[pspp-builds.git] / src / data / sys-file-writer.c

/* PSPP - a program for statistical analysis.
   Copyright (C) 1997-9, 2000, 2006, 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
   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.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>. */

#include <config.h>

#include "sys-file-writer.h"
#include "sys-file-private.h"

#include <ctype.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <time.h>

#include <libpspp/float-format.h>
#include <libpspp/integer-format.h>
#include <libpspp/message.h>
#include <libpspp/misc.h>
#include <libpspp/str.h>
#include <libpspp/version.h>

#include <data/attributes.h>
#include <data/case.h>
#include <data/casewriter-provider.h>
#include <data/casewriter.h>
#include <data/dictionary.h>
#include <data/file-handle-def.h>
#include <data/file-name.h>
#include <data/format.h>
#include <data/make-file.h>
#include <data/missing-values.h>
#include <data/settings.h>
#include <data/short-names.h>
#include <data/value-labels.h>
#include <data/variable.h>

#include "minmax.h"
#include "unlocked-io.h"
#include "xalloc.h"

#include "gettext.h"
#define _(msgid) gettext (msgid)
#define N_(msgid) (msgid)

/* Compression bias used by PSPP.  Values between (1 -
   COMPRESSION_BIAS) and (251 - COMPRESSION_BIAS) inclusive can be
   compressed. */
#define COMPRESSION_BIAS 100

/* System file writer. */
struct sfm_writer
  {
    struct file_handle *fh;     /* File handle. */
    struct fh_lock *lock;       /* Mutual exclusion for file. */
    FILE *file;                 /* File stream. */
    struct replace_file *rf;    /* Ticket for replacing output file. */

    bool compress;              /* 1=compressed, 0=not compressed. */
    casenumber case_cnt;        /* Number of cases written so far. */

    /* Compression buffering.

       Compressed data is output as groups of 8 1-byte opcodes
       followed by up to 8 (depending on the opcodes) 8-byte data
       items.  Data items and opcodes arrive at the same time but
       must be reordered for writing to disk, thus a small amount
       of buffering here. */
    uint8_t opcodes[8];         /* Buffered opcodes. */
    int opcode_cnt;             /* Number of buffered opcodes. */
    uint8_t data[8][8];         /* Buffered data. */
    int data_cnt;               /* Number of buffered data items. */

    /* Variables. */
    struct sfm_var *sfm_vars;   /* Variables. */
    size_t sfm_var_cnt;         /* Number of variables. */
    size_t segment_cnt;         /* Number of variables including extra segments
                                   for long string variables. */
  };

static const struct casewriter_class sys_file_casewriter_class;

static void write_header (struct sfm_writer *, const struct dictionary *);
static void write_variable (struct sfm_writer *, const struct variable *);
static void write_value_labels (struct sfm_writer *,
                                struct variable *, int idx);
static void write_integer_info_record (struct sfm_writer *);
static void write_float_info_record (struct sfm_writer *);

static void write_longvar_table (struct sfm_writer *w,
                                 const struct dictionary *dict);

static void write_encoding_record (struct sfm_writer *w,
                                   const struct dictionary *);

static void write_vls_length_table (struct sfm_writer *w,
                              const struct dictionary *dict);


static void write_variable_display_parameters (struct sfm_writer *w,
                                               const struct dictionary *dict);

static void write_documents (struct sfm_writer *, const struct dictionary *);

static void write_data_file_attributes (struct sfm_writer *,
                                        const struct dictionary *);
static void write_variable_attributes (struct sfm_writer *,
                                       const struct dictionary *);

static void write_int (struct sfm_writer *, int32_t);
static inline void convert_double_to_output_format (double, uint8_t[8]);
static void write_float (struct sfm_writer *, double);
static void write_string (struct sfm_writer *, const char *, size_t);
static void write_bytes (struct sfm_writer *, const void *, size_t);
static void write_zeros (struct sfm_writer *, size_t);
static void write_spaces (struct sfm_writer *, size_t);
static void write_value (struct sfm_writer *, const union value *, int width);

static void write_case_uncompressed (struct sfm_writer *,
                                     const struct ccase *);
static void write_case_compressed (struct sfm_writer *, const struct ccase *);
static void flush_compressed (struct sfm_writer *);
static void put_cmp_opcode (struct sfm_writer *, uint8_t);
static void put_cmp_number (struct sfm_writer *, double);
static void put_cmp_string (struct sfm_writer *, const void *, size_t);

bool write_error (const struct sfm_writer *);
bool close_writer (struct sfm_writer *);

