid(packfile)) {
    close(fd);
    return -1;
  }

  bitmap_git->pack = packfile;
  bitmap_git->map_size = xsize_t(st.st_size);
  bitmap_git->map = xmmap(NULL, bitmap_git->map_size, PROT_READ, MAP_PRIVATE, fd, 0);
  bitmap_git->map_pos = 0;
  close(fd);

  if (load_bitmap_header(bitmap_git) < 0) {
    munmap(bitmap_git->map, bitmap_git->map_size);
    bitmap_git->map = NULL;
    bitmap_git->map_size = 0;
    bitmap_git->map_pos = 0;
    bitmap_git->pack = NULL;
    return -1;
  }

  trace2_data_string("bitmap", the_repository, "opened bitmap file",
         packfile->pack_name);
  return 0;
}

static int load_reverse_index(struct repository *r, struct bitmap_index *bitmap_git)
{
  if (bitmap_is_midx(bitmap_git)) {
    uint32_t i;
    int ret;

    /*
     * The multi-pack-index's .rev file is already loaded via
     * open_pack_bitmap_1().
     *
     * But we still need to open the individual pack .rev files,
     * since we will need to make use of them in pack-objects.
     */
    for (i = 0; i < bitmap_git->midx->num_packs; i++) {
      ret = load_pack_revindex(r, bitmap_git->midx->packs[i]);
      if (ret)
        return ret;
    }
    return 0;
  }
  return load_pack_revindex(r, bitmap_git->pack);
}

static int load_bitmap(struct repository *r, struct bitmap_index *bitmap_git)
{
  assert(bitmap_git->map);

  bitmap_git->bitmaps = kh_init_oid_map();
  bitmap_git->ext_index.positions = kh_init_oid_pos();

  if (load_reverse_index(r, bitmap_git))
    goto failed;

  if (!(bitmap_git->commits = read_bitmap_1(bitmap_git)) ||
    !(bitmap_git->trees = read_bitmap_1(bitmap_git)) ||
    !(bitmap_git->blobs = read_bitmap_1(bitmap_git)) ||
    !(bitmap_git->tags = read_bitmap_1(bitmap_git)))
    goto failed;

  if (!bitmap_git->table_lookup && load_bitmap_entries_v1(bitmap_git) < 0)
    goto failed;

  return 0;

failed:
  munmap(bitmap_git->map, bitmap_git->map_size);
  bitmap_git->map = NULL;
  bitmap_git->map_size = 0;

  kh_destroy_oid_map(bitmap_git->bitmaps);
  bitmap_git->bitmaps = NULL;

  kh_destroy_oid_pos(bitmap_git->ext_index.positions);
  bitmap_git->ext_index.positions = NULL;

  return -1;
}

static int open_pack_bitmap(struct repository *r,
          struct bitmap_index *bitmap_git)
{
  struct packed_git *p;
  int ret = -1;

  for (p = get_all_packs(r); p; p = p->next) {
    if (open_pack_bitmap_1(bitmap_git, p) == 0) {
      ret = 0;
      /*
       * The only reason to keep looking is to report
       * duplicates.
       */
      if (!trace2_is_enabled())
        break;
    }
  }

  return ret;
}

static int open_midx_bitmap(struct repository *r,
          struct bitmap_index *bitmap_git)
{
  int ret = -1;
  struct multi_pack_index *midx;

  assert(!bitmap_git->map);

  for (midx = get_multi_pack_index(r); midx; midx = midx->next) {
    if (!open_midx_bitmap_1(bitmap_git, midx))
      ret = 0;
  }
  return ret;
}

static int open_bitmap(struct repository *r,
           struct bitmap_index *bitmap_git)
{
  int found;

  assert(!bitmap_git->map);

  found = !open_midx_bitmap(r, bitmap_git);

  /*
   * these will all be skipped if we opened a midx bitmap; but run it
   * anyway if tracing is enabled to report the duplicates
   */
  if (!found || trace2_is_enabled())
    found |= !open_pack_bitmap(r, bitmap_git);

  return found ? 0 : -1;
}

struct bitmap_index *prepare_bitmap_git(struct repository *r)
{
  struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));

  if (!open_bitmap(r, bitmap_git) && !load_bitmap(r, bitmap_git))
    return bitmap_git;

  free_bitmap_index(bitmap_git);
  return NULL;
}

struct bitmap_index *prepare_midx_bitmap_git(struct multi_pack_index *midx)
{
  struct repository *r = the_repository;
  struct bitmap_index *bitmap_git = xcalloc(1, sizeof(*bitmap_git));

  if (!open_midx_bitmap_1(bitmap_git, midx) && !load_bitmap(r, bitmap_git))
    return bitmap_git;

  free_bitmap_index(bitmap_git);
  return NULL;
}

struct include_data {
  struct bitmap_index *bitmap_git;
  struct bitmap *base;
  struct bitmap *seen;
};

struct bitmap_lookup_table_triplet {
  uint32_t commit_pos;
  uint64_t offset;
  uint32_t xor_row;
};

struct bitmap_lookup_table_xor_item {
  struct object_id oid;
  uint64_t offset;
};

/*
 * Given a `triplet` struct pointer and pointer `p`, this
 * function reads the triplet beginning at `p` into the struct.
 * Note that this function assumes that there is enough memory
 * left for filling the `triplet` struct from `p`.
 */
static int bitmap_lookup_table_get_triplet_by_pointer(struct bitmap_lookup_table_triplet *triplet,
                  const unsigned char *p)
{
  if (!triplet)
    return -1;

  triplet->commit_pos = get_be32(p);
  p += sizeof(uint32_t);
  triplet->offset = get_be64(p);
  p += sizeof(uint64_t);
  triplet->xor_row = get_be32(p);
  return 0;
}

/*
 * This function gets the raw triplet from `row`'th row in the
 * lookup table and fills that data to the `triplet`.
 */
static int bitmap_lookup_table_get_triplet(struct bitmap_index *bitmap_git,
             uint32_t pos,
             struct bitmap_lookup_table_triplet *triplet)
{
  unsigned char *p = NULL;
  if (pos >= bitmap_git->entry_count)
    return error(_("corrupt bitmap lookup table: triplet position out of index"));

  p = bitmap_git->table_lookup + st_mult(pos, BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH);

  return bitmap_lookup_table_get_triplet_by_pointer(triplet, p);
}

/*
 * Searches for a matching triplet. `commit_pos` is a pointer
 * to the wanted commit position value. `table_entry` points to
 * a triplet in lookup table. The first 4 bytes of each
 * triplet (pointed by `table_entry`) are compared with `*commit_pos`.
 */
static int triplet_cmp(const void *commit_pos, const void *table_entry)
{

  uint32_t a = *(uint32_t *)commit_pos;
  uint32_t b = get_be32(table_entry);
  if (a > b)
    return 1;
  else if (a < b)
    return -1;

  return 0;
}

static uint32_t bitmap_bsearch_pos(struct bitmap_index *bitmap_git,
          struct object_id *oid,
          uint32_t *result)
{
  int found;

  if (bitmap_is_midx(bitmap_git))
    found = bsearch_midx(oid, bitmap_git->midx, result);
  else
    found = bsearch_pack(oid, bitmap_git->pack, result);

  return found;
}

/*
 * `bsearch_triplet_by_pos` function searches for the raw triplet
 * having commit position same as `commit_pos` and fills `triplet`
 * object from the raw triplet. Returns 1 on success and 0 on
 * failure.
 */
static int bitmap_bsearch_triplet_by_pos(uint32_t commit_pos,
          struct bitmap_index *bitmap_git,
          struct bitmap_lookup_table_triplet *triplet)
{
  unsigned char *p = bsearch(&commit_pos, bitmap_git->table_lookup, bitmap_git->entry_count,
           BITMAP_LOOKUP_TABLE_TRIPLET_WIDTH, triplet_cmp);

  if (!p)
    return -1;

  return bitmap_lookup_table_get_triplet_by_pointer(triplet, p);
}

static struct stored_bitmap *lazy_bitmap_for_commit(struct bitmap_index *bitmap_git,
                struct commit *commit)
{
  uint32_t commit_pos, xor_row;
  uint64_t offset;
  int flags;
  struct bitmap_lookup_table_triplet triplet;
  struct object_id *oid = &commit->object.oid;
  struct ewah_bitmap *bitmap;
  struct stored_bitmap *xor_bitmap = NULL;
  const int bitmap_header_size = 6;
  static struct bitmap_lookup_table_xor_item *xor_items = NULL;
  static size_t xor_items_nr = 0, xor_items_alloc = 0;
  static int is_corrupt = 0;
  int xor_flags;
  khiter_t hash_pos;
  struct bitmap_lookup_table_xor_item *xor_item;

  if (is_corrupt)
    return NULL;

  if (!bitmap_bsearch_pos(bitmap_git, oid, &commit_pos))
    return NULL;

  if (bitmap_bsearch_triplet_by_pos(commit_pos, bitmap_git, &triplet) < 0)
    return NULL;

  xor_items_nr = 0;
  offset = triplet.offset;
  xor_row = triplet.xor_row;

  while (xor_row != 0xffffffff) {
    ALLOC_GROW(xor_items, xor_items_nr + 1, xor_items_alloc);

    if (xor_items_nr + 1 >= bitmap_git->entry_count) {
      error(_("corrupt bitmap lookup table: xor chain exceeds entry count"));
      goto corrupt;
    }

    if (bitmap_lookup_table_get_triplet(bitmap_git, xor_row, &triplet) < 0)
      goto corrupt;

    xor_item = &xor_items[xor_items_nr];
    xor_item->offset = triplet.offset;

    if (nth_bitmap_object_oid(bitmap_git, &xor_item->oid, triplet.commit_pos) < 0) {
      error(_("corrupt bitmap lookup table: commit index %u out of range"),
        triplet.commit_pos);
      goto corrupt;
    }

    hash_pos = kh_get_oid_map(bitmap_git->bitmaps, xor_item->oid);

