auto_mask.c

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/**
 * \file auto_mask.c
 *
 * \brief Raster Library - Auto masking routines.
 *
 * (C) 2001-2024 by Vaclav Petras and 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 GRASS Development Team
 * \author Vaclav Petras (environmental variable and refactoring)
 */
 
#include <stdlib.h>
 
#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/glocale.h>
 
#include "R.h"
 
/**
 * \brief Checks for auto masking.
 *
 * On first call, opens the mask file if declared and available and
 * allocates buffer for reading mask rows.
 * On second call, returns 0 or 1.
 *
 * \return 0 if mask unset or unavailable
 * \return 1 if mask set and available and ready to use
 */
int Rast__check_for_auto_masking(void)
{
    struct Cell_head cellhd;
 
    Rast__init();
 
    /* if mask is switched off (-2) return -2
       if R__.auto_mask is not set (-1) or set (>=0) recheck the mask */
 
    // TODO: This needs to be documented or modified accordingly.
    if (R__.auto_mask < -1)
        return R__.auto_mask;
 
    /* if(R__.mask_fd > 0) G_free (R__.mask_buf); */
 
    /* Decide between default mask name and env var specified one. */
    char *mask_name = Rast_mask_name();
    char *mask_mapset = "";
 
    /* Check for the existence of the mask raster. */
    R__.auto_mask = (G_find_raster2(mask_name, mask_mapset) != 0);
 
    if (R__.auto_mask <= 0)
        return 0;
 
    /* Check mask raster projection/zone against current region */
    Rast_get_cellhd(mask_name, mask_mapset, &cellhd);
    if (cellhd.zone != G_zone() || cellhd.proj != G_projection()) {
        R__.auto_mask = 0;
        return 0;
    }
 
    if (R__.mask_fd >= 0)
        Rast_unopen(R__.mask_fd);
    R__.mask_fd = Rast__open_old(mask_name, mask_mapset);
    if (R__.mask_fd < 0) {
        R__.auto_mask = 0;
        G_warning(_("Unable to open automatic mask <%s>"), mask_name);
        return 0;
    }
 
    /*    R__.mask_buf = Rast_allocate_c_buf(); */
 
    R__.auto_mask = 1;
    G_free(mask_name);
 
    return 1;
}
 
/**
 * \brief Suppresses masking.
 *
 * \return
 */
void Rast_suppress_masking(void)
{
    Rast__init();
 
    if (R__.auto_mask > 0) {
        Rast_close(R__.mask_fd);
        /* G_free (R__.mask_buf); */
        R__.mask_fd = -1;
    }
    R__.auto_mask = -2;
}
 
/**
 * \brief Unsuppresses masking.
 *
 * \return
 */
void Rast_unsuppress_masking(void)
{
    Rast__init();
 
    if (R__.auto_mask < -1) {
        R__.mask_fd = -1;
        Rast__check_for_auto_masking();
    }
}