src/data/scratch-writer.c

   1 /* PSPP - computes sample statistics.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    License, or (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software
  16    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17    02110-1301, USA. */
  18
  19 #include <config.h>
  20
  21 #include "scratch-writer.h"
  22
  23 #include <stdlib.h>
  24
  25 #include <data/case.h>
  26 #include <data/casereader.h>
  27 #include <data/casewriter-provider.h>
  28 #include <data/casewriter.h>
  29 #include <data/dictionary.h>
  30 #include <data/file-handle-def.h>
  31 #include <data/scratch-handle.h>
  32 #include <libpspp/compiler.h>
  33 #include <libpspp/taint.h>
  34
  35 #include "xalloc.h"
  36
  37 /* A scratch file writer. */
  38 struct scratch_writer
  39   {
  40     struct scratch_handle *handle;      /* Underlying scratch handle. */
  41     struct file_handle *fh;             /* Underlying file handle. */
  42     struct dict_compactor *compactor;   /* Compacts into handle->dictionary. */
  43     struct casewriter *subwriter;       /* Data output. */
  44   };
  45
  46 static struct casewriter_class scratch_writer_casewriter_class;
  47
  48 /* Opens FH, which must have referent type FH_REF_SCRATCH, and
  49    returns a scratch_writer for it, or a null pointer on
  50    failure.  Cases stored in the scratch_writer will be expected
  51    to be drawn from DICTIONARY. */
  52 struct casewriter *
  53 scratch_writer_open (struct file_handle *fh,
  54                      const struct dictionary *dictionary)
  55 {
  56   struct scratch_handle *sh;
  57   struct scratch_writer *writer;
  58   struct dictionary *scratch_dict;
  59   struct dict_compactor *compactor;
  60   struct casewriter *casewriter;
  61
  62   if (!fh_open (fh, FH_REF_SCRATCH, "scratch file", "we"))
  63     return NULL;
  64
  65   /* Destroy previous contents of handle. */
  66   sh = fh_get_scratch_handle (fh);
  67   if (sh != NULL)
  68     scratch_handle_destroy (sh);
  69
  70   /* Copy the dictionary and compact if needed. */
  71   scratch_dict = dict_clone (dictionary);
  72   if (dict_compacting_would_shrink (scratch_dict))
  73     {
  74       compactor = dict_make_compactor (scratch_dict);
  75       dict_compact_values (scratch_dict);
  76     }
  77   else
  78     compactor = NULL;
  79
  80   /* Create new contents. */
  81   sh = xmalloc (sizeof *sh);
  82   sh->dictionary = scratch_dict;
  83   sh->casereader = NULL;
  84
  85   /* Create writer. */
  86   writer = xmalloc (sizeof *writer);
  87   writer->handle = sh;
  88   writer->fh = fh;
  89   writer->compactor = compactor;
  90   writer->subwriter = autopaging_writer_create (dict_get_next_value_idx (
  91                                                scratch_dict));
  92
  93   fh_set_scratch_handle (fh, sh);
  94   casewriter = casewriter_create (&scratch_writer_casewriter_class, writer);
  95   taint_propagate (casewriter_get_taint (writer->subwriter),
  96                    casewriter_get_taint (casewriter));
  97   return casewriter;
  98 }
  99
 100 /* Writes case C to WRITER. */
 101 static void
 102 scratch_writer_casewriter_write (struct casewriter *w UNUSED, void *writer_,
 103                                  struct ccase *c)
 104 {
 105   struct scratch_writer *writer = writer_;
 106   struct scratch_handle *handle = writer->handle;
 107   struct ccase tmp;
 108   if (writer->compactor)
 109     {
 110       case_create (&tmp, dict_get_next_value_idx (handle->dictionary));
 111       dict_compactor_compact (writer->compactor, &tmp, c);
 112       case_destroy (c);
 113     }
 114   else
 115     case_move (&tmp, c);
 116   casewriter_write (writer->subwriter, &tmp);
 117 }
 118
 119 /* Closes WRITER. */
 120 static void
 121 scratch_writer_casewriter_destroy (struct casewriter *w UNUSED, void *writer_)
 122 {
 123   struct scratch_writer *writer = writer_;
 124   struct casereader *reader = casewriter_make_reader (writer->subwriter);
 125   if (!casereader_error (reader))
 126     writer->handle->casereader = reader;
 127   fh_close (writer->fh, "scratch file", "we");
 128   free (writer);
 129 }
 130
 131 static struct casewriter_class scratch_writer_casewriter_class =
 132   {
 133     scratch_writer_casewriter_write,
 134     scratch_writer_casewriter_destroy,
 135     NULL,
 136   };