/* Returns default options for writing a system file. */
struct sfm_write_options
sfm_writer_default_options (void)
{
  struct sfm_write_options opts;
  opts.create_writeable = true;
  opts.compress = settings_get_scompression ();
  opts.version = 3;
  return opts;
}

/* Opens the system file designated by file handle FH for writing
   cases from dictionary D according to the given OPTS.  If
   COMPRESS is nonzero, the system file will be compressed.

   No reference to D is retained, so it may be modified or
   destroyed at will after this function returns.  D is not
   modified by this function, except to assign short names. */
struct casewriter *
sfm_open_writer (struct file_handle *fh, struct dictionary *d,
                 struct sfm_write_options opts)
{
  struct sfm_writer *w;
  mode_t mode;
  int idx;
  int i;

  /* Check version. */
  if (opts.version != 2 && opts.version != 3)
    {
      msg (ME, _("Unknown system file version %d. Treating as version %d."),
           opts.version, 3);
      opts.version = 3;
    }

  /* Create and initialize writer. */
  w = xmalloc (sizeof *w);
  w->fh = fh_ref (fh);
  w->lock = NULL;
  w->file = NULL;
  w->rf = NULL;

  w->compress = opts.compress;
  w->case_cnt = 0;

  w->opcode_cnt = w->data_cnt = 0;

  /* Figure out how to map in-memory case data to on-disk case
     data.  Also count the number of segments.  Very long strings
     occupy multiple segments, otherwise each variable only takes
     one segment. */
  w->segment_cnt = sfm_dictionary_to_sfm_vars (d, &w->sfm_vars,
                                               &w->sfm_var_cnt);

  /* Open file handle as an exclusive writer. */
  /* TRANSLATORS: this fragment will be interpolated into
     messages in fh_lock() that identify types of files. */
  w->lock = fh_lock (fh, FH_REF_FILE, N_("system file"), FH_ACC_WRITE, true);
  if (w->lock == NULL)
    goto error;

  /* Create the file on disk. */
  mode = S_IRUSR | S_IRGRP | S_IROTH;
  if (opts.create_writeable)
    mode |= S_IWUSR | S_IWGRP | S_IWOTH;
  w->rf = replace_file_start (fh_get_file_name (fh), "wb", mode,
                              &w->file, NULL);
  if (w->rf == NULL)
    {
      msg (ME, _("Error opening \"%s\" for writing as a system file: %s."),
           fh_get_file_name (fh), strerror (errno));
      goto error;
    }

  /* Write the file header. */
  write_header (w, d);

  /* Write basic variable info. */
  short_names_assign (d);
  for (i = 0; i < dict_get_var_cnt (d); i++)
    write_variable (w, dict_get_var (d, i));

  /* Write out value labels. */
  idx = 0;
  for (i = 0; i < dict_get_var_cnt (d); i++)
    {
      struct variable *v = dict_get_var (d, i);

      write_value_labels (w, v, idx);
      idx += sfm_width_to_octs (var_get_width (v));
    }

  if (dict_get_documents (d) != NULL)
    write_documents (w, d);

  write_integer_info_record (w);
  write_float_info_record (w);

  write_variable_display_parameters (w, d);

  if (opts.version >= 3)
    write_longvar_table (w, d);

  write_vls_length_table (w, d);

  if (attrset_count (dict_get_attributes (d)))
    write_data_file_attributes (w, d);
  write_variable_attributes (w, d);

  write_encoding_record (w, d);

  /* Write end-of-headers record. */
  write_int (w, 999);
  write_int (w, 0);

  if (write_error (w))
    {
      close_writer (w);
      return NULL;
    }

  return casewriter_create (dict_get_proto (d), &sys_file_casewriter_class, w);

error:
  close_writer (w);
  return NULL;
}

/* Returns value of X truncated to two least-significant digits. */
static int
rerange (int x)
{
  if (x < 0)
    x = -x;
  if (x >= 100)
    x %= 100;
  return x;
}

