Add casereaders and casewriters, the basis of the new data processing

[pspp-builds.git] / src / data / casewriter-provider.h

diff --git a/src/data/casewriter-provider.h b/src/data/casewriter-provider.h
new file mode 100644 (file)
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+++ b/src/data/casewriter-provider.h
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+/* PSPP - computes sample statistics.
+   Copyright (C) 2006 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 the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+   02110-1301, USA. */
+
+#ifndef DATA_CASEWRITER_PROVIDER_H
+#define DATA_CASEWRITER_PROVIDER_H 1
+
+#include <data/casewriter.h>
+
+struct casewriter_class 
+  {
+    /* Mandatory.
+
+       Writes case C to WRITER.  Destroys C before returning.
+
+       If an I/O error occurs, this function should call
+       casewriter_force_error on WRITER.  Some I/O error
+       detection may be deferred to the "destroy" member function
+       (e.g. writes to disk need not be flushed by "write") . */
+    void (*write) (struct casewriter *writer, void *aux, struct ccase *c);
+
+    /* Mandatory.
+
+       Finalizes output and destroys WRITER.
+
+       If an I/O error is detected while finalizing output
+       (e.g. while flushing output to disk), this function should
+       call casewriter_force_error on WRITER. */
+    void (*destroy) (struct casewriter *writer, void *aux);
+
+    /* Optional: supply if practical and desired by clients.
+
+       Finalizes output to WRITER, destroys WRITER, and in its
+       place returns a casereader that can be used to read back
+       the data written to WRITER.  WRITER will not be used again
+       after calling this function, even as an argument to
+       casewriter_destroy.
+
+       If an I/O error is detected while finalizing output
+       (e.g. while flushing output to disk), this function should
+       call casewriter_force_error on WRITER.  The caller will
+       ensure that the error is propagated to the returned
+       casereader. */
+    struct casereader *(*convert_to_reader) (struct casewriter *, void *aux);
+  };
+
+struct casewriter *casewriter_create (const struct casewriter_class *, void *);
+
+#endif /* data/casewriter-provider.h */