lib/PublicInbox/gcf2_libgit2.h

   1 /*
   2  * Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
   3  * License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
   4  *
   5  * libgit2 for Inline::C
   6  * Avoiding Git::Raw since it doesn't guarantee a stable API,
   7  * while libgit2 itself seems reasonably stable.
   8  */
   9 #include <git2.h>
  10 #include <sys/uio.h>
  11 #include <errno.h>
  12 #include <poll.h>
  13
  14 static void croak_if_err(int rc, const char *msg)
  15 {
  16         if (rc != GIT_OK) {
  17                 const git_error *e = giterr_last();
  18
  19                 croak("%d %s (%s)", rc, msg, e ? e->message : "unknown");
  20         }
  21 }
  22
  23 SV *new()
  24 {
  25         git_odb *odb;
  26         SV *ref, *self;
  27         int rc = git_odb_new(&odb);
  28         croak_if_err(rc, "git_odb_new");
  29
  30         ref = newSViv((IV)odb);
  31         self = newRV_noinc(ref);
  32         sv_bless(self, gv_stashpv("PublicInbox::Gcf2", GV_ADD));
  33         SvREADONLY_on(ref);
  34
  35         return self;
  36 }
  37
  38 static git_odb *odb_ptr(SV *self)
  39 {
  40         return (git_odb *)SvIV(SvRV(self));
  41 }
  42
  43 void DESTROY(SV *self)
  44 {
  45         git_odb_free(odb_ptr(self));
  46 }
  47
  48 /* needs "$GIT_DIR/objects", not $GIT_DIR */
  49 void add_alternate(SV *self, const char *objects_path)
  50 {
  51         int rc = git_odb_add_disk_alternate(odb_ptr(self), objects_path);
  52         croak_if_err(rc, "git_odb_add_disk_alternate");
  53 }
  54
  55 #define CAPA(v) (sizeof(v) / sizeof((v)[0]))
  56
  57 /*
  58  * returns true on success, false on failure
  59  * this requires an unabbreviated git OID
  60  */
  61 int cat_oid(SV *self, int fd, SV *oidsv)
  62 {
  63         /*
  64          * adjust when libgit2 gets SHA-256 support, we return the
  65          * same header as git-cat-file --batch "$OID $TYPE $SIZE\n"
  66          */
  67         char hdr[GIT_OID_HEXSZ + sizeof(" commit 18446744073709551615")];
  68         struct iovec vec[3];
  69         size_t nvec = CAPA(vec);
  70         git_oid oid;
  71         git_odb_object *object = NULL;
  72         int rc, err = 0;
  73         STRLEN oidlen;
  74         char *oidptr = SvPV(oidsv, oidlen);
  75
  76         /* same trailer as git-cat-file --batch */
  77         vec[2].iov_len = 1;
  78         vec[2].iov_base = "\n";
  79
  80         rc = git_oid_fromstrn(&oid, oidptr, oidlen);
  81         if (rc == GIT_OK)
  82                 rc = git_odb_read(&object, odb_ptr(self), &oid);
  83         if (rc == GIT_OK) {
  84                 vec[0].iov_base = hdr;
  85                 vec[1].iov_base = (void *)git_odb_object_data(object);
  86                 vec[1].iov_len = git_odb_object_size(object);
  87
  88                 git_oid_nfmt(hdr, GIT_OID_HEXSZ, git_odb_object_id(object));
  89                 vec[0].iov_len = GIT_OID_HEXSZ +
  90                                 snprintf(hdr + GIT_OID_HEXSZ,
  91                                         sizeof(hdr) - GIT_OID_HEXSZ,
  92                                         " %s %zu\n",
  93                                         git_object_type2string(
  94                                                 git_odb_object_type(object)),
  95                                         vec[1].iov_len);
  96         } else { /* caller retries */
  97                 nvec = 0;
  98         }
  99         while (nvec && !err) {
 100                 ssize_t w = writev(fd, vec + CAPA(vec) - nvec, nvec);
 101
 102                 if (w > 0) {
 103                         size_t done = 0;
 104                         size_t i;
 105
 106                         for (i = CAPA(vec) - nvec; i < CAPA(vec); i++) {
 107                                 if (w >= vec[i].iov_len) {
 108                                         /* fully written vec */
 109                                         w -= vec[i].iov_len;
 110                                         done++;
 111                                 } else { /* partially written vec */
 112                                         char *p = vec[i].iov_base;
 113                                         vec[i].iov_base = p + w;
 114                                         vec[i].iov_len -= w;
 115                                         break;
 116                                 }
 117                         }
 118                         nvec -= done;
 119                 } else if (w < 0) {
 120                         err = errno;
 121                         switch (err) {
 122                         case EAGAIN: {
 123                                 struct pollfd pfd;
 124                                 pfd.events = POLLOUT;
 125                                 pfd.fd = fd;
 126                                 poll(&pfd, 1, -1);
 127                         }
 128                                 /* fall-through */
 129                         case EINTR:
 130                                 err = 0;
 131                         }
 132                 } else { /* w == 0 */
 133                         err = ENOSPC;
 134                 }
 135         }
 136         if (object)
 137                 git_odb_object_free(object);
 138         if (err)
 139                 croak("writev error: %s", strerror(err));
 140
 141         return rc == GIT_OK;
 142 }