/* Calculates the offset of data for TARGET_VAR from the
   beginning of each case's data for dictionary D.  The return
   value is in "octs" (8-byte units). */
static int
calc_oct_idx (const struct dictionary *d, struct variable *target_var)
{
  int oct_idx;
  int i;

  oct_idx = 0;
  for (i = 0; i < dict_get_var_cnt (d); i++)
    {
      struct variable *var = dict_get_var (d, i);
      if (var == target_var)
        break;
      oct_idx += sfm_width_to_octs (var_get_width (var));
    }
  return oct_idx;
}

/* Write the sysfile_header header to system file W. */
static void
write_header (struct sfm_writer *w, const struct dictionary *d)
{
  char prod_name[61];
  char creation_date[10];
  char creation_time[9];
  const char *file_label;
  struct variable *weight;

  time_t t;

  /* Record-type code. */
  write_string (w, "$FL2", 4);

  /* Product identification. */
  snprintf (prod_name, sizeof prod_name, "@(#) SPSS DATA FILE %s - %s",
            version, host_system);
  write_string (w, prod_name, 60);

  /* Layout code. */
  write_int (w, 2);

  /* Number of `union value's per case. */
  write_int (w, calc_oct_idx (d, NULL));

  /* Compressed? */
  write_int (w, w->compress);

  /* Weight variable. */
  weight = dict_get_weight (d);
  write_int (w, weight != NULL ? calc_oct_idx (d, weight) + 1 : 0);

  /* Number of cases.  We don't know this in advance, so we write
     -1 to indicate an unknown number of cases.  Later we can
     come back and overwrite it with the true value. */
  write_int (w, -1);

  /* Compression bias. */
  write_float (w, COMPRESSION_BIAS);

  /* Creation date and time. */
  if (time (&t) == (time_t) -1)
    {
      strcpy (creation_date, "01 Jan 70");
      strcpy (creation_time, "00:00:00");
    }
  else
    {
      static const char *const month_name[12] =
        {
          "Jan", "Feb", "Mar", "Apr", "May", "Jun",
          "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
        };
      struct tm *tmp = localtime (&t);
      int day = rerange (tmp->tm_mday);
      int mon = rerange (tmp->tm_mon + 1);
      int year = rerange (tmp->tm_year);
      int hour = rerange (tmp->tm_hour + 1);
      int min = rerange (tmp->tm_min + 1);
      int sec = rerange (tmp->tm_sec + 1);

      snprintf (creation_date, sizeof creation_date,
                "%02d %s %02d", day, month_name[mon - 1], year);
      snprintf (creation_time, sizeof creation_time,
                "%02d:%02d:%02d", hour - 1, min - 1, sec - 1);
    }
  write_string (w, creation_date, 9);
  write_string (w, creation_time, 8);

  /* File label. */
  file_label = dict_get_label (d);
  if (file_label == NULL)
    file_label = "";
  write_string (w, file_label, 64);

  /* Padding. */
  write_zeros (w, 3);
}

/* Write format spec FMT to W, after adjusting it to be
   compatible with the given WIDTH. */
static void
write_format (struct sfm_writer *w, struct fmt_spec fmt, int width)
{
  assert (fmt_check_output (&fmt));
  assert (sfm_width_to_segments (width) == 1);

  if (width > 0)
    fmt_resize (&fmt, width);
  write_int (w, (fmt_to_io (fmt.type) << 16) | (fmt.w << 8) | fmt.d);
}

/* Write a string continuation variable record for each 8-byte
   section beyond the initial 8 bytes, for a variable of the
   given WIDTH. */
static void
write_variable_continuation_records (struct sfm_writer *w, int width)
{
  int position;

  assert (sfm_width_to_segments (width) == 1);
  for (position = 8; position < width; position += 8)
    {
      write_int (w, 2);   /* Record type. */
      write_int (w, -1);  /* Width. */
      write_int (w, 0);   /* No variable label. */
      write_int (w, 0);   /* No missing values. */
      write_int (w, 0);   /* Print format. */
      write_int (w, 0);   /* Write format. */
      write_zeros (w, 8);   /* Name. */
    }
}

