The sixth batch

[alt-git.git] / midx.c

#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "config.h"
#include "dir.h"
#include "hex.h"
#include "packfile.h"
#include "object-file.h"
#include "hash-lookup.h"
#include "midx.h"
#include "progress.h"
#include "trace2.h"
#include "chunk-format.h"
#include "pack-bitmap.h"
#include "pack-revindex.h"

int midx_checksum_valid(struct multi_pack_index *m);
void clear_midx_files_ext(const char *object_dir, const char *ext,
                          const char *keep_hash);
void clear_incremental_midx_files_ext(const char *object_dir, const char *ext,
                                      char **keep_hashes,
                                      uint32_t hashes_nr);
int cmp_idx_or_pack_name(const char *idx_or_pack_name,
                         const char *idx_name);

const unsigned char *get_midx_checksum(struct multi_pack_index *m)
{
        return m->data + m->data_len - m->repo->hash_algo->rawsz;
}

void get_midx_filename(const struct git_hash_algo *hash_algo,
                       struct strbuf *out, const char *object_dir)
{
        get_midx_filename_ext(hash_algo, out, object_dir, NULL, NULL);
}

void get_midx_filename_ext(const struct git_hash_algo *hash_algo,
                           struct strbuf *out, const char *object_dir,
                           const unsigned char *hash, const char *ext)
{
        strbuf_addf(out, "%s/pack/multi-pack-index", object_dir);
        if (ext)
                strbuf_addf(out, "-%s.%s", hash_to_hex_algop(hash, hash_algo), ext);
}

static int midx_read_oid_fanout(const unsigned char *chunk_start,
                                size_t chunk_size, void *data)
{
        int i;
        struct multi_pack_index *m = data;
        m->chunk_oid_fanout = (uint32_t *)chunk_start;

        if (chunk_size != 4 * 256) {
                error(_("multi-pack-index OID fanout is of the wrong size"));
                return 1;
        }
        for (i = 0; i < 255; i++) {
                uint32_t oid_fanout1 = ntohl(m->chunk_oid_fanout[i]);
                uint32_t oid_fanout2 = ntohl(m->chunk_oid_fanout[i+1]);

                if (oid_fanout1 > oid_fanout2) {
                        error(_("oid fanout out of order: fanout[%d] = %"PRIx32" > %"PRIx32" = fanout[%d]"),
                              i, oid_fanout1, oid_fanout2, i + 1);
                        return 1;
                }
        }
        m->num_objects = ntohl(m->chunk_oid_fanout[255]);
        return 0;
}

static int midx_read_oid_lookup(const unsigned char *chunk_start,
                                size_t chunk_size, void *data)
{
        struct multi_pack_index *m = data;
        m->chunk_oid_lookup = chunk_start;

        if (chunk_size != st_mult(m->hash_len, m->num_objects)) {
                error(_("multi-pack-index OID lookup chunk is the wrong size"));
                return 1;
        }
        return 0;
}

static int midx_read_object_offsets(const unsigned char *chunk_start,
                                    size_t chunk_size, void *data)
{
        struct multi_pack_index *m = data;
        m->chunk_object_offsets = chunk_start;

        if (chunk_size != st_mult(m->num_objects, MIDX_CHUNK_OFFSET_WIDTH)) {
                error(_("multi-pack-index object offset chunk is the wrong size"));
                return 1;
        }
        return 0;
}

static struct multi_pack_index *load_multi_pack_index_one(struct repository *r,
                                                          const char *object_dir,
                                                          const char *midx_name,
                                                          int local)
{
        struct multi_pack_index *m = NULL;
        int fd;
        struct stat st;
        size_t midx_size;
        void *midx_map = NULL;
        uint32_t hash_version;
        uint32_t i;
        const char *cur_pack_name;
        struct chunkfile *cf = NULL;

        fd = git_open(midx_name);

        if (fd < 0)
                goto cleanup_fail;
        if (fstat(fd, &st)) {
                error_errno(_("failed to read %s"), midx_name);
                goto cleanup_fail;
        }

        midx_size = xsize_t(st.st_size);

        if (midx_size < (MIDX_HEADER_SIZE + r->hash_algo->rawsz)) {
                error(_("multi-pack-index file %s is too small"), midx_name);
                goto cleanup_fail;
        }

        midx_map = xmmap(NULL, midx_size, PROT_READ, MAP_PRIVATE, fd, 0);
        close(fd);

