gis/open.c

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/*!
 * \file lib/gis/open.c
 *
 * \brief GIS Library - Open file functions
 *
 * (C) 1999-2015 by the GRASS Development Team
 *
 * This program is free software under the GNU General Public
 * License (>=v2). Read the file COPYING that comes with GRASS
 * for details.
 *
 * \author USACERL and many others
 */
 
#include <grass/config.h>
#include <errno.h>
#include <string.h>
 
#include <unistd.h>
#include <fcntl.h>
 
#include <grass/gis.h>
#include <grass/glocale.h>
 
#include "gis_local_proto.h"
 
/*!
   \brief Lowest level open routine.
 
   Opens the file <i>name</i> in <i>element</i> ("cell", etc.) in mapset
   <i>mapset</i> according to the i/o <i>mode</i>.
 
   - mode = 0 (read) will look for <i>name</i> in <i>mapset</i> and
   open the file for read only the file must exist
 
   - mode = 1 (write) will create an empty file <i>name</i> in the
   current mapset and open the file for write only
   <i>mapset</i> ignored
 
   - mode = 2 (read and write) will open a file in the current mapset
   for reading and writing creating a new file if
   necessary <i>mapset</i> ignored
 
   \param element database element name
   \param name map file name
   \param mapset mapset containing map <i>name</i>
   \param mode r/w mode 0=read, 1=write, 2=read/write
 
   \return open file descriptor (int)
   \return -1 could not open
 */
static int G__open(const char *element, const char *name, const char *mapset,
                   int mode)
{
    int fd;
    int is_tmp;
    char path[GPATH_MAX];
    char xname[GNAME_MAX], xmapset[GMAPSET_MAX];
 
    G__check_gisinit();
 
    is_tmp = (element && strncmp(element, ".tmp", 4) == 0);
 
    /* READ */
    if (mode == 0) {
        if (G_name_is_fully_qualified(name, xname, xmapset)) {
            if (*mapset && strcmp(xmapset, mapset) != 0) {
                G_warning(
                    _("G__open(read): mapset <%s> doesn't match xmapset <%s>"),
                    mapset, xmapset);
                return -1;
            }
            name = xname;
            mapset = xmapset;
        }
 
        if (!is_tmp) {
            mapset = G_find_file2(element, name, mapset);
 
            if (!mapset)
                return -1;
 
            G_file_name(path, element, name, mapset);
        }
        else {
            G_file_name_tmp(path, element, name, mapset);
        }
 
        if ((fd = open(path, 0)) < 0)
            G_warning(_("G__open(read): Unable to open '%s': %s"), path,
                      strerror(errno));
        return fd;
    }
    /* WRITE */
    if (mode == 1 || mode == 2) {
        mapset = G_mapset();
        if (G_name_is_fully_qualified(name, xname, xmapset)) {
            if (strcmp(xmapset, mapset) != 0) {
                G_warning(_("G__open(write): xmapset <%s> != G_mapset() <%s>"),
                          xmapset, mapset);
                return -1;
            }
            name = xname;
        }
 
        if (*name && G_legal_filename(name) == -1)
            return -1;
 
        if (!is_tmp)
            G_file_name(path, element, name, mapset);
        else
            G_file_name_tmp(path, element, name, mapset);
 
        if (mode == 1 || access(path, 0) != 0) {
            if (is_tmp)
                G_make_mapset_object_group_tmp(element);
            else
                G_make_mapset_object_group(element);
            close(open(path, O_WRONLY | O_CREAT | O_TRUNC, 0666));
        }
 
        if ((fd = open(path, mode)) < 0)
            G_warning(_("G__open(write): Unable to open '%s': %s"), path,
                      strerror(errno));
        return fd;
    }
    return -1;
}
 
/*!
   \brief Open a new database file
 
   Creates <i>name</i> in the current mapset and opens it
   for write only.
 
   The database file <i>name</i> under the <i>element</i> in the
   current mapset is created and opened for writing (but not reading).
   The UNIX open() routine is used to open the file. If the file does
   not exist, -1 is returned. Otherwise the file is positioned at the
   end of the file and the file descriptor from the open() is returned.
 
   \param element database element name
   \param name map file name
 
   \return open file descriptor (int)
   \return -1 could not open
 */
int G_open_new(const char *element, const char *name)
{
    return G__open(element, name, G_mapset(), 1);
}
 
/*!
   \brief Open a database file for reading
 
   The database file <i>name</i> under the <i>element</i> in the
   specified <i>mapset</i> is opened for reading (but not for writing).
   The UNIX open() routine is used to open the file. If the file does
   not exist, -1 is returned. Otherwise the file descriptor from the
   open() is returned.
 