/* Write the variable record(s) for variable V to system file
   W. */
static void
write_variable (struct sfm_writer *w, const struct variable *v)
{
  int width = var_get_width (v);
  int segment_cnt = sfm_width_to_segments (width);
  int seg0_width = sfm_segment_alloc_width (width, 0);
  const struct missing_values *mv = var_get_missing_values (v);
  int i;

  /* Record type. */
  write_int (w, 2);

  /* Width. */
  write_int (w, seg0_width);

  /* Variable has a variable label? */
  write_int (w, var_has_label (v));

  /* Number of missing values.  If there is a range, then the
     range counts as 2 missing values and causes the number to be
     negated. */
  write_int (w, mv_has_range (mv) ? -2 - mv_n_values (mv) : mv_n_values (mv));

  /* Print and write formats. */
  write_format (w, *var_get_print_format (v), seg0_width);
  write_format (w, *var_get_write_format (v), seg0_width);

  /* Short name.
     The full name is in a translation table written
     separately. */
  write_string (w, var_get_short_name (v, 0), 8);

  /* Value label. */
  if (var_has_label (v))
    {
      const char *label = var_get_label (v);
      size_t padded_len = ROUND_UP (MIN (strlen (label), 255), 4);
      write_int (w, padded_len);
      write_string (w, label, padded_len);
    }

  /* Write the missing values, if any, range first. */
  if (mv_has_range (mv))
    {
      double x, y;
      mv_get_range (mv, &x, &y);
      write_float (w, x);
      write_float (w, y);
    }
  for (i = 0; i < mv_n_values (mv); i++)
    {
      union value value;
      mv_get_value (mv, &value, i);
      write_value (w, &value, seg0_width);
    }

  write_variable_continuation_records (w, seg0_width);

  /* Write additional segments for very long string variables. */
  for (i = 1; i < segment_cnt; i++)
    {
      int seg_width = sfm_segment_alloc_width (width, i);
      struct fmt_spec fmt = fmt_for_output (FMT_A, MAX (seg_width, 1), 0);

      write_int (w, 2);           /* Variable record. */
      write_int (w, seg_width);   /* Width. */
      write_int (w, 0);           /* No variable label. */
      write_int (w, 0);           /* No missing values. */
      write_format (w, fmt, seg_width); /* Print format. */
      write_format (w, fmt, seg_width); /* Write format. */
      write_string (w, var_get_short_name (v, i), 8);

      write_variable_continuation_records (w, seg_width);
    }
}

/* Writes the value labels for variable V having system file
   variable index IDX to system file W. */
static void
write_value_labels (struct sfm_writer *w, struct variable *v, int idx)
{
  const struct val_labs *val_labs;
  const struct val_lab **labels;
  size_t n_labels;
  size_t i;

  val_labs = var_get_value_labels (v);
  n_labels = val_labs_count (val_labs);
  if (n_labels == 0)
    return;

  /* Value label record. */
  write_int (w, 3);             /* Record type. */
  write_int (w, val_labs_count (val_labs));
  labels = val_labs_sorted (val_labs);
  for (i = 0; i < n_labels; i++)
    {
      const struct val_lab *vl = labels[i];
      const char *label = val_lab_get_label (vl);
      uint8_t len = MIN (strlen (label), 255);

      write_value (w, val_lab_get_value (vl), var_get_width (v));
      write_bytes (w, &len, 1);
      write_bytes (w, label, len);
      write_zeros (w, REM_RND_UP (len + 1, 8));
    }
  free (labels);

  /* Value label variable record. */
  write_int (w, 4);             /* Record type. */
  write_int (w, 1);             /* Number of variables. */
  write_int (w, idx + 1);       /* Variable's dictionary index. */
}