        FLEX_ALLOC_STR(m, object_dir, object_dir);
        m->data = midx_map;
        m->data_len = midx_size;
        m->local = local;
        m->repo = r;

        m->signature = get_be32(m->data);
        if (m->signature != MIDX_SIGNATURE)
                die(_("multi-pack-index signature 0x%08x does not match signature 0x%08x"),
                      m->signature, MIDX_SIGNATURE);

        m->version = m->data[MIDX_BYTE_FILE_VERSION];
        if (m->version != MIDX_VERSION)
                die(_("multi-pack-index version %d not recognized"),
                      m->version);

        hash_version = m->data[MIDX_BYTE_HASH_VERSION];
        if (hash_version != oid_version(r->hash_algo)) {
                error(_("multi-pack-index hash version %u does not match version %u"),
                      hash_version, oid_version(r->hash_algo));
                goto cleanup_fail;
        }
        m->hash_len = r->hash_algo->rawsz;

        m->num_chunks = m->data[MIDX_BYTE_NUM_CHUNKS];

        m->num_packs = get_be32(m->data + MIDX_BYTE_NUM_PACKS);

        m->preferred_pack_idx = -1;

        cf = init_chunkfile(NULL);

        if (read_table_of_contents(cf, m->data, midx_size,
                                   MIDX_HEADER_SIZE, m->num_chunks,
                                   MIDX_CHUNK_ALIGNMENT))
                goto cleanup_fail;

        if (pair_chunk(cf, MIDX_CHUNKID_PACKNAMES, &m->chunk_pack_names, &m->chunk_pack_names_len))
                die(_("multi-pack-index required pack-name chunk missing or corrupted"));
        if (read_chunk(cf, MIDX_CHUNKID_OIDFANOUT, midx_read_oid_fanout, m))
                die(_("multi-pack-index required OID fanout chunk missing or corrupted"));
        if (read_chunk(cf, MIDX_CHUNKID_OIDLOOKUP, midx_read_oid_lookup, m))
                die(_("multi-pack-index required OID lookup chunk missing or corrupted"));
        if (read_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS, midx_read_object_offsets, m))
                die(_("multi-pack-index required object offsets chunk missing or corrupted"));

        pair_chunk(cf, MIDX_CHUNKID_LARGEOFFSETS, &m->chunk_large_offsets,
                   &m->chunk_large_offsets_len);
        if (git_env_bool("GIT_TEST_MIDX_READ_BTMP", 1))
                pair_chunk(cf, MIDX_CHUNKID_BITMAPPEDPACKS,
                           (const unsigned char **)&m->chunk_bitmapped_packs,
                           &m->chunk_bitmapped_packs_len);

        if (git_env_bool("GIT_TEST_MIDX_READ_RIDX", 1))
                pair_chunk(cf, MIDX_CHUNKID_REVINDEX, &m->chunk_revindex,
                           &m->chunk_revindex_len);

        CALLOC_ARRAY(m->pack_names, m->num_packs);
        CALLOC_ARRAY(m->packs, m->num_packs);

        cur_pack_name = (const char *)m->chunk_pack_names;
        for (i = 0; i < m->num_packs; i++) {
                const char *end;
                size_t avail = m->chunk_pack_names_len -
                                (cur_pack_name - (const char *)m->chunk_pack_names);

                m->pack_names[i] = cur_pack_name;

                end = memchr(cur_pack_name, '\0', avail);
                if (!end)
                        die(_("multi-pack-index pack-name chunk is too short"));
                cur_pack_name = end + 1;

                if (i && strcmp(m->pack_names[i], m->pack_names[i - 1]) <= 0)
                        die(_("multi-pack-index pack names out of order: '%s' before '%s'"),
                              m->pack_names[i - 1],
                              m->pack_names[i]);
        }

        trace2_data_intmax("midx", r, "load/num_packs", m->num_packs);
        trace2_data_intmax("midx", r, "load/num_objects", m->num_objects);

        free_chunkfile(cf);
        return m;

