/src/git/object-file.c

Source (jump to first uncovered line)
/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 *
 * This handles basic git object files - packing, unpacking,
 * creation etc.
 */

#define USE_THE_REPOSITORY_VARIABLE

#include "git-compat-util.h"
#include "abspath.h"
#include "config.h"
#include "convert.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "string-list.h"
#include "lockfile.h"
#include "pack.h"
#include "commit.h"
#include "run-command.h"
#include "refs.h"
#include "bulk-checkin.h"
#include "repository.h"
#include "replace-object.h"
#include "streaming.h"
#include "dir.h"
#include "list.h"
#include "quote.h"
#include "packfile.h"
#include "object-file.h"
#include "object-store.h"
#include "oidtree.h"
#include "path.h"
#include "promisor-remote.h"
#include "setup.h"
#include "submodule.h"
#include "fsck.h"
#include "loose.h"
#include "object-file-convert.h"

/* The maximum size for an object header. */
#define MAX_HEADER_LEN 32


#define EMPTY_TREE_SHA1_BIN_LITERAL \
   "\x4b\x82\x5d\xc6\x42\xcb\x6e\xb9\xa0\x60" \
   "\xe5\x4b\xf8\xd6\x92\x88\xfb\xee\x49\x04"
#define EMPTY_TREE_SHA256_BIN_LITERAL \
  "\x6e\xf1\x9b\x41\x22\x5c\x53\x69\xf1\xc1" \
  "\x04\xd4\x5d\x8d\x85\xef\xa9\xb0\x57\xb5" \
  "\x3b\x14\xb4\xb9\xb9\x39\xdd\x74\xde\xcc" \
  "\x53\x21"

#define EMPTY_BLOB_SHA1_BIN_LITERAL \
  "\xe6\x9d\xe2\x9b\xb2\xd1\xd6\x43\x4b\x8b" \
  "\x29\xae\x77\x5a\xd8\xc2\xe4\x8c\x53\x91"
#define EMPTY_BLOB_SHA256_BIN_LITERAL \
  "\x47\x3a\x0f\x4c\x3b\xe8\xa9\x36\x81\xa2" \
  "\x67\xe3\xb1\xe9\xa7\xdc\xda\x11\x85\x43" \
  "\x6f\xe1\x41\xf7\x74\x91\x20\xa3\x03\x72" \
  "\x18\x13"

static const struct object_id empty_tree_oid = {
  .hash = EMPTY_TREE_SHA1_BIN_LITERAL,
  .algo = GIT_HASH_SHA1,
};
static const struct object_id empty_blob_oid = {
  .hash = EMPTY_BLOB_SHA1_BIN_LITERAL,
  .algo = GIT_HASH_SHA1,
};
static const struct object_id null_oid_sha1 = {
  .hash = {0},
  .algo = GIT_HASH_SHA1,
};
static const struct object_id empty_tree_oid_sha256 = {
  .hash = EMPTY_TREE_SHA256_BIN_LITERAL,
  .algo = GIT_HASH_SHA256,
};
static const struct object_id empty_blob_oid_sha256 = {
  .hash = EMPTY_BLOB_SHA256_BIN_LITERAL,
  .algo = GIT_HASH_SHA256,
};
static const struct object_id null_oid_sha256 = {
  .hash = {0},
  .algo = GIT_HASH_SHA256,
};

static void git_hash_sha1_init(git_hash_ctx *ctx)
{
  git_SHA1_Init(&ctx->sha1);
}

static void git_hash_sha1_clone(git_hash_ctx *dst, const git_hash_ctx *src)
{
  git_SHA1_Clone(&dst->sha1, &src->sha1);
}

static void git_hash_sha1_update(git_hash_ctx *ctx, const void *data, size_t len)
{
  git_SHA1_Update(&ctx->sha1, data, len);
}

static void git_hash_sha1_final(unsigned char *hash, git_hash_ctx *ctx)
{
  git_SHA1_Final(hash, &ctx->sha1);
}

static void git_hash_sha1_final_oid(struct object_id *oid, git_hash_ctx *ctx)
{
  git_SHA1_Final(oid->hash, &ctx->sha1);
  memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
  oid->algo = GIT_HASH_SHA1;
}


static void git_hash_sha256_init(git_hash_ctx *ctx)
{
  git_SHA256_Init(&ctx->sha256);
}

static void git_hash_sha256_clone(git_hash_ctx *dst, const git_hash_ctx *src)
{
  git_SHA256_Clone(&dst->sha256, &src->sha256);
}

static void git_hash_sha256_update(git_hash_ctx *ctx, const void *data, size_t len)
{
  git_SHA256_Update(&ctx->sha256, data, len);
}

static void git_hash_sha256_final(unsigned char *hash, git_hash_ctx *ctx)
{
  git_SHA256_Final(hash, &ctx->sha256);
}

static void git_hash_sha256_final_oid(struct object_id *oid, git_hash_ctx *ctx)
{
  git_SHA256_Final(oid->hash, &ctx->sha256);
  /*
   * This currently does nothing, so the compiler should optimize it out,
   * but keep it in case we extend the hash size again.
   */
  memset(oid->hash + GIT_SHA256_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA256_RAWSZ);
  oid->algo = GIT_HASH_SHA256;
}

static void git_hash_unknown_init(git_hash_ctx *ctx UNUSED)
{
  BUG("trying to init unknown hash");
}

static void git_hash_unknown_clone(git_hash_ctx *dst UNUSED,
           const git_hash_ctx *src UNUSED)
{
  BUG("trying to clone unknown hash");
}

static void git_hash_unknown_update(git_hash_ctx *ctx UNUSED,
            const void *data UNUSED,
            size_t len UNUSED)
{
  BUG("trying to update unknown hash");
}

static void git_hash_unknown_final(unsigned char *hash UNUSED,
           git_hash_ctx *ctx UNUSED)
{
  BUG("trying to finalize unknown hash");
}

static void git_hash_unknown_final_oid(struct object_id *oid UNUSED,
               git_hash_ctx *ctx UNUSED)
{
  BUG("trying to finalize unknown hash");
}

const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
  {
    .name = NULL,
    .format_id = 0x00000000,
    .rawsz = 0,
    .hexsz = 0,
    .blksz = 0,
    .init_fn = git_hash_unknown_init,
    .clone_fn = git_hash_unknown_clone,
    .update_fn = git_hash_unknown_update,
    .final_fn = git_hash_unknown_final,
    .final_oid_fn = git_hash_unknown_final_oid,
    .empty_tree = NULL,
    .empty_blob = NULL,
    .null_oid = NULL,
  },
  {
    .name = "sha1",
    .format_id = GIT_SHA1_FORMAT_ID,
    .rawsz = GIT_SHA1_RAWSZ,
    .hexsz = GIT_SHA1_HEXSZ,
    .blksz = GIT_SHA1_BLKSZ,
    .init_fn = git_hash_sha1_init,
    .clone_fn = git_hash_sha1_clone,
    .update_fn = git_hash_sha1_update,
    .final_fn = git_hash_sha1_final,
    .final_oid_fn = git_hash_sha1_final_oid,
    .empty_tree = &empty_tree_oid,
    .empty_blob = &empty_blob_oid,
    .null_oid = &null_oid_sha1,
  },
  {
    .name = "sha256",
    .format_id = GIT_SHA256_FORMAT_ID,
    .rawsz = GIT_SHA256_RAWSZ,
    .hexsz = GIT_SHA256_HEXSZ,
    .blksz = GIT_SHA256_BLKSZ,
    .init_fn = git_hash_sha256_init,
    .clone_fn = git_hash_sha256_clone,
    .update_fn = git_hash_sha256_update,
    .final_fn = git_hash_sha256_final,
    .final_oid_fn = git_hash_sha256_final_oid,
    .empty_tree = &empty_tree_oid_sha256,
    .empty_blob = &empty_blob_oid_sha256,
    .null_oid = &null_oid_sha256,
  }
};

const struct object_id *null_oid(void)
{
  return the_hash_algo->null_oid;
}

const char *empty_tree_oid_hex(const struct git_hash_algo *algop)
{
  static char buf[GIT_MAX_HEXSZ + 1];
  return oid_to_hex_r(buf, algop->empty_tree);
}

int hash_algo_by_name(const char *name)
{
  int i;
  if (!name)
    return GIT_HASH_UNKNOWN;
  for (i = 1; i < GIT_HASH_NALGOS; i++)
    if (!strcmp(name, hash_algos[i].name))
      return i;
  return GIT_HASH_UNKNOWN;
}

int hash_algo_by_id(uint32_t format_id)
{
  int i;
  for (i = 1; i < GIT_HASH_NALGOS; i++)
    if (format_id == hash_algos[i].format_id)
      return i;
  return GIT_HASH_UNKNOWN;
}

int hash_algo_by_length(int len)
{
  int i;
  for (i = 1; i < GIT_HASH_NALGOS; i++)
    if (len == hash_algos[i].rawsz)
      return i;
  return GIT_HASH_UNKNOWN;
}

/*
 * This is meant to hold a *small* number of objects that you would
 * want repo_read_object_file() to be able to return, but yet you do not want
 * to write them into the object store (e.g. a browse-only
 * application).
 */
static struct cached_object {
  struct object_id oid;
  enum object_type type;
  const void *buf;
  unsigned long size;
} *cached_objects;
static int cached_object_nr, cached_object_alloc;

static struct cached_object empty_tree = {
  .oid = {
    .hash = EMPTY_TREE_SHA1_BIN_LITERAL,
  },
  .type = OBJ_TREE,
  .buf = "",
};

static struct cached_object *find_cached_object(const struct object_id *oid)
{
  int i;
  struct cached_object *co = cached_objects;

  for (i = 0; i < cached_object_nr; i++, co++) {
    if (oideq(&co->oid, oid))
      return co;
  }
  if (oideq(oid, the_hash_algo->empty_tree))
    return &empty_tree;
  return NULL;
}


static int get_conv_flags(unsigned flags)
{
  if (flags & HASH_RENORMALIZE)
    return CONV_EOL_RENORMALIZE;
  else if (flags & HASH_WRITE_OBJECT)
    return global_conv_flags_eol | CONV_WRITE_OBJECT;
  else
    return 0;
}


int mkdir_in_gitdir(const char *path)
{
  if (mkdir(path, 0777)) {
    int saved_errno = errno;
    struct stat st;
    struct strbuf sb = STRBUF_INIT;

    if (errno != EEXIST)
      return -1;
    /*
     * Are we looking at a path in a symlinked worktree
     * whose original repository does not yet have it?
     * e.g. .git/rr-cache pointing at its original
     * repository in which the user hasn't performed any
     * conflict resolution yet?
     */
    if (lstat(path, &st) || !S_ISLNK(st.st_mode) ||
        strbuf_readlink(&sb, path, st.st_size) ||
        !is_absolute_path(sb.buf) ||
        mkdir(sb.buf, 0777)) {
      strbuf_release(&sb);
      errno = saved_errno;
      return -1;
    }
    strbuf_release(&sb);
  }
  return adjust_shared_perm(path);
}

static enum scld_error safe_create_leading_directories_1(char *path, int share)
{
  char *next_component = path + offset_1st_component(path);
  enum scld_error ret = SCLD_OK;

  while (ret == SCLD_OK && next_component) {
    struct stat st;
    char *slash = next_component, slash_character;