/* Writes record type 6, document record. */
static void
write_documents (struct sfm_writer *w, const struct dictionary *d)
{
  size_t line_cnt = dict_get_document_line_cnt (d);

  write_int (w, 6);             /* Record type. */
  write_int (w, line_cnt);
  write_bytes (w, dict_get_documents (d), line_cnt * DOC_LINE_LENGTH);
}

static void
put_attrset (struct string *string, const struct attrset *attrs)
{
  const struct attribute *attr;
  struct attrset_iterator i;

  for (attr = attrset_first (attrs, &i); attr != NULL;
       attr = attrset_next (attrs, &i)) 
    {
      size_t n_values = attribute_get_n_values (attr);
      size_t j;

      ds_put_cstr (string, attribute_get_name (attr));
      ds_put_char (string, '(');
      for (j = 0; j < n_values; j++) 
        ds_put_format (string, "'%s'\n", attribute_get_value (attr, j));
      ds_put_char (string, ')');
    }
}

static void
write_attribute_record (struct sfm_writer *w, const struct string *content,
                        int subtype) 
{
  write_int (w, 7);
  write_int (w, subtype);
  write_int (w, 1);
  write_int (w, ds_length (content));
  write_bytes (w, ds_data (content), ds_length (content));
}

static void
write_data_file_attributes (struct sfm_writer *w,
                            const struct dictionary *d)
{
  struct string s = DS_EMPTY_INITIALIZER;
  put_attrset (&s, dict_get_attributes (d));
  write_attribute_record (w, &s, 17);
  ds_destroy (&s);
}

static void
write_variable_attributes (struct sfm_writer *w, const struct dictionary *d)
{
  struct string s = DS_EMPTY_INITIALIZER;
  size_t n_vars = dict_get_var_cnt (d);
  size_t n_attrsets = 0;
  size_t i;

  for (i = 0; i < n_vars; i++)
    { 
      struct variable *v = dict_get_var (d, i);
      struct attrset *attrs = var_get_attributes (v);
      if (attrset_count (attrs)) 
        {
          if (n_attrsets++)
            ds_put_char (&s, '/');
          ds_put_format (&s, "%s:", var_get_short_name (v, 0));
          put_attrset (&s, attrs);
        }
    }
  if (n_attrsets) 
    write_attribute_record (w, &s, 18);
  ds_destroy (&s);
}

/* Write the alignment, width and scale values. */
static void
write_variable_display_parameters (struct sfm_writer *w,
                                   const struct dictionary *dict)
{
  int i;

  write_int (w, 7);             /* Record type. */
  write_int (w, 11);            /* Record subtype. */
  write_int (w, 4);             /* Data item (int32) size. */
  write_int (w, w->segment_cnt * 3); /* Number of data items. */

  for (i = 0; i < dict_get_var_cnt (dict); ++i)
    {
      struct variable *v = dict_get_var (dict, i);
      int width = var_get_width (v);
      int segment_cnt = sfm_width_to_segments (width);
      int measure = (var_get_measure (v) == MEASURE_NOMINAL ? 1
                     : var_get_measure (v) == MEASURE_ORDINAL ? 2
                     : 3);
      int alignment = (var_get_alignment (v) == ALIGN_LEFT ? 0
                       : var_get_alignment (v) == ALIGN_RIGHT ? 1
                       : 2);
      int i;

      for (i = 0; i < segment_cnt; i++)
        {
          int width_left = width - sfm_segment_effective_offset (width, i);
          write_int (w, measure);
          write_int (w, (i == 0 ? var_get_display_width (v)
                         : var_default_display_width (width_left)));
          write_int (w, alignment);
        }
    }
}

/* Writes the table of lengths for very long string variables. */
static void
write_vls_length_table (struct sfm_writer *w,
                        const struct dictionary *dict)
{
  struct string map;
  int i;

  ds_init_empty (&map);
  for (i = 0; i < dict_get_var_cnt (dict); ++i)
    {
      const struct variable *v = dict_get_var (dict, i);
      if (sfm_width_to_segments (var_get_width (v)) > 1)
        ds_put_format (&map, "%s=%05d%c\t",
                       var_get_short_name (v, 0), var_get_width (v), 0);
    }
  if (!ds_is_empty (&map))
    {
      write_int (w, 7);         /* Record type. */
      write_int (w, 14);        /* Record subtype. */
      write_int (w, 1);         /* Data item (char) size. */
      write_int (w, ds_length (&map)); /* Number of data items. */
      write_bytes (w, ds_data (&map), ds_length (&map));
    }
  ds_destroy (&map);
}


static void
write_encoding_record (struct sfm_writer *w,
                       const struct dictionary *d)
{
  const char *enc = dict_get_encoding (d);

  if ( NULL == enc)
    return;

  write_int (w, 7);             /* Record type. */
  write_int (w, 20);            /* Record subtype. */
  write_int (w, 1);             /* Data item (char) size. */
  write_int (w, strlen (enc));  /* Number of data items. */
  write_string (w, enc, strlen (enc));
}