cleanup_fail:
        free(m);
        free_chunkfile(cf);
        if (midx_map)
                munmap(midx_map, midx_size);
        if (0 <= fd)
                close(fd);
        return NULL;
}

void get_midx_chain_dirname(struct strbuf *buf, const char *object_dir)
{
        strbuf_addf(buf, "%s/pack/multi-pack-index.d", object_dir);
}

void get_midx_chain_filename(struct strbuf *buf, const char *object_dir)
{
        get_midx_chain_dirname(buf, object_dir);
        strbuf_addstr(buf, "/multi-pack-index-chain");
}

void get_split_midx_filename_ext(const struct git_hash_algo *hash_algo,
                                 struct strbuf *buf, const char *object_dir,
                                 const unsigned char *hash, const char *ext)
{
        get_midx_chain_dirname(buf, object_dir);
        strbuf_addf(buf, "/multi-pack-index-%s.%s",
                    hash_to_hex_algop(hash, hash_algo), ext);
}

static int open_multi_pack_index_chain(const struct git_hash_algo *hash_algo,
                                       const char *chain_file, int *fd,
                                       struct stat *st)
{
        *fd = git_open(chain_file);
        if (*fd < 0)
                return 0;
        if (fstat(*fd, st)) {
                close(*fd);
                return 0;
        }
        if (st->st_size < hash_algo->hexsz) {
                close(*fd);
                if (!st->st_size) {
                        /* treat empty files the same as missing */
                        errno = ENOENT;
                } else {
                        warning(_("multi-pack-index chain file too small"));
                        errno = EINVAL;
                }
                return 0;
        }
        return 1;
}

static int add_midx_to_chain(struct multi_pack_index *midx,
                             struct multi_pack_index *midx_chain)
{
        if (midx_chain) {
                if (unsigned_add_overflows(midx_chain->num_packs,
                                           midx_chain->num_packs_in_base)) {
                        warning(_("pack count in base MIDX too high: %"PRIuMAX),
                                (uintmax_t)midx_chain->num_packs_in_base);
                        return 0;
                }
                if (unsigned_add_overflows(midx_chain->num_objects,
                                           midx_chain->num_objects_in_base)) {
                        warning(_("object count in base MIDX too high: %"PRIuMAX),
                                (uintmax_t)midx_chain->num_objects_in_base);
                        return 0;
                }
                midx->num_packs_in_base = midx_chain->num_packs +
                        midx_chain->num_packs_in_base;
                midx->num_objects_in_base = midx_chain->num_objects +
                        midx_chain->num_objects_in_base;
        }

        midx->base_midx = midx_chain;
        midx->has_chain = 1;

        return 1;
}

static struct multi_pack_index *load_midx_chain_fd_st(struct repository *r,
                                                      const char *object_dir,
                                                      int local,
                                                      int fd, struct stat *st,
                                                      int *incomplete_chain)
{
        struct multi_pack_index *midx_chain = NULL;
        struct strbuf buf = STRBUF_INIT;
        int valid = 1;
        uint32_t i, count;
        FILE *fp = xfdopen(fd, "r");

        count = st->st_size / (r->hash_algo->hexsz + 1);

        for (i = 0; i < count; i++) {
                struct multi_pack_index *m;
                struct object_id layer;

                if (strbuf_getline_lf(&buf, fp) == EOF)
                        break;

                if (get_oid_hex_algop(buf.buf, &layer, r->hash_algo)) {
                        warning(_("invalid multi-pack-index chain: line '%s' "
                                  "not a hash"),
                                buf.buf);
                        valid = 0;
                        break;
                }

                valid = 0;

                strbuf_reset(&buf);
                get_split_midx_filename_ext(r->hash_algo, &buf, object_dir,
                                            layer.hash, MIDX_EXT_MIDX);
                m = load_multi_pack_index_one(r, object_dir, buf.buf, local);

                if (m) {
                        if (add_midx_to_chain(m, midx_chain)) {
                                midx_chain = m;
                                valid = 1;
                        } else {
                                close_midx(m);
                        }
                }
                if (!valid) {
                        warning(_("unable to find all multi-pack index files"));
                        break;
                }
        }

        fclose(fp);
        strbuf_release(&buf);