    while (*slash && !is_dir_sep(*slash))
      slash++;

    if (!*slash)
      break;

    next_component = slash + 1;
    while (is_dir_sep(*next_component))
      next_component++;
    if (!*next_component)
      break;

    slash_character = *slash;
    *slash = '\0';
    if (!stat(path, &st)) {
      /* path exists */
      if (!S_ISDIR(st.st_mode)) {
        errno = ENOTDIR;
        ret = SCLD_EXISTS;
      }
    } else if (mkdir(path, 0777)) {
      if (errno == EEXIST &&
          !stat(path, &st) && S_ISDIR(st.st_mode))
        ; /* somebody created it since we checked */
      else if (errno == ENOENT)
        /*
         * Either mkdir() failed because
         * somebody just pruned the containing
         * directory, or stat() failed because
         * the file that was in our way was
         * just removed.  Either way, inform
         * the caller that it might be worth
         * trying again:
         */
        ret = SCLD_VANISHED;
      else
        ret = SCLD_FAILED;
    } else if (share && adjust_shared_perm(path)) {
      ret = SCLD_PERMS;
    }
    *slash = slash_character;
  }
  return ret;
}

enum scld_error safe_create_leading_directories(char *path)
{
  return safe_create_leading_directories_1(path, 1);
}

enum scld_error safe_create_leading_directories_no_share(char *path)
{
  return safe_create_leading_directories_1(path, 0);
}

enum scld_error safe_create_leading_directories_const(const char *path)
{
  int save_errno;
  /* path points to cache entries, so xstrdup before messing with it */
  char *buf = xstrdup(path);
  enum scld_error result = safe_create_leading_directories(buf);

  save_errno = errno;
  free(buf);
  errno = save_errno;
  return result;
}

static void fill_loose_path(struct strbuf *buf, const struct object_id *oid)
{
  int i;
  for (i = 0; i < the_hash_algo->rawsz; i++) {
    static char hex[] = "0123456789abcdef";
    unsigned int val = oid->hash[i];
    strbuf_addch(buf, hex[val >> 4]);
    strbuf_addch(buf, hex[val & 0xf]);
    if (!i)
      strbuf_addch(buf, '/');
  }
}

static const char *odb_loose_path(struct object_directory *odb,
          struct strbuf *buf,
          const struct object_id *oid)
{
  strbuf_reset(buf);
  strbuf_addstr(buf, odb->path);
  strbuf_addch(buf, '/');
  fill_loose_path(buf, oid);
  return buf->buf;
}

const char *loose_object_path(struct repository *r, struct strbuf *buf,
            const struct object_id *oid)
{
  return odb_loose_path(r->objects->odb, buf, oid);
}

/*
 * Return non-zero iff the path is usable as an alternate object database.
 */
static int alt_odb_usable(struct raw_object_store *o,
        struct strbuf *path,
        const char *normalized_objdir, khiter_t *pos)
{
  int r;

  /* Detect cases where alternate disappeared */
  if (!is_directory(path->buf)) {
    error(_("object directory %s does not exist; "
      "check .git/objects/info/alternates"),
          path->buf);
    return 0;
  }

  /*
   * Prevent the common mistake of listing the same
   * thing twice, or object directory itself.
   */
  if (!o->odb_by_path) {
    khiter_t p;

    o->odb_by_path = kh_init_odb_path_map();
    assert(!o->odb->next);
    p = kh_put_odb_path_map(o->odb_by_path, o->odb->path, &r);
    assert(r == 1); /* never used */
    kh_value(o->odb_by_path, p) = o->odb;
  }
  if (fspatheq(path->buf, normalized_objdir))
    return 0;
  *pos = kh_put_odb_path_map(o->odb_by_path, path->buf, &r);
  /* r: 0 = exists, 1 = never used, 2 = deleted */
  return r == 0 ? 0 : 1;
}

/*
 * Prepare alternate object database registry.
 *
 * The variable alt_odb_list points at the list of struct
 * object_directory.  The elements on this list come from
 * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
 * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
 * whose contents is similar to that environment variable but can be
 * LF separated.  Its base points at a statically allocated buffer that
 * contains "/the/directory/corresponding/to/.git/objects/...", while
 * its name points just after the slash at the end of ".git/objects/"
 * in the example above, and has enough space to hold all hex characters
 * of the object ID, an extra slash for the first level indirection, and
 * the terminating NUL.
 */
static void read_info_alternates(struct repository *r,
         const char *relative_base,
         int depth);
static int link_alt_odb_entry(struct repository *r, const struct strbuf *entry,
  const char *relative_base, int depth, const char *normalized_objdir)
{
  struct object_directory *ent;
  struct strbuf pathbuf = STRBUF_INIT;
  struct strbuf tmp = STRBUF_INIT;
  khiter_t pos;
  int ret = -1;

  if (!is_absolute_path(entry->buf) && relative_base) {
    strbuf_realpath(&pathbuf, relative_base, 1);
    strbuf_addch(&pathbuf, '/');
  }
  strbuf_addbuf(&pathbuf, entry);

  if (!strbuf_realpath(&tmp, pathbuf.buf, 0)) {
    error(_("unable to normalize alternate object path: %s"),
          pathbuf.buf);
    goto error;
  }
  strbuf_swap(&pathbuf, &tmp);

  /*
   * The trailing slash after the directory name is given by
   * this function at the end. Remove duplicates.
   */
  while (pathbuf.len && pathbuf.buf[pathbuf.len - 1] == '/')
    strbuf_setlen(&pathbuf, pathbuf.len - 1);

  if (!alt_odb_usable(r->objects, &pathbuf, normalized_objdir, &pos))
    goto error;

  CALLOC_ARRAY(ent, 1);
  /* pathbuf.buf is already in r->objects->odb_by_path */
  ent->path = strbuf_detach(&pathbuf, NULL);

  /* add the alternate entry */
  *r->objects->odb_tail = ent;
  r->objects->odb_tail = &(ent->next);
  ent->next = NULL;
  assert(r->objects->odb_by_path);
  kh_value(r->objects->odb_by_path, pos) = ent;

  /* recursively add alternates */
  read_info_alternates(r, ent->path, depth + 1);
  ret = 0;
 error:
  strbuf_release(&tmp);
  strbuf_release(&pathbuf);
  return ret;
}

static const char *parse_alt_odb_entry(const char *string,
               int sep,
               struct strbuf *out)
{
  const char *end;

  strbuf_reset(out);

  if (*string == '#') {
    /* comment; consume up to next separator */
    end = strchrnul(string, sep);
  } else if (*string == '"' && !unquote_c_style(out, string, &end)) {
    /*
     * quoted path; unquote_c_style has copied the
     * data for us and set "end". Broken quoting (e.g.,
     * an entry that doesn't end with a quote) falls
     * back to the unquoted case below.
     */
  } else {
    /* normal, unquoted path */
    end = strchrnul(string, sep);
    strbuf_add(out, string, end - string);
  }

  if (*end)
    end++;
  return end;
}

static void link_alt_odb_entries(struct repository *r, const char *alt,
         int sep, const char *relative_base, int depth)
{
  struct strbuf objdirbuf = STRBUF_INIT;
  struct strbuf entry = STRBUF_INIT;

  if (!alt || !*alt)
    return;

  if (depth > 5) {
    error(_("%s: ignoring alternate object stores, nesting too deep"),
        relative_base);
    return;
  }

  strbuf_realpath(&objdirbuf, r->objects->odb->path, 1);

  while (*alt) {
    alt = parse_alt_odb_entry(alt, sep, &entry);
    if (!entry.len)
      continue;
    link_alt_odb_entry(r, &entry,
           relative_base, depth, objdirbuf.buf);
  }
  strbuf_release(&entry);
  strbuf_release(&objdirbuf);
}

static void read_info_alternates(struct repository *r,
         const char *relative_base,
         int depth)
{
  char *path;
  struct strbuf buf = STRBUF_INIT;

  path = xstrfmt("%s/info/alternates", relative_base);
  if (strbuf_read_file(&buf, path, 1024) < 0) {
    warn_on_fopen_errors(path);
    free(path);
    return;
  }

  link_alt_odb_entries(r, buf.buf, '\n', relative_base, depth);
  strbuf_release(&buf);
  free(path);
}

void add_to_alternates_file(const char *reference)
{
  struct lock_file lock = LOCK_INIT;
  char *alts = git_pathdup("objects/info/alternates");
  FILE *in, *out;
  int found = 0;

  hold_lock_file_for_update(&lock, alts, LOCK_DIE_ON_ERROR);
  out = fdopen_lock_file(&lock, "w");
  if (!out)
    die_errno(_("unable to fdopen alternates lockfile"));

  in = fopen(alts, "r");
  if (in) {
    struct strbuf line = STRBUF_INIT;

    while (strbuf_getline(&line, in) != EOF) {
      if (!strcmp(reference, line.buf)) {
        found = 1;
        break;
      }
      fprintf_or_die(out, "%s\n", line.buf);
    }

    strbuf_release(&line);
    fclose(in);
  }
  else if (errno != ENOENT)
    die_errno(_("unable to read alternates file"));

  if (found) {
    rollback_lock_file(&lock);
  } else {
    fprintf_or_die(out, "%s\n", reference);
    if (commit_lock_file(&lock))
      die_errno(_("unable to move new alternates file into place"));
    if (the_repository->objects->loaded_alternates)
      link_alt_odb_entries(the_repository, reference,
               '\n', NULL, 0);
  }
  free(alts);
}

void add_to_alternates_memory(const char *reference)
{
  /*
   * Make sure alternates are initialized, or else our entry may be
   * overwritten when they are.
   */
  prepare_alt_odb(the_repository);

  link_alt_odb_entries(the_repository, reference,
           '\n', NULL, 0);
}

struct object_directory *set_temporary_primary_odb(const char *dir, int will_destroy)
{
  struct object_directory *new_odb;

  /*
   * Make sure alternates are initialized, or else our entry may be
   * overwritten when they are.
   */
  prepare_alt_odb(the_repository);

  /*
   * Make a new primary odb and link the old primary ODB in as an
   * alternate
   */
  new_odb = xcalloc(1, sizeof(*new_odb));
  new_odb->path = xstrdup(dir);