    /*
     * If desired bitmap is already stored, we don't need
     * to iterate further. Because we know that bitmaps
     * that are needed to be parsed to parse this bitmap
     * has already been stored. So, assign this stored bitmap
     * to the xor_bitmap.
     */
    if (hash_pos < kh_end(bitmap_git->bitmaps) &&
      (xor_bitmap = kh_value(bitmap_git->bitmaps, hash_pos)))
      break;
    xor_items_nr++;
    xor_row = triplet.xor_row;
  }

  while (xor_items_nr) {
    xor_item = &xor_items[xor_items_nr - 1];
    bitmap_git->map_pos = xor_item->offset;
    if (bitmap_git->map_size - bitmap_git->map_pos < bitmap_header_size) {
      error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""),
        oid_to_hex(&xor_item->oid));
      goto corrupt;
    }

    bitmap_git->map_pos += sizeof(uint32_t) + sizeof(uint8_t);
    xor_flags = read_u8(bitmap_git->map, &bitmap_git->map_pos);
    bitmap = read_bitmap_1(bitmap_git);

    if (!bitmap)
      goto corrupt;

    xor_bitmap = store_bitmap(bitmap_git, bitmap, &xor_item->oid, xor_bitmap, xor_flags);
    xor_items_nr--;
  }

  bitmap_git->map_pos = offset;
  if (bitmap_git->map_size - bitmap_git->map_pos < bitmap_header_size) {
    error(_("corrupt ewah bitmap: truncated header for bitmap of commit \"%s\""),
      oid_to_hex(oid));
    goto corrupt;
  }

  /*
   * Don't bother reading the commit's index position or its xor
   * offset:
   *
   *   - The commit's index position is irrelevant to us, since
   *     load_bitmap_entries_v1 only uses it to learn the object
   *     id which is used to compute the hashmap's key. We already
   *     have an object id, so no need to look it up again.
   *
   *   - The xor_offset is unusable for us, since it specifies how
   *     many entries previous to ours we should look at. This
   *     makes sense when reading the bitmaps sequentially (as in
   *     load_bitmap_entries_v1()), since we can keep track of
   *     each bitmap as we read them.
   *
   *     But it can't work for us, since the bitmap's don't have a
   *     fixed size. So we learn the position of the xor'd bitmap
   *     from the commit table (and resolve it to a bitmap in the
   *     above if-statement).
   *
   * Instead, we can skip ahead and immediately read the flags and
   * ewah bitmap.
   */
  bitmap_git->map_pos += sizeof(uint32_t) + sizeof(uint8_t);
  flags = read_u8(bitmap_git->map, &bitmap_git->map_pos);
  bitmap = read_bitmap_1(bitmap_git);

  if (!bitmap)
    goto corrupt;

  return store_bitmap(bitmap_git, bitmap, oid, xor_bitmap, flags);

corrupt:
  free(xor_items);
  is_corrupt = 1;
  return NULL;
}

struct ewah_bitmap *bitmap_for_commit(struct bitmap_index *bitmap_git,
              struct commit *commit)
{
  khiter_t hash_pos = kh_get_oid_map(bitmap_git->bitmaps,
             commit->object.oid);
  if (hash_pos >= kh_end(bitmap_git->bitmaps)) {
    struct stored_bitmap *bitmap = NULL;
    if (!bitmap_git->table_lookup)
      return NULL;

    /* this is a fairly hot codepath - no trace2_region please */
    /* NEEDSWORK: cache misses aren't recorded */
    bitmap = lazy_bitmap_for_commit(bitmap_git, commit);
    if (!bitmap)
      return NULL;
    return lookup_stored_bitmap(bitmap);
  }
  return lookup_stored_bitmap(kh_value(bitmap_git->bitmaps, hash_pos));
}

static inline int bitmap_position_extended(struct bitmap_index *bitmap_git,
             const struct object_id *oid)
{
  kh_oid_pos_t *positions = bitmap_git->ext_index.positions;
  khiter_t pos = kh_get_oid_pos(positions, *oid);

  if (pos < kh_end(positions)) {
    int bitmap_pos = kh_value(positions, pos);
    return bitmap_pos + bitmap_num_objects(bitmap_git);
  }

  return -1;
}

static inline int bitmap_position_packfile(struct bitmap_index *bitmap_git,
             const struct object_id *oid)
{
  uint32_t pos;
  off_t offset = find_pack_entry_one(oid->hash, bitmap_git->pack);
  if (!offset)
    return -1;

  if (offset_to_pack_pos(bitmap_git->pack, offset, &pos) < 0)
    return -1;
  return pos;
}

static int bitmap_position_midx(struct bitmap_index *bitmap_git,
        const struct object_id *oid)
{
  uint32_t want, got;
  if (!bsearch_midx(oid, bitmap_git->midx, &want))
    return -1;

  if (midx_to_pack_pos(bitmap_git->midx, want, &got) < 0)
    return -1;
  return got;
}

static int bitmap_position(struct bitmap_index *bitmap_git,
         const struct object_id *oid)
{
  int pos;
  if (bitmap_is_midx(bitmap_git))
    pos = bitmap_position_midx(bitmap_git, oid);
  else
    pos = bitmap_position_packfile(bitmap_git, oid);
  return (pos >= 0) ? pos : bitmap_position_extended(bitmap_git, oid);
}

static int ext_index_add_object(struct bitmap_index *bitmap_git,
        struct object *object, const char *name)
{
  struct eindex *eindex = &bitmap_git->ext_index;

  khiter_t hash_pos;
  int hash_ret;
  int bitmap_pos;

  hash_pos = kh_put_oid_pos(eindex->positions, object->oid, &hash_ret);
  if (hash_ret > 0) {
    if (eindex->count >= eindex->alloc) {
      eindex->alloc = (eindex->alloc + 16) * 3 / 2;
      REALLOC_ARRAY(eindex->objects, eindex->alloc);
      REALLOC_ARRAY(eindex->hashes, eindex->alloc);
    }

    bitmap_pos = eindex->count;
    eindex->objects[eindex->count] = object;
    eindex->hashes[eindex->count] = pack_name_hash(name);
    kh_value(eindex->positions, hash_pos) = bitmap_pos;
    eindex->count++;
  } else {
    bitmap_pos = kh_value(eindex->positions, hash_pos);
  }

  return bitmap_pos + bitmap_num_objects(bitmap_git);
}

struct bitmap_show_data {
  struct bitmap_index *bitmap_git;
  struct bitmap *base;
};

static void show_object(struct object *object, const char *name, void *data_)
{
  struct bitmap_show_data *data = data_;
  int bitmap_pos;

  bitmap_pos = bitmap_position(data->bitmap_git, &object->oid);

  if (bitmap_pos < 0)
    bitmap_pos = ext_index_add_object(data->bitmap_git, object,
              name);

  bitmap_set(data->base, bitmap_pos);
}

static void show_commit(struct commit *commit UNUSED,
      void *data UNUSED)
{
}

static unsigned apply_pseudo_merges_for_commit_1(struct bitmap_index *bitmap_git,
             struct bitmap *result,
             struct commit *commit,
             uint32_t commit_pos)
{
  int ret;

  ret = apply_pseudo_merges_for_commit(&bitmap_git->pseudo_merges,
               result, commit, commit_pos);

  if (ret)
    pseudo_merges_satisfied_nr += ret;

  return ret;
}

static int add_to_include_set(struct bitmap_index *bitmap_git,
            struct include_data *data,
            struct commit *commit,
            int bitmap_pos)
{
  struct ewah_bitmap *partial;

  if (data->seen && bitmap_get(data->seen, bitmap_pos))
    return 0;

  if (bitmap_get(data->base, bitmap_pos))
    return 0;

  partial = bitmap_for_commit(bitmap_git, commit);
  if (partial) {
    existing_bitmaps_hits_nr++;

    bitmap_or_ewah(data->base, partial);
    return 0;
  }

  existing_bitmaps_misses_nr++;

  bitmap_set(data->base, bitmap_pos);
  if (apply_pseudo_merges_for_commit_1(bitmap_git, data->base, commit,
               bitmap_pos))
    return 0;

  return 1;
}

static int should_include(struct commit *commit, void *_data)
{
  struct include_data *data = _data;
  int bitmap_pos;

  bitmap_pos = bitmap_position(data->bitmap_git, &commit->object.oid);
  if (bitmap_pos < 0)
    bitmap_pos = ext_index_add_object(data->bitmap_git,
              (struct object *)commit,
              NULL);

  if (!add_to_include_set(data->bitmap_git, data, commit, bitmap_pos)) {
    struct commit_list *parent = commit->parents;

    while (parent) {
      parent->item->object.flags |= SEEN;
      parent = parent->next;
    }

    return 0;
  }

  return 1;
}

static int should_include_obj(struct object *obj, void *_data)
{
  struct include_data *data = _data;
  int bitmap_pos;

  bitmap_pos = bitmap_position(data->bitmap_git, &obj->oid);
  if (bitmap_pos < 0)
    return 1;
  if ((data->seen && bitmap_get(data->seen, bitmap_pos)) ||
       bitmap_get(data->base, bitmap_pos)) {
    obj->flags |= SEEN;
    return 0;
  }
  return 1;
}

static int add_commit_to_bitmap(struct bitmap_index *bitmap_git,
        struct bitmap **base,
        struct commit *commit)
{
  struct ewah_bitmap *or_with = bitmap_for_commit(bitmap_git, commit);

  if (!or_with) {
    existing_bitmaps_misses_nr++;
    return 0;
  }

  existing_bitmaps_hits_nr++;

  if (!*base)
    *base = ewah_to_bitmap(or_with);
  else
    bitmap_or_ewah(*base, or_with);

  return 1;
}

static struct bitmap *fill_in_bitmap(struct bitmap_index *bitmap_git,
             struct rev_info *revs,
             struct bitmap *base,
             struct bitmap *seen)
{
  struct include_data incdata;
  struct bitmap_show_data show_data;

  if (!base)
    base = bitmap_new();

  incdata.bitmap_git = bitmap_git;
  incdata.base = base;
  incdata.seen = seen;

