Improve error messages for zlib decompression errors

ZlibDecompressor.cpp

@@ -49,7 +49,7 @@ ustring ZlibDecompressor::decompress()
 	strm.avail_in = size;
 
 	if (inflateInit(&strm) != Z_OK) {
-		throw DecompressError();
+		throw DecompressError(strm.msg);
 	}
 
 	strm.next_in = const_cast<unsigned char *>(data);
@@ -61,7 +61,7 @@ ustring ZlibDecompressor::decompress()
 		buffer += ustring(reinterpret_cast<unsigned char *>(temp_buffer), BUFSIZE - strm.avail_out);
 	} while (ret == Z_OK);
 	if (ret != Z_STREAM_END) {
-		throw DecompressError();
+		throw DecompressError(strm.msg);
 	}
 	m_seekPos += strm.next_in - data;
 	(void)inflateEnd(&strm);

ZlibDecompressor.h

@@ -18,7 +18,9 @@
 class ZlibDecompressor
 {
 public:
-	class DecompressError {
+	struct DecompressError {
+		DecompressError(std::string m = "(unknown error)") : message(m) {}
+		const std::string message;
 	};
 
 	ZlibDecompressor(const unsigned char *data, std::size_t size);

mapper.cpp

@@ -15,6 +15,7 @@
 #include <sstream>
 #include <stdexcept>
 #include "TileGenerator.h"
+#include "ZlibDecompressor.h"
 
 using namespace std;
 
@@ -379,6 +380,9 @@ int main(int argc, char *argv[])
 	} catch(std::runtime_error e) {
 		std::cout<<"Exception: "<<e.what()<<std::endl;
 		return 1;
+	} catch(ZlibDecompressor::DecompressError e) {
+		std::cout<<"Block decompression failure: "<<e.message<<std::endl;
+		return 1;
 	}
 	return 0;
 }