/* PSPP - a program for statistical analysis.
Copyright (C) 2007, 2009, 2010 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 . */
#include
#include "data/casereader-shim.h"
#include
#include "data/casereader.h"
#include "data/casereader-provider.h"
#include "data/casewindow.h"
#include "data/settings.h"
#include "libpspp/taint.h"
#include "gl/xalloc.h"
/* A buffering shim casereader. */
struct casereader_shim
{
struct casewindow *window; /* Window of buffered cases. */
struct casereader *subreader; /* Subordinate casereader. */
};
static const struct casereader_random_class shim_class;
static bool buffer_case (struct casereader_shim *s);
/* Interposes a buffering shim on READER.
Returns the new shim. The only legitimate use of the returned
casereader_shim is for calling casereader_shim_slurp(). If READER has no
clones already (which the caller should ensure, if it plans to use the
return value), then the returned casreader_shim is valid for that purpose
until, and only until, the READER's 'destroy' function is called. */
struct casereader_shim *
casereader_shim_insert (struct casereader *reader)
{
const struct caseproto *proto = casereader_get_proto (reader);
casenumber case_cnt = casereader_get_case_cnt (reader);
struct casereader_shim *s = xmalloc (sizeof *s);
s->window = casewindow_create (proto, settings_get_workspace_cases (proto));
s->subreader = casereader_create_random (proto, case_cnt, &shim_class, s);
casereader_swap (reader, s->subreader);
taint_propagate (casewindow_get_taint (s->window),
casereader_get_taint (reader));
taint_propagate (casereader_get_taint (s->subreader),
casereader_get_taint (reader));
return s;
}
/* Reads all of the cases from S's subreader into S's buffer and destroys S's
subreader. (This is a no-op if the subreader has already been
destroyed.)
Refer to the comment on casereader_shim_insert() for information on when
this function may be used. */
void
casereader_shim_slurp (struct casereader_shim *s)
{
while (buffer_case (s))
continue;
}
/* Reads a case from S's subreader and appends it to S's window. Returns true
if successful, false at the end of S's subreader or upon an I/O error. */
static bool
buffer_case (struct casereader_shim *s)
{
struct ccase *tmp;
if (s->subreader == NULL)
return false;
tmp = casereader_read (s->subreader);
if (tmp == NULL)
{
casereader_destroy (s->subreader);
s->subreader = NULL;
return false;
}
casewindow_push_head (s->window, tmp);
return true;
}
/* Reads the case at the given 0-based OFFSET from the front of the window into
C. Returns the case if successful, or a null pointer if OFFSET is beyond
the end of file or upon I/O error. The caller must call case_unref() on the
returned case when it is no longer needed. */
static struct ccase *
casereader_shim_read (struct casereader *reader UNUSED, void *s_,
casenumber offset)
{
struct casereader_shim *s = s_;
while (casewindow_get_case_cnt (s->window) <= offset)
if (!buffer_case (s))
return false;
return casewindow_get_case (s->window, offset);
}
/* Destroys S. */
static void
casereader_shim_destroy (struct casereader *reader UNUSED, void *s_)
{
struct casereader_shim *s = s_;
casewindow_destroy (s->window);
casereader_destroy (s->subreader);
free (s);
}
/* Discards CNT cases from the front of S's window. */
static void
casereader_shim_advance (struct casereader *reader UNUSED, void *s_,
casenumber case_cnt)
{
struct casereader_shim *s = s_;
casewindow_pop_tail (s->window, case_cnt);
}
/* Class for the buffered reader. */
static const struct casereader_random_class shim_class =
{
casereader_shim_read,
casereader_shim_destroy,
casereader_shim_advance,
};