        *incomplete_chain = !valid;
        return midx_chain;
}

static struct multi_pack_index *load_multi_pack_index_chain(struct repository *r,
                                                            const char *object_dir,
                                                            int local)
{
        struct strbuf chain_file = STRBUF_INIT;
        struct stat st;
        int fd;
        struct multi_pack_index *m = NULL;

        get_midx_chain_filename(&chain_file, object_dir);
        if (open_multi_pack_index_chain(r->hash_algo, chain_file.buf, &fd, &st)) {
                int incomplete;
                /* ownership of fd is taken over by load function */
                m = load_midx_chain_fd_st(r, object_dir, local, fd, &st,
                                          &incomplete);
        }

        strbuf_release(&chain_file);
        return m;
}

struct multi_pack_index *load_multi_pack_index(struct repository *r,
                                               const char *object_dir,
                                               int local)
{
        struct strbuf midx_name = STRBUF_INIT;
        struct multi_pack_index *m;

        get_midx_filename(r->hash_algo, &midx_name, object_dir);

        m = load_multi_pack_index_one(r, object_dir,
                                      midx_name.buf, local);
        if (!m)
                m = load_multi_pack_index_chain(r, object_dir, local);

        strbuf_release(&midx_name);

        return m;
}

void close_midx(struct multi_pack_index *m)
{
        uint32_t i;

        if (!m)
                return;

        close_midx(m->next);
        close_midx(m->base_midx);

        munmap((unsigned char *)m->data, m->data_len);

        for (i = 0; i < m->num_packs; i++) {
                if (m->packs[i])
                        m->packs[i]->multi_pack_index = 0;
        }
        FREE_AND_NULL(m->packs);
        FREE_AND_NULL(m->pack_names);
        free(m);
}

static uint32_t midx_for_object(struct multi_pack_index **_m, uint32_t pos)
{
        struct multi_pack_index *m = *_m;
        while (m && pos < m->num_objects_in_base)
                m = m->base_midx;

        if (!m)
                BUG("NULL multi-pack-index for object position: %"PRIu32, pos);

        if (pos >= m->num_objects + m->num_objects_in_base)
                die(_("invalid MIDX object position, MIDX is likely corrupt"));

        *_m = m;

        return pos - m->num_objects_in_base;
}

static uint32_t midx_for_pack(struct multi_pack_index **_m,
                              uint32_t pack_int_id)
{
        struct multi_pack_index *m = *_m;
        while (m && pack_int_id < m->num_packs_in_base)
                m = m->base_midx;

        if (!m)
                BUG("NULL multi-pack-index for pack ID: %"PRIu32, pack_int_id);

        if (pack_int_id >= m->num_packs + m->num_packs_in_base)
                die(_("bad pack-int-id: %u (%u total packs)"),
                    pack_int_id, m->num_packs + m->num_packs_in_base);

        *_m = m;

        return pack_int_id - m->num_packs_in_base;
}

int prepare_midx_pack(struct repository *r, struct multi_pack_index *m,
                      uint32_t pack_int_id)
{
        struct strbuf pack_name = STRBUF_INIT;
        struct strbuf key = STRBUF_INIT;
        struct packed_git *p;

        pack_int_id = midx_for_pack(&m, pack_int_id);

        if (m->packs[pack_int_id])
                return 0;

        strbuf_addf(&pack_name, "%s/pack/%s", m->object_dir,
                    m->pack_names[pack_int_id]);

        /* pack_map holds the ".pack" name, but we have the .idx */
        strbuf_addbuf(&key, &pack_name);
        strbuf_strip_suffix(&key, ".idx");
        strbuf_addstr(&key, ".pack");
        p = hashmap_get_entry_from_hash(&r->objects->pack_map,
                                        strhash(key.buf), key.buf,
                                        struct packed_git, packmap_ent);
        if (!p) {
                p = add_packed_git(r, pack_name.buf, pack_name.len, m->local);
                if (p) {
                        install_packed_git(r, p);
                        list_add_tail(&p->mru, &r->objects->packed_git_mru);
                }
        }

        strbuf_release(&pack_name);
        strbuf_release(&key);

        if (!p)
                return 1;

        p->multi_pack_index = 1;
        m->packs[pack_int_id] = p;

        return 0;
}

struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
                                   uint32_t pack_int_id)
{
        uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id);
        return m->packs[local_pack_int_id];
}