  /*
   * Disable ref updates while a temporary odb is active, since
   * the objects in the database may roll back.
   */
  new_odb->disable_ref_updates = 1;
  new_odb->will_destroy = will_destroy;
  new_odb->next = the_repository->objects->odb;
  the_repository->objects->odb = new_odb;
  return new_odb->next;
}

void restore_primary_odb(struct object_directory *restore_odb, const char *old_path)
{
  struct object_directory *cur_odb = the_repository->objects->odb;

  if (strcmp(old_path, cur_odb->path))
    BUG("expected %s as primary object store; found %s",
        old_path, cur_odb->path);

  if (cur_odb->next != restore_odb)
    BUG("we expect the old primary object store to be the first alternate");

  the_repository->objects->odb = restore_odb;
  free_object_directory(cur_odb);
}

/*
 * Compute the exact path an alternate is at and returns it. In case of
 * error NULL is returned and the human readable error is added to `err`
 * `path` may be relative and should point to $GIT_DIR.
 * `err` must not be null.
 */
char *compute_alternate_path(const char *path, struct strbuf *err)
{
  char *ref_git = NULL;
  const char *repo;
  int seen_error = 0;

  ref_git = real_pathdup(path, 0);
  if (!ref_git) {
    seen_error = 1;
    strbuf_addf(err, _("path '%s' does not exist"), path);
    goto out;
  }

  repo = read_gitfile(ref_git);
  if (!repo)
    repo = read_gitfile(mkpath("%s/.git", ref_git));
  if (repo) {
    free(ref_git);
    ref_git = xstrdup(repo);
  }

  if (!repo && is_directory(mkpath("%s/.git/objects", ref_git))) {
    char *ref_git_git = mkpathdup("%s/.git", ref_git);
    free(ref_git);
    ref_git = ref_git_git;
  } else if (!is_directory(mkpath("%s/objects", ref_git))) {
    struct strbuf sb = STRBUF_INIT;
    seen_error = 1;
    if (get_common_dir(&sb, ref_git)) {
      strbuf_addf(err,
            _("reference repository '%s' as a linked "
              "checkout is not supported yet."),
            path);
      goto out;
    }

    strbuf_addf(err, _("reference repository '%s' is not a "
          "local repository."), path);
    goto out;
  }

  if (!access(mkpath("%s/shallow", ref_git), F_OK)) {
    strbuf_addf(err, _("reference repository '%s' is shallow"),
          path);
    seen_error = 1;
    goto out;
  }

  if (!access(mkpath("%s/info/grafts", ref_git), F_OK)) {
    strbuf_addf(err,
          _("reference repository '%s' is grafted"),
          path);
    seen_error = 1;
    goto out;
  }

out:
  if (seen_error) {
    FREE_AND_NULL(ref_git);
  }

  return ref_git;
}

struct object_directory *find_odb(struct repository *r, const char *obj_dir)
{
  struct object_directory *odb;
  char *obj_dir_real = real_pathdup(obj_dir, 1);
  struct strbuf odb_path_real = STRBUF_INIT;

  prepare_alt_odb(r);
  for (odb = r->objects->odb; odb; odb = odb->next) {
    strbuf_realpath(&odb_path_real, odb->path, 1);
    if (!strcmp(obj_dir_real, odb_path_real.buf))
      break;
  }

  free(obj_dir_real);
  strbuf_release(&odb_path_real);

  if (!odb)
    die(_("could not find object directory matching %s"), obj_dir);
  return odb;
}

static void fill_alternate_refs_command(struct child_process *cmd,
          const char *repo_path)
{
  const char *value;

  if (!git_config_get_value("core.alternateRefsCommand", &value)) {
    cmd->use_shell = 1;

    strvec_push(&cmd->args, value);
    strvec_push(&cmd->args, repo_path);
  } else {
    cmd->git_cmd = 1;

    strvec_pushf(&cmd->args, "--git-dir=%s", repo_path);
    strvec_push(&cmd->args, "for-each-ref");
    strvec_push(&cmd->args, "--format=%(objectname)");

    if (!git_config_get_value("core.alternateRefsPrefixes", &value)) {
      strvec_push(&cmd->args, "--");
      strvec_split(&cmd->args, value);
    }
  }

  strvec_pushv(&cmd->env, (const char **)local_repo_env);
  cmd->out = -1;
}

static void read_alternate_refs(const char *path,
        alternate_ref_fn *cb,
        void *data)
{
  struct child_process cmd = CHILD_PROCESS_INIT;
  struct strbuf line = STRBUF_INIT;
  FILE *fh;

  fill_alternate_refs_command(&cmd, path);

  if (start_command(&cmd))
    return;

  fh = xfdopen(cmd.out, "r");
  while (strbuf_getline_lf(&line, fh) != EOF) {
    struct object_id oid;
    const char *p;

    if (parse_oid_hex(line.buf, &oid, &p) || *p) {
      warning(_("invalid line while parsing alternate refs: %s"),
        line.buf);
      break;
    }

    cb(&oid, data);
  }

  fclose(fh);
  finish_command(&cmd);
  strbuf_release(&line);
}

struct alternate_refs_data {
  alternate_ref_fn *fn;
  void *data;
};

static int refs_from_alternate_cb(struct object_directory *e,
          void *data)
{
  struct strbuf path = STRBUF_INIT;
  size_t base_len;
  struct alternate_refs_data *cb = data;

  if (!strbuf_realpath(&path, e->path, 0))
    goto out;
  if (!strbuf_strip_suffix(&path, "/objects"))
    goto out;
  base_len = path.len;

  /* Is this a git repository with refs? */
  strbuf_addstr(&path, "/refs");
  if (!is_directory(path.buf))
    goto out;
  strbuf_setlen(&path, base_len);

  read_alternate_refs(path.buf, cb->fn, cb->data);

out:
  strbuf_release(&path);
  return 0;
}

void for_each_alternate_ref(alternate_ref_fn fn, void *data)
{
  struct alternate_refs_data cb;
  cb.fn = fn;
  cb.data = data;
  foreach_alt_odb(refs_from_alternate_cb, &cb);
}

int foreach_alt_odb(alt_odb_fn fn, void *cb)
{
  struct object_directory *ent;
  int r = 0;

  prepare_alt_odb(the_repository);
  for (ent = the_repository->objects->odb->next; ent; ent = ent->next) {
    r = fn(ent, cb);
    if (r)
      break;
  }
  return r;
}

void prepare_alt_odb(struct repository *r)
{
  if (r->objects->loaded_alternates)
    return;

  link_alt_odb_entries(r, r->objects->alternate_db, PATH_SEP, NULL, 0);

  read_info_alternates(r, r->objects->odb->path, 0);
  r->objects->loaded_alternates = 1;
}

int has_alt_odb(struct repository *r)
{
  prepare_alt_odb(r);
  return !!r->objects->odb->next;
}

/* Returns 1 if we have successfully freshened the file, 0 otherwise. */
static int freshen_file(const char *fn)
{
  return !utime(fn, NULL);
}

/*
 * All of the check_and_freshen functions return 1 if the file exists and was
 * freshened (if freshening was requested), 0 otherwise. If they return
 * 0, you should not assume that it is safe to skip a write of the object (it
 * either does not exist on disk, or has a stale mtime and may be subject to
 * pruning).
 */
int check_and_freshen_file(const char *fn, int freshen)
{
  if (access(fn, F_OK))
    return 0;
  if (freshen && !freshen_file(fn))
    return 0;
  return 1;
}

static int check_and_freshen_odb(struct object_directory *odb,
         const struct object_id *oid,
         int freshen)
{
  static struct strbuf path = STRBUF_INIT;
  odb_loose_path(odb, &path, oid);
  return check_and_freshen_file(path.buf, freshen);
}

static int check_and_freshen_local(const struct object_id *oid, int freshen)
{
  return check_and_freshen_odb(the_repository->objects->odb, oid, freshen);
}

static int check_and_freshen_nonlocal(const struct object_id *oid, int freshen)
{
  struct object_directory *odb;

  prepare_alt_odb(the_repository);
  for (odb = the_repository->objects->odb->next; odb; odb = odb->next) {
    if (check_and_freshen_odb(odb, oid, freshen))
      return 1;
  }
  return 0;
}

static int check_and_freshen(const struct object_id *oid, int freshen)
{
  return check_and_freshen_local(oid, freshen) ||
         check_and_freshen_nonlocal(oid, freshen);
}

int has_loose_object_nonlocal(const struct object_id *oid)
{
  return check_and_freshen_nonlocal(oid, 0);
}

int has_loose_object(const struct object_id *oid)
{
  return check_and_freshen(oid, 0);
}

static void mmap_limit_check(size_t length)
{
  static size_t limit = 0;
  if (!limit) {
    limit = git_env_ulong("GIT_MMAP_LIMIT", 0);
    if (!limit)
      limit = SIZE_MAX;
  }
  if (length > limit)
    die(_("attempting to mmap %"PRIuMAX" over limit %"PRIuMAX),
        (uintmax_t)length, (uintmax_t)limit);
}

void *xmmap_gently(void *start, size_t length,
      int prot, int flags, int fd, off_t offset)
{
  void *ret;

  mmap_limit_check(length);
  ret = mmap(start, length, prot, flags, fd, offset);
  if (ret == MAP_FAILED && !length)
    ret = NULL;
  return ret;
}

const char *mmap_os_err(void)
{
  static const char blank[] = "";
#if defined(__linux__)
  if (errno == ENOMEM) {
    /* this continues an existing error message: */
    static const char enomem[] =
", check sys.vm.max_map_count and/or RLIMIT_DATA";
    return enomem;
  }
#endif /* OS-specific bits */
  return blank;
}

void *xmmap(void *start, size_t length,
  int prot, int flags, int fd, off_t offset)
{
  void *ret = xmmap_gently(start, length, prot, flags, fd, offset);
  if (ret == MAP_FAILED)
    die_errno(_("mmap failed%s"), mmap_os_err());
  return ret;
}

static int format_object_header_literally(char *str, size_t size,
            const char *type, size_t objsize)
{
  return xsnprintf(str, size, "%s %"PRIuMAX, type, (uintmax_t)objsize) + 1;
}

int format_object_header(char *str, size_t size, enum object_type type,
       size_t objsize)
{
  const char *name = type_name(type);

  if (!name)
    BUG("could not get a type name for 'enum object_type' value %d", type);

  return format_object_header_literally(str, size, name, objsize);
}

int check_object_signature(struct repository *r, const struct object_id *oid,
         void *buf, unsigned long size,
         enum object_type type)
{
  const struct git_hash_algo *algo =
    oid->algo ? &hash_algos[oid->algo] : r->hash_algo;
  struct object_id real_oid;

  hash_object_file(algo, buf, size, type, &real_oid);

  return !oideq(oid, &real_oid) ? -1 : 0;
}

int stream_object_signature(struct repository *r, const struct object_id *oid)
{
  struct object_id real_oid;
  unsigned long size;
  enum object_type obj_type;
  struct git_istream *st;
  git_hash_ctx c;
  char hdr[MAX_HEADER_LEN];
  int hdrlen;

  st = open_istream(r, oid, &obj_type, &size, NULL);
  if (!st)
    return -1;

  /* Generate the header */
  hdrlen = format_object_header(hdr, sizeof(hdr), obj_type, size);

  /* Sha1.. */
  r->hash_algo->init_fn(&c);
  r->hash_algo->update_fn(&c, hdr, hdrlen);
  for (;;) {
    char buf[1024 * 16];
    ssize_t readlen = read_istream(st, buf, sizeof(buf));

    if (readlen < 0) {
      close_istream(st);
      return -1;
    }
    if (!readlen)
      break;
    r->hash_algo->update_fn(&c, buf, readlen);
  }
  r->hash_algo->final_oid_fn(&real_oid, &c);
  close_istream(st);
  return !oideq(oid, &real_oid) ? -1 : 0;
}

int git_open_cloexec(const char *name, int flags)
{
  int fd;
  static int o_cloexec = O_CLOEXEC;

  fd = open(name, flags | o_cloexec);
  if ((o_cloexec & O_CLOEXEC) && fd < 0 && errno == EINVAL) {
    /* Try again w/o O_CLOEXEC: the kernel might not support it */
    o_cloexec &= ~O_CLOEXEC;
    fd = open(name, flags | o_cloexec);
  }

