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## Copyright (C) 2014-2022 Philip Nienhuis
##
## 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/>.
## -*- texinfo -*-
## @deftypefn {Function File} [ @var{infs} ] = shapeinfo (@var{fname})
## Returns a struct with info on shapefile @var{fname}.
##
## Input:
## @table @code
## @item @var{fname}
## (character string). Does not need to have a .shp suffix.
## @end table
##
## Output: a struct with fields:
##
## @table @code
## @item Filename
## Contains the filename of the shapefile.
##
## @item ShapeType
## The type of shapefile.
##
## @item ShapeTypeName
## The name of the shape type.
##
## @item BoundingBox
## The minimum and maximum X and Y coordinates of all items in the shapefile in
## a 2 X 2 array, upper rox min and min Y, lower row max X and max Y.
##
## @item NumFeatures
## The number of features (items, records) in the shapefile.
##
## @item Attributes
## A structure with fields Name and Type (containng the names and types of all
## attributes in the shapefile). Type can be Numeric, Character or Data.
## @end table
##
## @seealso{geoshow, mapshow, shapedraw, shaperead, shapewrite}
## @end deftypefn
## Author: Philip Nienhuis <prnienhuis@users.sf.net
## Created: 2014-11-15
## Updates:
## 2015-01-18 Use .shx file (if present) to get nr. of records
## 2016-01-05 Add shape type name to output struct
function [infs] = shapeinfo (fname)
persistent shptypnames = { ...
1, "Point"; ...
11, "PointZ"; ...
21, "PointM"; ...
8, "MultiPoint"; ...
18, "MultiPointZ"; ...
28, "MultiPointM"; ...
3, "PolyLine"; ...
13, "PolyLineZ"; ...
23, "PolyLineM"; ...
5, "PolyGon"; ...
15, "PolyGonZ"; ...
25, "PolyGonM"; ...
31, "MultiPatch"};
## ====================== 1. Read .shp file proper ======================
## Check file name
[pth, fnm, ext] = fileparts (fname);
if (isempty (ext))
bname = fname;
fname = [fname ".shp"];
else
## Later on bname.shx and bname.dbf will be read
bname = [pth filesep fnm];
endif
## Put filename in info struct
infs.Filename = fname;
## Start reading header
fidp = fopen (fname, "r");
if (fidp < 0)
error ("shapeinfo: can't open file %s\n", fname);
endif
fseek (fidp, 0, "bof");
## Read & check file code
fcode = fread (fidp, 1, "int32", 20, "ieee-be");
if (fcode != 9994)
error ("%s is not a valid shapefile\n", fname);
endif
flngt = fread (fidp, 1, "int32", 0, "ieee-be") * 2;
fvsn = fread (fidp, 1, "int32", 0, "ieee-le");
shpt = fread (fidp, 1, "int32"); ## Shape file type
## Put shapetype in info struct
infs.ShapeType = shpt;
infs.ShapeTypeName = ...
shptypnames {find (ismember ([shptypnames(:, 1){:}], shpt)), 2};
shpbox.X(1) = fread (fidp, 1, "double");
shpbox.Y(1) = fread (fidp, 1, "double");
shpbox.X(2) = fread (fidp, 1, "double");
shpbox.Y(2) = fread (fidp, 1, "double");
shpbox.Z(1) = fread (fidp, 1, "double");
shpbox.Z(2) = fread (fidp, 1, "double");
shpbox.M(1) = fread (fidp, 1, "double");
shpbox.M(2) = fread (fidp, 1, "double");
## Put in info struct
infs.BoundingBox = [shpbox.X(1), shpbox.Y(1); shpbox.X(2), shpbox.Y(2)];
## Count records
fidx = fopen ([bname ".shx"], "r");
if (fidx < 0)
## Only way to get nr. of records is to count (or use .dbf file)
printf ("shapeinfo: index file %s not found.\nCounting records...\n", ...
[bname ".shx"]);
reclr = 0;
do
## Read record index number
recn = fread (fidp, 1, "int32", 0, "ieee-be");
## Record length
rlen = (fread (fidp, 1, "int32", 0, "ieee-be") * 2);
## Skip rest of record
fread (fidp, rlen, "char=>char");
until (ftell (fidp) > flngt - 3); ## i.e., within last
## file byte
printf (" \n"); ## Wipe "Counting.."
else
## shx file found; no counting required
fseek (fidx, 24, "bof");
fxlng = fread (fidx, 1, "int32", 72, "ieee-be");
recn = (fxlng - 50) / 4;
fclose (fidx);
endif
fclose (fidp);
finfo = dir (fname);
## Return info
infs.NumFeatures = recn;
infs.FileSize = finfo.bytes;
infs.LastModified = datestr (finfo.datenum, 0);
## ====================== 3. .dbf ======================
## Check if dbfread is available
if (isempty (which ("dbfread")))
printf ("shaperead: dbfread function not found. No attributes will be added.\n");
printf (" (io package installed and loaded?)\n");
else
## Try to read the .dbf file
try
[~, B] = dbfread ([bname ".dbf"], 0);
infs.Attributes.Name = {B.data.fldnam};
types = {B.data.fldtyp};
types = strrep (types, "N", "Numeric");
types = strrep (types, "C", "Character");
types = strrep (types, "D", "Date");
types = strrep (types, "F", "Floating");
## FIXME dbase also has type "Logical"
infs.Attributes.Type = types;
catch
printf ("shaperead: file %s couldn't be opened;\n", [ bname ".dbf" ]);
printf (" no attributes appended\n");
end_try_catch
endif
endfunction
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