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+#ifndef HEADER_CURL_ASYN_H
+#define HEADER_CURL_ASYN_H
+/***************************************************************************
+ * _ _ ____ _
+ * Project ___| | | | _ \| |
+ * / __| | | | |_) | |
+ * | (__| |_| | _ <| |___
+ * \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at http://curl.haxx.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "setup.h"
+#include "curl_addrinfo.h"
+
+struct addrinfo;
+struct hostent;
+struct SessionHandle;
+struct connectdata;
+struct Curl_dns_entry;
+
+/*
+ * This header defines all functions in the internal asynch resolver interface.
+ * All asynch resolvers need to provide these functions.
+ * asyn-ares.c and asyn-thread.c are the current implementations of asynch
+ * resolver backends.
+ */
+
+/*
+ * Curl_resolver_global_init()
+ *
+ * Called from curl_global_init() to initialize global resolver environment.
+ * Returning anything else than CURLE_OK fails curl_global_init().
+ */
+int Curl_resolver_global_init(void);
+
+/*
+ * Curl_resolver_global_cleanup()
+ * Called from curl_global_cleanup() to destroy global resolver environment.
+ */
+void Curl_resolver_global_cleanup(void);
+
+/*
+ * Curl_resolver_init()
+ * Called from curl_easy_init() -> Curl_open() to initialize resolver
+ * URL-state specific environment ('resolver' member of the UrlState
+ * structure). Should fill the passed pointer by the initialized handler.
+ * Returning anything else than CURLE_OK fails curl_easy_init() with the
+ * correspondent code.
+ */
+CURLcode Curl_resolver_init(void **resolver);
+
+/*
+ * Curl_resolver_cleanup()
+ * Called from curl_easy_cleanup() -> Curl_close() to cleanup resolver
+ * URL-state specific environment ('resolver' member of the UrlState
+ * structure). Should destroy the handler and free all resources connected to
+ * it.
+ */
+void Curl_resolver_cleanup(void *resolver);
+
+/*
+ * Curl_resolver_duphandle()
+ * Called from curl_easy_duphandle() to duplicate resolver URL-state specific
+ * environment ('resolver' member of the UrlState structure). Should
+ * duplicate the 'from' handle and pass the resulting handle to the 'to'
+ * pointer. Returning anything else than CURLE_OK causes failed
+ * curl_easy_duphandle() call.
+ */
+int Curl_resolver_duphandle(void **to, void *from);
+
+/*
+ * Curl_resolver_cancel().
+ *
+ * It is called from inside other functions to cancel currently performing
+ * resolver request. Should also free any temporary resources allocated to
+ * perform a request.
+ */
+void Curl_resolver_cancel(struct connectdata *conn);
+
+/* Curl_resolver_getsock()
+ *
+ * This function is called from the multi_getsock() function. 'sock' is a
+ * pointer to an array to hold the file descriptors, with 'numsock' being the
+ * size of that array (in number of entries). This function is supposed to
+ * return bitmask indicating what file descriptors (referring to array indexes
+ * in the 'sock' array) to wait for, read/write.
+ */
+int Curl_resolver_getsock(struct connectdata *conn, curl_socket_t *sock,
+ int numsocks);
+
+/*
+ * Curl_resolver_is_resolved()
+ *
+ * Called repeatedly to check if a previous name resolve request has
+ * completed. It should also make sure to time-out if the operation seems to
+ * take too long.
+ *
+ * Returns normal CURLcode errors.
+ */
+CURLcode Curl_resolver_is_resolved(struct connectdata *conn,
+ struct Curl_dns_entry **dns);
+
+/*
+ * Curl_resolver_wait_resolv()
+ *
+ * waits for a resolve to finish. This function should be avoided since using
+ * this risk getting the multi interface to "hang".
+ *
+ * If 'entry' is non-NULL, make it point to the resolved dns entry
+ *
+ * Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved, and
+ * CURLE_OPERATION_TIMEDOUT if a time-out occurred.
+
+ */
+CURLcode Curl_resolver_wait_resolv(struct connectdata *conn,
+ struct Curl_dns_entry **dnsentry);
+
+/*
+ * Curl_resolver_getaddrinfo() - when using this resolver
+ *
+ * Returns name information about the given hostname and port number. If
+ * successful, the 'hostent' is returned and the forth argument will point to
+ * memory we need to free after use. That memory *MUST* be freed with
+ * Curl_freeaddrinfo(), nothing else.
+ *
+ * Each resolver backend must of course make sure to return data in the
+ * correct format to comply with this.
+ */
+Curl_addrinfo *Curl_resolver_getaddrinfo(struct connectdata *conn,
+ const char *hostname,
+ int port,
+ int *waitp);
+
+#ifndef CURLRES_ASYNCH
+/* convert these functions if an asynch resolver isn't used */
+#define Curl_resolver_cancel(x) Curl_nop_stmt
+#define Curl_resolver_is_resolved(x,y) CURLE_COULDNT_RESOLVE_HOST
+#define Curl_resolver_wait_resolv(x,y) CURLE_COULDNT_RESOLVE_HOST
+#define Curl_resolver_getsock(x,y,z) 0
+#define Curl_resolver_duphandle(x,y) CURLE_OK
+#define Curl_resolver_init(x) CURLE_OK
+#define Curl_resolver_global_init() CURLE_OK
+#define Curl_resolver_global_cleanup() Curl_nop_stmt
+#define Curl_resolver_cleanup(x) Curl_nop_stmt
+#endif
+
+#ifdef CURLRES_ASYNCH
+#define Curl_resolver_asynch() 1
+#else
+#define Curl_resolver_asynch() 0
+#endif
+
+
+/********** end of generic resolver interface functions *****************/
+#endif /* HEADER_CURL_ASYN_H */