#define MIDX_CHUNK_BITMAPPED_PACKS_WIDTH (2 * sizeof(uint32_t))

int nth_bitmapped_pack(struct repository *r, struct multi_pack_index *m,
                       struct bitmapped_pack *bp, uint32_t pack_int_id)
{
        uint32_t local_pack_int_id = midx_for_pack(&m, pack_int_id);

        if (!m->chunk_bitmapped_packs)
                return error(_("MIDX does not contain the BTMP chunk"));

        if (prepare_midx_pack(r, m, pack_int_id))
                return error(_("could not load bitmapped pack %"PRIu32), pack_int_id);

        bp->p = m->packs[local_pack_int_id];
        bp->bitmap_pos = get_be32((char *)m->chunk_bitmapped_packs +
                                  MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * local_pack_int_id);
        bp->bitmap_nr = get_be32((char *)m->chunk_bitmapped_packs +
                                 MIDX_CHUNK_BITMAPPED_PACKS_WIDTH * local_pack_int_id +
                                 sizeof(uint32_t));
        bp->pack_int_id = pack_int_id;
        bp->from_midx = m;

        return 0;
}

int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
                     uint32_t *result)
{
        int ret = bsearch_hash(oid->hash, m->chunk_oid_fanout,
                               m->chunk_oid_lookup, m->repo->hash_algo->rawsz,
                               result);
        if (result)
                *result += m->num_objects_in_base;
        return ret;
}

int bsearch_midx(const struct object_id *oid, struct multi_pack_index *m,
                 uint32_t *result)
{
        for (; m; m = m->base_midx)
                if (bsearch_one_midx(oid, m, result))
                        return 1;
        return 0;
}

int midx_has_oid(struct multi_pack_index *m, const struct object_id *oid)
{
        return bsearch_midx(oid, m, NULL);
}

struct object_id *nth_midxed_object_oid(struct object_id *oid,
                                        struct multi_pack_index *m,
                                        uint32_t n)
{
        if (n >= m->num_objects + m->num_objects_in_base)
                return NULL;

        n = midx_for_object(&m, n);

        oidread(oid, m->chunk_oid_lookup + st_mult(m->hash_len, n),
                m->repo->hash_algo);
        return oid;
}

off_t nth_midxed_offset(struct multi_pack_index *m, uint32_t pos)
{
        const unsigned char *offset_data;
        uint32_t offset32;

        pos = midx_for_object(&m, pos);

        offset_data = m->chunk_object_offsets + (off_t)pos * MIDX_CHUNK_OFFSET_WIDTH;
        offset32 = get_be32(offset_data + sizeof(uint32_t));

        if (m->chunk_large_offsets && offset32 & MIDX_LARGE_OFFSET_NEEDED) {
                if (sizeof(off_t) < sizeof(uint64_t))
                        die(_("multi-pack-index stores a 64-bit offset, but off_t is too small"));

                offset32 ^= MIDX_LARGE_OFFSET_NEEDED;
                if (offset32 >= m->chunk_large_offsets_len / sizeof(uint64_t))
                        die(_("multi-pack-index large offset out of bounds"));
                return get_be64(m->chunk_large_offsets + sizeof(uint64_t) * offset32);
        }

        return offset32;
}

uint32_t nth_midxed_pack_int_id(struct multi_pack_index *m, uint32_t pos)
{
        pos = midx_for_object(&m, pos);

        return m->num_packs_in_base + get_be32(m->chunk_object_offsets +
                                               (off_t)pos * MIDX_CHUNK_OFFSET_WIDTH);
}

int fill_midx_entry(struct repository *r,
                    const struct object_id *oid,
                    struct pack_entry *e,
                    struct multi_pack_index *m)
{
        uint32_t pos;
        uint32_t pack_int_id;
        struct packed_git *p;

        if (!bsearch_midx(oid, m, &pos))
                return 0;

        midx_for_object(&m, pos);
        pack_int_id = nth_midxed_pack_int_id(m, pos);

        if (prepare_midx_pack(r, m, pack_int_id))
                return 0;
        p = m->packs[pack_int_id - m->num_packs_in_base];

