Disclaimer: tenhle program zdaleka není korektní! Existuje spousta vstupů, které jsou korektní a budou špatně parsovány. Třeba 'COMMENT = ...'. V ukázkových datech se ale takové věci nevyskytují.

gistfile1.cpp

#include <string>
#include <vector>
#include <iostream>
#include <fstream>
#include <sstream>
#include <regex>
#include <numeric>

using namespace std;

struct BlockInfo {
	int naxis, bitpix;
	vector<int> axes;
};

regex simple_block("SIMPLE  =.*");
regex extension_block("XTENSION= '([\\w+]*)'.*");
regex segment("(\\S+)\\s*\\=\\s*([^' ]+|'[^']+')\\s*(\\/.*)?");
regex axes_info("NAXIS(\\d+)");

string readSegment(istream & in) {
	char buffer[81];
	in.read(buffer, 80);
	buffer[80] = '\0';
	return string(buffer);
}

int toInt(string s) {
	int tmp;
	stringstream(s) >> tmp;
	return tmp;
}

void printSegment(string seg, BlockInfo & bi) {
	smatch res;
	if (regex_match(seg, res, segment)) {
		cout << res[1] << "=" << res[2] << endl;
		if (res[1] == "NAXIS") {
			bi.naxis = toInt(res[2]);
		} else if (regex_match(string(res[1]), axes_info)) {
			bi.axes.push_back(toInt(res[2]));
		} else if (res[1] == "BITPIX") {
			bi.bitpix = toInt(res[2]);
		}
	}
}

void handleBlock(istream & in) {
	BlockInfo bi;
	smatch res;
	string first = readSegment(in);
	
	if (regex_match(first, simple_block))
		cout << "Primary" << endl;
	else if (regex_match(first, res, extension_block))
		cout << "Extension" << endl;
	
	printSegment(first, bi);
	string segment;
	int read = 1;
	while (segment.find("END") != 0) {
		segment = readSegment(in);
		printSegment(segment, bi);
		++read;
	}
	in.ignore(80 * (36 - read % 36));
	cout << endl;

	int skip = 0;
	if (bi.naxis) 
		skip= abs(bi.bitpix/8) * accumulate(bi.axes.begin(), bi.axes.end(), 1, std::multiplies<int>());
	cout << "Data content: " << skip << "B" << endl;
	skip = (skip / 2880) + (skip % 2880 ? 1 : 0);
	if (skip)
	for (int i = 0; i < skip; ++i)
		//WTF WTF WTF
		for (int i=0; i<36; i++) readSegment(in);
	cout << endl;
}

int main(int argc, char * * argv) {
	vector<string> params(argv, argv + argc);
	ifstream in; in.open(params[1], ifstream::binary);
	in.exceptions(istream::failbit | istream::badbit);
	try { while (1) { handleBlock(in); } } 
	catch (ios_base::failure) {}
	return 0;
}