-/* PSPP - computes sample statistics.
- Copyright (C) 2006 Free Software Foundation, Inc.
+/* PSPP - a program for statistical analysis.
+ Copyright (C) 2006, 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 the Free Software Foundation; either version 2 of the
- License, or (at your option) any later version.
+ 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 3 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.
+ 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. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
-#include "sys-file-private.h"
+#include <data/sys-file-private.h>
+
+#include <data/dictionary.h>
#include <data/value.h>
+#include <data/variable.h>
#include <libpspp/assertion.h>
+#include <libpspp/misc.h>
-/* Return the number of bytes used when writing case_data for a variable
- of WIDTH */
-int
+#include "minmax.h"
+#include "xalloc.h"
+
+/* Number of bytes really stored in each segment of a very long
+ string variable. */
+#define REAL_VLS_CHUNK 255
+
+/* Number of bytes per segment by which the amount of space for
+ very long string variables is allocated. */
+#define EFFECTIVE_VLS_CHUNK 252
+
+/* Returns true if WIDTH is a very long string width,
+ false otherwise. */
+static bool
+is_very_long (int width)
+{
+ return width >= 256;
+}
+
+/* Returns the smaller of A or B.
+ (Defined as a function to avoid evaluating A or B more than
+ once.) */
+static int
+min_int (int a, int b)
+{
+ return MIN (a, b);
+}
+
+/* Returns the larger of A or B.
+ (Defined as a function to avoid evaluating A or B more than
+ once.) */
+static int
+max_int (int a, int b)
+{
+ return MAX (a, b);
+}
+
+/* Returns the number of bytes of uncompressed case data used for
+ writing a variable of the given WIDTH to a system file. All
+ required space is included, including trailing padding and
+ internal padding. */
+static int
sfm_width_to_bytes (int width)
{
+ int bytes;
+
assert (width >= 0);
- if (width == 0)
- return MAX_SHORT_STRING;
- else if (width < MIN_VERY_LONG_STRING)
- return ROUND_UP (width, MAX_SHORT_STRING);
- else
+ if (width == 0)
+ bytes = 8;
+ else if (!is_very_long (width))
+ bytes = width;
+ else
{
- int chunks = width / EFFECTIVE_LONG_STRING_LENGTH ;
- int remainder = width % EFFECTIVE_LONG_STRING_LENGTH ;
- int bytes = remainder + (chunks * MIN_VERY_LONG_STRING);
- return ROUND_UP (bytes, MAX_SHORT_STRING);
+ int chunks = width / EFFECTIVE_VLS_CHUNK;
+ int remainder = width % EFFECTIVE_VLS_CHUNK;
+ bytes = remainder + (chunks * ROUND_UP (REAL_VLS_CHUNK, 8));
}
+ return ROUND_UP (bytes, 8);
}
+/* Returns the number of 8-byte units (octs) used to write data
+ for a variable of the given WIDTH. */
+int
+sfm_width_to_octs (int width)
+{
+ return sfm_width_to_bytes (width) / 8;
+}
+
+/* Returns the number of "segments" used for writing case data
+ for a variable of the given WIDTH. A segment is a physical
+ variable in the system file that represents some piece of a
+ logical variable as seen by a PSPP user. Only very long
+ string variables have more than one segment. */
+int
+sfm_width_to_segments (int width)
+{
+ assert (width >= 0);
+
+ return !is_very_long (width) ? 1 : DIV_RND_UP (width, EFFECTIVE_VLS_CHUNK);
+}
+
+/* Returns the width to allocate to the given SEGMENT within a
+ variable of the given WIDTH. A segment is a physical variable
+ in the system file that represents some piece of a logical
+ variable as seen by a PSPP user. */
+int
+sfm_segment_alloc_width (int width, int segment)
+{
+ assert (segment < sfm_width_to_segments (width));
+
+ return (!is_very_long (width) ? width
+ : segment < sfm_width_to_segments (width) - 1 ? 255
+ : width - segment * EFFECTIVE_VLS_CHUNK);
+}
+/* Returns the number of bytes to allocate to the given SEGMENT
+ within a variable of the given width. This is the same as
+ sfm_segment_alloc_width, except that a numeric value takes up
+ 8 bytes despite having a width of 0. */
+static int
+sfm_segment_alloc_bytes (int width, int segment)
+{
+ assert (segment < sfm_width_to_segments (width));
+ return (width == 0 ? 8
+ : ROUND_UP (sfm_segment_alloc_width (width, segment), 8));
+}
+
+/* Returns the number of bytes in the given SEGMENT within a
+ variable of the given WIDTH that are actually used to store
+ data. For a numeric value (WIDTH of 0), this is 8 bytes; for
+ a string value less than 256 bytes wide, it is WIDTH bytes.
