New wrapper for access to temporary files.

diff --git a/src/libpspp/tmpfile.c b/src/libpspp/tmpfile.c
new file mode 100644 (file)
index 0000000..0d30936
--- /dev/null
+++ b/src/libpspp/tmpfile.c
@@ -0,0 +1,165 @@
+/* PSPP - a program for statistical analysis.
+   Copyright (C) 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/>. */
+
+/* A interface to allow a temporary file to be treated as an
+   array of data. */
+
+#include <config.h>
+
+#include <libpspp/tmpfile.h>
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libpspp/assertion.h>
+
+#include "error.h"
+#include "xalloc.h"
+
+#include "gettext.h"
+#define _(msgid) gettext (msgid)
+
+struct tmpfile
+  {
+    FILE *file;                 /* Underlying file. */
+
+    /* Current byte offset in file.  We track this manually,
+       instead of using ftello, because in glibc ftello flushes
+       the stream buffer, making the common case of sequential
+       access to cases unreasonably slow. */
+    off_t position;
+  };
+
+/* Creates and returns a new temporary file.  The temporary file
+   will be automatically deleted when the process exits. */
+struct tmpfile *
+tmpfile_create (void)
+{
+  struct tmpfile *tf = xmalloc (sizeof *tf);
+  tf->file = tmpfile ();
+  if (tf->file == NULL)
+    error (0, errno, _("failed to create temporary file"));
+  tf->position = 0;
+  return tf;
+}
+
+/* Closes and destroys temporary file TF.  Returns true if I/O on
+   TF always succeeded, false if an I/O error occurred at some
+   point. */
+bool
+tmpfile_destroy (struct tmpfile *tf)
+{
+  bool ok = true;
+  if (tf != NULL)
+    {
+      ok = !tmpfile_error (tf);
+      if (tf->file != NULL)
+        fclose (tf->file);
+      free (tf);
+    }
+  return ok;
+}
+
+/* Seeks TF's underlying file to the start of `union value'
+   VALUE_IDX within case CASE_IDX.
+   Returns true if the seek is successful and TF is not
+   otherwise tainted, false otherwise. */
+static bool
+do_seek (const struct tmpfile *tf_, off_t offset)
+{
+  struct tmpfile *tf = (struct tmpfile *) tf_;
+
+  if (!tmpfile_error (tf))
+    {
+      if (tf->position == offset)
+        return true;
+      else if (fseeko (tf->file, offset, SEEK_SET) == 0)
+        {
+          tf->position = offset;
+          return true;
+        }
+      else
+        error (0, errno, _("seeking in temporary file"));
+    }
+
+  return false;
+}
+
+/* Reads BYTES bytes from TF's underlying file into BUFFER.
+   TF must not be tainted upon entry into this function.
+   Returns true if successful, false upon an I/O error (in which
+   case TF is marked tainted). */
+static bool
+do_read (const struct tmpfile *tf_, void *buffer, size_t bytes)
+{
+  struct tmpfile *tf = (struct tmpfile *) tf_;
+
+  assert (!tmpfile_error (tf));
+  if (bytes > 0 && fread (buffer, bytes, 1, tf->file) != 1)
+    {
+      if (ferror (tf->file))
+        error (0, errno, _("reading temporary file"));
+      else if (feof (tf->file))
+        error (0, 0, _("unexpected end of file reading temporary file"));
+      else
+        NOT_REACHED ();
+      return false;
+    }
+  tf->position += bytes;
+  return true;
+}
+
+/* Writes BYTES bytes from BUFFER into TF's underlying file.
+   TF must not be tainted upon entry into this function.
+   Returns true if successful, false upon an I/O error (in which
+   case TF is marked tainted). */
+static bool
+do_write (struct tmpfile *tf, const void *buffer, size_t bytes)
+{
+  assert (!tmpfile_error (tf));
+  if (bytes > 0 && fwrite (buffer, bytes, 1, tf->file) != 1)
+    {
+      error (0, errno, _("writing to temporary file"));
+      return false;
+    }
+  tf->position += bytes;
+  return true;
+}
+
+/* Reads N bytes from TF at byte offset OFFSET into DATA.
+   Returns true if successful, false on failure.  */
+bool
+tmpfile_read (const struct tmpfile *tf, off_t offset, size_t n, void *data)
+{
+  return do_seek (tf, offset) && do_read (tf, data, n);
+}
+
+/* Writes the N bytes in DATA to TF at byte offset OFFSET.
+   Returns true if successful, false on failure.  */
+bool
+tmpfile_write (struct tmpfile *tf, off_t offset, size_t n, const void *data)
+{
+  return do_seek (tf, offset) && do_write (tf, data, n);
+}
+
+/* Returns true if an error has occurred in I/O on TF,
+   false if no error has been detected. */
+bool
+tmpfile_error (const struct tmpfile *tf)
+{
+  return tf->file == NULL || ferror (tf->file) || feof (tf->file);
+}

diff --git a/src/libpspp/tmpfile.h b/src/libpspp/tmpfile.h
new file mode 100644 (file)
index 0000000..e679a2f
--- /dev/null
+++ b/src/libpspp/tmpfile.h
@@ -0,0 +1,32 @@
+/* PSPP - a program for statistical analysis.
+   Copyright (C) 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/>. */
+
+/* A interface to allow a temporary file to be treated as an
+   array of data. */
+
+#ifndef LIBPSPP_TMPFILE_H
+#define LIBPSPP_TMPFILE_H 1
+
+#include <stdbool.h>
+#include <sys/types.h>
+
+struct tmpfile *tmpfile_create (void);
+bool tmpfile_destroy (struct tmpfile *);
+bool tmpfile_read (const struct tmpfile *, off_t offset, size_t n, void *);
+bool tmpfile_write (struct tmpfile *, off_t offset, size_t n, const void *);
+bool tmpfile_error (const struct tmpfile *);
+
+#endif /* libpspp/tmpfile.h */