#if defined(F_GETFD) && defined(F_SETFD) && defined(FD_CLOEXEC)
  {
    static int fd_cloexec = FD_CLOEXEC;

    if (!o_cloexec && 0 <= fd && fd_cloexec) {
      /* Opened w/o O_CLOEXEC?  try with fcntl(2) to add it */
      int flags = fcntl(fd, F_GETFD);
      if (fcntl(fd, F_SETFD, flags | fd_cloexec))
        fd_cloexec = 0;
    }
  }
#endif
  return fd;
}

/*
 * Find "oid" as a loose object in the local repository or in an alternate.
 * Returns 0 on success, negative on failure.
 *
 * The "path" out-parameter will give the path of the object we found (if any).
 * Note that it may point to static storage and is only valid until another
 * call to stat_loose_object().
 */
static int stat_loose_object(struct repository *r, const struct object_id *oid,
           struct stat *st, const char **path)
{
  struct object_directory *odb;
  static struct strbuf buf = STRBUF_INIT;

  prepare_alt_odb(r);
  for (odb = r->objects->odb; odb; odb = odb->next) {
    *path = odb_loose_path(odb, &buf, oid);
    if (!lstat(*path, st))
      return 0;
  }

  return -1;
}

/*
 * Like stat_loose_object(), but actually open the object and return the
 * descriptor. See the caveats on the "path" parameter above.
 */
static int open_loose_object(struct repository *r,
           const struct object_id *oid, const char **path)
{
  int fd;
  struct object_directory *odb;
  int most_interesting_errno = ENOENT;
  static struct strbuf buf = STRBUF_INIT;

  prepare_alt_odb(r);
  for (odb = r->objects->odb; odb; odb = odb->next) {
    *path = odb_loose_path(odb, &buf, oid);
    fd = git_open(*path);
    if (fd >= 0)
      return fd;

    if (most_interesting_errno == ENOENT)
      most_interesting_errno = errno;
  }
  errno = most_interesting_errno;
  return -1;
}

static int quick_has_loose(struct repository *r,
         const struct object_id *oid)
{
  struct object_directory *odb;

  prepare_alt_odb(r);
  for (odb = r->objects->odb; odb; odb = odb->next) {
    if (oidtree_contains(odb_loose_cache(odb, oid), oid))
      return 1;
  }
  return 0;
}

/*
 * Map and close the given loose object fd. The path argument is used for
 * error reporting.
 */
static void *map_fd(int fd, const char *path, unsigned long *size)
{
  void *map = NULL;
  struct stat st;

  if (!fstat(fd, &st)) {
    *size = xsize_t(st.st_size);
    if (!*size) {
      /* mmap() is forbidden on empty files */
      error(_("object file %s is empty"), path);
      close(fd);
      return NULL;
    }
    map = xmmap(NULL, *size, PROT_READ, MAP_PRIVATE, fd, 0);
  }
  close(fd);
  return map;
}

void *map_loose_object(struct repository *r,
           const struct object_id *oid,
           unsigned long *size)
{
  const char *p;
  int fd = open_loose_object(r, oid, &p);

  if (fd < 0)
    return NULL;
  return map_fd(fd, p, size);
}

enum unpack_loose_header_result unpack_loose_header(git_zstream *stream,
                unsigned char *map,
                unsigned long mapsize,
                void *buffer,
                unsigned long bufsiz,
                struct strbuf *header)
{
  int status;

  /* Get the data stream */
  memset(stream, 0, sizeof(*stream));
  stream->next_in = map;
  stream->avail_in = mapsize;
  stream->next_out = buffer;
  stream->avail_out = bufsiz;

  git_inflate_init(stream);
  obj_read_unlock();
  status = git_inflate(stream, 0);
  obj_read_lock();
  if (status < Z_OK)
    return ULHR_BAD;

  /*
   * Check if entire header is unpacked in the first iteration.
   */
  if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
    return ULHR_OK;

  /*
   * We have a header longer than MAX_HEADER_LEN. The "header"
   * here is only non-NULL when we run "cat-file
   * --allow-unknown-type".
   */
  if (!header)
    return ULHR_TOO_LONG;

  /*
   * buffer[0..bufsiz] was not large enough.  Copy the partial
   * result out to header, and then append the result of further
   * reading the stream.
   */
  strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
  stream->next_out = buffer;
  stream->avail_out = bufsiz;

  do {
    obj_read_unlock();
    status = git_inflate(stream, 0);
    obj_read_lock();
    strbuf_add(header, buffer, stream->next_out - (unsigned char *)buffer);
    if (memchr(buffer, '\0', stream->next_out - (unsigned char *)buffer))
      return 0;
    stream->next_out = buffer;
    stream->avail_out = bufsiz;
  } while (status != Z_STREAM_END);
  return ULHR_TOO_LONG;
}

static void *unpack_loose_rest(git_zstream *stream,
             void *buffer, unsigned long size,
             const struct object_id *oid)
{
  int bytes = strlen(buffer) + 1;
  unsigned char *buf = xmallocz(size);
  unsigned long n;
  int status = Z_OK;

  n = stream->total_out - bytes;
  if (n > size)
    n = size;
  memcpy(buf, (char *) buffer + bytes, n);
  bytes = n;
  if (bytes <= size) {
    /*
     * The above condition must be (bytes <= size), not
     * (bytes < size).  In other words, even though we
     * expect no more output and set avail_out to zero,
     * the input zlib stream may have bytes that express
     * "this concludes the stream", and we *do* want to
     * eat that input.
     *
     * Otherwise we would not be able to test that we
     * consumed all the input to reach the expected size;
     * we also want to check that zlib tells us that all
     * went well with status == Z_STREAM_END at the end.
     */
    stream->next_out = buf + bytes;
    stream->avail_out = size - bytes;
    while (status == Z_OK) {
      obj_read_unlock();
      status = git_inflate(stream, Z_FINISH);
      obj_read_lock();
    }
  }
  if (status == Z_STREAM_END && !stream->avail_in) {
    git_inflate_end(stream);
    return buf;
  }

  if (status < 0)
    error(_("corrupt loose object '%s'"), oid_to_hex(oid));
  else if (stream->avail_in)
    error(_("garbage at end of loose object '%s'"),
          oid_to_hex(oid));
  free(buf);
  return NULL;
}

/*
 * We used to just use "sscanf()", but that's actually way
 * too permissive for what we want to check. So do an anal
 * object header parse by hand.
 */
int parse_loose_header(const char *hdr, struct object_info *oi)
{
  const char *type_buf = hdr;
  size_t size;
  int type, type_len = 0;

  /*
   * The type can be of any size but is followed by
   * a space.
   */
  for (;;) {
    char c = *hdr++;
    if (!c)
      return -1;
    if (c == ' ')
      break;
    type_len++;
  }

  type = type_from_string_gently(type_buf, type_len, 1);
  if (oi->type_name)
    strbuf_add(oi->type_name, type_buf, type_len);
  if (oi->typep)
    *oi->typep = type;

  /*
   * The length must follow immediately, and be in canonical
   * decimal format (ie "010" is not valid).
   */
  size = *hdr++ - '0';
  if (size > 9)
    return -1;
  if (size) {
    for (;;) {
      unsigned long c = *hdr - '0';
      if (c > 9)
        break;
      hdr++;
      size = st_add(st_mult(size, 10), c);
    }
  }

  if (oi->sizep)
    *oi->sizep = cast_size_t_to_ulong(size);

  /*
   * The length must be followed by a zero byte
   */
  if (*hdr)
    return -1;

  /*
   * The format is valid, but the type may still be bogus. The
   * Caller needs to check its oi->typep.
   */
  return 0;
}

static int loose_object_info(struct repository *r,
           const struct object_id *oid,
           struct object_info *oi, int flags)
{
  int status = 0;
  int fd;
  unsigned long mapsize;
  const char *path;
  void *map;
  git_zstream stream;
  char hdr[MAX_HEADER_LEN];
  struct strbuf hdrbuf = STRBUF_INIT;
  unsigned long size_scratch;
  enum object_type type_scratch;
  int allow_unknown = flags & OBJECT_INFO_ALLOW_UNKNOWN_TYPE;

  if (oi->delta_base_oid)
    oidclr(oi->delta_base_oid, the_repository->hash_algo);

  /*
   * If we don't care about type or size, then we don't
   * need to look inside the object at all. Note that we
   * do not optimize out the stat call, even if the
   * caller doesn't care about the disk-size, since our
   * return value implicitly indicates whether the
   * object even exists.
   */
  if (!oi->typep && !oi->type_name && !oi->sizep && !oi->contentp) {
    struct stat st;
    if (!oi->disk_sizep && (flags & OBJECT_INFO_QUICK))
      return quick_has_loose(r, oid) ? 0 : -1;
    if (stat_loose_object(r, oid, &st, &path) < 0)
      return -1;
    if (oi->disk_sizep)
      *oi->disk_sizep = st.st_size;
    return 0;
  }

  fd = open_loose_object(r, oid, &path);
  if (fd < 0) {
    if (errno != ENOENT)
      error_errno(_("unable to open loose object %s"), oid_to_hex(oid));
    return -1;
  }
  map = map_fd(fd, path, &mapsize);
  if (!map)
    return -1;

  if (!oi->sizep)
    oi->sizep = &size_scratch;
  if (!oi->typep)
    oi->typep = &type_scratch;

  if (oi->disk_sizep)
    *oi->disk_sizep = mapsize;

  switch (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr),
            allow_unknown ? &hdrbuf : NULL)) {
  case ULHR_OK:
    if (parse_loose_header(hdrbuf.len ? hdrbuf.buf : hdr, oi) < 0)
      status = error(_("unable to parse %s header"), oid_to_hex(oid));
    else if (!allow_unknown && *oi->typep < 0)
      die(_("invalid object type"));

    if (!oi->contentp)
      break;
    *oi->contentp = unpack_loose_rest(&stream, hdr, *oi->sizep, oid);
    if (*oi->contentp)
      goto cleanup;

    status = -1;
    break;
  case ULHR_BAD:
    status = error(_("unable to unpack %s header"),
             oid_to_hex(oid));
    break;
  case ULHR_TOO_LONG:
    status = error(_("header for %s too long, exceeds %d bytes"),
             oid_to_hex(oid), MAX_HEADER_LEN);
    break;
  }

  if (status && (flags & OBJECT_INFO_DIE_IF_CORRUPT))
    die(_("loose object %s (stored in %s) is corrupt"),
        oid_to_hex(oid), path);

  git_inflate_end(&stream);
cleanup:
  munmap(map, mapsize);
  if (oi->sizep == &size_scratch)
    oi->sizep = NULL;
  strbuf_release(&hdrbuf);
  if (oi->typep == &type_scratch)
    oi->typep = NULL;
  oi->whence = OI_LOOSE;
  return status;
}

int obj_read_use_lock = 0;
pthread_mutex_t obj_read_mutex;

void enable_obj_read_lock(void)
{
  if (obj_read_use_lock)
    return;

  obj_read_use_lock = 1;
  init_recursive_mutex(&obj_read_mutex);
}

void disable_obj_read_lock(void)
{
  if (!obj_read_use_lock)
    return;

  obj_read_use_lock = 0;
  pthread_mutex_destroy(&obj_read_mutex);
}

int fetch_if_missing = 1;

static int do_oid_object_info_extended(struct repository *r,
               const struct object_id *oid,
               struct object_info *oi, unsigned flags)
{
  static struct object_info blank_oi = OBJECT_INFO_INIT;
  struct cached_object *co;
  struct pack_entry e;
  int rtype;
  const struct object_id *real = oid;
  int already_retried = 0;


  if (flags & OBJECT_INFO_LOOKUP_REPLACE)
    real = lookup_replace_object(r, oid);

  if (is_null_oid(real))
    return -1;

  if (!oi)
    oi = &blank_oi;

  co = find_cached_object(real);
  if (co) {
    if (oi->typep)
      *(oi->typep) = co->type;
    if (oi->sizep)
      *(oi->sizep) = co->size;
    if (oi->disk_sizep)
      *(oi->disk_sizep) = 0;
    if (oi->delta_base_oid)
      oidclr(oi->delta_base_oid, the_repository->hash_algo);
    if (oi->type_name)
      strbuf_addstr(oi->type_name, type_name(co->type));
    if (oi->contentp)
      *oi->contentp = xmemdupz(co->buf, co->size);
    oi->whence = OI_CACHED;
    return 0;
  }

  while (1) {
    if (find_pack_entry(r, real, &e))
      break;

