func CreateMarkovChain(prefixlen int, dbpath string, create bool, getchan func() (chan Token, error)) (mc *MarkovChain, err error) {
var opts = new(kv.Options)
var conerr error
mc = new(MarkovChain)
opts.Compare = bytes.Compare
mc.prefixLen = prefixlen
if create {
mc.CorpusDB, conerr = kv.Create(dbpath, opts)
if conerr != nil {
if mc.CorpusDB, conerr = kv.Open(dbpath, opts); conerr != nil {
err = errors.New(fmt.Sprintf("cannot create new database %s : %s", dbpath, conerr))
return
}
} else {
c, e := getchan()
if e != nil {
mc.CorpusDB.Close()
os.Remove(dbpath)
err = nil
return
}
mc.PopulateCorpus(c)
}
} else {
mc.CorpusDB, conerr = kv.Open(dbpath, opts)
if conerr != nil {
err = errors.New(fmt.Sprintf("cannot open database %s : %s", dbpath, conerr))
return
}
}
return
}
// Open opens the named kv DB file for reading/writing. It
// creates the file if it does not exist yet.
func Open(dbFile string, opts *kv.Options) (*kv.DB, error) {
createOpen := kv.Open
verb := "opening"
if _, err := os.Stat(dbFile); os.IsNotExist(err) {
createOpen = kv.Create
verb = "creating"
}
if opts == nil {
opts = &kv.Options{}
}
if opts.Locker == nil {
opts.Locker = func(dbFile string) (io.Closer, error) {
lkfile := dbFile + ".lock"
cl, err := lock.Lock(lkfile)
if err != nil {
return nil, fmt.Errorf("failed to acquire lock on %s: %v", lkfile, err)
}
return cl, nil
}
}
if v, _ := strconv.ParseBool(os.Getenv("CAMLI_KV_VERIFY")); v {
opts.VerifyDbBeforeOpen = true
opts.VerifyDbAfterOpen = true
opts.VerifyDbBeforeClose = true
opts.VerifyDbAfterClose = true
}
db, err := createOpen(dbFile, opts)
if err != nil {
return nil, fmt.Errorf("error %s %s: %v", verb, dbFile, err)
}
return db, nil
}