/* PSPP - a program for statistical analysis.
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007, 2009 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
{
struct casewriter *subwriter;
- void (*translate) (const struct ccase *input, struct ccase *output,
- void *aux);
+ struct ccase *(*translate) (struct ccase *, void *aux);
bool (*destroy) (void *aux);
void *aux;
};
-static struct casewriter_class casewriter_translator_class;
+static const struct casewriter_class casewriter_translator_class;
+/* Creates and returns a new casewriter whose cases are passed
+ through TRANSLATE, which must return a case with
+ OUTPUT_VALUE_CNT values, based on INPUT and auxiliary data
+ AUX. (TRANSLATE may also return a null pointer, in which case
+ no case is written to the output.) The translated cases are
+ then written to SUBWRITER.
+
+ TRANSLATE takes ownership of each case passed to it. Thus, it
+ should either unref each case and return a new case, or
+ (unshare and then) modify and return the same case.
+
+ When the translating casewriter is destroyed, DESTROY will be
+ called to allow any state maintained by TRANSLATE to be freed.
+
+ After this function is called, SUBWRITER must not ever again
+ be referenced directly. It will be destroyed automatically
+ when the translating casewriter is destroyed. */
struct casewriter *
casewriter_create_translator (struct casewriter *subwriter,
size_t translated_value_cnt,
- void (*translate) (const struct ccase *input,
- struct ccase *output,
- void *aux),
+ struct ccase *(*translate) (struct ccase *,
+ void *aux),
bool (*destroy) (void *aux),
void *aux)
{
void *ct_, struct ccase *c)
{
struct casewriter_translator *ct = ct_;
- struct ccase tmp;
-
- ct->translate (c, &tmp, ct->aux);
- casewriter_write (ct->subwriter, &tmp);
+ c = ct->translate (c, ct->aux);
+ if (c != NULL)
+ casewriter_write (ct->subwriter, c);
}
static void
return reader;
}
-static struct casewriter_class casewriter_translator_class =
+static const struct casewriter_class casewriter_translator_class =
{
casewriter_translator_write,
casewriter_translator_destroy,