Disable reading OSM files from network on Windows.

Windows doesn't have pipes and fork, so the current implementation that calls
the curl binary doesn't work. This patch disables the code using #ifdefs. In
the future libcurl or something like it should be used internally, so we don't
need the fork any more.

include/osmium/io/reader.hpp

@@ -86,6 +86,7 @@ namespace osmium {
 
             std::unique_ptr<osmium::io::detail::InputFormat> m_input;
 
+#ifndef _WIN32
             /**
              * Fork and execute the given command in the child.
              * A pipe is created between the child and the parent.
@@ -132,6 +133,7 @@ namespace osmium {
                 ::close(pipefd[1]);
                 return pipefd[0];
             }
+#endif
 
             /**
              * Open File for reading. Handles URLs or normal files. URLs
@@ -144,7 +146,11 @@ namespace osmium {
             static int open_input_file_or_url(const std::string& filename, int* childpid) {
                 std::string protocol = filename.substr(0, filename.find_first_of(':'));
                 if (protocol == "http" || protocol == "https" || protocol == "ftp" || protocol == "file") {
+#ifndef _WIN32
                     return execute("curl", filename, childpid);
+#else
+                    throw std::runtime_error("Reading OSM files from the network currently not supported on Windows.");
+#endif
                 } else {
                     return osmium::io::detail::open_for_reading(filename);
                 }
@@ -201,6 +207,7 @@ namespace osmium {
 
                 m_input->close();
 
+#ifndef _WIN32
                 if (m_childpid) {
                     int status;
                     pid_t pid = ::waitpid(m_childpid, &status, 0);
@@ -212,6 +219,7 @@ namespace osmium {
 #pragma GCC diagnostic pop
                     m_childpid = 0;
                 }
+#endif
 
                 m_read_task.close();
             }