  revs->include_check = should_include;
  revs->include_check_obj = should_include_obj;
  revs->include_check_data = &incdata;

  if (prepare_revision_walk(revs))
    die(_("revision walk setup failed"));

  show_data.bitmap_git = bitmap_git;
  show_data.base = base;

  traverse_commit_list(revs, show_commit, show_object, &show_data);

  revs->include_check = NULL;
  revs->include_check_obj = NULL;
  revs->include_check_data = NULL;

  return base;
}

struct bitmap_boundary_cb {
  struct bitmap_index *bitmap_git;
  struct bitmap *base;

  struct object_array boundary;
};

static void show_boundary_commit(struct commit *commit, void *_data)
{
  struct bitmap_boundary_cb *data = _data;

  if (commit->object.flags & BOUNDARY)
    add_object_array(&commit->object, "", &data->boundary);

  if (commit->object.flags & UNINTERESTING) {
    if (bitmap_walk_contains(data->bitmap_git, data->base,
           &commit->object.oid))
      return;

    add_commit_to_bitmap(data->bitmap_git, &data->base, commit);
  }
}

static void show_boundary_object(struct object *object UNUSED,
         const char *name UNUSED,
         void *data UNUSED)
{
  BUG("should not be called");
}

static unsigned cascade_pseudo_merges_1(struct bitmap_index *bitmap_git,
          struct bitmap *result,
          struct bitmap *roots)
{
  int ret = cascade_pseudo_merges(&bitmap_git->pseudo_merges,
          result, roots);
  if (ret) {
    pseudo_merges_cascades_nr++;
    pseudo_merges_satisfied_nr += ret;
  }

  return ret;
}

static struct bitmap *find_boundary_objects(struct bitmap_index *bitmap_git,
              struct rev_info *revs,
              struct object_list *roots)
{
  struct bitmap_boundary_cb cb;
  struct object_list *root;
  unsigned int i;
  unsigned int tmp_blobs, tmp_trees, tmp_tags;
  int any_missing = 0;
  int existing_bitmaps = 0;

  cb.bitmap_git = bitmap_git;
  cb.base = bitmap_new();
  object_array_init(&cb.boundary);

  revs->ignore_missing_links = 1;

  if (bitmap_git->pseudo_merges.nr) {
    struct bitmap *roots_bitmap = bitmap_new();
    struct object_list *objects = NULL;

    for (objects = roots; objects; objects = objects->next) {
      struct object *object = objects->item;
      int pos;

      pos = bitmap_position(bitmap_git, &object->oid);
      if (pos < 0)
        continue;

      bitmap_set(roots_bitmap, pos);
    }

    if (!cascade_pseudo_merges_1(bitmap_git, cb.base, roots_bitmap))
      bitmap_free(roots_bitmap);
  }

  /*
   * OR in any existing reachability bitmaps among `roots` into
   * `cb.base`.
   */
  for (root = roots; root; root = root->next) {
    struct object *object = root->item;
    if (object->type != OBJ_COMMIT ||
        bitmap_walk_contains(bitmap_git, cb.base, &object->oid))
      continue;

    if (add_commit_to_bitmap(bitmap_git, &cb.base,
           (struct commit *)object)) {
      existing_bitmaps = 1;
      continue;
    }

    any_missing = 1;
  }

  if (!any_missing)
    goto cleanup;

  if (existing_bitmaps)
    cascade_pseudo_merges_1(bitmap_git, cb.base, NULL);

  tmp_blobs = revs->blob_objects;
  tmp_trees = revs->tree_objects;
  tmp_tags = revs->blob_objects;
  revs->blob_objects = 0;
  revs->tree_objects = 0;
  revs->tag_objects = 0;

  /*
   * We didn't have complete coverage of the roots. First setup a
   * revision walk to (a) OR in any bitmaps that are UNINTERESTING
   * between the tips and boundary, and (b) record the boundary.
   */
  trace2_region_enter("pack-bitmap", "boundary-prepare", the_repository);
  if (prepare_revision_walk(revs))
    die("revision walk setup failed");
  trace2_region_leave("pack-bitmap", "boundary-prepare", the_repository);

  trace2_region_enter("pack-bitmap", "boundary-traverse", the_repository);
  revs->boundary = 1;
  traverse_commit_list_filtered(revs,
              show_boundary_commit,
              show_boundary_object,
              &cb, NULL);
  revs->boundary = 0;
  trace2_region_leave("pack-bitmap", "boundary-traverse", the_repository);

  revs->blob_objects = tmp_blobs;
  revs->tree_objects = tmp_trees;
  revs->tag_objects = tmp_tags;

  reset_revision_walk();
  clear_object_flags(UNINTERESTING);

  /*
   * Then add the boundary commit(s) as fill-in traversal tips.
   */
  trace2_region_enter("pack-bitmap", "boundary-fill-in", the_repository);
  for (i = 0; i < cb.boundary.nr; i++) {
    struct object *obj = cb.boundary.objects[i].item;
    if (bitmap_walk_contains(bitmap_git, cb.base, &obj->oid))
      obj->flags |= SEEN;
    else
      add_pending_object(revs, obj, "");
  }
  if (revs->pending.nr)
    cb.base = fill_in_bitmap(bitmap_git, revs, cb.base, NULL);
  trace2_region_leave("pack-bitmap", "boundary-fill-in", the_repository);

cleanup:
  object_array_clear(&cb.boundary);
  revs->ignore_missing_links = 0;

  return cb.base;
}

struct ewah_bitmap *pseudo_merge_bitmap_for_commit(struct bitmap_index *bitmap_git,
               struct commit *commit)
{
  struct commit_list *p;
  struct bitmap *parents;
  struct pseudo_merge *match = NULL;

  if (!bitmap_git->pseudo_merges.nr)
    return NULL;

  parents = bitmap_new();

  for (p = commit->parents; p; p = p->next) {
    int pos = bitmap_position(bitmap_git, &p->item->object.oid);
    if (pos < 0 || pos >= bitmap_num_objects(bitmap_git))
      goto done;

    bitmap_set(parents, pos);
  }

  match = pseudo_merge_for_parents(&bitmap_git->pseudo_merges,
            parents);

done:
  bitmap_free(parents);
  if (match)
    return pseudo_merge_bitmap(&bitmap_git->pseudo_merges, match);

  return NULL;
}

static void unsatisfy_all_pseudo_merges(struct bitmap_index *bitmap_git)
{
  uint32_t i;
  for (i = 0; i < bitmap_git->pseudo_merges.nr; i++)
    bitmap_git->pseudo_merges.v[i].satisfied = 0;
}

static struct bitmap *find_objects(struct bitmap_index *bitmap_git,
           struct rev_info *revs,
           struct object_list *roots,
           struct bitmap *seen)
{
  struct bitmap *base = NULL;
  int needs_walk = 0;
  unsigned existing_bitmaps = 0;

  struct object_list *not_mapped = NULL;

  unsatisfy_all_pseudo_merges(bitmap_git);

  if (bitmap_git->pseudo_merges.nr) {
    struct bitmap *roots_bitmap = bitmap_new();
    struct object_list *objects = NULL;

    for (objects = roots; objects; objects = objects->next) {
      struct object *object = objects->item;
      int pos;

      pos = bitmap_position(bitmap_git, &object->oid);
      if (pos < 0)
        continue;

      bitmap_set(roots_bitmap, pos);
    }

    base = bitmap_new();
    if (!cascade_pseudo_merges_1(bitmap_git, base, roots_bitmap))
      bitmap_free(roots_bitmap);
  }

  /*
   * Go through all the roots for the walk. The ones that have bitmaps
   * on the bitmap index will be `or`ed together to form an initial
   * global reachability analysis.
   *
   * The ones without bitmaps in the index will be stored in the
   * `not_mapped_list` for further processing.
   */
  while (roots) {
    struct object *object = roots->item;

    roots = roots->next;

    if (base) {
      int pos = bitmap_position(bitmap_git, &object->oid);
      if (pos > 0 && bitmap_get(base, pos)) {
        object->flags |= SEEN;
        continue;
      }
    }

    if (object->type == OBJ_COMMIT &&
        add_commit_to_bitmap(bitmap_git, &base, (struct commit *)object)) {
      object->flags |= SEEN;
      existing_bitmaps = 1;
      continue;
    }

    object_list_insert(object, &not_mapped);
  }

  /*
   * Best case scenario: We found bitmaps for all the roots,
   * so the resulting `or` bitmap has the full reachability analysis
   */
  if (!not_mapped)
    return base;

  roots = not_mapped;

  if (existing_bitmaps)
    cascade_pseudo_merges_1(bitmap_git, base, NULL);