/* Writes the long variable name table. */
static void
write_longvar_table (struct sfm_writer *w, const struct dictionary *dict)
{
  struct string map;
  size_t i;

  ds_init_empty (&map);
  for (i = 0; i < dict_get_var_cnt (dict); i++)
    {
      struct variable *v = dict_get_var (dict, i);

      if (i)
        ds_put_char (&map, '\t');
      ds_put_format (&map, "%s=%s",
                     var_get_short_name (v, 0), var_get_name (v));
    }

  write_int (w, 7);             /* Record type. */
  write_int (w, 13);            /* Record subtype. */
  write_int (w, 1);             /* Data item (char) size. */
  write_int (w, ds_length (&map)); /* Number of data items. */
  write_bytes (w, ds_data (&map), ds_length (&map));

  ds_destroy (&map);
}

/* Write integer information record. */
static void
write_integer_info_record (struct sfm_writer *w)
{
  int version_component[3];
  int float_format;

  /* Parse the version string. */
  memset (version_component, 0, sizeof version_component);
  sscanf (bare_version, "%d.%d.%d",
          &version_component[0], &version_component[1], &version_component[2]);

  /* Figure out the floating-point format. */
  if (FLOAT_NATIVE_64_BIT == FLOAT_IEEE_DOUBLE_LE
      || FLOAT_NATIVE_64_BIT == FLOAT_IEEE_DOUBLE_BE)
    float_format = 1;
  else if (FLOAT_NATIVE_64_BIT == FLOAT_Z_LONG)
    float_format = 2;
  else if (FLOAT_NATIVE_64_BIT == FLOAT_VAX_D)
    float_format = 3;
  else
    abort ();

  /* Write record. */
  write_int (w, 7);             /* Record type. */
  write_int (w, 3);             /* Record subtype. */
  write_int (w, 4);             /* Data item (int32) size. */
  write_int (w, 8);             /* Number of data items. */
  write_int (w, version_component[0]);
  write_int (w, version_component[1]);
  write_int (w, version_component[2]);
  write_int (w, -1);          /* Machine code. */
  write_int (w, float_format);
  write_int (w, 1);           /* Compression code. */
  write_int (w, INTEGER_NATIVE == INTEGER_MSB_FIRST ? 1 : 2);
  write_int (w, 2);           /* 7-bit ASCII. */
}

/* Write floating-point information record. */
static void
write_float_info_record (struct sfm_writer *w)
{
  write_int (w, 7);             /* Record type. */
  write_int (w, 4);             /* Record subtype. */
  write_int (w, 8);             /* Data item (flt64) size. */
  write_int (w, 3);             /* Number of data items. */
  write_float (w, SYSMIS);      /* System-missing value. */
  write_float (w, HIGHEST);     /* Value used for HIGHEST in missing values. */
  write_float (w, LOWEST);      /* Value used for LOWEST in missing values. */
}
\f
/* Writes case C to system file W. */
static void
sys_file_casewriter_write (struct casewriter *writer, void *w_,
                           struct ccase *c)
{
  struct sfm_writer *w = w_;

  if (ferror (w->file))
    {
      casewriter_force_error (writer);
      case_unref (c);
      return;
    }

  w->case_cnt++;

  if (!w->compress)
    write_case_uncompressed (w, c);
  else
    write_case_compressed (w, c);

  case_unref (c);
}

/* Destroys system file writer W. */
static void
sys_file_casewriter_destroy (struct casewriter *writer, void *w_)
{
  struct sfm_writer *w = w_;
  if (!close_writer (w))
    casewriter_force_error (writer);
}

