namespace lemon {
/*!
\page graph-io-page Graph Input-Output
The standard graph IO enables to store graphs and additional maps
in a flexible and efficient way.
\section format The general file format
The file contains at most four sections in the following order:
\li nodeset
\li edgeset
\li nodes
\li edges
The nodeset section starts with the following line:
\@nodeset
The next line contains the names of the nodemaps, separated by whitespaces. Each
following line describes a node in the graph: it contains the values of the
maps in the right order. The map named "id" should contain unique values
because it is regarded as an ID-map. For example:
\code
@nodeset
id x-coord y-coord color
3 1.0 4.0 blue
5 2.3 5.7 red
12 7.8 2.3 green
\endcode
The edgeset section is very similar to the nodeset section, it has
the same coloumn oriented structure. It starts with the line
\@edgeset
The next line contains the whitespace separated list of names of the maps.
Each of the next lines describes one edge. The first two elements in the line
are the IDs of the source and target (or tail and head) node of the edge as they occur in the ID node
map. You can also have an optional ID map on the edges for later reference.
\code
@edgeset
id weight label
3 5 a 4.3 a-edge
5 12 c 2.6 c-edge
3 12 g 3.4 g-edge
\endcode
The next section contains labeled nodes (i.e. nodes having a special
label on them). The section starts with
\@nodes
Each of the next lines contains a label for a node in the graph
and then the ID described in the nodeset section.
\code
@nodes
source 3
target 12
\endcode
The last section describes the labeled edges
(i.e. edges having a special label on them). It starts with \c \@edges
and then each line contains the name of the edge and the ID.
\code
@nodes
observed c
\endcode
The file may contain empty lines and comment lines. The comment lines
start with an \c # character.
The file ends with the
\@end
line.
\section use Using graph input-output
The graph input and output is based on reading and writing commands. The user
adds reading and writing commands to the reader or writer class, then he
calls the \c run() method that executes all the given commands.
\subsection write Writing a graph
The \c GraphWriter class provides the graph output. To write a graph
you should first give writing commands to the writer. You can declare
write command as \c NodeMap or \c EdgeMap writing and labeled Node and
Edge writing.
\code
GraphWriter writer(std::cout, graph);
\endcode
The \c writeNodeMap() function declares a \c NodeMap writing command in the
\c GraphWriter. You should give a name of the map and the map
object as parameters. The NodeMap writing command with name "id" should write a
unique map because it is regarded as ID map.
\see IdMap, DescriptorMap
\code
IdMap nodeIdMap;
writer.writeNodeMap("id", nodeIdMap);
writer.writeNodeMap("x-coord", xCoordMap);
writer.writeNodeMap("y-coord", yCoordMap);
writer.writeNodeMap("color", colorMap);
\endcode
With the \c writeEdgeMap() member function you can give an edge map
writing command similar to the NodeMaps.
\see IdMap, DescriptorMap
\code
DescriptorMap > edgeDescMap(graph);
writer.writeEdgeMap("descriptor", edgeDescMap);
writer.writeEdgeMap("weight", weightMap);
writer.writeEdgeMap("label", labelMap);
\endcode
With \c writeNode() and \c writeEdge() functions you can designate Nodes and
Edges in the graph. For example, you can write out the source and target node
of a maximum flow instance.
\code
writer.writeNode("source", sourceNode);
writer.writeNode("target", targetNode);
writer.writeEdge("observed", edge);
\endcode
After you give all write commands you must call the \c run() member
function, which executes all the writing commands.
\code
writer.run();
\endcode
\subsection reading Reading a graph
The given file format may contain several maps and labeled nodes or edges.
If you read a graph you need not read all the maps and items just those
that you need. The interface of the \c GraphReader is very similar to
the GraphWriter but the reading method does not depend on the order of the
given commands.
The reader object assumes that each not readed value does not contain
whitespaces, therefore it has some extra possibilities to control how
it should skip the values when the string representation contains spaces.
\code
GraphReader reader(std::cin, graph);
\endcode
The \c readNodeMap() function reads a map from the \c \@nodeset section.
If there is a map that you do not want to read from the file and there are
whitespaces in the string represenation of the values then you should
call the \c skipNodeMap() template member function with proper parameters.
\see QuotedStringReader
\code
reader.readNodeMap("x-coord", xCoordMap);
reader.readNodeMap("y-coord", yCoordMap);
reader.readNodeMap("label", labelMap);
reader.skipNodeMap("description");
reader.readNodeMap("color", colorMap);
\endcode
With the \c readEdgeMap() member function you can give an edge map
reading command similar to the NodeMaps.
\code
reader.readEdgeMap("weight", weightMap);
reader.readEdgeMap("label", labelMap);
\endcode
With \c readNode() and \c readEdge() functions you can read labeled Nodes and
Edges.
\code
reader.readNode("source", sourceNode);
reader.readNode("target", targetNode);
reader.readEdge("observed", edge);
\endcode
After you give all read commands you must call the \c run() member
function, which executes all the commands.
\code
reader.run();
\endcode
\section types The background of Reading and Writing
The \c GraphReader should know how to read a Value from the given map.
By the default implementation the input operator reads a value from
the stream and the type of the readed value is the value type of the given map.
When the reader should skip a value in the stream, because you do not
want to store it in map, the reader skips a character sequence without
whitespace.
If you want to change the functionality of the reader, you can use
template parameters to specialize it. When you give a reading
command for a map you can give a Reader type as template parameter.
With this template parameter you can control how the Reader reads
a value from the stream.
The reader has the next structure:
\code
struct TypeReader {
typedef TypeName Value;
void read(std::istream& is, Value& value);
};
\endcode
By example, the \c "strings" nodemap contains strings and you do not need
the value of the string just the length. Then you can implement own Reader
struct.
\code
struct LengthReader {
typedef int Value;
void read(std::istream& is, Value& value) {
std::string tmp;
is >> tmp;
value = tmp.length();
}
};
...
reader.readNodeMap("strings", lengthMap);
\endcode
The global functionality of the reader class can be changed by giving a
special template parameter to the GraphReader class. By default, the
template parameter is \c DefaultReaderTraits. A reader traits class
should provide an inner template class Reader for each type, and an
DefaultReader for skipping a value.
The specialization of the writing should be very similar to the reading.
\author Balazs Dezso
*/
}