adding libgnunetcurl

8 files changed, 774 insertions, 0 deletions

diff --git a/configure.ac b/configure.ac
index 2b90bc1ee..369ad99ee 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1534,6 +1534,7 @@ src/consensus/Makefile
 src/consensus/consensus.conf
 src/conversation/Makefile
 src/conversation/conversation.conf
+src/curl/Makefile
 src/datacache/Makefile
 src/datastore/Makefile
 src/datastore/datastore.conf
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 84bf8735e..06d180231 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -74,6 +74,7 @@ src/core/gnunet-service-core_kx.c
 src/core/gnunet-service-core_neighbours.c
 src/core/gnunet-service-core_sessions.c
 src/core/gnunet-service-core_typemap.c
+src/curl/curl.c
 src/datacache/datacache.c
 src/datacache/plugin_datacache_heap.c
 src/datacache/plugin_datacache_postgres.c
diff --git a/src/Makefile.am b/src/Makefile.am
index f38dd19d3..5244c795d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,6 +24,13 @@ endif
 
 if HAVE_JSON
   JSON_DIR = json
+if HAVE_LIBGNURL
+  JSON_DIR += curl
+else
+if HAVE_LIBCURL
+  JSON_DIR += curl
+endif
+endif
 endif
 
 if BUILD_PULSE_HELPERS
diff --git a/src/curl/Makefile.am b/src/curl/Makefile.am
new file mode 100644
index 000000000..4bdd03039
--- /dev/null
+++ b/src/curl/Makefile.am
@@ -0,0 +1,33 @@
+# This Makefile.am is in the public domain
+AM_CPPFLAGS = -I$(top_srcdir)/src/include
+
+if USE_COVERAGE
+  AM_CFLAGS = --coverage -O0
+  XLIB = -lgcov
+endif
+
+lib_LTLIBRARIES = \
+  libgnunetcurl.la
+
+libgnunetcurl_la_LDFLAGS = \
+  -version-info 0:0:0 \
+  -no-undefined
+libgnunetcurl_la_SOURCES = \
+  curl.c
+libgnunetcurl_la_LIBADD = \
+  $(top_builddir)/src/util/libgnunetutil.la \
+  -ljansson \
+  $(XLIB)
+
+#check_PROGRAMS = \
+#  test_curl
+
+#TESTS = \
+#  $(check_PROGRAMS)
+
+#test_curl_SOURCES = \
+#  test_curl.c
+#test_curl_LDADD = \
+#  libgnunetcurl.la \
+#  $(top_builddir)/src/util/libgnunetutil.la \
+#  -ljansson -lcurl
diff --git a/src/curl/curl.c b/src/curl/curl.c
new file mode 100644
index 000000000..10ba7f719
--- /dev/null
+++ b/src/curl/curl.c
@@ -0,0 +1,574 @@
+/*
+  This file is part of GNUnet
+  Copyright (C) 2014, 2015, 2016 GNUnet e.V.
+
+  GNUnet 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; either version 3, or (at your option) any later version.
+
+  GNUnet 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
+  GNUnet; see the file COPYING.  If not, If not, see
+  <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file curl/curl.c
+ * @brief API for downloading JSON via CURL
+ * @author Sree Harsha Totakura <sreeharsha@totakura.in>
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <curl/curl.h>
+#include <jansson.h>
+#include "gnunet_curl_lib.h"
+
+
+/**
+ * Log error related to CURL operations.
+ *
+ * @param type log level
+ * @param function which function failed to run
+ * @param code what was the curl error code
+ */
+#define CURL_STRERROR(type, function, code)      \
+ GNUNET_log (type,                               \
+             "Curl function `%s' has failed at `%s:%d' with error: %s\n", \
+             function, __FILE__, __LINE__, curl_easy_strerror (code));
+
+/**
+ * Print JSON parsing related error information
+ */
+#define JSON_WARN(error)                                                \
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,                              \
+                "JSON parsing failed at %s:%u: %s (%s)\n",              \
+                __FILE__, __LINE__, error.text, error.source)
+
+
+/**
+ * Failsafe flag. Raised if our constructor fails to initialize
+ * the Curl library.
+ */
+static int curl_fail;
+
+
+/**
+ * @brief Buffer data structure we use to buffer the HTTP download
+ * before giving it to the JSON parser.
+ */
+struct DownloadBuffer
+{
+
+  /**
+   * Download buffer
+   */
+  void *buf;
+
+  /**
+   * The size of the download buffer
+   */
+  size_t buf_size;
+
+  /**
+   * Error code (based on libc errno) if we failed to download
+   * (i.e. response too large).
+   */
+  int eno;
+
+};
+
+
+/**
+ * Jobs are CURL requests running within a `struct GNUNET_CURL_Context`.
+ */
+struct GNUNET_CURL_Job
+{
+
+  /**
+   * We keep jobs in a DLL.
+   */
+  struct GNUNET_CURL_Job *next;
+
+  /**
+   * We keep jobs in a DLL.
+   */
+  struct GNUNET_CURL_Job *prev;
+
+  /**
+   * Easy handle of the job.
+   */
+  CURL *easy_handle;
+
+  /**
+   * Context this job runs in.
+   */
+  struct GNUNET_CURL_Context *ctx;
+
+  /**
+   * Function to call upon completion.
+   */
+  GNUNET_CURL_JobCompletionCallback jcc;
+
+  /**
+   * Closure for @e jcc.
+   */
+  void *jcc_cls;
+
+  /**
+   * Buffer for response received from CURL.
+   */
+  struct DownloadBuffer db;
+
+};
+
+
+/**