/* Returns true if an I/O error has occurred on WRITER, false otherwise. */
bool
write_error (const struct sfm_writer *writer)
{
  return ferror (writer->file);
}

/* Closes a system file after we're done with it.
   Returns true if successful, false if an I/O error occurred. */
bool
close_writer (struct sfm_writer *w)
{
  bool ok;

  if (w == NULL)
    return true;

  ok = true;
  if (w->file != NULL)
    {
      /* Flush buffer. */
      if (w->opcode_cnt > 0)
        flush_compressed (w);
      fflush (w->file);

      ok = !write_error (w);

      /* Seek back to the beginning and update the number of cases.
         This is just a courtesy to later readers, so there's no need
         to check return values or report errors. */
      if (ok && w->case_cnt <= INT32_MAX && !fseek (w->file, 80, SEEK_SET))
        {
          write_int (w, w->case_cnt);
          clearerr (w->file);
        }

      if (fclose (w->file) == EOF)
        ok = false;

      if (!ok)
        msg (ME, _("An I/O error occurred writing system file \"%s\"."),
             fh_get_file_name (w->fh));

      if (ok ? !replace_file_commit (w->rf) : !replace_file_abort (w->rf))
        ok = false;
    }

  fh_unlock (w->lock);
  fh_unref (w->fh);

  free (w->sfm_vars);
  free (w);

  return ok;
}

/* System file writer casewriter class. */
static const struct casewriter_class sys_file_casewriter_class =
  {
    sys_file_casewriter_write,
    sys_file_casewriter_destroy,
    NULL,
  };
\f
/* Writes case C to system file W, without compressing it. */
static void
write_case_uncompressed (struct sfm_writer *w, const struct ccase *c)
{
  size_t i;

  for (i = 0; i < w->sfm_var_cnt; i++)
    {
      struct sfm_var *v = &w->sfm_vars[i];

      if (v->var_width == 0)
        write_float (w, case_num_idx (c, v->case_index));
      else
        {
          write_bytes (w, case_str_idx (c, v->case_index) + v->offset,
                       v->segment_width);
          write_spaces (w, v->padding);
        }
    }
}

/* Writes case C to system file W, with compression. */
static void
write_case_compressed (struct sfm_writer *w, const struct ccase *c)
{
  size_t i;

  for (i = 0; i < w->sfm_var_cnt; i++)
    {
      struct sfm_var *v = &w->sfm_vars[i];

      if (v->var_width == 0)
        {
          double d = case_num_idx (c, v->case_index);
          if (d == SYSMIS)
            put_cmp_opcode (w, 255);
          else if (d >= 1 - COMPRESSION_BIAS
                   && d <= 251 - COMPRESSION_BIAS
                   && d == (int) d)
            put_cmp_opcode (w, (int) d + COMPRESSION_BIAS);
          else
            {
              put_cmp_opcode (w, 253);
              put_cmp_number (w, d);
            }
        }
      else
        {
          int offset = v->offset;
          int width, padding;

          /* This code properly deals with a width that is not a
             multiple of 8, by ensuring that the final partial
             oct (8 byte unit) is treated as padded with spaces
             on the right. */
          for (width = v->segment_width; width > 0; width -= 8, offset += 8)
            {
              const void *data = case_str_idx (c, v->case_index) + offset;
              int chunk_size = MIN (width, 8);
              if (!memcmp (data, "        ", chunk_size))
                put_cmp_opcode (w, 254);
              else
                {
                  put_cmp_opcode (w, 253);
                  put_cmp_string (w, data, chunk_size);
                }
            }

          /* This code deals properly with padding that is not a
             multiple of 8 bytes, by discarding the remainder,
             which was already effectively padded with spaces in
             the previous loop.  (Note that v->width + v->padding
             is always a multiple of 8.) */
          for (padding = v->padding / 8; padding > 0; padding--)
            put_cmp_opcode (w, 254);
        }
    }
}