  /*
   * Let's iterate through all the roots that don't have bitmaps to
   * check if we can determine them to be reachable from the existing
   * global bitmap.
   *
   * If we cannot find them in the existing global bitmap, we'll need
   * to push them to an actual walk and run it until we can confirm
   * they are reachable
   */
  while (roots) {
    struct object *object = roots->item;
    int pos;

    roots = roots->next;
    pos = bitmap_position(bitmap_git, &object->oid);

    if (pos < 0 || base == NULL || !bitmap_get(base, pos)) {
      object->flags &= ~UNINTERESTING;
      add_pending_object(revs, object, "");
      needs_walk = 1;

      roots_without_bitmaps_nr++;
    } else {
      object->flags |= SEEN;

      roots_with_bitmaps_nr++;
    }
  }

  if (needs_walk) {
    /*
     * This fill-in traversal may walk over some objects
     * again, since we have already traversed in order to
     * find the boundary.
     *
     * But this extra walk should be extremely cheap, since
     * all commit objects are loaded into memory, and
     * because we skip walking to parents that are
     * UNINTERESTING, since it will be marked in the haves
     * bitmap already (or it has an on-disk bitmap, since
     * OR-ing it in covers all of its ancestors).
     */
    base = fill_in_bitmap(bitmap_git, revs, base, seen);
  }

  object_list_free(&not_mapped);

  return base;
}

static void show_extended_objects(struct bitmap_index *bitmap_git,
          struct rev_info *revs,
          show_reachable_fn show_reach)
{
  struct bitmap *objects = bitmap_git->result;
  struct eindex *eindex = &bitmap_git->ext_index;
  uint32_t i;

  for (i = 0; i < eindex->count; ++i) {
    struct object *obj;

    if (!bitmap_get(objects, st_add(bitmap_num_objects(bitmap_git), i)))
      continue;

    obj = eindex->objects[i];
    if ((obj->type == OBJ_BLOB && !revs->blob_objects) ||
        (obj->type == OBJ_TREE && !revs->tree_objects) ||
        (obj->type == OBJ_TAG && !revs->tag_objects))
      continue;

    show_reach(&obj->oid, obj->type, 0, eindex->hashes[i], NULL, 0);
  }
}

static void init_type_iterator(struct ewah_iterator *it,
             struct bitmap_index *bitmap_git,
             enum object_type type)
{
  switch (type) {
  case OBJ_COMMIT:
    ewah_iterator_init(it, bitmap_git->commits);
    break;

  case OBJ_TREE:
    ewah_iterator_init(it, bitmap_git->trees);
    break;

  case OBJ_BLOB:
    ewah_iterator_init(it, bitmap_git->blobs);
    break;

  case OBJ_TAG:
    ewah_iterator_init(it, bitmap_git->tags);
    break;

  default:
    BUG("object type %d not stored by bitmap type index", type);
    break;
  }
}

static void show_objects_for_type(
  struct bitmap_index *bitmap_git,
  enum object_type object_type,
  show_reachable_fn show_reach)
{
  size_t i = 0;
  uint32_t offset;

  struct ewah_iterator it;
  eword_t filter;

  struct bitmap *objects = bitmap_git->result;

  init_type_iterator(&it, bitmap_git, object_type);

  for (i = 0; i < objects->word_alloc &&
      ewah_iterator_next(&filter, &it); i++) {
    eword_t word = objects->words[i] & filter;
    size_t pos = (i * BITS_IN_EWORD);

    if (!word)
      continue;

    for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
      struct packed_git *pack;
      struct object_id oid;
      uint32_t hash = 0, index_pos;
      off_t ofs;

      if ((word >> offset) == 0)
        break;

      offset += ewah_bit_ctz64(word >> offset);

      if (bitmap_is_midx(bitmap_git)) {
        struct multi_pack_index *m = bitmap_git->midx;
        uint32_t pack_id;

        index_pos = pack_pos_to_midx(m, pos + offset);
        ofs = nth_midxed_offset(m, index_pos);
        nth_midxed_object_oid(&oid, m, index_pos);

        pack_id = nth_midxed_pack_int_id(m, index_pos);
        pack = bitmap_git->midx->packs[pack_id];
      } else {
        index_pos = pack_pos_to_index(bitmap_git->pack, pos + offset);
        ofs = pack_pos_to_offset(bitmap_git->pack, pos + offset);
        nth_bitmap_object_oid(bitmap_git, &oid, index_pos);

        pack = bitmap_git->pack;
      }

      if (bitmap_git->hashes)
        hash = get_be32(bitmap_git->hashes + index_pos);

      show_reach(&oid, object_type, 0, hash, pack, ofs);
    }
  }
}

static int in_bitmapped_pack(struct bitmap_index *bitmap_git,
           struct object_list *roots)
{
  while (roots) {
    struct object *object = roots->item;
    roots = roots->next;

    if (bitmap_is_midx(bitmap_git)) {
      if (bsearch_midx(&object->oid, bitmap_git->midx, NULL))
        return 1;
    } else {
      if (find_pack_entry_one(object->oid.hash, bitmap_git->pack) > 0)
        return 1;
    }
  }

  return 0;
}

static struct bitmap *find_tip_objects(struct bitmap_index *bitmap_git,
               struct object_list *tip_objects,
               enum object_type type)
{
  struct bitmap *result = bitmap_new();
  struct object_list *p;

  for (p = tip_objects; p; p = p->next) {
    int pos;

    if (p->item->type != type)
      continue;

    pos = bitmap_position(bitmap_git, &p->item->oid);
    if (pos < 0)
      continue;

    bitmap_set(result, pos);
  }

  return result;
}

static void filter_bitmap_exclude_type(struct bitmap_index *bitmap_git,
               struct object_list *tip_objects,
               struct bitmap *to_filter,
               enum object_type type)
{
  struct eindex *eindex = &bitmap_git->ext_index;
  struct bitmap *tips;
  struct ewah_iterator it;
  eword_t mask;
  uint32_t i;

  /*
   * The non-bitmap version of this filter never removes
   * objects which the other side specifically asked for,
   * so we must match that behavior.
   */
  tips = find_tip_objects(bitmap_git, tip_objects, type);

  /*
   * We can use the type-level bitmap for 'type' to work in whole
   * words for the objects that are actually in the bitmapped
   * packfile.
   */
  for (i = 0, init_type_iterator(&it, bitmap_git, type);
       i < to_filter->word_alloc && ewah_iterator_next(&mask, &it);
       i++) {
    if (i < tips->word_alloc)
      mask &= ~tips->words[i];
    to_filter->words[i] &= ~mask;
  }

  /*
   * Clear any objects that weren't in the packfile (and so would
   * not have been caught by the loop above. We'll have to check
   * them individually.
   */
  for (i = 0; i < eindex->count; i++) {
    size_t pos = st_add(i, bitmap_num_objects(bitmap_git));
    if (eindex->objects[i]->type == type &&
        bitmap_get(to_filter, pos) &&
        !bitmap_get(tips, pos))
      bitmap_unset(to_filter, pos);
  }

  bitmap_free(tips);
}

static void filter_bitmap_blob_none(struct bitmap_index *bitmap_git,
            struct object_list *tip_objects,
            struct bitmap *to_filter)
{
  filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter,
           OBJ_BLOB);
}

static unsigned long get_size_by_pos(struct bitmap_index *bitmap_git,
             uint32_t pos)
{
  unsigned long size;
  struct object_info oi = OBJECT_INFO_INIT;

  oi.sizep = &size;

  if (pos < bitmap_num_objects(bitmap_git)) {
    struct packed_git *pack;
    off_t ofs;

    if (bitmap_is_midx(bitmap_git)) {
      uint32_t midx_pos = pack_pos_to_midx(bitmap_git->midx, pos);
      uint32_t pack_id = nth_midxed_pack_int_id(bitmap_git->midx, midx_pos);

      pack = bitmap_git->midx->packs[pack_id];
      ofs = nth_midxed_offset(bitmap_git->midx, midx_pos);
    } else {
      pack = bitmap_git->pack;
      ofs = pack_pos_to_offset(pack, pos);
    }

    if (packed_object_info(the_repository, pack, ofs, &oi) < 0) {
      struct object_id oid;
      nth_bitmap_object_oid(bitmap_git, &oid,
                pack_pos_to_index(pack, pos));
      die(_("unable to get size of %s"), oid_to_hex(&oid));
    }
  } else {
    struct eindex *eindex = &bitmap_git->ext_index;
    struct object *obj = eindex->objects[pos - bitmap_num_objects(bitmap_git)];
    if (oid_object_info_extended(the_repository, &obj->oid, &oi, 0) < 0)
      die(_("unable to get size of %s"), oid_to_hex(&obj->oid));
  }

  return size;
}

static void filter_bitmap_blob_limit(struct bitmap_index *bitmap_git,
             struct object_list *tip_objects,
             struct bitmap *to_filter,
             unsigned long limit)
{
  struct eindex *eindex = &bitmap_git->ext_index;
  struct bitmap *tips;
  struct ewah_iterator it;
  eword_t mask;
  uint32_t i;

  tips = find_tip_objects(bitmap_git, tip_objects, OBJ_BLOB);

  for (i = 0, init_type_iterator(&it, bitmap_git, OBJ_BLOB);
       i < to_filter->word_alloc && ewah_iterator_next(&mask, &it);
       i++) {
    eword_t word = to_filter->words[i] & mask;
    unsigned offset;

    for (offset = 0; offset < BITS_IN_EWORD; offset++) {
      uint32_t pos;

      if ((word >> offset) == 0)
        break;
      offset += ewah_bit_ctz64(word >> offset);
      pos = i * BITS_IN_EWORD + offset;

      if (!bitmap_get(tips, pos) &&
          get_size_by_pos(bitmap_git, pos) >= limit)
        bitmap_unset(to_filter, pos);
    }
  }

  for (i = 0; i < eindex->count; i++) {
    size_t pos = st_add(i, bitmap_num_objects(bitmap_git));
    if (eindex->objects[i]->type == OBJ_BLOB &&
        bitmap_get(to_filter, pos) &&
        !bitmap_get(tips, pos) &&
        get_size_by_pos(bitmap_git, pos) >= limit)
      bitmap_unset(to_filter, pos);
  }

  bitmap_free(tips);
}

static void filter_bitmap_tree_depth(struct bitmap_index *bitmap_git,
             struct object_list *tip_objects,
             struct bitmap *to_filter,
             unsigned long limit)
{
  if (limit)
    BUG("filter_bitmap_tree_depth given non-zero limit");

  filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter,
           OBJ_TREE);
  filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter,
           OBJ_BLOB);
}

static void filter_bitmap_object_type(struct bitmap_index *bitmap_git,
              struct object_list *tip_objects,
              struct bitmap *to_filter,
              enum object_type object_type)
{
  if (object_type < OBJ_COMMIT || object_type > OBJ_TAG)
    BUG("filter_bitmap_object_type given invalid object");

  if (object_type != OBJ_TAG)
    filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter, OBJ_TAG);
  if (object_type != OBJ_COMMIT)
    filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter, OBJ_COMMIT);
  if (object_type != OBJ_TREE)
    filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter, OBJ_TREE);
  if (object_type != OBJ_BLOB)
    filter_bitmap_exclude_type(bitmap_git, tip_objects, to_filter, OBJ_BLOB);
}