    /* Most likely it's a loose object. */
    if (!loose_object_info(r, real, oi, flags))
      return 0;

    /* Not a loose object; someone else may have just packed it. */
    if (!(flags & OBJECT_INFO_QUICK)) {
      reprepare_packed_git(r);
      if (find_pack_entry(r, real, &e))
        break;
    }

    /*
     * If r is the_repository, this might be an attempt at
     * accessing a submodule object as if it were in the_repository
     * (having called add_submodule_odb() on that submodule's ODB).
     * If any such ODBs exist, register them and try again.
     */
    if (r == the_repository &&
        register_all_submodule_odb_as_alternates())
      /* We added some alternates; retry */
      continue;

    /* Check if it is a missing object */
    if (fetch_if_missing && repo_has_promisor_remote(r) &&
        !already_retried &&
        !(flags & OBJECT_INFO_SKIP_FETCH_OBJECT)) {
      promisor_remote_get_direct(r, real, 1);
      already_retried = 1;
      continue;
    }

    if (flags & OBJECT_INFO_DIE_IF_CORRUPT) {
      const struct packed_git *p;
      if ((flags & OBJECT_INFO_LOOKUP_REPLACE) && !oideq(real, oid))
        die(_("replacement %s not found for %s"),
            oid_to_hex(real), oid_to_hex(oid));
      if ((p = has_packed_and_bad(r, real)))
        die(_("packed object %s (stored in %s) is corrupt"),
            oid_to_hex(real), p->pack_name);
    }
    return -1;
  }

  if (oi == &blank_oi)
    /*
     * We know that the caller doesn't actually need the
     * information below, so return early.
     */
    return 0;
  rtype = packed_object_info(r, e.p, e.offset, oi);
  if (rtype < 0) {
    mark_bad_packed_object(e.p, real);
    return do_oid_object_info_extended(r, real, oi, 0);
  } else if (oi->whence == OI_PACKED) {
    oi->u.packed.offset = e.offset;
    oi->u.packed.pack = e.p;
    oi->u.packed.is_delta = (rtype == OBJ_REF_DELTA ||
           rtype == OBJ_OFS_DELTA);
  }

  return 0;
}

static int oid_object_info_convert(struct repository *r,
           const struct object_id *input_oid,
           struct object_info *input_oi, unsigned flags)
{
  const struct git_hash_algo *input_algo = &hash_algos[input_oid->algo];
  int do_die = flags & OBJECT_INFO_DIE_IF_CORRUPT;
  struct strbuf type_name = STRBUF_INIT;
  struct object_id oid, delta_base_oid;
  struct object_info new_oi, *oi;
  unsigned long size;
  void *content;
  int ret;

  if (repo_oid_to_algop(r, input_oid, the_hash_algo, &oid)) {
    if (do_die)
      die(_("missing mapping of %s to %s"),
          oid_to_hex(input_oid), the_hash_algo->name);
    return -1;
  }

  /* Is new_oi needed? */
  oi = input_oi;
  if (input_oi && (input_oi->delta_base_oid || input_oi->sizep ||
       input_oi->contentp)) {
    new_oi = *input_oi;
    /* Does delta_base_oid need to be converted? */
    if (input_oi->delta_base_oid)
      new_oi.delta_base_oid = &delta_base_oid;
    /* Will the attributes differ when converted? */
    if (input_oi->sizep || input_oi->contentp) {
      new_oi.contentp = &content;
      new_oi.sizep = &size;
      new_oi.type_name = &type_name;
    }
    oi = &new_oi;
  }

  ret = oid_object_info_extended(r, &oid, oi, flags);
  if (ret)
    return -1;
  if (oi == input_oi)
    return ret;

  if (new_oi.contentp) {
    struct strbuf outbuf = STRBUF_INIT;
    enum object_type type;

    type = type_from_string_gently(type_name.buf, type_name.len,
                 !do_die);
    if (type == -1)
      return -1;
    if (type != OBJ_BLOB) {
      ret = convert_object_file(&outbuf,
              the_hash_algo, input_algo,
              content, size, type, !do_die);
      free(content);
      if (ret == -1)
        return -1;
      size = outbuf.len;
      content = strbuf_detach(&outbuf, NULL);
    }
    if (input_oi->sizep)
      *input_oi->sizep = size;
    if (input_oi->contentp)
      *input_oi->contentp = content;
    else
      free(content);
    if (input_oi->type_name)
      *input_oi->type_name = type_name;
    else
      strbuf_release(&type_name);
  }
  if (new_oi.delta_base_oid == &delta_base_oid) {
    if (repo_oid_to_algop(r, &delta_base_oid, input_algo,
         input_oi->delta_base_oid)) {
      if (do_die)
        die(_("missing mapping of %s to %s"),
            oid_to_hex(&delta_base_oid),
            input_algo->name);
      return -1;
    }
  }
  input_oi->whence = new_oi.whence;
  input_oi->u = new_oi.u;
  return ret;
}

int oid_object_info_extended(struct repository *r, const struct object_id *oid,
           struct object_info *oi, unsigned flags)
{
  int ret;

  if (oid->algo && (hash_algo_by_ptr(r->hash_algo) != oid->algo))
    return oid_object_info_convert(r, oid, oi, flags);

  obj_read_lock();
  ret = do_oid_object_info_extended(r, oid, oi, flags);
  obj_read_unlock();
  return ret;
}


/* returns enum object_type or negative */
int oid_object_info(struct repository *r,
        const struct object_id *oid,
        unsigned long *sizep)
{
  enum object_type type;
  struct object_info oi = OBJECT_INFO_INIT;

  oi.typep = &type;
  oi.sizep = sizep;
  if (oid_object_info_extended(r, oid, &oi,
              OBJECT_INFO_LOOKUP_REPLACE) < 0)
    return -1;
  return type;
}

int pretend_object_file(void *buf, unsigned long len, enum object_type type,
      struct object_id *oid)
{
  struct cached_object *co;
  char *co_buf;

  hash_object_file(the_hash_algo, buf, len, type, oid);
  if (repo_has_object_file_with_flags(the_repository, oid, OBJECT_INFO_QUICK | OBJECT_INFO_SKIP_FETCH_OBJECT) ||
      find_cached_object(oid))
    return 0;
  ALLOC_GROW(cached_objects, cached_object_nr + 1, cached_object_alloc);
  co = &cached_objects[cached_object_nr++];
  co->size = len;
  co->type = type;
  co_buf = xmalloc(len);
  memcpy(co_buf, buf, len);
  co->buf = co_buf;
  oidcpy(&co->oid, oid);
  return 0;
}

/*
 * This function dies on corrupt objects; the callers who want to
 * deal with them should arrange to call oid_object_info_extended() and give
 * error messages themselves.
 */
void *repo_read_object_file(struct repository *r,
          const struct object_id *oid,
          enum object_type *type,
          unsigned long *size)
{
  struct object_info oi = OBJECT_INFO_INIT;
  unsigned flags = OBJECT_INFO_DIE_IF_CORRUPT | OBJECT_INFO_LOOKUP_REPLACE;
  void *data;

  oi.typep = type;
  oi.sizep = size;
  oi.contentp = &data;
  if (oid_object_info_extended(r, oid, &oi, flags))
    return NULL;

  return data;
}

void *read_object_with_reference(struct repository *r,
         const struct object_id *oid,
         enum object_type required_type,
         unsigned long *size,
         struct object_id *actual_oid_return)
{
  enum object_type type;
  void *buffer;
  unsigned long isize;
  struct object_id actual_oid;

  oidcpy(&actual_oid, oid);
  while (1) {
    int ref_length = -1;
    const char *ref_type = NULL;

    buffer = repo_read_object_file(r, &actual_oid, &type, &isize);
    if (!buffer)
      return NULL;
    if (type == required_type) {
      *size = isize;
      if (actual_oid_return)
        oidcpy(actual_oid_return, &actual_oid);
      return buffer;
    }
    /* Handle references */
    else if (type == OBJ_COMMIT)
      ref_type = "tree ";
    else if (type == OBJ_TAG)
      ref_type = "object ";
    else {
      free(buffer);
      return NULL;
    }
    ref_length = strlen(ref_type);

    if (ref_length + the_hash_algo->hexsz > isize ||
        memcmp(buffer, ref_type, ref_length) ||
        get_oid_hex((char *) buffer + ref_length, &actual_oid)) {
      free(buffer);
      return NULL;
    }
    free(buffer);
    /* Now we have the ID of the referred-to object in
     * actual_oid.  Check again. */
  }
}

static void hash_object_body(const struct git_hash_algo *algo, git_hash_ctx *c,
           const void *buf, unsigned long len,
           struct object_id *oid,
           char *hdr, int *hdrlen)
{
  algo->init_fn(c);
  algo->update_fn(c, hdr, *hdrlen);
  algo->update_fn(c, buf, len);
  algo->final_oid_fn(oid, c);
}

static void write_object_file_prepare(const struct git_hash_algo *algo,
              const void *buf, unsigned long len,
              enum object_type type, struct object_id *oid,
              char *hdr, int *hdrlen)
{
  git_hash_ctx c;

  /* Generate the header */
  *hdrlen = format_object_header(hdr, *hdrlen, type, len);

  /* Sha1.. */
  hash_object_body(algo, &c, buf, len, oid, hdr, hdrlen);
}

static void write_object_file_prepare_literally(const struct git_hash_algo *algo,
              const void *buf, unsigned long len,
              const char *type, struct object_id *oid,
              char *hdr, int *hdrlen)
{
  git_hash_ctx c;

  *hdrlen = format_object_header_literally(hdr, *hdrlen, type, len);
  hash_object_body(algo, &c, buf, len, oid, hdr, hdrlen);
}

/*
 * Move the just written object into its final resting place.
 */
int finalize_object_file(const char *tmpfile, const char *filename)
{
  int ret = 0;

  if (object_creation_mode == OBJECT_CREATION_USES_RENAMES)
    goto try_rename;
  else if (link(tmpfile, filename))
    ret = errno;

