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diff --git a/content/fetchers/doi.c b/content/fetchers/doi.c
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+/*
+ * Copyright 2011 Fran├žois Revol <mmu_man@users.sourceforge.net>
+ *
+ * This file is part of NetSurf.
+ *
+ * NetSurf is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * NetSurf is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/* doi: URL handling. Based on the resource fetcher by Vincent Sanders */
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <inttypes.h>
+#include <string.h>
+#include <strings.h>
+#include <time.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <limits.h>
+#include <stdarg.h>
+
+#include "utils/config.h"
+#include "content/dirlist.h"
+#include "content/fetch.h"
+#include "content/fetchers/doi.h"
+#include "content/urldb.h"
+#include "desktop/netsurf.h"
+#include "desktop/options.h"
+#include "utils/log.h"
+#include "utils/messages.h"
+#include "utils/url.h"
+#include "utils/utils.h"
+#include "utils/ring.h"
+
+struct fetch_doi_context;
+
+/** Context for an resource fetch */
+struct fetch_doi_context {
+ struct fetch_doi_context *r_next, *r_prev;
+
+ struct fetch *fetchh; /**< Handle for this fetch */
+
+ bool aborted; /**< Flag indicating fetch has been aborted */
+ bool locked; /**< Flag indicating entry is already entered */
+
+ char redirect_url[1]; /**< The url the fetch redirects to */
+};
+
+static struct fetch_doi_context *ring = NULL;
+
+static const char *fetch_doi_redirect_base = "http://dx.doi.org/";
+
+/** issue fetch callbacks with locking */
+static inline bool fetch_doi_send_callback(fetch_msg msg,
+ struct fetch_doi_context *ctx, const void *data,
+ unsigned long size, fetch_error_code errorcode)
+{
+ ctx->locked = true;
+ fetch_send_callback(msg, ctx->fetchh, data, size, errorcode);
+ ctx->locked = false;
+
+ return ctx->aborted;
+}
+
+static bool fetch_doi_redirect_handler(struct fetch_doi_context *ctx)
+{
+ /* content is going to return redirect */
+ fetch_set_http_code(ctx->fetchh, 302);
+
+ fetch_doi_send_callback(FETCH_REDIRECT, ctx, ctx->redirect_url, 0,
+ FETCH_ERROR_NO_ERROR);
+
+ return true;
+}
+
+
+/** callback to initialise the resource fetcher. */
+static bool fetch_doi_initialise(const char *scheme)
+{
+ return true;
+}
+
+/** callback to initialise the resource fetcher. */
+static void fetch_doi_finalise(const char *scheme)
+{
+}
+
+/** callback to set up a resource fetch context. */
+static void *
+fetch_doi_setup(struct fetch *fetchh,
+ const char *url,
+ bool only_2xx,
+ const char *post_urlenc,
+ const struct fetch_multipart_data *post_multipart,
+ const char **headers)
+{
+ struct fetch_doi_context *ctx;
+
+ ctx = calloc(1, sizeof(*ctx) + strlen(fetch_doi_redirect_base) +
+ strlen(url) + 1);
+ if (ctx == NULL)
+ return NULL;
+
+ sprintf(ctx->redirect_url, "%s%s", fetch_doi_redirect_base,
+ url + SLEN("doi:"));
+
+ ctx->fetchh = fetchh;
+
+ RING_INSERT(ring, ctx);
+
+ return ctx;
+}
+
+/** callback to free a resource fetch */
+static void fetch_doi_free(void *ctx)
+{
+ struct fetch_doi_context *c = ctx;
+ RING_REMOVE(ring, c);
+ free(ctx);
+}
+
+/** callback to start a resource fetch */
+static bool fetch_doi_start(void *ctx)
+{
+ return true;
+}
+
+/** callback to abort a resource fetch */
+static void fetch_doi_abort(void *ctx)
+{
+ struct fetch_doi_context *c = ctx;
+
+ /* To avoid the poll loop having to deal with the fetch context
+ * disappearing from under it, we simply flag the abort here.
+ * The poll loop itself will perform the appropriate cleanup.
+ */
+ c->aborted = true;
+}
+
+
+/** callback to poll for additional resource fetch contents */
+static void fetch_doi_poll(const char *scheme)
+{
+ struct fetch_doi_context *c, *next;
+
+ if (ring == NULL) return;
+
+ /* Iterate over ring, processing each pending fetch */
+ c = ring;
+ do {
+ /* Ignore fetches that have been flagged as locked.
+ * This allows safe re-entrant calls to this function.
+ * Re-entrancy can occur if, as a result of a callback,
+ * the interested party causes fetch_poll() to be called
+ * again.
+ */
+ if (c->locked == true) {
+ next = c->r_next;
+ continue;
+ }
+
+ /* Only process non-aborted fetches */
+ if (c->aborted == false) {
+ /* resource fetches can be processed in one go */
+ fetch_doi_redirect_handler(c);
+ }
+
+ /* Compute next fetch item at the last possible moment
+ * as processing this item may have added to the ring
+ */
+ next = c->r_next;
+
+ fetch_remove_from_queues(c->fetchh);
+ fetch_free(c->fetchh);
+
+ /* Advance to next ring entry, exiting if we've reached
+ * the start of the ring or the ring has become empty
+ */
+ } while ( (c = next) != ring && ring != NULL);
+}
+
+void fetch_doi_register(void)
+{
+ fetch_add_fetcher("doi",
+ fetch_doi_initialise,
+ fetch_doi_setup,
+ fetch_doi_start,
+ fetch_doi_abort,
+ fetch_doi_free,
+ fetch_doi_poll,
+ fetch_doi_finalise);
+}