static int filter_bitmap(struct bitmap_index *bitmap_git,
       struct object_list *tip_objects,
       struct bitmap *to_filter,
       struct list_objects_filter_options *filter)
{
  if (!filter || filter->choice == LOFC_DISABLED)
    return 0;

  if (filter->choice == LOFC_BLOB_NONE) {
    if (bitmap_git)
      filter_bitmap_blob_none(bitmap_git, tip_objects,
            to_filter);
    return 0;
  }

  if (filter->choice == LOFC_BLOB_LIMIT) {
    if (bitmap_git)
      filter_bitmap_blob_limit(bitmap_git, tip_objects,
             to_filter,
             filter->blob_limit_value);
    return 0;
  }

  if (filter->choice == LOFC_TREE_DEPTH &&
      filter->tree_exclude_depth == 0) {
    if (bitmap_git)
      filter_bitmap_tree_depth(bitmap_git, tip_objects,
             to_filter,
             filter->tree_exclude_depth);
    return 0;
  }

  if (filter->choice == LOFC_OBJECT_TYPE) {
    if (bitmap_git)
      filter_bitmap_object_type(bitmap_git, tip_objects,
              to_filter,
              filter->object_type);
    return 0;
  }

  if (filter->choice == LOFC_COMBINE) {
    int i;
    for (i = 0; i < filter->sub_nr; i++) {
      if (filter_bitmap(bitmap_git, tip_objects, to_filter,
            &filter->sub[i]) < 0)
        return -1;
    }
    return 0;
  }

  /* filter choice not handled */
  return -1;
}

static int can_filter_bitmap(struct list_objects_filter_options *filter)
{
  return !filter_bitmap(NULL, NULL, NULL, filter);
}


static void filter_packed_objects_from_bitmap(struct bitmap_index *bitmap_git,
                struct bitmap *result)
{
  struct eindex *eindex = &bitmap_git->ext_index;
  uint32_t objects_nr;
  size_t i, pos;

  objects_nr = bitmap_num_objects(bitmap_git);
  pos = objects_nr / BITS_IN_EWORD;

  if (pos > result->word_alloc)
    pos = result->word_alloc;

  memset(result->words, 0x00, sizeof(eword_t) * pos);
  for (i = pos * BITS_IN_EWORD; i < objects_nr; i++)
    bitmap_unset(result, i);

  for (i = 0; i < eindex->count; ++i) {
    if (has_object_pack(&eindex->objects[i]->oid))
      bitmap_unset(result, objects_nr + i);
  }
}

struct bitmap_index *prepare_bitmap_walk(struct rev_info *revs,
           int filter_provided_objects)
{
  unsigned int i;
  int use_boundary_traversal;

  struct object_list *wants = NULL;
  struct object_list *haves = NULL;

  struct bitmap *wants_bitmap = NULL;
  struct bitmap *haves_bitmap = NULL;

  struct bitmap_index *bitmap_git;

  /*
   * We can't do pathspec limiting with bitmaps, because we don't know
   * which commits are associated with which object changes (let alone
   * even which objects are associated with which paths).
   */
  if (revs->prune)
    return NULL;

  if (!can_filter_bitmap(&revs->filter))
    return NULL;

  /* try to open a bitmapped pack, but don't parse it yet
   * because we may not need to use it */
  CALLOC_ARRAY(bitmap_git, 1);
  if (open_bitmap(revs->repo, bitmap_git) < 0)
    goto cleanup;

  for (i = 0; i < revs->pending.nr; ++i) {
    struct object *object = revs->pending.objects[i].item;

    if (object->type == OBJ_NONE)
      parse_object_or_die(&object->oid, NULL);

    while (object->type == OBJ_TAG) {
      struct tag *tag = (struct tag *) object;

      if (object->flags & UNINTERESTING)
        object_list_insert(object, &haves);
      else
        object_list_insert(object, &wants);

      object = parse_object_or_die(get_tagged_oid(tag), NULL);
      object->flags |= (tag->object.flags & UNINTERESTING);
    }

    if (object->flags & UNINTERESTING)
      object_list_insert(object, &haves);
    else
      object_list_insert(object, &wants);
  }

  use_boundary_traversal = git_env_bool(GIT_TEST_PACK_USE_BITMAP_BOUNDARY_TRAVERSAL, -1);
  if (use_boundary_traversal < 0) {
    prepare_repo_settings(revs->repo);
    use_boundary_traversal = revs->repo->settings.pack_use_bitmap_boundary_traversal;
  }

  if (!use_boundary_traversal) {
    /*
     * if we have a HAVES list, but none of those haves is contained
     * in the packfile that has a bitmap, we don't have anything to
     * optimize here
     */
    if (haves && !in_bitmapped_pack(bitmap_git, haves))
      goto cleanup;
  }

  /* if we don't want anything, we're done here */
  if (!wants)
    goto cleanup;

  /*
   * now we're going to use bitmaps, so load the actual bitmap entries
   * from disk. this is the point of no return; after this the rev_list
   * becomes invalidated and we must perform the revwalk through bitmaps
   */
  if (load_bitmap(revs->repo, bitmap_git) < 0)
    goto cleanup;

  if (!use_boundary_traversal)
    object_array_clear(&revs->pending);

  if (haves) {
    if (use_boundary_traversal) {
      trace2_region_enter("pack-bitmap", "haves/boundary", the_repository);
      haves_bitmap = find_boundary_objects(bitmap_git, revs, haves);
      trace2_region_leave("pack-bitmap", "haves/boundary", the_repository);
    } else {
      trace2_region_enter("pack-bitmap", "haves/classic", the_repository);
      revs->ignore_missing_links = 1;
      haves_bitmap = find_objects(bitmap_git, revs, haves, NULL);
      reset_revision_walk();
      revs->ignore_missing_links = 0;
      trace2_region_leave("pack-bitmap", "haves/classic", the_repository);
    }

    if (!haves_bitmap)
      BUG("failed to perform bitmap walk");
  }

  if (use_boundary_traversal) {
    object_array_clear(&revs->pending);
    reset_revision_walk();
  }

  wants_bitmap = find_objects(bitmap_git, revs, wants, haves_bitmap);

  if (!wants_bitmap)
    BUG("failed to perform bitmap walk");

  if (haves_bitmap)
    bitmap_and_not(wants_bitmap, haves_bitmap);

  filter_bitmap(bitmap_git,
          (revs->filter.choice && filter_provided_objects) ? NULL : wants,
          wants_bitmap,
          &revs->filter);

  if (revs->unpacked)
    filter_packed_objects_from_bitmap(bitmap_git, wants_bitmap);

  bitmap_git->result = wants_bitmap;
  bitmap_git->haves = haves_bitmap;

  object_list_free(&wants);
  object_list_free(&haves);

  trace2_data_intmax("bitmap", the_repository, "pseudo_merges_satisfied",
         pseudo_merges_satisfied_nr);
  trace2_data_intmax("bitmap", the_repository, "pseudo_merges_cascades",
         pseudo_merges_cascades_nr);
  trace2_data_intmax("bitmap", the_repository, "bitmap/hits",
         existing_bitmaps_hits_nr);
  trace2_data_intmax("bitmap", the_repository, "bitmap/misses",
         existing_bitmaps_misses_nr);
  trace2_data_intmax("bitmap", the_repository, "bitmap/roots_with_bitmap",
         roots_with_bitmaps_nr);
  trace2_data_intmax("bitmap", the_repository, "bitmap/roots_without_bitmap",
         roots_without_bitmaps_nr);

  return bitmap_git;

cleanup:
  free_bitmap_index(bitmap_git);
  object_list_free(&wants);
  object_list_free(&haves);
  return NULL;
}

/*
 * -1 means "stop trying further objects"; 0 means we may or may not have
 * reused, but you can keep feeding bits.
 */
static int try_partial_reuse(struct bitmap_index *bitmap_git,
           struct bitmapped_pack *pack,
           size_t bitmap_pos,
           uint32_t pack_pos,
           off_t offset,
           struct bitmap *reuse,
           struct pack_window **w_curs)
{
  off_t delta_obj_offset;
  enum object_type type;
  unsigned long size;

  if (pack_pos >= pack->p->num_objects)
    return -1; /* not actually in the pack */

  delta_obj_offset = offset;
  type = unpack_object_header(pack->p, w_curs, &offset, &size);
  if (type < 0)
    return -1; /* broken packfile, punt */

  if (type == OBJ_REF_DELTA || type == OBJ_OFS_DELTA) {
    off_t base_offset;
    uint32_t base_pos;
    uint32_t base_bitmap_pos;

    /*
     * Find the position of the base object so we can look it up
     * in our bitmaps. If we can't come up with an offset, or if
     * that offset is not in the revidx, the pack is corrupt.
     * There's nothing we can do, so just punt on this object,
     * and the normal slow path will complain about it in
     * more detail.
     */
    base_offset = get_delta_base(pack->p, w_curs, &offset, type,
               delta_obj_offset);
    if (!base_offset)
      return 0;

    offset_to_pack_pos(pack->p, base_offset, &base_pos);

    if (bitmap_is_midx(bitmap_git)) {
      /*
       * Cross-pack deltas are rejected for now, but could
       * theoretically be supported in the future.
       *
       * We would need to ensure that we're sending both
       * halves of the delta/base pair, regardless of whether
       * or not the two cross a pack boundary. If they do,
       * then we must convert the delta to an REF_DELTA to
       * refer back to the base in the other pack.
       * */
      if (midx_pair_to_pack_pos(bitmap_git->midx,
              pack->pack_int_id,
              base_offset,
              &base_bitmap_pos) < 0) {
        return 0;
      }
    } else {
      if (offset_to_pack_pos(pack->p, base_offset,
                 &base_pos) < 0)
        return 0;
      /*
       * We assume delta dependencies always point backwards.
       * This lets us do a single pass, and is basically
       * always true due to the way OFS_DELTAs work. You would
       * not typically find REF_DELTA in a bitmapped pack,
       * since we only bitmap packs we write fresh, and
       * OFS_DELTA is the default). But let's double check to
       * make sure the pack wasn't written with odd
       * parameters.
       */
      if (base_pos >= pack_pos)
        return 0;
      base_bitmap_pos = pack->bitmap_pos + base_pos;
    }