  /*
   * Coda hack - coda doesn't like cross-directory links,
   * so we fall back to a rename, which will mean that it
   * won't be able to check collisions, but that's not a
   * big deal.
   *
   * The same holds for FAT formatted media.
   *
   * When this succeeds, we just return.  We have nothing
   * left to unlink.
   */
  if (ret && ret != EEXIST) {
  try_rename:
    if (!rename(tmpfile, filename))
      goto out;
    ret = errno;
  }
  unlink_or_warn(tmpfile);
  if (ret) {
    if (ret != EEXIST) {
      return error_errno(_("unable to write file %s"), filename);
    }
    /* FIXME!!! Collision check here ? */
  }

out:
  if (adjust_shared_perm(filename))
    return error(_("unable to set permission to '%s'"), filename);
  return 0;
}

static void hash_object_file_literally(const struct git_hash_algo *algo,
               const void *buf, unsigned long len,
               const char *type, struct object_id *oid)
{
  char hdr[MAX_HEADER_LEN];
  int hdrlen = sizeof(hdr);

  write_object_file_prepare_literally(algo, buf, len, type, oid, hdr, &hdrlen);
}

void hash_object_file(const struct git_hash_algo *algo, const void *buf,
          unsigned long len, enum object_type type,
          struct object_id *oid)
{
  hash_object_file_literally(algo, buf, len, type_name(type), oid);
}

/* Finalize a file on disk, and close it. */
static void close_loose_object(int fd, const char *filename)
{
  if (the_repository->objects->odb->will_destroy)
    goto out;

  if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
    fsync_loose_object_bulk_checkin(fd, filename);
  else if (fsync_object_files > 0)
    fsync_or_die(fd, filename);
  else
    fsync_component_or_die(FSYNC_COMPONENT_LOOSE_OBJECT, fd,
               filename);

out:
  if (close(fd) != 0)
    die_errno(_("error when closing loose object file"));
}

/* Size of directory component, including the ending '/' */
static inline int directory_size(const char *filename)
{
  const char *s = strrchr(filename, '/');
  if (!s)
    return 0;
  return s - filename + 1;
}

/*
 * This creates a temporary file in the same directory as the final
 * 'filename'
 *
 * We want to avoid cross-directory filename renames, because those
 * can have problems on various filesystems (FAT, NFS, Coda).
 */
static int create_tmpfile(struct strbuf *tmp, const char *filename)
{
  int fd, dirlen = directory_size(filename);

  strbuf_reset(tmp);
  strbuf_add(tmp, filename, dirlen);
  strbuf_addstr(tmp, "tmp_obj_XXXXXX");
  fd = git_mkstemp_mode(tmp->buf, 0444);
  if (fd < 0 && dirlen && errno == ENOENT) {
    /*
     * Make sure the directory exists; note that the contents
     * of the buffer are undefined after mkstemp returns an
     * error, so we have to rewrite the whole buffer from
     * scratch.
     */
    strbuf_reset(tmp);
    strbuf_add(tmp, filename, dirlen - 1);
    if (mkdir(tmp->buf, 0777) && errno != EEXIST)
      return -1;
    if (adjust_shared_perm(tmp->buf))
      return -1;

    /* Try again */
    strbuf_addstr(tmp, "/tmp_obj_XXXXXX");
    fd = git_mkstemp_mode(tmp->buf, 0444);
  }
  return fd;
}

/**
 * Common steps for loose object writers to start writing loose
 * objects:
 *
 * - Create tmpfile for the loose object.
 * - Setup zlib stream for compression.
 * - Start to feed header to zlib stream.
 *
 * Returns a "fd", which should later be provided to
 * end_loose_object_common().
 */
static int start_loose_object_common(struct strbuf *tmp_file,
             const char *filename, unsigned flags,
             git_zstream *stream,
             unsigned char *buf, size_t buflen,
             git_hash_ctx *c, git_hash_ctx *compat_c,
             char *hdr, int hdrlen)
{
  struct repository *repo = the_repository;
  const struct git_hash_algo *algo = repo->hash_algo;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  int fd;

  fd = create_tmpfile(tmp_file, filename);
  if (fd < 0) {
    if (flags & HASH_SILENT)
      return -1;
    else if (errno == EACCES)
      return error(_("insufficient permission for adding "
               "an object to repository database %s"),
             get_object_directory());
    else
      return error_errno(
        _("unable to create temporary file"));
  }

  /*  Setup zlib stream for compression */
  git_deflate_init(stream, zlib_compression_level);
  stream->next_out = buf;
  stream->avail_out = buflen;
  algo->init_fn(c);
  if (compat && compat_c)
    compat->init_fn(compat_c);

  /*  Start to feed header to zlib stream */
  stream->next_in = (unsigned char *)hdr;
  stream->avail_in = hdrlen;
  while (git_deflate(stream, 0) == Z_OK)
    ; /* nothing */
  algo->update_fn(c, hdr, hdrlen);
  if (compat && compat_c)
    compat->update_fn(compat_c, hdr, hdrlen);

  return fd;
}

/**
 * Common steps for the inner git_deflate() loop for writing loose
 * objects. Returns what git_deflate() returns.
 */
static int write_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c,
             git_zstream *stream, const int flush,
             unsigned char *in0, const int fd,
             unsigned char *compressed,
             const size_t compressed_len)
{
  struct repository *repo = the_repository;
  const struct git_hash_algo *algo = repo->hash_algo;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  int ret;

  ret = git_deflate(stream, flush ? Z_FINISH : 0);
  algo->update_fn(c, in0, stream->next_in - in0);
  if (compat && compat_c)
    compat->update_fn(compat_c, in0, stream->next_in - in0);
  if (write_in_full(fd, compressed, stream->next_out - compressed) < 0)
    die_errno(_("unable to write loose object file"));
  stream->next_out = compressed;
  stream->avail_out = compressed_len;

  return ret;
}

/**
 * Common steps for loose object writers to end writing loose objects:
 *
 * - End the compression of zlib stream.
 * - Get the calculated oid to "oid".
 */
static int end_loose_object_common(git_hash_ctx *c, git_hash_ctx *compat_c,
           git_zstream *stream, struct object_id *oid,
           struct object_id *compat_oid)
{
  struct repository *repo = the_repository;
  const struct git_hash_algo *algo = repo->hash_algo;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  int ret;

  ret = git_deflate_end_gently(stream);
  if (ret != Z_OK)
    return ret;
  algo->final_oid_fn(oid, c);
  if (compat && compat_c)
    compat->final_oid_fn(compat_oid, compat_c);

  return Z_OK;
}

static int write_loose_object(const struct object_id *oid, char *hdr,
            int hdrlen, const void *buf, unsigned long len,
            time_t mtime, unsigned flags)
{
  int fd, ret;
  unsigned char compressed[4096];
  git_zstream stream;
  git_hash_ctx c;
  struct object_id parano_oid;
  static struct strbuf tmp_file = STRBUF_INIT;
  static struct strbuf filename = STRBUF_INIT;

  if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
    prepare_loose_object_bulk_checkin();

  loose_object_path(the_repository, &filename, oid);

  fd = start_loose_object_common(&tmp_file, filename.buf, flags,
               &stream, compressed, sizeof(compressed),
               &c, NULL, hdr, hdrlen);
  if (fd < 0)
    return -1;

  /* Then the data itself.. */
  stream.next_in = (void *)buf;
  stream.avail_in = len;
  do {
    unsigned char *in0 = stream.next_in;

    ret = write_loose_object_common(&c, NULL, &stream, 1, in0, fd,
            compressed, sizeof(compressed));
  } while (ret == Z_OK);

  if (ret != Z_STREAM_END)
    die(_("unable to deflate new object %s (%d)"), oid_to_hex(oid),
        ret);
  ret = end_loose_object_common(&c, NULL, &stream, &parano_oid, NULL);
  if (ret != Z_OK)
    die(_("deflateEnd on object %s failed (%d)"), oid_to_hex(oid),
        ret);
  if (!oideq(oid, &parano_oid))
    die(_("confused by unstable object source data for %s"),
        oid_to_hex(oid));

  close_loose_object(fd, tmp_file.buf);

  if (mtime) {
    struct utimbuf utb;
    utb.actime = mtime;
    utb.modtime = mtime;
    if (utime(tmp_file.buf, &utb) < 0 &&
        !(flags & HASH_SILENT))
      warning_errno(_("failed utime() on %s"), tmp_file.buf);
  }

  return finalize_object_file(tmp_file.buf, filename.buf);
}

static int freshen_loose_object(const struct object_id *oid)
{
  return check_and_freshen(oid, 1);
}

static int freshen_packed_object(const struct object_id *oid)
{
  struct pack_entry e;
  if (!find_pack_entry(the_repository, oid, &e))
    return 0;
  if (e.p->is_cruft)
    return 0;
  if (e.p->freshened)
    return 1;
  if (!freshen_file(e.p->pack_name))
    return 0;
  e.p->freshened = 1;
  return 1;
}

int stream_loose_object(struct input_stream *in_stream, size_t len,
      struct object_id *oid)
{
  const struct git_hash_algo *compat = the_repository->compat_hash_algo;
  struct object_id compat_oid;
  int fd, ret, err = 0, flush = 0;
  unsigned char compressed[4096];
  git_zstream stream;
  git_hash_ctx c, compat_c;
  struct strbuf tmp_file = STRBUF_INIT;
  struct strbuf filename = STRBUF_INIT;
  int dirlen;
  char hdr[MAX_HEADER_LEN];
  int hdrlen;

  if (batch_fsync_enabled(FSYNC_COMPONENT_LOOSE_OBJECT))
    prepare_loose_object_bulk_checkin();

  /* Since oid is not determined, save tmp file to odb path. */
  strbuf_addf(&filename, "%s/", get_object_directory());
  hdrlen = format_object_header(hdr, sizeof(hdr), OBJ_BLOB, len);

  /*
   * Common steps for write_loose_object and stream_loose_object to
   * start writing loose objects:
   *
   *  - Create tmpfile for the loose object.
   *  - Setup zlib stream for compression.
   *  - Start to feed header to zlib stream.
   */
  fd = start_loose_object_common(&tmp_file, filename.buf, 0,
               &stream, compressed, sizeof(compressed),
               &c, &compat_c, hdr, hdrlen);
  if (fd < 0) {
    err = -1;
    goto cleanup;
  }

  /* Then the data itself.. */
  do {
    unsigned char *in0 = stream.next_in;

    if (!stream.avail_in && !in_stream->is_finished) {
      const void *in = in_stream->read(in_stream, &stream.avail_in);
      stream.next_in = (void *)in;
      in0 = (unsigned char *)in;
      /* All data has been read. */
      if (in_stream->is_finished)
        flush = 1;
    }
    ret = write_loose_object_common(&c, &compat_c, &stream, flush, in0, fd,
            compressed, sizeof(compressed));
    /*
     * Unlike write_loose_object(), we do not have the entire
     * buffer. If we get Z_BUF_ERROR due to too few input bytes,
     * then we'll replenish them in the next input_stream->read()
     * call when we loop.
     */
  } while (ret == Z_OK || ret == Z_BUF_ERROR);

  if (stream.total_in != len + hdrlen)
    die(_("write stream object %ld != %"PRIuMAX), stream.total_in,
        (uintmax_t)len + hdrlen);

