view audioDB-internals.h @ 404:1fb8bee777e5 api-inversion

Begin working towards inverting audioDB::insert() / audiodb_insert().

New data type audiodb_datum_t, roughly corresponding to a "track" in
current audioDB parlance; it contains exactly the feature information
and metadata to record.

New function audiodb_insert_datum() to insert one of these
audiodb_datum_t objects into the database; the intention is that not
only can insertion of feature files be implemented in terms of this
function, but that it will be a useful function in its own right,
callable perhaps from PD, Max/MSP, and/or a VAMP plugin.  This function
is complicated enough that it actually gets a comment.

Implement audioDB::insert() in terms of audiodb_insert_datum(), via a
wrapper which handles the slightly wacky error/non-error case of
attempting to insert features with a key that already exists in the
database.

Delete whole rafts of code.  We can't quite delete everything because
there's batchinsert / batchinsert_large_adb to sort out; the good news
is that the batchinsert operation can simply be implemented as a loop
around audiodb_insert_datum() without loss of efficiency.

(There's also a stray extra audiodb_insert() in libtests/0027/, found
through an earlier iteration of this patch.)

struct adb {
  char *path;
  int fd;
  int flags;
  adb_header_t *header;
  std::set<std::string> *keys;
};

/* We could go gcc-specific here and use typeof() instead of passing
 * in an explicit type.  Answers on a postcard as to whether that's a
 * good plan or not. */
#define mmap_or_goto_error(type, var, start, length) \
  { void *tmp = mmap(0, length, PROT_READ, MAP_SHARED, adb->fd, (start)); \
    if(tmp == (void *) -1) { \
      goto error; \
    } \
    var = (type) tmp; \
  }

#define maybe_munmap(table, length) \
  { if(table) { \
      munmap(table, length); \
    } \
  }

static inline int audiodb_sync_header(adb_t *adb) {
  off_t pos;
  pos = lseek(adb->fd, (off_t) 0, SEEK_CUR);
  if(pos == (off_t) -1) {
    goto error;
  }
  if(lseek(adb->fd, (off_t) 0, SEEK_SET) == (off_t) -1) {
    goto error;
  }
  if(write(adb->fd, adb->header, O2_HEADERSIZE) != O2_HEADERSIZE) {
    goto error;
  }

  /* can be fsync() if fdatasync() is racily exciting and new */
  fdatasync(adb->fd);
  if(lseek(adb->fd, pos, SEEK_SET) == (off_t) -1) {
    goto error;
  }
  return 0;

 error:
  return 1;
}