        /*
        * We are about to tell the caller where they can locate the
        * requested object.  We better make sure the packfile is
        * still here and can be accessed before supplying that
        * answer, as it may have been deleted since the MIDX was
        * loaded!
        */
        if (!is_pack_valid(p))
                return 0;

        if (oidset_size(&p->bad_objects) &&
            oidset_contains(&p->bad_objects, oid))
                return 0;

        e->offset = nth_midxed_offset(m, pos);
        e->p = p;

        return 1;
}

/* Match "foo.idx" against either "foo.pack" _or_ "foo.idx". */
int cmp_idx_or_pack_name(const char *idx_or_pack_name,
                         const char *idx_name)
{
        /* Skip past any initial matching prefix. */
        while (*idx_name && *idx_name == *idx_or_pack_name) {
                idx_name++;
                idx_or_pack_name++;
        }

        /*
         * If we didn't match completely, we may have matched "pack-1234." and
         * be left with "idx" and "pack" respectively, which is also OK. We do
         * not have to check for "idx" and "idx", because that would have been
         * a complete match (and in that case these strcmps will be false, but
         * we'll correctly return 0 from the final strcmp() below.
         *
         * Technically this matches "fooidx" and "foopack", but we'd never have
         * such names in the first place.
         */
        if (!strcmp(idx_name, "idx") && !strcmp(idx_or_pack_name, "pack"))
                return 0;

        /*
         * This not only checks for a complete match, but also orders based on
         * the first non-identical character, which means our ordering will
         * match a raw strcmp(). That makes it OK to use this to binary search
         * a naively-sorted list.
         */
        return strcmp(idx_or_pack_name, idx_name);
}

static int midx_contains_pack_1(struct multi_pack_index *m,
                                const char *idx_or_pack_name)
{
        uint32_t first = 0, last = m->num_packs;

        while (first < last) {
                uint32_t mid = first + (last - first) / 2;
                const char *current;
                int cmp;

                current = m->pack_names[mid];
                cmp = cmp_idx_or_pack_name(idx_or_pack_name, current);
                if (!cmp)
                        return 1;
                if (cmp > 0) {
                        first = mid + 1;
                        continue;
                }
                last = mid;
        }

        return 0;
}

int midx_contains_pack(struct multi_pack_index *m, const char *idx_or_pack_name)
{
        for (; m; m = m->base_midx)
                if (midx_contains_pack_1(m, idx_or_pack_name))
                        return 1;
        return 0;
}

int midx_preferred_pack(struct multi_pack_index *m, uint32_t *pack_int_id)
{
        if (m->preferred_pack_idx == -1) {
                uint32_t midx_pos;
                if (load_midx_revindex(m) < 0) {
                        m->preferred_pack_idx = -2;
                        return -1;
                }

                midx_pos = pack_pos_to_midx(m, m->num_objects_in_base);

                m->preferred_pack_idx = nth_midxed_pack_int_id(m, midx_pos);

        } else if (m->preferred_pack_idx == -2)
                return -1; /* no revindex */

        *pack_int_id = m->preferred_pack_idx;
        return 0;
}

int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, int local)
{
        struct multi_pack_index *m;
        struct multi_pack_index *m_search;

        prepare_repo_settings(r);
        if (!r->settings.core_multi_pack_index)
                return 0;

        for (m_search = r->objects->multi_pack_index; m_search; m_search = m_search->next)
                if (!strcmp(object_dir, m_search->object_dir))
                        return 1;

        m = load_multi_pack_index(r, object_dir, local);

        if (m) {
                struct multi_pack_index *mp = r->objects->multi_pack_index;
                if (mp) {
                        m->next = mp->next;
                        mp->next = m;
                } else
                        r->objects->multi_pack_index = m;
                return 1;
        }

        return 0;
}

int midx_checksum_valid(struct multi_pack_index *m)
{
        return hashfile_checksum_valid(m->data, m->data_len);
}

struct clear_midx_data {
        char **keep;
        uint32_t keep_nr;
        const char *ext;
};

static void clear_midx_file_ext(const char *full_path, size_t full_path_len UNUSED,
                                const char *file_name, void *_data)
{
        struct clear_midx_data *data = _data;
        uint32_t i;

