view audioDB-internals.h @ 405:ef4792df8f93 api-inversion

invert audioDB::insert / audiodb_insert().

Start off by removing audioDB::insertDatum, and essentially reusing it
as audiodb_insert.  We now ignore the fact that the command-line parsing
code has "helpfully" opened a std::ifstream for the times file and an fd
for the power file, and simply go ahead and do our own dirty work.

We can delete audioDB::insertDatum entirely, but unfortunately we can't
delete audioDB::insertPowerData and audioDB::insertTimestamps, because
the index and query code respectively use them.  Instead, move the two
methods closer to their single uses.

audiodb_insert() is perhaps not as short and simple as it might have
been hoped given the existence of audiodb_insert_datum(); some of that
is C and its terribly way of making you pay every time you use dynamic
memory; some of it is the fact that the three different files (feature,
times, power) each requires slightly different treatment.  Hey ho.

We can implement audiodb_batchinsert() in terms of audiodb_insert(); the
function is pleasingly small.  We can't quite use it for
audioDB::batchinsert yet, as we have to deal with the O2_FLAG_LARGE_ADB
case (which codepath is untested in libtests/).

This means that we can delete whole swathes of hideous code from
audioDB.cpp, including not just the versions of audiodb_insert() and
audiodb_batchinsert() but also an entire audioDB constructor.  Yay.
(audioDB::unitNormAndInsertL2 has also died a deserved death).

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;
}