helpers.cpp

#include "helpers.h"
#include <string>
#include <stdexcept>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <cstring>

#define MOD_GZIP_ZLIB_WINDOWSIZE 15
#define MOD_GZIP_ZLIB_CFACTOR 9
#define MOD_GZIP_ZLIB_BSIZE 8096

namespace geom = boost::geometry;
using namespace std;

// zlib routines from http://panthema.net/2007/0328-ZLibString.html

// Compress a STL string using zlib with given compression level, and return the binary data
std::string compress_string(const std::string& str,
                            int compressionlevel,
                            bool asGzip) {
    z_stream zs;                        // z_stream is zlib's control structure
    memset(&zs, 0, sizeof(zs));

	if (asGzip) {
		if (deflateInit2(&zs, compressionlevel, Z_DEFLATED,
		                MOD_GZIP_ZLIB_WINDOWSIZE + 16, MOD_GZIP_ZLIB_CFACTOR, Z_DEFAULT_STRATEGY) != Z_OK)
	        throw(std::runtime_error("deflateInit2 failed while compressing."));
	} else {
	    if (deflateInit(&zs, compressionlevel) != Z_OK)
	        throw(std::runtime_error("deflateInit failed while compressing."));
	}

    zs.next_in = (Bytef*)str.data();
    zs.avail_in = str.size();           // set the z_stream's input

    int ret;
    char outbuffer[32768];
    std::string outstring;

    // retrieve the compressed bytes blockwise
    do {
        zs.next_out = reinterpret_cast<Bytef*>(outbuffer);
        zs.avail_out = sizeof(outbuffer);

        ret = deflate(&zs, Z_FINISH);

        if (outstring.size() < zs.total_out) {
            // append the block to the output string
            outstring.append(outbuffer,
                             zs.total_out - outstring.size());
        }
    } while (ret == Z_OK);

    deflateEnd(&zs);

    if (ret != Z_STREAM_END) {          // an error occurred that was not EOF
        std::ostringstream oss;
        oss << "Exception during zlib compression: (" << ret << ") " << zs.msg;
        throw(std::runtime_error(oss.str()));
    }

    return outstring;
}

// Decompress an STL string using zlib and return the original data.
std::string decompress_string(const std::string& str, bool asGzip) {
    z_stream zs;                        // z_stream is zlib's control structure
    memset(&zs, 0, sizeof(zs));

	if (asGzip) {
		if (inflateInit2(&zs, 16+MAX_WBITS) != Z_OK)
			throw(std::runtime_error("inflateInit2 failed while decompressing."));
	} else {
		if (inflateInit(&zs) != Z_OK)
			throw(std::runtime_error("inflateInit failed while decompressing."));
	}

    zs.next_in = (Bytef*)str.data();
    zs.avail_in = str.size();

    int ret;
    char outbuffer[32768];
    std::string outstring;

    // get the decompressed bytes blockwise using repeated calls to inflate
    do {
        zs.next_out = reinterpret_cast<Bytef*>(outbuffer);
        zs.avail_out = sizeof(outbuffer);

        ret = inflate(&zs, 0);

        if (outstring.size() < zs.total_out) {
            outstring.append(outbuffer,
                             zs.total_out - outstring.size());
        }

    } while (ret == Z_OK);

    inflateEnd(&zs);

    if (ret != Z_STREAM_END) {          // an error occurred that was not EOF
        std::ostringstream oss;
        oss << "Exception during zlib decompression: (" << ret << ") "
            << zs.msg;
        throw(std::runtime_error(oss.str()));
    }

    return outstring;
}

// Parse a Boost error
std::string boost_validity_error(unsigned failure) {
	switch (failure) {
		case 10: return "too few points";
		case 11: return "wrong topological dimension";
		case 12: return "spikes (nodes go back on themselves)";
		case 13: return "consecutive duplicate points";
		case 20: return "not been closed";
		case 21: return "self-intersections";
		case 22: return "the wrong orientation";
		case 30: return "interior rings outside";
		case 31: return "nested interior rings";
		case 32: return "disconnected interior (contains polygons whose interiors are not disjoint)";
		case 40: return "intersecting interiors";
		default: return "something mysterious wrong with it, Boost validity_failure_type " + to_string(failure);
	}
}