    /*
     * And finally, if we're not sending the base as part of our
     * reuse chunk, then don't send this object either. The base
     * would come after us, along with other objects not
     * necessarily in the pack, which means we'd need to convert
     * to REF_DELTA on the fly. Better to just let the normal
     * object_entry code path handle it.
     */
    if (!bitmap_get(reuse, base_bitmap_pos))
      return 0;
  }

  /*
   * If we got here, then the object is OK to reuse. Mark it.
   */
  bitmap_set(reuse, bitmap_pos);
  return 0;
}

static void reuse_partial_packfile_from_bitmap_1(struct bitmap_index *bitmap_git,
             struct bitmapped_pack *pack,
             struct bitmap *reuse)
{
  struct bitmap *result = bitmap_git->result;
  struct pack_window *w_curs = NULL;
  size_t pos = pack->bitmap_pos / BITS_IN_EWORD;

  if (!pack->bitmap_pos) {
    /*
     * If we're processing the first (in the case of a MIDX, the
     * preferred pack) or the only (in the case of single-pack
     * bitmaps) pack, then we can reuse whole words at a time.
     *
     * This is because we know that any deltas in this range *must*
     * have their bases chosen from the same pack, since:
     *
     * - In the single pack case, there is no other pack to choose
     *   them from.
     *
     * - In the MIDX case, the first pack is the preferred pack, so
     *   all ties are broken in favor of that pack (i.e. the one
     *   we're currently processing). So any duplicate bases will be
     *   resolved in favor of the pack we're processing.
     */
    while (pos < result->word_alloc &&
           pos < pack->bitmap_nr / BITS_IN_EWORD &&
           result->words[pos] == (eword_t)~0)
      pos++;
    memset(reuse->words, 0xFF, pos * sizeof(eword_t));
  }

  for (; pos < result->word_alloc; pos++) {
    eword_t word = result->words[pos];
    size_t offset;

    for (offset = 0; offset < BITS_IN_EWORD; offset++) {
      size_t bit_pos;
      uint32_t pack_pos;
      off_t ofs;

      if (word >> offset == 0)
        break;

      offset += ewah_bit_ctz64(word >> offset);

      bit_pos = pos * BITS_IN_EWORD + offset;
      if (bit_pos < pack->bitmap_pos)
        continue;
      if (bit_pos >= pack->bitmap_pos + pack->bitmap_nr)
        goto done;

      if (bitmap_is_midx(bitmap_git)) {
        uint32_t midx_pos;

        midx_pos = pack_pos_to_midx(bitmap_git->midx, bit_pos);
        ofs = nth_midxed_offset(bitmap_git->midx, midx_pos);

        if (offset_to_pack_pos(pack->p, ofs, &pack_pos) < 0)
          BUG("could not find object in pack %s "
              "at offset %"PRIuMAX" in MIDX",
              pack_basename(pack->p), (uintmax_t)ofs);
      } else {
        pack_pos = cast_size_t_to_uint32_t(st_sub(bit_pos, pack->bitmap_pos));
        if (pack_pos >= pack->p->num_objects)
          BUG("advanced beyond the end of pack %s (%"PRIuMAX" > %"PRIu32")",
              pack_basename(pack->p), (uintmax_t)pack_pos,
              pack->p->num_objects);

        ofs = pack_pos_to_offset(pack->p, pack_pos);
      }

      if (try_partial_reuse(bitmap_git, pack, bit_pos,
                pack_pos, ofs, reuse, &w_curs) < 0) {
        /*
         * try_partial_reuse indicated we couldn't reuse
         * any bits, so there is no point in trying more
         * bits in the current word, or any other words
         * in result.
         *
         * Jump out of both loops to avoid future
         * unnecessary calls to try_partial_reuse.
         */
        goto done;
      }
    }
  }

done:
  unuse_pack(&w_curs);
}

static int bitmapped_pack_cmp(const void *va, const void *vb)
{
  const struct bitmapped_pack *a = va;
  const struct bitmapped_pack *b = vb;

  if (a->bitmap_pos < b->bitmap_pos)
    return -1;
  if (a->bitmap_pos > b->bitmap_pos)
    return 1;
  return 0;
}

void reuse_partial_packfile_from_bitmap(struct bitmap_index *bitmap_git,
          struct bitmapped_pack **packs_out,
          size_t *packs_nr_out,
          struct bitmap **reuse_out,
          int multi_pack_reuse)
{
  struct repository *r = the_repository;
  struct bitmapped_pack *packs = NULL;
  struct bitmap *result = bitmap_git->result;
  struct bitmap *reuse;
  size_t i;
  size_t packs_nr = 0, packs_alloc = 0;
  size_t word_alloc;
  uint32_t objects_nr = 0;

  assert(result);

  load_reverse_index(r, bitmap_git);

  if (!bitmap_is_midx(bitmap_git) || !bitmap_git->midx->chunk_bitmapped_packs)
    multi_pack_reuse = 0;

  if (multi_pack_reuse) {
    for (i = 0; i < bitmap_git->midx->num_packs; i++) {
      struct bitmapped_pack pack;
      if (nth_bitmapped_pack(r, bitmap_git->midx, &pack, i) < 0) {
        warning(_("unable to load pack: '%s', disabling pack-reuse"),
          bitmap_git->midx->pack_names[i]);
        free(packs);
        return;
      }

      if (!pack.bitmap_nr)
        continue;

      ALLOC_GROW(packs, packs_nr + 1, packs_alloc);
      memcpy(&packs[packs_nr++], &pack, sizeof(pack));

      objects_nr += pack.p->num_objects;
    }

    QSORT(packs, packs_nr, bitmapped_pack_cmp);
  } else {
    struct packed_git *pack;
    uint32_t pack_int_id;

    if (bitmap_is_midx(bitmap_git)) {
      uint32_t preferred_pack_pos;

      if (midx_preferred_pack(bitmap_git->midx, &preferred_pack_pos) < 0) {
        warning(_("unable to compute preferred pack, disabling pack-reuse"));
        return;
      }

      pack = bitmap_git->midx->packs[preferred_pack_pos];
      pack_int_id = preferred_pack_pos;
    } else {
      pack = bitmap_git->pack;
      /*
       * Any value for 'pack_int_id' will do here. When we
       * process the pack via try_partial_reuse(), we won't
       * use the `pack_int_id` field since we have a non-MIDX
       * bitmap.
       *
       * Use '-1' as a sentinel value to make it clear
       * that we do not expect to read this field.
       */
      pack_int_id = -1;
    }

    ALLOC_GROW(packs, packs_nr + 1, packs_alloc);
    packs[packs_nr].p = pack;
    packs[packs_nr].pack_int_id = pack_int_id;
    packs[packs_nr].bitmap_nr = pack->num_objects;
    packs[packs_nr].bitmap_pos = 0;
    packs[packs_nr].from_midx = bitmap_git->midx;

    objects_nr = packs[packs_nr++].bitmap_nr;
  }

  word_alloc = objects_nr / BITS_IN_EWORD;
  if (objects_nr % BITS_IN_EWORD)
    word_alloc++;
  reuse = bitmap_word_alloc(word_alloc);

  for (i = 0; i < packs_nr; i++)
    reuse_partial_packfile_from_bitmap_1(bitmap_git, &packs[i], reuse);

  if (bitmap_is_empty(reuse)) {
    free(packs);
    bitmap_free(reuse);
    return;
  }

  /*
   * Drop any reused objects from the result, since they will not
   * need to be handled separately.
   */
  bitmap_and_not(result, reuse);
  *packs_out = packs;
  *packs_nr_out = packs_nr;
  *reuse_out = reuse;
}

int bitmap_walk_contains(struct bitmap_index *bitmap_git,
       struct bitmap *bitmap, const struct object_id *oid)
{
  int idx;

  if (!bitmap)
    return 0;

  idx = bitmap_position(bitmap_git, oid);
  return idx >= 0 && bitmap_get(bitmap, idx);
}

void traverse_bitmap_commit_list(struct bitmap_index *bitmap_git,
         struct rev_info *revs,
         show_reachable_fn show_reachable)
{
  assert(bitmap_git->result);

  show_objects_for_type(bitmap_git, OBJ_COMMIT, show_reachable);
  if (revs->tree_objects)
    show_objects_for_type(bitmap_git, OBJ_TREE, show_reachable);
  if (revs->blob_objects)
    show_objects_for_type(bitmap_git, OBJ_BLOB, show_reachable);
  if (revs->tag_objects)
    show_objects_for_type(bitmap_git, OBJ_TAG, show_reachable);

  show_extended_objects(bitmap_git, revs, show_reachable);
}

static uint32_t count_object_type(struct bitmap_index *bitmap_git,
          enum object_type type)
{
  struct bitmap *objects = bitmap_git->result;
  struct eindex *eindex = &bitmap_git->ext_index;

  uint32_t i = 0, count = 0;
  struct ewah_iterator it;
  eword_t filter;

  init_type_iterator(&it, bitmap_git, type);

  while (i < objects->word_alloc && ewah_iterator_next(&filter, &it)) {
    eword_t word = objects->words[i++] & filter;
    count += ewah_bit_popcount64(word);
  }

  for (i = 0; i < eindex->count; ++i) {
    if (eindex->objects[i]->type == type &&
        bitmap_get(objects,
             st_add(bitmap_num_objects(bitmap_git), i)))
      count++;
  }

  return count;
}

void count_bitmap_commit_list(struct bitmap_index *bitmap_git,
            uint32_t *commits, uint32_t *trees,
            uint32_t *blobs, uint32_t *tags)
{
  assert(bitmap_git->result);

  if (commits)
    *commits = count_object_type(bitmap_git, OBJ_COMMIT);