/* Flushes buffered compressed opcodes and data to W.
   The compression buffer must not be empty. */
static void
flush_compressed (struct sfm_writer *w)
{
  assert (w->opcode_cnt > 0 && w->opcode_cnt <= 8);

  write_bytes (w, w->opcodes, w->opcode_cnt);
  write_zeros (w, 8 - w->opcode_cnt);

  write_bytes (w, w->data, w->data_cnt * sizeof *w->data);

  w->opcode_cnt = w->data_cnt = 0;
}

/* Appends OPCODE to the buffered set of compression opcodes in
   W.  Flushes the compression buffer beforehand if necessary. */
static void
put_cmp_opcode (struct sfm_writer *w, uint8_t opcode)
{
  if (w->opcode_cnt >= 8)
    flush_compressed (w);

  w->opcodes[w->opcode_cnt++] = opcode;
}

/* Appends NUMBER to the buffered compression data in W.  The
   buffer must not be full; the way to assure that is to call
   this function only just after a call to put_cmp_opcode, which
   will flush the buffer as necessary. */
static void
put_cmp_number (struct sfm_writer *w, double number)
{
  assert (w->opcode_cnt > 0);
  assert (w->data_cnt < 8);

  convert_double_to_output_format (number, w->data[w->data_cnt++]);
}

/* Appends SIZE bytes of DATA to the buffered compression data in
   W, followed by enough spaces to pad the output data to exactly
   8 bytes (thus, SIZE must be no greater than 8).  The buffer
   must not be full; the way to assure that is to call this
   function only just after a call to put_cmp_opcode, which will
   flush the buffer as necessary. */
static void
put_cmp_string (struct sfm_writer *w, const void *data, size_t size)
{
  assert (w->opcode_cnt > 0);
  assert (w->data_cnt < 8);
  assert (size <= 8);

  memset (w->data[w->data_cnt], ' ', 8);
  memcpy (w->data[w->data_cnt], data, size);
  w->data_cnt++;
}
\f
/* Writes 32-bit integer X to the output file for writer W. */
static void
write_int (struct sfm_writer *w, int32_t x)
{
  write_bytes (w, &x, sizeof x);
}

/* Converts NATIVE to the 64-bit format used in output files in
   OUTPUT. */
static inline void
convert_double_to_output_format (double native, uint8_t output[8])
{
  /* If "double" is not a 64-bit type, then convert it to a
     64-bit type.  Otherwise just copy it. */
  if (FLOAT_NATIVE_DOUBLE != FLOAT_NATIVE_64_BIT)
    float_convert (FLOAT_NATIVE_DOUBLE, &native, FLOAT_NATIVE_64_BIT, output);
  else
    memcpy (output, &native, sizeof native);
}

/* Writes floating-point number X to the output file for writer
   W. */
static void
write_float (struct sfm_writer *w, double x)
{
  uint8_t output[8];
  convert_double_to_output_format (x, output);
  write_bytes (w, output, sizeof output);
}

/* Writes contents of VALUE with the given WIDTH to W, padding
   with zeros to a multiple of 8 bytes.
   To avoid a branch, and because we don't actually need to
   support it, WIDTH must be no bigger than 8. */
static void
write_value (struct sfm_writer *w, const union value *value, int width)
{
  assert (width <= 8);
  if (width == 0)
    write_float (w, value->f);
  else
    {
      write_bytes (w, value_str (value, width), width);
      write_zeros (w, 8 - width);
    }
}

/* Writes null-terminated STRING in a field of the given WIDTH to
   W.  If STRING is longer than WIDTH, it is truncated; if WIDTH
   is narrowed, it is padded on the right with spaces. */
static void
write_string (struct sfm_writer *w, const char *string, size_t width)
{
  size_t data_bytes = MIN (strlen (string), width);
  size_t pad_bytes = width - data_bytes;
  write_bytes (w, string, data_bytes);
  while (pad_bytes-- > 0)
    putc (' ', w->file);
}

/* Writes SIZE bytes of DATA to W's output file. */
static void
write_bytes (struct sfm_writer *w, const void *data, size_t size)
{
  fwrite (data, 1, size, w->file);
}

/* Writes N zeros to W's output file. */
static void
write_zeros (struct sfm_writer *w, size_t n)
{
  while (n-- > 0)
    putc (0, w->file);
}

/* Writes N spaces to W's output file. */
static void
write_spaces (struct sfm_writer *w, size_t n)
{
  while (n-- > 0)
    putc (' ', w->file);
}