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## Copyright (C) 2024 David Legland
## All rights reserved.
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are met:
##
## 1 Redistributions of source code must retain the above copyright notice,
## this list of conditions and the following disclaimer.
## 2 Redistributions in binary form must reproduce the above copyright
## notice, this list of conditions and the following disclaimer in the
## documentation and/or other materials provided with the distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ''AS IS''
## AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
## IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
## ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
## ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
## DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
## SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
## CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
## OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
##
## The views and conclusions contained in the software and documentation are
## those of the authors and should not be interpreted as representing official
## policies, either expressed or implied, of the copyright holders.
function [nodes, edges] = readGraph(fileName)
%READGRAPH Read a graph from a text file.
%
% [NODES EDGES] = readGraph(FILENAME)
%
% Example
% % create a basic graph, save it to a file, and read it again
% nodes = [10 10;20 10;10 20;20 20;27 15];
% edges = [1 2;1 3;2 4;2 5;3 4;4 5];
% writeGraph(nodes, edges, 'simpleGraph.txt');
% [n2 e2] = readGraph('simpleGraph.txt');
% figure; drawGraph(n2, e2); axis equal; axis([0 40 0 30]);
%
% See also
% writeGraph
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2014-01-21, using Matlab 7.9.0.529 (R2009b)
% Copyright 2014-2023 INRA - Cepia Software Platform
%% Open file and read header
% open file for reading in text mode
f = fopen(fileName, 'rt');
if f == -1
error(['could not open file for reading: ' fileName]);
end
% check header
line = fgetl(f);
if ~ischar(line)
error(['can not read graph from empty file: ' fileName]);
end
if ~strcmpi(strtrim(line(2:end)), 'graph')
error(['Wrong header line in file:' fileName]);
end
%% read node section
% check sub-header
line = fgetl(f);
if ~strcmpi(strtrim(line(2:end)), 'nodes')
error(['Could not interpret node section in file:' fileName]);
end
% read the number of nodes
line = fgetl(f);
[nNodesStr, line] = strtok(line);
nNodes = str2double(nNodesStr);
% read number of dimension, assumes 2 by default if not specified
nDims = 2;
if ~isempty(line)
nDims = str2double(strtok(line));
end
% read node coordinates
[nodes, nRead] = fscanf(f, '%g', [nDims nNodes]);
assert(nRead == nNodes * nDims, ...
'Could not read all node info in file %s', fileName);
nodes = nodes';
% terminate the reading of current line
fgetl(f);
%% read edge section
% check sub-header
line = fgetl(f);
if ~strcmpi(strtrim(line(2:end)), 'edges')
error(['Could not interpret edge section in file:' fileName]);
end
% read the number of nodes
line = fgetl(f);
nEdgesStr = strtok(line);
nEdges = str2double(nEdgesStr);
% read node indices of each edge
[edges, nRead] = fscanf(f, '%d %d\n', [2 nEdges]);
assert(nRead == nEdges * 2, ...
'Could not read all edge info in file %s', fileName);
edges = edges';
%% Clean up
fclose(f);
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