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/*
EXAMPLE osmium_filter_discussions
Read OSM changesets with discussions from a changeset dump like the one
you get from https://planet.osm.org/planet/discussions-latest.osm.bz2
and write out only those changesets which have discussions (ie comments).
DEMONSTRATES USE OF:
* file input and output
* setting file formats using the osmium::io::File class
* OSM file headers
* input and output iterators
SIMPLER EXAMPLES you might want to understand first:
* osmium_read
* osmium_count
LICENSE
The code in this example file is released into the Public Domain.
*/
#include <algorithm> // for std::copy_if
#include <cstdlib> // for std::exit
#include <iostream> // for std::cout, std::cerr
// We want to read OSM files in XML format
// (other formats don't support full changesets, so only XML is needed here).
#include <osmium/io/xml_input.hpp>
// We want to write OSM files in XML format.
#include <osmium/io/xml_output.hpp>
// We want to use input and output iterators for easy integration with the
// algorithms of the standard library.
#include <osmium/io/input_iterator.hpp>
#include <osmium/io/output_iterator.hpp>
// We want to support any compression (none, gzip, and bzip2).
#include <osmium/io/any_compression.hpp>
int main(int argc, char* argv[]) {
if (argc != 3) {
std::cout << "Usage: " << argv[0] << " INFILE OUTFILE\n";
std::exit(1);
}
try {
// The input file, deduce file format from file suffix.
osmium::io::File input_file{argv[1]};
// The output file, force XML OSM file format.
osmium::io::File output_file{argv[2], "osm"};
// Initialize Reader for the input file.
// Read only changesets (will ignore nodes, ways, and
// relations if there are any).
osmium::io::Reader reader{input_file, osmium::osm_entity_bits::changeset};
// Get the header from the input file.
osmium::io::Header header = reader.header();
// Set the "generator" on the header to ourselves.
header.set("generator", "osmium_filter_discussions");
// Initialize writer for the output file. Use the header from the input
// file for the output file. This will copy over some header information.
// The last parameter will tell the writer that it is allowed to overwrite
// an existing file. Without it, it will refuse to do so.
osmium::io::Writer writer{output_file, header, osmium::io::overwrite::allow};
// Create range of input iterators that will iterator over all changesets
// delivered from input file through the "reader".
auto input_range = osmium::io::make_input_iterator_range<osmium::Changeset>(reader);
// Create an output iterator writing through the "writer" object to the
// output file.
auto output_iterator = osmium::io::make_output_iterator(writer);
// Copy all changesets from input to output that have at least one comment.
std::copy_if(input_range.begin(), input_range.end(), output_iterator, [](const osmium::Changeset& changeset) {
return changeset.num_comments() > 0;
});
// Explicitly close the writer and reader. Will throw an exception if
// there is a problem. If you wait for the destructor to close the writer
// and reader, you will not notice the problem, because destructors must
// not throw.
writer.close();
reader.close();
} catch (const std::exception& e) {
// All exceptions used by the Osmium library derive from std::exception.
std::cerr << e.what() << '\n';
std::exit(1);
}
}
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