  /*
   * Common steps for write_loose_object and stream_loose_object to
   * end writing loose oject:
   *
   *  - End the compression of zlib stream.
   *  - Get the calculated oid.
   */
  if (ret != Z_STREAM_END)
    die(_("unable to stream deflate new object (%d)"), ret);
  ret = end_loose_object_common(&c, &compat_c, &stream, oid, &compat_oid);
  if (ret != Z_OK)
    die(_("deflateEnd on stream object failed (%d)"), ret);
  close_loose_object(fd, tmp_file.buf);

  if (freshen_packed_object(oid) || freshen_loose_object(oid)) {
    unlink_or_warn(tmp_file.buf);
    goto cleanup;
  }

  loose_object_path(the_repository, &filename, oid);

  /* We finally know the object path, and create the missing dir. */
  dirlen = directory_size(filename.buf);
  if (dirlen) {
    struct strbuf dir = STRBUF_INIT;
    strbuf_add(&dir, filename.buf, dirlen);

    if (mkdir_in_gitdir(dir.buf) && errno != EEXIST) {
      err = error_errno(_("unable to create directory %s"), dir.buf);
      strbuf_release(&dir);
      goto cleanup;
    }
    strbuf_release(&dir);
  }

  err = finalize_object_file(tmp_file.buf, filename.buf);
  if (!err && compat)
    err = repo_add_loose_object_map(the_repository, oid, &compat_oid);
cleanup:
  strbuf_release(&tmp_file);
  strbuf_release(&filename);
  return err;
}

int write_object_file_flags(const void *buf, unsigned long len,
          enum object_type type, struct object_id *oid,
          struct object_id *compat_oid_in, unsigned flags)
{
  struct repository *repo = the_repository;
  const struct git_hash_algo *algo = repo->hash_algo;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  struct object_id compat_oid;
  char hdr[MAX_HEADER_LEN];
  int hdrlen = sizeof(hdr);

  /* Generate compat_oid */
  if (compat) {
    if (compat_oid_in)
      oidcpy(&compat_oid, compat_oid_in);
    else if (type == OBJ_BLOB)
      hash_object_file(compat, buf, len, type, &compat_oid);
    else {
      struct strbuf converted = STRBUF_INIT;
      convert_object_file(&converted, algo, compat,
              buf, len, type, 0);
      hash_object_file(compat, converted.buf, converted.len,
           type, &compat_oid);
      strbuf_release(&converted);
    }
  }

  /* Normally if we have it in the pack then we do not bother writing
   * it out into .git/objects/??/?{38} file.
   */
  write_object_file_prepare(algo, buf, len, type, oid, hdr, &hdrlen);
  if (freshen_packed_object(oid) || freshen_loose_object(oid))
    return 0;
  if (write_loose_object(oid, hdr, hdrlen, buf, len, 0, flags))
    return -1;
  if (compat)
    return repo_add_loose_object_map(repo, oid, &compat_oid);
  return 0;
}

int write_object_file_literally(const void *buf, unsigned long len,
        const char *type, struct object_id *oid,
        unsigned flags)
{
  char *header;
  struct repository *repo = the_repository;
  const struct git_hash_algo *algo = repo->hash_algo;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  struct object_id compat_oid;
  int hdrlen, status = 0;
  int compat_type = -1;

  if (compat) {
    compat_type = type_from_string_gently(type, -1, 1);
    if (compat_type == OBJ_BLOB)
      hash_object_file(compat, buf, len, compat_type,
           &compat_oid);
    else if (compat_type != -1) {
      struct strbuf converted = STRBUF_INIT;
      convert_object_file(&converted, algo, compat,
              buf, len, compat_type, 0);
      hash_object_file(compat, converted.buf, converted.len,
           compat_type, &compat_oid);
      strbuf_release(&converted);
    }
  }

  /* type string, SP, %lu of the length plus NUL must fit this */
  hdrlen = strlen(type) + MAX_HEADER_LEN;
  header = xmalloc(hdrlen);
  write_object_file_prepare_literally(the_hash_algo, buf, len, type,
              oid, header, &hdrlen);

  if (!(flags & HASH_WRITE_OBJECT))
    goto cleanup;
  if (freshen_packed_object(oid) || freshen_loose_object(oid))
    goto cleanup;
  status = write_loose_object(oid, header, hdrlen, buf, len, 0, 0);
  if (compat_type != -1)
    return repo_add_loose_object_map(repo, oid, &compat_oid);

cleanup:
  free(header);
  return status;
}

int force_object_loose(const struct object_id *oid, time_t mtime)
{
  struct repository *repo = the_repository;
  const struct git_hash_algo *compat = repo->compat_hash_algo;
  void *buf;
  unsigned long len;
  struct object_info oi = OBJECT_INFO_INIT;
  struct object_id compat_oid;
  enum object_type type;
  char hdr[MAX_HEADER_LEN];
  int hdrlen;
  int ret;

  if (has_loose_object(oid))
    return 0;
  oi.typep = &type;
  oi.sizep = &len;
  oi.contentp = &buf;
  if (oid_object_info_extended(the_repository, oid, &oi, 0))
    return error(_("cannot read object for %s"), oid_to_hex(oid));
  if (compat) {
    if (repo_oid_to_algop(repo, oid, compat, &compat_oid))
      return error(_("cannot map object %s to %s"),
             oid_to_hex(oid), compat->name);
  }
  hdrlen = format_object_header(hdr, sizeof(hdr), type, len);
  ret = write_loose_object(oid, hdr, hdrlen, buf, len, mtime, 0);
  if (!ret && compat)
    ret = repo_add_loose_object_map(the_repository, oid, &compat_oid);
  free(buf);

  return ret;
}

int has_object(struct repository *r, const struct object_id *oid,
         unsigned flags)
{
  int quick = !(flags & HAS_OBJECT_RECHECK_PACKED);
  unsigned object_info_flags = OBJECT_INFO_SKIP_FETCH_OBJECT |
    (quick ? OBJECT_INFO_QUICK : 0);

  if (!startup_info->have_repository)
    return 0;
  return oid_object_info_extended(r, oid, NULL, object_info_flags) >= 0;
}

int repo_has_object_file_with_flags(struct repository *r,
            const struct object_id *oid, int flags)
{
  if (!startup_info->have_repository)
    return 0;
  return oid_object_info_extended(r, oid, NULL, flags) >= 0;
}

int repo_has_object_file(struct repository *r,
       const struct object_id *oid)
{
  return repo_has_object_file_with_flags(r, oid, 0);
}

/*
 * We can't use the normal fsck_error_function() for index_mem(),
 * because we don't yet have a valid oid for it to report. Instead,
 * report the minimal fsck error here, and rely on the caller to
 * give more context.
 */
static int hash_format_check_report(struct fsck_options *opts UNUSED,
            void *fsck_report UNUSED,
            enum fsck_msg_type msg_type UNUSED,
            enum fsck_msg_id msg_id UNUSED,
            const char *message)
{
  error(_("object fails fsck: %s"), message);
  return 1;
}

static int index_mem(struct index_state *istate,
         struct object_id *oid,
         const void *buf, size_t size,
         enum object_type type,
         const char *path, unsigned flags)
{
  struct strbuf nbuf = STRBUF_INIT;
  int ret = 0;
  int write_object = flags & HASH_WRITE_OBJECT;

  if (!type)
    type = OBJ_BLOB;

  /*
   * Convert blobs to git internal format
   */
  if ((type == OBJ_BLOB) && path) {
    if (convert_to_git(istate, path, buf, size, &nbuf,
           get_conv_flags(flags))) {
      buf = nbuf.buf;
      size = nbuf.len;
    }
  }
  if (flags & HASH_FORMAT_CHECK) {
    struct fsck_options opts = FSCK_OPTIONS_DEFAULT;

    opts.strict = 1;
    opts.error_func = hash_format_check_report;
    if (fsck_buffer(null_oid(), type, buf, size, &opts))
      die(_("refusing to create malformed object"));
    fsck_finish(&opts);
  }

  if (write_object)
    ret = write_object_file(buf, size, type, oid);
  else
    hash_object_file(the_hash_algo, buf, size, type, oid);

  strbuf_release(&nbuf);
  return ret;
}

static int index_stream_convert_blob(struct index_state *istate,
             struct object_id *oid,
             int fd,
             const char *path,
             unsigned flags)
{
  int ret = 0;
  const int write_object = flags & HASH_WRITE_OBJECT;
  struct strbuf sbuf = STRBUF_INIT;

  assert(path);
  assert(would_convert_to_git_filter_fd(istate, path));

  convert_to_git_filter_fd(istate, path, fd, &sbuf,
         get_conv_flags(flags));

  if (write_object)
    ret = write_object_file(sbuf.buf, sbuf.len, OBJ_BLOB,
          oid);
  else
    hash_object_file(the_hash_algo, sbuf.buf, sbuf.len, OBJ_BLOB,
         oid);
  strbuf_release(&sbuf);
  return ret;
}

static int index_pipe(struct index_state *istate, struct object_id *oid,
          int fd, enum object_type type,
          const char *path, unsigned flags)
{
  struct strbuf sbuf = STRBUF_INIT;
  int ret;

  if (strbuf_read(&sbuf, fd, 4096) >= 0)
    ret = index_mem(istate, oid, sbuf.buf, sbuf.len, type, path, flags);
  else
    ret = -1;
  strbuf_release(&sbuf);
  return ret;
}

#define SMALL_FILE_SIZE (32*1024)

static int index_core(struct index_state *istate,
          struct object_id *oid, int fd, size_t size,
          enum object_type type, const char *path,
          unsigned flags)
{
  int ret;

  if (!size) {
    ret = index_mem(istate, oid, "", size, type, path, flags);
  } else if (size <= SMALL_FILE_SIZE) {
    char *buf = xmalloc(size);
    ssize_t read_result = read_in_full(fd, buf, size);
    if (read_result < 0)
      ret = error_errno(_("read error while indexing %s"),
            path ? path : "<unknown>");
    else if (read_result != size)
      ret = error(_("short read while indexing %s"),
            path ? path : "<unknown>");
    else
      ret = index_mem(istate, oid, buf, size, type, path, flags);
    free(buf);
  } else {
    void *buf = xmmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
    ret = index_mem(istate, oid, buf, size, type, path, flags);
    munmap(buf, size);
  }
  return ret;
}

/*
 * This creates one packfile per large blob unless bulk-checkin
 * machinery is "plugged".
 *
 * This also bypasses the usual "convert-to-git" dance, and that is on
 * purpose. We could write a streaming version of the converting
 * functions and insert that before feeding the data to fast-import
 * (or equivalent in-core API described above). However, that is
 * somewhat complicated, as we do not know the size of the filter
 * result, which we need to know beforehand when writing a git object.
 * Since the primary motivation for trying to stream from the working
 * tree file and to avoid mmaping it in core is to deal with large
 * binary blobs, they generally do not want to get any conversion, and
 * callers should avoid this code path when filters are requested.
 */
static int index_blob_stream(struct object_id *oid, int fd, size_t size,
           const char *path,
           unsigned flags)
{
  return index_blob_bulk_checkin(oid, fd, size, path, flags);
}

int index_fd(struct index_state *istate, struct object_id *oid,
       int fd, struct stat *st,
       enum object_type type, const char *path, unsigned flags)
{
  int ret;