+ For very long string values, the calculation is more
+ complicated and ranges between 255 bytes for the first segment
+ to as little as 0 bytes for final segments. */
+static int
+sfm_segment_used_bytes (int width, int segment)
+{
+ assert (segment < sfm_width_to_segments (width));
+ return (width == 0 ? 8
+ : !is_very_long (width) ? width
+ : max_int (0, min_int (width - REAL_VLS_CHUNK * segment,
+ REAL_VLS_CHUNK)));
+}
+
+/* Returns the number of bytes at the end of the given SEGMENT
+ within a variable of the given WIDTH that are not used for
+ data; that is, the number of bytes that must be padded with
+ data that a reader ignores. */
+static int
+sfm_segment_padding (int width, int segment)
+{
+ return (sfm_segment_alloc_bytes (width, segment)
+ - sfm_segment_used_bytes (width, segment));
+}
+
+/* Returns the byte offset of the start of the given SEGMENT
+ within a variable of the given WIDTH. The first segment
+ starts at offset 0; only very long string variables have any
+ other segments. */
+static int
+sfm_segment_offset (int width, int segment)
+{
+ assert (segment < sfm_width_to_segments (width));
+ return min_int (REAL_VLS_CHUNK * segment, width);
+}
+
+/* Returns the byte offset of the start of the given SEGMENT
+ within a variable of the given WIDTH, given the (incorrect)
+ assumption that there are EFFECTIVE_VLS_CHUNK bytes per
+ segment. (Use of this function is questionable at best.) */
+int
+sfm_segment_effective_offset (int width, int segment)
+{
+ assert (segment < sfm_width_to_segments (width));
+ return EFFECTIVE_VLS_CHUNK * segment;
+}
+
+/* Creates and initializes an array of struct sfm_vars that
+ describe how a case drawn from dictionary DICT is laid out in
+ a system file. Returns the number of segments in a case. A
+ segment is a physical variable in the system file that
+ represents some piece of a logical variable as seen by a PSPP
+ user.
+
+ The array is allocated with malloc and stored in *SFM_VARS,
+ and its number of elements is stored in *SFM_VAR_CNT. The
+ caller is responsible for freeing it when it is no longer
+ needed. */
+int
+sfm_dictionary_to_sfm_vars (const struct dictionary *dict,
+ struct sfm_var **sfm_vars, size_t *sfm_var_cnt)
+{
+ size_t var_cnt = dict_get_var_cnt (dict);
+ size_t segment_cnt;
+ size_t i;
+
+ /* Estimate the number of sfm_vars that will be needed.
+ We might not need all of these, because very long string
+ variables can have segments that are all padding, which do
+ not need sfm_vars of their own. */
+ segment_cnt = 0;
+ for (i = 0; i < var_cnt; i++)
+ {
+ const struct variable *v = dict_get_var (dict, i);
+ segment_cnt += sfm_width_to_segments (var_get_width (v));
+ }
+
+ /* Compose the sfm_vars. */
+ *sfm_vars = xnmalloc (segment_cnt, sizeof **sfm_vars);
+ *sfm_var_cnt = 0;
+ for (i = 0; i < var_cnt; i++)
+ {
+ const struct variable *dv = dict_get_var (dict, i);
+ int width = var_get_width (dv);
+ int j;
+
+ for (j = 0; j < sfm_width_to_segments (width); j++)
+ {
+ int used_bytes = sfm_segment_used_bytes (width, j);
+ int padding = sfm_segment_padding (width, j);
+ struct sfm_var *sv;
+ if (used_bytes != 0)
+ {
+ sv = &(*sfm_vars)[(*sfm_var_cnt)++];
+ sv->var_width = width;
+ sv->segment_width = width == 0 ? 0 : used_bytes;
+ sv->case_index = var_get_case_index (dv);
+ sv->offset = sfm_segment_offset (width, j);
+ sv->padding = padding;
+ }
+ else
+ {
+ /* Segment is all padding. Just add it to the
+ previous segment. */
+ sv = &(*sfm_vars)[*sfm_var_cnt - 1];
+ sv->padding += padding;
+ }
+ assert ((sv->segment_width + sv->padding) % 8 == 0);
+ }
+ }
+
+ return segment_cnt;
+}
projects / pspp-builds.git / blobdiff