   \param element database element name
   \param name map file name
   \param mapset mapset containing map <i>name</i>
 
   \return open file descriptor (int)
   \return -1 could not open
 */
int G_open_old(const char *element, const char *name, const char *mapset)
{
    return G__open(element, name, mapset, 0);
}
 
/*!
   \brief Open a database file for update
 
   The database file <i>name</i> under the <i>element</i> in the
   current mapset is opened for reading and writing.  The UNIX open()
   routine is used to open the file. If the file does not exist, -1 is
   returned. Otherwise the file is positioned at the end of the file
   and the file descriptor from the open() is returned.
 
   \param element database element name
   \param name map file name
 
   \return open file descriptor (int)
   \return -1 could not open
 */
int G_open_update(const char *element, const char *name)
{
    int fd;
 
    fd = G__open(element, name, G_mapset(), 2);
    if (fd >= 0)
        if (lseek(fd, 0L, SEEK_END) == -1) {
            int err = errno;
            G_warning(_("File read/write operation failed: %s (%d)"),
                      strerror(err), err);
            return -1;
        }
 
    return fd;
}
 
/*!
   \brief Open a new database file
 
   The database file <i>name</i> under the <i>element</i> in the
   current mapset is created and opened for writing (but not reading).
   The UNIX fopen() routine, with "w" write mode, is used to open the
   file.  If the file does not exist, the NULL pointer is
   returned. Otherwise the file is positioned at the end of the file
   and the file descriptor from the fopen() is returned.
 
   \param element database element name
   \param name map file name
 
   \return open file descriptor (FILE *)
   \return NULL on error
 */
FILE *G_fopen_new(const char *element, const char *name)
{
    int fd;
 
    fd = G__open(element, name, G_mapset(), 1);
    if (fd < 0) {
        G_debug(1, "G_fopen_new(): element = %s, name = %s : NULL", element,
                name);
        return (FILE *)0;
    }
 
    G_debug(2, "\tfile open: new (mode = w)");
    return fdopen(fd, "w");
}
 
/*!
   \brief Open a database file for reading
 
   The database file <i>name</i> under the <i>element</i> in the
   specified <i>mapset</i> is opened for reading (but not for writing).
   The UNIX fopen() routine, with "r" read mode, is used to open the
   file.  If the file does not exist, the NULL pointer is
   returned. Otherwise the file descriptor from the fopen() is
   returned.
 
   \param element database element name
   \param name map file name
   \param mapset mapset name containing map <i>name</i>
 
   \return open file descriptor (FILE *)
   \return NULL on error
 */
FILE *G_fopen_old(const char *element, const char *name, const char *mapset)
{
    int fd;
 
    fd = G__open(element, name, mapset, 0);
    if (fd < 0)
        return (FILE *)NULL;
 
    G_debug(2, "\tfile open: read (mode = r)");
    return fdopen(fd, "r");
}
 
/*!
   \brief Open a database file for update (append mode)
 
   The database file <i>name</i> under the <i>element</i> in the
   current mapset is opened for for writing. The UNIX fopen() routine,
   with "a" append mode, is used to open the file.  If the file does not
   exist, the NULL pointer is returned. Otherwise the file descriptor
   from the fopen() is returned.
 
   \param element database element name
   \param name map file name
 
   \return open file descriptor (FILE *)
   \return NULL on error
 */
FILE *G_fopen_append(const char *element, const char *name)
{
    int fd;
 
    fd = G__open(element, name, G_mapset(), 2);
    if (fd < 0)
        return (FILE *)0;
    if (lseek(fd, 0L, SEEK_END) == -1) {
        int err = errno;
        G_warning(_("File read/write operation failed: %s (%d)"), strerror(err),
                  err);
        return NULL;
    }
 
    G_debug(2, "\tfile open: append (mode = a)");
    return fdopen(fd, "a");
}
 
/*!
   \brief Open a database file for update (r+ mode)
 
   The database file <i>name</i> under the <i>element</i> in the
   current mapset is opened for for writing. The UNIX fopen() routine,
   with "r+" append mode, is used to open the file.  If the file does not
   exist, the NULL pointer is returned. Otherwise the file descriptor
   from the fopen() is returned.
 
   \param element database element name
   \param name map file name
 
   \return open file descriptor (FILE *)
   \return NULL on error
 */
FILE *G_fopen_modify(const char *element, const char *name)
{
    int fd;
 
    fd = G__open(element, name, G_mapset(), 2);
    if (fd < 0)
        return (FILE *)0;
    if (lseek(fd, 0L, SEEK_END) == -1) {
        int err = errno;
        G_warning(_("File read/write operation failed: %s (%d)"), strerror(err),
                  err);
        return NULL;
    }
 
    G_debug(2, "\tfile open: modify (mode = r+)");
    return fdopen(fd, "r+");
}