  /*
   * Call xsize_t() only when needed to avoid potentially unnecessary
   * die() for large files.
   */
  if (type == OBJ_BLOB && path && would_convert_to_git_filter_fd(istate, path))
    ret = index_stream_convert_blob(istate, oid, fd, path, flags);
  else if (!S_ISREG(st->st_mode))
    ret = index_pipe(istate, oid, fd, type, path, flags);
  else if (st->st_size <= big_file_threshold || type != OBJ_BLOB ||
     (path && would_convert_to_git(istate, path)))
    ret = index_core(istate, oid, fd, xsize_t(st->st_size),
         type, path, flags);
  else
    ret = index_blob_stream(oid, fd, xsize_t(st->st_size), path,
          flags);
  close(fd);
  return ret;
}

int index_path(struct index_state *istate, struct object_id *oid,
         const char *path, struct stat *st, unsigned flags)
{
  int fd;
  struct strbuf sb = STRBUF_INIT;
  int rc = 0;

  switch (st->st_mode & S_IFMT) {
  case S_IFREG:
    fd = open(path, O_RDONLY);
    if (fd < 0)
      return error_errno("open(\"%s\")", path);
    if (index_fd(istate, oid, fd, st, OBJ_BLOB, path, flags) < 0)
      return error(_("%s: failed to insert into database"),
             path);
    break;
  case S_IFLNK:
    if (strbuf_readlink(&sb, path, st->st_size))
      return error_errno("readlink(\"%s\")", path);
    if (!(flags & HASH_WRITE_OBJECT))
      hash_object_file(the_hash_algo, sb.buf, sb.len,
           OBJ_BLOB, oid);
    else if (write_object_file(sb.buf, sb.len, OBJ_BLOB, oid))
      rc = error(_("%s: failed to insert into database"), path);
    strbuf_release(&sb);
    break;
  case S_IFDIR:
    return repo_resolve_gitlink_ref(the_repository, path, "HEAD", oid);
  default:
    return error(_("%s: unsupported file type"), path);
  }
  return rc;
}

int read_pack_header(int fd, struct pack_header *header)
{
  if (read_in_full(fd, header, sizeof(*header)) != sizeof(*header))
    /* "eof before pack header was fully read" */
    return PH_ERROR_EOF;

  if (header->hdr_signature != htonl(PACK_SIGNATURE))
    /* "protocol error (pack signature mismatch detected)" */
    return PH_ERROR_PACK_SIGNATURE;
  if (!pack_version_ok(header->hdr_version))
    /* "protocol error (pack version unsupported)" */
    return PH_ERROR_PROTOCOL;
  return 0;
}

void assert_oid_type(const struct object_id *oid, enum object_type expect)
{
  enum object_type type = oid_object_info(the_repository, oid, NULL);
  if (type < 0)
    die(_("%s is not a valid object"), oid_to_hex(oid));
  if (type != expect)
    die(_("%s is not a valid '%s' object"), oid_to_hex(oid),
        type_name(expect));
}

int for_each_file_in_obj_subdir(unsigned int subdir_nr,
        struct strbuf *path,
        each_loose_object_fn obj_cb,
        each_loose_cruft_fn cruft_cb,
        each_loose_subdir_fn subdir_cb,
        void *data)
{
  size_t origlen, baselen;
  DIR *dir;
  struct dirent *de;
  int r = 0;
  struct object_id oid;

  if (subdir_nr > 0xff)
    BUG("invalid loose object subdirectory: %x", subdir_nr);

  origlen = path->len;
  strbuf_complete(path, '/');
  strbuf_addf(path, "%02x", subdir_nr);

  dir = opendir(path->buf);
  if (!dir) {
    if (errno != ENOENT)
      r = error_errno(_("unable to open %s"), path->buf);
    strbuf_setlen(path, origlen);
    return r;
  }

  oid.hash[0] = subdir_nr;
  strbuf_addch(path, '/');
  baselen = path->len;

  while ((de = readdir_skip_dot_and_dotdot(dir))) {
    size_t namelen;

    namelen = strlen(de->d_name);
    strbuf_setlen(path, baselen);
    strbuf_add(path, de->d_name, namelen);
    if (namelen == the_hash_algo->hexsz - 2 &&
        !hex_to_bytes(oid.hash + 1, de->d_name,
          the_hash_algo->rawsz - 1)) {
      oid_set_algo(&oid, the_hash_algo);
      memset(oid.hash + the_hash_algo->rawsz, 0,
             GIT_MAX_RAWSZ - the_hash_algo->rawsz);
      if (obj_cb) {
        r = obj_cb(&oid, path->buf, data);
        if (r)
          break;
      }
      continue;
    }

    if (cruft_cb) {
      r = cruft_cb(de->d_name, path->buf, data);
      if (r)
        break;
    }
  }
  closedir(dir);

  strbuf_setlen(path, baselen - 1);
  if (!r && subdir_cb)
    r = subdir_cb(subdir_nr, path->buf, data);

  strbuf_setlen(path, origlen);

  return r;
}

int for_each_loose_file_in_objdir_buf(struct strbuf *path,
          each_loose_object_fn obj_cb,
          each_loose_cruft_fn cruft_cb,
          each_loose_subdir_fn subdir_cb,
          void *data)
{
  int r = 0;
  int i;

  for (i = 0; i < 256; i++) {
    r = for_each_file_in_obj_subdir(i, path, obj_cb, cruft_cb,
            subdir_cb, data);
    if (r)
      break;
  }

  return r;
}

int for_each_loose_file_in_objdir(const char *path,
          each_loose_object_fn obj_cb,
          each_loose_cruft_fn cruft_cb,
          each_loose_subdir_fn subdir_cb,
          void *data)
{
  struct strbuf buf = STRBUF_INIT;
  int r;

  strbuf_addstr(&buf, path);
  r = for_each_loose_file_in_objdir_buf(&buf, obj_cb, cruft_cb,
                subdir_cb, data);
  strbuf_release(&buf);

  return r;
}

int for_each_loose_object(each_loose_object_fn cb, void *data,
        enum for_each_object_flags flags)
{
  struct object_directory *odb;

  prepare_alt_odb(the_repository);
  for (odb = the_repository->objects->odb; odb; odb = odb->next) {
    int r = for_each_loose_file_in_objdir(odb->path, cb, NULL,
                  NULL, data);
    if (r)
      return r;

    if (flags & FOR_EACH_OBJECT_LOCAL_ONLY)
      break;
  }

  return 0;
}

static int append_loose_object(const struct object_id *oid,
             const char *path UNUSED,
             void *data)
{
  oidtree_insert(data, oid);
  return 0;
}

struct oidtree *odb_loose_cache(struct object_directory *odb,
          const struct object_id *oid)
{
  int subdir_nr = oid->hash[0];
  struct strbuf buf = STRBUF_INIT;
  size_t word_bits = bitsizeof(odb->loose_objects_subdir_seen[0]);
  size_t word_index = subdir_nr / word_bits;
  size_t mask = (size_t)1u << (subdir_nr % word_bits);
  uint32_t *bitmap;

  if (subdir_nr < 0 ||
      subdir_nr >= bitsizeof(odb->loose_objects_subdir_seen))
    BUG("subdir_nr out of range");

  bitmap = &odb->loose_objects_subdir_seen[word_index];
  if (*bitmap & mask)
    return odb->loose_objects_cache;
  if (!odb->loose_objects_cache) {
    ALLOC_ARRAY(odb->loose_objects_cache, 1);
    oidtree_init(odb->loose_objects_cache);
  }
  strbuf_addstr(&buf, odb->path);
  for_each_file_in_obj_subdir(subdir_nr, &buf,
            append_loose_object,
            NULL, NULL,
            odb->loose_objects_cache);
  *bitmap |= mask;
  strbuf_release(&buf);
  return odb->loose_objects_cache;
}

void odb_clear_loose_cache(struct object_directory *odb)
{
  oidtree_clear(odb->loose_objects_cache);
  FREE_AND_NULL(odb->loose_objects_cache);
  memset(&odb->loose_objects_subdir_seen, 0,
         sizeof(odb->loose_objects_subdir_seen));
}

static int check_stream_oid(git_zstream *stream,
          const char *hdr,
          unsigned long size,
          const char *path,
          const struct object_id *expected_oid)
{
  git_hash_ctx c;
  struct object_id real_oid;
  unsigned char buf[4096];
  unsigned long total_read;
  int status = Z_OK;

  the_hash_algo->init_fn(&c);
  the_hash_algo->update_fn(&c, hdr, stream->total_out);

  /*
   * We already read some bytes into hdr, but the ones up to the NUL
   * do not count against the object's content size.
   */
  total_read = stream->total_out - strlen(hdr) - 1;

  /*
   * This size comparison must be "<=" to read the final zlib packets;
   * see the comment in unpack_loose_rest for details.
   */
  while (total_read <= size &&
         (status == Z_OK ||
    (status == Z_BUF_ERROR && !stream->avail_out))) {
    stream->next_out = buf;
    stream->avail_out = sizeof(buf);
    if (size - total_read < stream->avail_out)
      stream->avail_out = size - total_read;
    status = git_inflate(stream, Z_FINISH);
    the_hash_algo->update_fn(&c, buf, stream->next_out - buf);
    total_read += stream->next_out - buf;
  }
  git_inflate_end(stream);

  if (status != Z_STREAM_END) {
    error(_("corrupt loose object '%s'"), oid_to_hex(expected_oid));
    return -1;
  }
  if (stream->avail_in) {
    error(_("garbage at end of loose object '%s'"),
          oid_to_hex(expected_oid));
    return -1;
  }

  the_hash_algo->final_oid_fn(&real_oid, &c);
  if (!oideq(expected_oid, &real_oid)) {
    error(_("hash mismatch for %s (expected %s)"), path,
          oid_to_hex(expected_oid));
    return -1;
  }

  return 0;
}

int read_loose_object(const char *path,
          const struct object_id *expected_oid,
          struct object_id *real_oid,
          void **contents,
          struct object_info *oi)
{
  int ret = -1;
  int fd;
  void *map = NULL;
  unsigned long mapsize;
  git_zstream stream;
  char hdr[MAX_HEADER_LEN];
  unsigned long *size = oi->sizep;

  fd = git_open(path);
  if (fd >= 0)
    map = map_fd(fd, path, &mapsize);
  if (!map) {
    error_errno(_("unable to mmap %s"), path);
    goto out;
  }

  if (unpack_loose_header(&stream, map, mapsize, hdr, sizeof(hdr),
        NULL) != ULHR_OK) {
    error(_("unable to unpack header of %s"), path);
    git_inflate_end(&stream);
    goto out;
  }

  if (parse_loose_header(hdr, oi) < 0) {
    error(_("unable to parse header of %s"), path);
    git_inflate_end(&stream);
    goto out;
  }

  if (*oi->typep == OBJ_BLOB && *size > big_file_threshold) {
    if (check_stream_oid(&stream, hdr, *size, path, expected_oid) < 0)
      goto out;
  } else {
    *contents = unpack_loose_rest(&stream, hdr, *size, expected_oid);
    if (!*contents) {
      error(_("unable to unpack contents of %s"), path);
      git_inflate_end(&stream);
      goto out;
    }
    hash_object_file_literally(the_repository->hash_algo,
             *contents, *size,
             oi->type_name->buf, real_oid);
    if (!oideq(expected_oid, real_oid))
      goto out;
  }

  ret = 0; /* everything checks out */

out:
  if (map)
    munmap(map, mapsize);
  return ret;
}

Coverage Report

Created: 2024-09-08 06:23