  if (trees)
    *trees = count_object_type(bitmap_git, OBJ_TREE);

  if (blobs)
    *blobs = count_object_type(bitmap_git, OBJ_BLOB);

  if (tags)
    *tags = count_object_type(bitmap_git, OBJ_TAG);
}

struct bitmap_test_data {
  struct bitmap_index *bitmap_git;
  struct bitmap *base;
  struct bitmap *commits;
  struct bitmap *trees;
  struct bitmap *blobs;
  struct bitmap *tags;
  struct progress *prg;
  size_t seen;
};

static void test_bitmap_type(struct bitmap_test_data *tdata,
           struct object *obj, int pos)
{
  enum object_type bitmap_type = OBJ_NONE;
  int bitmaps_nr = 0;

  if (bitmap_get(tdata->commits, pos)) {
    bitmap_type = OBJ_COMMIT;
    bitmaps_nr++;
  }
  if (bitmap_get(tdata->trees, pos)) {
    bitmap_type = OBJ_TREE;
    bitmaps_nr++;
  }
  if (bitmap_get(tdata->blobs, pos)) {
    bitmap_type = OBJ_BLOB;
    bitmaps_nr++;
  }
  if (bitmap_get(tdata->tags, pos)) {
    bitmap_type = OBJ_TAG;
    bitmaps_nr++;
  }

  if (bitmap_type == OBJ_NONE)
    die(_("object '%s' not found in type bitmaps"),
        oid_to_hex(&obj->oid));

  if (bitmaps_nr > 1)
    die(_("object '%s' does not have a unique type"),
        oid_to_hex(&obj->oid));

  if (bitmap_type != obj->type)
    die(_("object '%s': real type '%s', expected: '%s'"),
        oid_to_hex(&obj->oid),
        type_name(obj->type),
        type_name(bitmap_type));
}

static void test_show_object(struct object *object,
           const char *name UNUSED,
           void *data)
{
  struct bitmap_test_data *tdata = data;
  int bitmap_pos;

  bitmap_pos = bitmap_position(tdata->bitmap_git, &object->oid);
  if (bitmap_pos < 0)
    die(_("object not in bitmap: '%s'"), oid_to_hex(&object->oid));
  test_bitmap_type(tdata, object, bitmap_pos);

  bitmap_set(tdata->base, bitmap_pos);
  display_progress(tdata->prg, ++tdata->seen);
}

static void test_show_commit(struct commit *commit, void *data)
{
  struct bitmap_test_data *tdata = data;
  int bitmap_pos;

  bitmap_pos = bitmap_position(tdata->bitmap_git,
             &commit->object.oid);
  if (bitmap_pos < 0)
    die(_("object not in bitmap: '%s'"), oid_to_hex(&commit->object.oid));
  test_bitmap_type(tdata, &commit->object, bitmap_pos);

  bitmap_set(tdata->base, bitmap_pos);
  display_progress(tdata->prg, ++tdata->seen);
}

void test_bitmap_walk(struct rev_info *revs)
{
  struct object *root;
  struct bitmap *result = NULL;
  size_t result_popcnt;
  struct bitmap_test_data tdata;
  struct bitmap_index *bitmap_git;
  struct ewah_bitmap *bm;

  if (!(bitmap_git = prepare_bitmap_git(revs->repo)))
    die(_("failed to load bitmap indexes"));

  if (revs->pending.nr != 1)
    die(_("you must specify exactly one commit to test"));

  fprintf_ln(stderr, "Bitmap v%d test (%d entries%s)",
    bitmap_git->version,
    bitmap_git->entry_count,
    bitmap_git->table_lookup ? "" : " loaded");

  root = revs->pending.objects[0].item;
  bm = bitmap_for_commit(bitmap_git, (struct commit *)root);

  if (bm) {
    fprintf_ln(stderr, "Found bitmap for '%s'. %d bits / %08x checksum",
      oid_to_hex(&root->oid), (int)bm->bit_size, ewah_checksum(bm));

    result = ewah_to_bitmap(bm);
  }

  if (!result)
    die(_("commit '%s' doesn't have an indexed bitmap"), oid_to_hex(&root->oid));

  revs->tag_objects = 1;
  revs->tree_objects = 1;
  revs->blob_objects = 1;

  result_popcnt = bitmap_popcount(result);

  if (prepare_revision_walk(revs))
    die(_("revision walk setup failed"));

  tdata.bitmap_git = bitmap_git;
  tdata.base = bitmap_new();
  tdata.commits = ewah_to_bitmap(bitmap_git->commits);
  tdata.trees = ewah_to_bitmap(bitmap_git->trees);
  tdata.blobs = ewah_to_bitmap(bitmap_git->blobs);
  tdata.tags = ewah_to_bitmap(bitmap_git->tags);
  tdata.prg = start_progress("Verifying bitmap entries", result_popcnt);
  tdata.seen = 0;

  traverse_commit_list(revs, &test_show_commit, &test_show_object, &tdata);

  stop_progress(&tdata.prg);

  if (bitmap_equals(result, tdata.base))
    fprintf_ln(stderr, "OK!");
  else
    die(_("mismatch in bitmap results"));

  bitmap_free(result);
  bitmap_free(tdata.base);
  bitmap_free(tdata.commits);
  bitmap_free(tdata.trees);
  bitmap_free(tdata.blobs);
  bitmap_free(tdata.tags);
  free_bitmap_index(bitmap_git);
}

int test_bitmap_commits(struct repository *r)
{
  struct object_id oid;
  MAYBE_UNUSED void *value;
  struct bitmap_index *bitmap_git = prepare_bitmap_git(r);

  if (!bitmap_git)
    die(_("failed to load bitmap indexes"));

  /*
   * As this function is only used to print bitmap selected
   * commits, we don't have to read the commit table.
   */
  if (bitmap_git->table_lookup) {
    if (load_bitmap_entries_v1(bitmap_git) < 0)
      die(_("failed to load bitmap indexes"));
  }

  kh_foreach(bitmap_git->bitmaps, oid, value, {
    printf_ln("%s", oid_to_hex(&oid));
  });

  free_bitmap_index(bitmap_git);

  return 0;
}

int test_bitmap_hashes(struct repository *r)
{
  struct bitmap_index *bitmap_git = prepare_bitmap_git(r);
  struct object_id oid;
  uint32_t i, index_pos;

  if (!bitmap_git || !bitmap_git->hashes)
    goto cleanup;

  for (i = 0; i < bitmap_num_objects(bitmap_git); i++) {
    if (bitmap_is_midx(bitmap_git))
      index_pos = pack_pos_to_midx(bitmap_git->midx, i);
    else
      index_pos = pack_pos_to_index(bitmap_git->pack, i);

    nth_bitmap_object_oid(bitmap_git, &oid, index_pos);

    printf_ln("%s %"PRIu32"",
           oid_to_hex(&oid), get_be32(bitmap_git->hashes + index_pos));
  }

cleanup:
  free_bitmap_index(bitmap_git);

  return 0;
}

static void bit_pos_to_object_id(struct bitmap_index *bitmap_git,
         uint32_t bit_pos,
         struct object_id *oid)
{
  uint32_t index_pos;

  if (bitmap_is_midx(bitmap_git))
    index_pos = pack_pos_to_midx(bitmap_git->midx, bit_pos);
  else
    index_pos = pack_pos_to_index(bitmap_git->pack, bit_pos);

  nth_bitmap_object_oid(bitmap_git, oid, index_pos);
}

int test_bitmap_pseudo_merges(struct repository *r)
{
  struct bitmap_index *bitmap_git;
  uint32_t i;

  bitmap_git = prepare_bitmap_git(r);
  if (!bitmap_git || !bitmap_git->pseudo_merges.nr)
    goto cleanup;

  for (i = 0; i < bitmap_git->pseudo_merges.nr; i++) {
    struct pseudo_merge *merge;
    struct ewah_bitmap *commits_bitmap, *merge_bitmap;

    merge = use_pseudo_merge(&bitmap_git->pseudo_merges,
           &bitmap_git->pseudo_merges.v[i]);
    commits_bitmap = merge->commits;
    merge_bitmap = pseudo_merge_bitmap(&bitmap_git->pseudo_merges,
               merge);

    printf("at=%"PRIuMAX", commits=%"PRIuMAX", objects=%"PRIuMAX"\n",
           (uintmax_t)merge->at,
           (uintmax_t)ewah_bitmap_popcount(commits_bitmap),
           (uintmax_t)ewah_bitmap_popcount(merge_bitmap));
  }

cleanup:
  free_bitmap_index(bitmap_git);
  return 0;
}

static void dump_ewah_object_ids(struct bitmap_index *bitmap_git,
         struct ewah_bitmap *bitmap)