        if (!(starts_with(file_name, "multi-pack-index-") &&
              ends_with(file_name, data->ext)))
                return;
        for (i = 0; i < data->keep_nr; i++) {
                if (!strcmp(data->keep[i], file_name))
                        return;
        }
        if (unlink(full_path))
                die_errno(_("failed to remove %s"), full_path);
}

void clear_midx_files_ext(const char *object_dir, const char *ext,
                          const char *keep_hash)
{
        struct clear_midx_data data;
        memset(&data, 0, sizeof(struct clear_midx_data));

        if (keep_hash) {
                ALLOC_ARRAY(data.keep, 1);

                data.keep[0] = xstrfmt("multi-pack-index-%s.%s", keep_hash, ext);
                data.keep_nr = 1;
        }
        data.ext = ext;

        for_each_file_in_pack_dir(object_dir,
                                  clear_midx_file_ext,
                                  &data);

        if (keep_hash)
                free(data.keep[0]);
        free(data.keep);
}

void clear_incremental_midx_files_ext(const char *object_dir, const char *ext,
                                      char **keep_hashes,
                                      uint32_t hashes_nr)
{
        struct clear_midx_data data;
        uint32_t i;

        memset(&data, 0, sizeof(struct clear_midx_data));

        ALLOC_ARRAY(data.keep, hashes_nr);
        for (i = 0; i < hashes_nr; i++)
                data.keep[i] = xstrfmt("multi-pack-index-%s.%s", keep_hashes[i],
                                       ext);
        data.keep_nr = hashes_nr;
        data.ext = ext;

        for_each_file_in_pack_subdir(object_dir, "multi-pack-index.d",
                                     clear_midx_file_ext, &data);

        for (i = 0; i < hashes_nr; i++)
                free(data.keep[i]);
        free(data.keep);
}

void clear_midx_file(struct repository *r)
{
        struct strbuf midx = STRBUF_INIT;

        get_midx_filename(r->hash_algo, &midx, r->objects->odb->path);

        if (r->objects && r->objects->multi_pack_index) {
                close_midx(r->objects->multi_pack_index);
                r->objects->multi_pack_index = NULL;
        }

        if (remove_path(midx.buf))
                die(_("failed to clear multi-pack-index at %s"), midx.buf);

        clear_midx_files_ext(r->objects->odb->path, MIDX_EXT_BITMAP, NULL);
        clear_midx_files_ext(r->objects->odb->path, MIDX_EXT_REV, NULL);

        strbuf_release(&midx);
}

static int verify_midx_error;

__attribute__((format (printf, 1, 2)))
static void midx_report(const char *fmt, ...)
{
        va_list ap;
        verify_midx_error = 1;
        va_start(ap, fmt);
        vfprintf(stderr, fmt, ap);
        fprintf(stderr, "\n");
        va_end(ap);
}

struct pair_pos_vs_id
{
        uint32_t pos;
        uint32_t pack_int_id;
};

static int compare_pair_pos_vs_id(const void *_a, const void *_b)
{
        struct pair_pos_vs_id *a = (struct pair_pos_vs_id *)_a;
        struct pair_pos_vs_id *b = (struct pair_pos_vs_id *)_b;

        return b->pack_int_id - a->pack_int_id;
}

/*
 * Limit calls to display_progress() for performance reasons.
 * The interval here was arbitrarily chosen.
 */
#define SPARSE_PROGRESS_INTERVAL (1 << 12)
#define midx_display_sparse_progress(progress, n) \
        do { \
                uint64_t _n = (n); \
                if ((_n & (SPARSE_PROGRESS_INTERVAL - 1)) == 0) \
                        display_progress(progress, _n); \
        } while (0)

int verify_midx_file(struct repository *r, const char *object_dir, unsigned flags)
{
        struct pair_pos_vs_id *pairs = NULL;
        uint32_t i;
        struct progress *progress = NULL;
        struct multi_pack_index *m = load_multi_pack_index(r, object_dir, 1);
        struct multi_pack_index *curr;
        verify_midx_error = 0;

        if (!m) {
                int result = 0;
                struct stat sb;
                struct strbuf filename = STRBUF_INIT;

                get_midx_filename(r->hash_algo, &filename, object_dir);

                if (!stat(filename.buf, &sb)) {
                        error(_("multi-pack-index file exists, but failed to parse"));
                        result = 1;
                }
                strbuf_release(&filename);
                return result;
        }

