+static const struct casereader_random_class
+casereader_stateless_translator_class;
+
+/* Creates and returns a new casereader whose cases are produced by reading
+ from SUBREADER and passing through the TRANSLATE function. TRANSLATE must
+ takes ownership of its input case and returns a translated case, populating
+ the translated case based on INPUT and auxiliary data AUX.
+
+ TRANSLATE must be stateless, that is, the output for a given case must not
+ depend on previous cases. This is because cases may be retrieved in
+ arbitrary order, and some cases may be retrieved multiple times, and some
+ cases may be skipped and never retrieved at all. If TRANSLATE is stateful,
+ use casereader_create_translator instead.
+
+ The cases returned by TRANSLATE must match OUTPUT_PROTO.
+
+ When the stateless translating casereader is destroyed, DESTROY will be
+ called to allow any auxiliary data maintained by TRANSLATE to be freed.
+
+ After this function is called, SUBREADER must not ever again be referenced
+ directly. It will be destroyed automatically when the translating
+ casereader is destroyed. */
+struct casereader *
+casereader_translate_stateless (
+ struct casereader *subreader,
+ const struct caseproto *output_proto,
+ const struct casereader_translator_class *class,
+ void *aux)
+{
+ struct casereader_stateless_translator *cst = xmalloc (sizeof *cst);
+ *cst = (struct casereader_stateless_translator) {
+ .subreader = casereader_rename (subreader),
+ .class = class,
+ .aux = aux,
+ };
+ struct casereader *reader = casereader_create_random (
+ output_proto, casereader_get_n_cases (cst->subreader),
+ &casereader_stateless_translator_class, cst);
+ taint_propagate (casereader_get_taint (cst->subreader),
+ casereader_get_taint (reader));
+ return reader;
+}
+
+/* Internal read function for stateless translating casereader. */
+static struct ccase *
+casereader_stateless_translator_read (struct casereader *reader UNUSED,
+ void *cst_, casenumber idx)
+{
+ struct casereader_stateless_translator *cst = cst_;
+ struct ccase *tmp = casereader_peek (cst->subreader, idx);
+ if (tmp != NULL)
+ tmp = cst->class->translate (tmp, cst->aux);
+ return tmp;
+}
+
+/* Internal destroy function for translating casereader. */
+static void
+casereader_stateless_translator_destroy (struct casereader *reader UNUSED,
+ void *cst_)
+{
+ struct casereader_stateless_translator *cst = cst_;
+ casereader_destroy (cst->subreader);
+ cst->class->destroy (cst->aux);
+ free (cst);
+}
+
+static void
+casereader_stateless_translator_advance (struct casereader *reader UNUSED,
+ void *cst_, casenumber n)
+{
+ struct casereader_stateless_translator *cst = cst_;
+ cst->case_offset += casereader_advance (cst->subreader, n);
+}
+
+/* Casereader class for stateless translating casereader. */
+static const struct casereader_random_class
+casereader_stateless_translator_class =
+ {
+ casereader_stateless_translator_read,
+ casereader_stateless_translator_destroy,
+ casereader_stateless_translator_advance,
+ };