{
  struct ewah_iterator it;
  eword_t word;
  uint32_t pos = 0;

  ewah_iterator_init(&it, bitmap);

  while (ewah_iterator_next(&word, &it)) {
    struct object_id oid;
    uint32_t offset;

    for (offset = 0; offset < BITS_IN_EWORD; offset++) {
      if (!(word >> offset))
        break;

      offset += ewah_bit_ctz64(word >> offset);

      bit_pos_to_object_id(bitmap_git, pos + offset, &oid);
      printf("%s\n", oid_to_hex(&oid));
    }
    pos += BITS_IN_EWORD;
  }
}

int test_bitmap_pseudo_merge_commits(struct repository *r, uint32_t n)
{
  struct bitmap_index *bitmap_git;
  struct pseudo_merge *merge;
  int ret = 0;

  bitmap_git = prepare_bitmap_git(r);
  if (!bitmap_git || !bitmap_git->pseudo_merges.nr)
    goto cleanup;

  if (n >= bitmap_git->pseudo_merges.nr) {
    ret = error(_("pseudo-merge index out of range "
            "(%"PRIu32" >= %"PRIuMAX")"),
          n, (uintmax_t)bitmap_git->pseudo_merges.nr);
    goto cleanup;
  }

  merge = use_pseudo_merge(&bitmap_git->pseudo_merges,
         &bitmap_git->pseudo_merges.v[n]);
  dump_ewah_object_ids(bitmap_git, merge->commits);

cleanup:
  free_bitmap_index(bitmap_git);
  return ret;
}

int test_bitmap_pseudo_merge_objects(struct repository *r, uint32_t n)
{
  struct bitmap_index *bitmap_git;
  struct pseudo_merge *merge;
  int ret = 0;

  bitmap_git = prepare_bitmap_git(r);
  if (!bitmap_git || !bitmap_git->pseudo_merges.nr)
    goto cleanup;

  if (n >= bitmap_git->pseudo_merges.nr) {
    ret = error(_("pseudo-merge index out of range "
            "(%"PRIu32" >= %"PRIuMAX")"),
          n, (uintmax_t)bitmap_git->pseudo_merges.nr);
    goto cleanup;
  }

  merge = use_pseudo_merge(&bitmap_git->pseudo_merges,
         &bitmap_git->pseudo_merges.v[n]);

  dump_ewah_object_ids(bitmap_git,
           pseudo_merge_bitmap(&bitmap_git->pseudo_merges,
             merge));

cleanup:
  free_bitmap_index(bitmap_git);
  return ret;
}

int rebuild_bitmap(const uint32_t *reposition,
       struct ewah_bitmap *source,
       struct bitmap *dest)
{
  uint32_t pos = 0;
  struct ewah_iterator it;
  eword_t word;

  ewah_iterator_init(&it, source);

  while (ewah_iterator_next(&word, &it)) {
    uint32_t offset, bit_pos;

    for (offset = 0; offset < BITS_IN_EWORD; ++offset) {
      if ((word >> offset) == 0)
        break;

      offset += ewah_bit_ctz64(word >> offset);

      bit_pos = reposition[pos + offset];
      if (bit_pos > 0)
        bitmap_set(dest, bit_pos - 1);
      else /* can't reuse, we don't have the object */
        return -1;
    }

    pos += BITS_IN_EWORD;
  }
  return 0;
}

uint32_t *create_bitmap_mapping(struct bitmap_index *bitmap_git,
        struct packing_data *mapping)
{
  struct repository *r = the_repository;
  uint32_t i, num_objects;
  uint32_t *reposition;

  if (!bitmap_is_midx(bitmap_git))
    load_reverse_index(r, bitmap_git);
  else if (load_midx_revindex(bitmap_git->midx))
    BUG("rebuild_existing_bitmaps: missing required rev-cache "
        "extension");

  num_objects = bitmap_num_objects(bitmap_git);
  CALLOC_ARRAY(reposition, num_objects);

  for (i = 0; i < num_objects; ++i) {
    struct object_id oid;
    struct object_entry *oe;
    uint32_t index_pos;

    if (bitmap_is_midx(bitmap_git))
      index_pos = pack_pos_to_midx(bitmap_git->midx, i);
    else
      index_pos = pack_pos_to_index(bitmap_git->pack, i);
    nth_bitmap_object_oid(bitmap_git, &oid, index_pos);
    oe = packlist_find(mapping, &oid);

    if (oe) {
      reposition[i] = oe_in_pack_pos(mapping, oe) + 1;
      if (bitmap_git->hashes && !oe->hash)
        oe->hash = get_be32(bitmap_git->hashes + index_pos);
    }
  }

  return reposition;
}

void free_bitmap_index(struct bitmap_index *b)
{
  if (!b)
    return;

  if (b->map)
    munmap(b->map, b->map_size);
  ewah_pool_free(b->commits);
  ewah_pool_free(b->trees);
  ewah_pool_free(b->blobs);
  ewah_pool_free(b->tags);
  if (b->bitmaps) {
    struct stored_bitmap *sb;
    kh_foreach_value(b->bitmaps, sb, {
      ewah_pool_free(sb->root);
      free(sb);
    });
  }
  kh_destroy_oid_map(b->bitmaps);
  free(b->ext_index.objects);
  free(b->ext_index.hashes);
  kh_destroy_oid_pos(b->ext_index.positions);
  bitmap_free(b->result);
  bitmap_free(b->haves);
  if (bitmap_is_midx(b)) {
    /*
     * Multi-pack bitmaps need to have resources associated with
     * their on-disk reverse indexes unmapped so that stale .rev and
     * .bitmap files can be removed.
     *
     * Unlike pack-based bitmaps, multi-pack bitmaps can be read and
     * written in the same 'git multi-pack-index write --bitmap'
     * process. Close resources so they can be removed safely on
     * platforms like Windows.
     */
    close_midx_revindex(b->midx);
  }
  free_pseudo_merge_map(&b->pseudo_merges);
  free(b);
}

int bitmap_has_oid_in_uninteresting(struct bitmap_index *bitmap_git,
            const struct object_id *oid)
{
  return bitmap_git &&
    bitmap_walk_contains(bitmap_git, bitmap_git->haves, oid);
}

static off_t get_disk_usage_for_type(struct bitmap_index *bitmap_git,
             enum object_type object_type)
{
  struct bitmap *result = bitmap_git->result;
  off_t total = 0;
  struct ewah_iterator it;
  eword_t filter;
  size_t i;

  init_type_iterator(&it, bitmap_git, object_type);
  for (i = 0; i < result->word_alloc &&
      ewah_iterator_next(&filter, &it); i++) {
    eword_t word = result->words[i] & filter;
    size_t base = (i * BITS_IN_EWORD);
    unsigned offset;

    if (!word)
      continue;

    for (offset = 0; offset < BITS_IN_EWORD; offset++) {
      if ((word >> offset) == 0)
        break;

      offset += ewah_bit_ctz64(word >> offset);

      if (bitmap_is_midx(bitmap_git)) {
        uint32_t pack_pos;
        uint32_t midx_pos = pack_pos_to_midx(bitmap_git->midx, base + offset);
        off_t offset = nth_midxed_offset(bitmap_git->midx, midx_pos);

        uint32_t pack_id = nth_midxed_pack_int_id(bitmap_git->midx, midx_pos);
        struct packed_git *pack = bitmap_git->midx->packs[pack_id];

        if (offset_to_pack_pos(pack, offset, &pack_pos) < 0) {
          struct object_id oid;
          nth_midxed_object_oid(&oid, bitmap_git->midx, midx_pos);

          die(_("could not find '%s' in pack '%s' at offset %"PRIuMAX),
              oid_to_hex(&oid),
              pack->pack_name,
              (uintmax_t)offset);
        }

        total += pack_pos_to_offset(pack, pack_pos + 1) - offset;
      } else {
        size_t pos = base + offset;
        total += pack_pos_to_offset(bitmap_git->pack, pos + 1) -
           pack_pos_to_offset(bitmap_git->pack, pos);
      }
    }
  }

  return total;
}

static off_t get_disk_usage_for_extended(struct bitmap_index *bitmap_git)
{
  struct bitmap *result = bitmap_git->result;
  struct eindex *eindex = &bitmap_git->ext_index;
  off_t total = 0;
  struct object_info oi = OBJECT_INFO_INIT;
  off_t object_size;
  size_t i;

  oi.disk_sizep = &object_size;

  for (i = 0; i < eindex->count; i++) {
    struct object *obj = eindex->objects[i];

    if (!bitmap_get(result,
        st_add(bitmap_num_objects(bitmap_git), i)))
      continue;

    if (oid_object_info_extended(the_repository, &obj->oid, &oi, 0) < 0)
      die(_("unable to get disk usage of '%s'"),
          oid_to_hex(&obj->oid));

    total += object_size;
  }
  return total;
}

off_t get_disk_usage_from_bitmap(struct bitmap_index *bitmap_git,
         struct rev_info *revs)
{
  off_t total = 0;

  total += get_disk_usage_for_type(bitmap_git, OBJ_COMMIT);
  if (revs->tree_objects)
    total += get_disk_usage_for_type(bitmap_git, OBJ_TREE);
  if (revs->blob_objects)
    total += get_disk_usage_for_type(bitmap_git, OBJ_BLOB);
  if (revs->tag_objects)
    total += get_disk_usage_for_type(bitmap_git, OBJ_TAG);

  total += get_disk_usage_for_extended(bitmap_git);

  return total;
}

int bitmap_is_midx(struct bitmap_index *bitmap_git)
{
  return !!bitmap_git->midx;
}

const struct string_list *bitmap_preferred_tips(struct repository *r)
{
  const struct string_list *dest;

  if (!repo_config_get_string_multi(r, "pack.preferbitmaptips", &dest))
    return dest;
  return NULL;
}

int bitmap_is_preferred_refname(struct repository *r, const char *refname)
{
  const struct string_list *preferred_tips = bitmap_preferred_tips(r);
  struct string_list_item *item;

  if (!preferred_tips)
    return 0;

  for_each_string_list_item(item, preferred_tips) {
    if (starts_with(refname, item->string))
      return 1;
  }

  return 0;
}

static int verify_bitmap_file(const char *name)
{
  struct stat st;
  unsigned char *data;
  int fd = git_open(name);
  int res = 0;

  /* It is OK to not have the file. */
  if (fd < 0 || fstat(fd, &st)) {
    if (fd >= 0)
      close(fd);
    return 0;
  }

  data = xmmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
  close(fd);
  if (!hashfile_checksum_valid(data, st.st_size))
    res = error(_("bitmap file '%s' has invalid checksum"),
          name);

  munmap(data, st.st_size);
  return res;
}

int verify_bitmap_files(struct repository *r)
{
  int res = 0;

  for (struct multi_pack_index *m = get_multi_pack_index(r);
       m; m = m->next) {
    char *midx_bitmap_name = midx_bitmap_filename(m);
    res |= verify_bitmap_file(midx_bitmap_name);
    free(midx_bitmap_name);
  }

  for (struct packed_git *p = get_all_packs(r);
       p; p = p->next) {
    char *pack_bitmap_name = pack_bitmap_filename(p);
    res |= verify_bitmap_file(pack_bitmap_name);
    free(pack_bitmap_name);
  }

  return res;
}

Coverage Report

Created: 2024-09-08 06:24