        if (!midx_checksum_valid(m))
                midx_report(_("incorrect checksum"));

        if (flags & MIDX_PROGRESS)
                progress = start_delayed_progress(r,
                                                  _("Looking for referenced packfiles"),
                                                  m->num_packs + m->num_packs_in_base);
        for (i = 0; i < m->num_packs + m->num_packs_in_base; i++) {
                if (prepare_midx_pack(r, m, i))
                        midx_report("failed to load pack in position %d", i);

                display_progress(progress, i + 1);
        }
        stop_progress(&progress);

        if (m->num_objects == 0) {
                midx_report(_("the midx contains no oid"));
                /*
                 * Remaining tests assume that we have objects, so we can
                 * return here.
                 */
                goto cleanup;
        }

        if (flags & MIDX_PROGRESS)
                progress = start_sparse_progress(r,
                                                 _("Verifying OID order in multi-pack-index"),
                                                 m->num_objects - 1);

        for (curr = m; curr; curr = curr->base_midx) {
                for (i = 0; i < m->num_objects - 1; i++) {
                        struct object_id oid1, oid2;

                        nth_midxed_object_oid(&oid1, m, m->num_objects_in_base + i);
                        nth_midxed_object_oid(&oid2, m, m->num_objects_in_base + i + 1);

                        if (oidcmp(&oid1, &oid2) >= 0)
                                midx_report(_("oid lookup out of order: oid[%d] = %s >= %s = oid[%d]"),
                                            i, oid_to_hex(&oid1), oid_to_hex(&oid2), i + 1);

                        midx_display_sparse_progress(progress, i + 1);
                }
        }
        stop_progress(&progress);

        /*
         * Create an array mapping each object to its packfile id.  Sort it
         * to group the objects by packfile.  Use this permutation to visit
         * each of the objects and only require 1 packfile to be open at a
         * time.
         */
        ALLOC_ARRAY(pairs, m->num_objects + m->num_objects_in_base);
        for (i = 0; i < m->num_objects + m->num_objects_in_base; i++) {
                pairs[i].pos = i;
                pairs[i].pack_int_id = nth_midxed_pack_int_id(m, i);
        }

        if (flags & MIDX_PROGRESS)
                progress = start_sparse_progress(r,
                                                 _("Sorting objects by packfile"),
                                                 m->num_objects);
        display_progress(progress, 0); /* TODO: Measure QSORT() progress */
        QSORT(pairs, m->num_objects, compare_pair_pos_vs_id);
        stop_progress(&progress);

        if (flags & MIDX_PROGRESS)
                progress = start_sparse_progress(r,
                                                 _("Verifying object offsets"),
                                                 m->num_objects);
        for (i = 0; i < m->num_objects + m->num_objects_in_base; i++) {
                struct object_id oid;
                struct pack_entry e;
                off_t m_offset, p_offset;

                if (i > 0 && pairs[i-1].pack_int_id != pairs[i].pack_int_id &&
                    nth_midxed_pack(m, pairs[i-1].pack_int_id)) {
                        uint32_t pack_int_id = pairs[i-1].pack_int_id;
                        struct packed_git *p = nth_midxed_pack(m, pack_int_id);

                        close_pack_fd(p);
                        close_pack_index(p);
                }

                nth_midxed_object_oid(&oid, m, pairs[i].pos);

                if (!fill_midx_entry(r, &oid, &e, m)) {
                        midx_report(_("failed to load pack entry for oid[%d] = %s"),
                                    pairs[i].pos, oid_to_hex(&oid));
                        continue;
                }

                if (open_pack_index(e.p)) {
                        midx_report(_("failed to load pack-index for packfile %s"),
                                    e.p->pack_name);
                        break;
                }

                m_offset = e.offset;
                p_offset = find_pack_entry_one(&oid, e.p);

                if (m_offset != p_offset)
                        midx_report(_("incorrect object offset for oid[%d] = %s: %"PRIx64" != %"PRIx64),
                                    pairs[i].pos, oid_to_hex(&oid), m_offset, p_offset);

                midx_display_sparse_progress(progress, i + 1);
        }
        stop_progress(&progress);

cleanup:
        free(pairs);
        close_midx(m);

        return verify_midx_error;
}