src/data/scratch-writer.c

   1 /* PSPP - a program for statistical analysis.
   2    Copyright (C) 2006 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU 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, see <http://www.gnu.org/licenses/>. */
  16
  17 #include <config.h>
  18
  19 #include "scratch-writer.h"
  20
  21 #include <stdlib.h>
  22
  23 #include <data/case.h>
  24 #include <data/case-map.h>
  25 #include <data/casereader.h>
  26 #include <data/casewriter-provider.h>
  27 #include <data/casewriter.h>
  28 #include <data/dictionary.h>
  29 #include <data/file-handle-def.h>
  30 #include <data/scratch-handle.h>
  31 #include <data/variable.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 file_handle *fh;             /* Underlying file handle. */
  41     struct fh_lock *lock;               /* Exclusive access to file handle. */
  42     struct dictionary *dict;            /* Dictionary for subwriter. */
  43     struct case_map *compactor;         /* Compacts into dictionary. */
  44     struct casewriter *subwriter;       /* Data output. */
  45   };
  46
  47 static struct casewriter_class scratch_writer_casewriter_class;
  48
  49 /* Opens FH, which must have referent type FH_REF_SCRATCH, and
  50    returns a scratch_writer for it, or a null pointer on
  51    failure.  Cases stored in the scratch_writer will be expected
  52    to be drawn from DICTIONARY. */
  53 struct casewriter *
  54 scratch_writer_open (struct file_handle *fh,
  55                      const struct dictionary *dictionary)
  56 {
  57   struct scratch_writer *writer;
  58   struct casewriter *casewriter;
  59   struct fh_lock *lock;
  60   size_t dict_value_cnt;
  61
  62   /* Get exclusive write access to handle. */
  63   lock = fh_lock (fh, FH_REF_SCRATCH, "scratch file", FH_ACC_WRITE, true);
  64   if (lock == NULL)
  65     return NULL;
  66
  67   /* Create writer. */
  68   writer = xmalloc (sizeof *writer);
  69   writer->lock = lock;
  70   writer->fh = fh_ref (fh);
  71
  72   writer->dict = dict_clone (dictionary);
  73   dict_delete_scratch_vars (writer->dict);
  74   if (dict_count_values (writer->dict, 0)
  75       < dict_get_next_value_idx (writer->dict))
  76     {
  77       writer->compactor = case_map_to_compact_dict (writer->dict, 0);
  78       dict_compact_values (writer->dict);
  79     }
  80   else
  81     writer->compactor = NULL;
  82   dict_value_cnt = dict_get_next_value_idx (writer->dict);
  83   writer->subwriter = autopaging_writer_create (dict_value_cnt);
  84
  85   casewriter = casewriter_create (dict_value_cnt,
  86                                   &scratch_writer_casewriter_class, writer);
  87   taint_propagate (casewriter_get_taint (writer->subwriter),
  88                    casewriter_get_taint (casewriter));
  89   return casewriter;
  90 }
  91
  92 /* Writes case C to WRITER. */
  93 static void
  94 scratch_writer_casewriter_write (struct casewriter *w UNUSED, void *writer_,
  95                                  struct ccase *c)
  96 {
  97   struct scratch_writer *writer = writer_;
  98   struct ccase tmp;
  99   if (writer->compactor)
 100     {
 101       case_map_execute (writer->compactor, c, &tmp);
 102       case_destroy (c);
 103     }
 104   else
 105     case_move (&tmp, c);
 106   casewriter_write (writer->subwriter, &tmp);
 107 }
 108
 109 /* Closes WRITER. */
 110 static void
 111 scratch_writer_casewriter_destroy (struct casewriter *w UNUSED, void *writer_)
 112 {
 113   static unsigned int next_unique_id = 0x12345678;
 114
 115   struct scratch_writer *writer = writer_;
 116   struct casereader *reader = casewriter_make_reader (writer->subwriter);
 117   if (!casereader_error (reader))
 118     {
 119       /* Destroy previous contents of handle. */
 120       struct scratch_handle *sh = fh_get_scratch_handle (writer->fh);
 121       if (sh != NULL)
 122         scratch_handle_destroy (sh);
 123
 124       /* Create new contents. */
 125       sh = xmalloc (sizeof *sh);
 126       sh->unique_id = ++next_unique_id;
 127       sh->dictionary = writer->dict;
 128       sh->casereader = reader;
 129       fh_set_scratch_handle (writer->fh, sh);
 130     }
 131   else
 132     {
 133       casereader_destroy (reader);
 134       dict_destroy (writer->dict);
 135     }
 136
 137   fh_unlock (writer->lock);
 138   fh_unref (writer->fh);
 139   free (writer);
 140 }
 141
 142 static struct casewriter_class scratch_writer_casewriter_class =
 143   {
 144     scratch_writer_casewriter_write,
 145     scratch_writer_casewriter_destroy,
 146     NULL,
 147   };