+ * Context
+ */
+struct GNUNET_CURL_Context
+{
+  /**
+   * Curl multi handle
+   */
+  CURLM *multi;
+
+  /**
+   * Curl share handle
+   */
+  CURLSH *share;
+
+  /**
+   * We keep jobs in a DLL.
+   */
+  struct GNUNET_CURL_Job *jobs_head;
+
+  /**
+   * We keep jobs in a DLL.
+   */
+  struct GNUNET_CURL_Job *jobs_tail;
+
+  /**
+   * HTTP header "application/json", created once and used
+   * for all requests that need it.
+   */
+  struct curl_slist *json_header;
+
+};
+
+
+/**
+ * Initialise this library.  This function should be called before using any of
+ * the following functions.
+ *
+ * @return library context
+ */
+struct GNUNET_CURL_Context *
+GNUNET_CURL_init ()
+{
+  struct GNUNET_CURL_Context *ctx;
+  CURLM *multi;
+  CURLSH *share;
+
+  if (curl_fail)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Curl was not initialised properly\n");
+    return NULL;
+  }
+  if (NULL == (multi = curl_multi_init ()))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to create a Curl multi handle\n");
+    return NULL;
+  }
+  if (NULL == (share = curl_share_init ()))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to create a Curl share handle\n");
+    return NULL;
+  }
+  ctx = GNUNET_new (struct GNUNET_CURL_Context);
+  ctx->multi = multi;
+  ctx->share = share;
+  GNUNET_assert (NULL != (ctx->json_header =
+                          curl_slist_append (NULL,
+                                             "Content-Type: application/json")));
+  return ctx;
+}
+
+
+/**
+ * Callback used when downloading the reply to an HTTP request.
+ * Just appends all of the data to the `buf` in the
+ * `struct DownloadBuffer` for further processing. The size of
+ * the download is limited to #GNUNET_MAX_MALLOC_CHECKED, if
+ * the download exceeds this size, we abort with an error.
+ *
+ * @param bufptr data downloaded via HTTP
+ * @param size size of an item in @a bufptr
+ * @param nitems number of items in @a bufptr
+ * @param cls the `struct DownloadBuffer`
+ * @return number of bytes processed from @a bufptr
+ */
+static size_t
+download_cb (char *bufptr,
+             size_t size,
+             size_t nitems,
+             void *cls)
+{
+  struct DownloadBuffer *db = cls;
+  size_t msize;
+  void *buf;
+
+  if (0 == size * nitems)
+  {
+    /* Nothing (left) to do */
+    return 0;
+  }
+  msize = size * nitems;
+  if ( (msize + db->buf_size) >= GNUNET_MAX_MALLOC_CHECKED)
+  {
+    db->eno = ENOMEM;
+    return 0; /* signals an error to curl */
+  }
+  db->buf = GNUNET_realloc (db->buf,
+                            db->buf_size + msize);
+  buf = db->buf + db->buf_size;
+  memcpy (buf, bufptr, msize);
+  db->buf_size += msize;
+  return msize;
+}
+
+
+/**
+ * Schedule a CURL request to be executed and call the given @a jcc
+ * upon its completion.  Note that the context will make use of the
+ * CURLOPT_PRIVATE facility of the CURL @a eh.
+ *
+ * This function modifies the CURL handle to add the
+ * "Content-Type: application/json" header if @a add_json is set.
+ *
+ * @param ctx context to execute the job in
+ * @param eh curl easy handle for the request, will
+ *           be executed AND cleaned up
+ * @param add_json add "application/json" content type header
+ * @param jcc callback to invoke upon completion
+ * @param jcc_cls closure for @a jcc
+ * @return NULL on error (in this case, @eh is still released!)
+ */
+struct GNUNET_CURL_Job *
+GNUNET_CURL_job_add (struct GNUNET_CURL_Context *ctx,
+                     CURL *eh,
+                     int add_json,
+                     GNUNET_CURL_JobCompletionCallback jcc,
+                     void *jcc_cls)
+{
+  struct GNUNET_CURL_Job *job;
+
+  if (GNUNET_YES == add_json)
+    if (CURLE_OK !=
+        curl_easy_setopt (eh,
+                          CURLOPT_HTTPHEADER,
+                          ctx->json_header))
+    {
+      GNUNET_break (0);
+      curl_easy_cleanup (eh);
+      return NULL;
+    }
+
+  job = GNUNET_new (struct GNUNET_CURL_Job);
+  if ( (CURLE_OK !=
+        curl_easy_setopt (eh,
+                          CURLOPT_PRIVATE,
+                          job)) ||
+       (CURLE_OK !=
+        curl_easy_setopt (eh,
+                          CURLOPT_WRITEFUNCTION,
+                          &download_cb)) ||
+       (CURLE_OK !=
+        curl_easy_setopt (eh,
+                          CURLOPT_WRITEDATA,
+                          &job->db)) ||
+       (CURLE_OK !=
+        curl_easy_setopt (eh,
+                          CURLOPT_SHARE,
+                          ctx->share)) ||
+       (CURLM_OK !=
+        curl_multi_add_handle (ctx->multi,
+                               eh)) )
+  {
+    GNUNET_break (0);
+    GNUNET_free (job);
+    curl_easy_cleanup (eh);
+    return NULL;
+  }
+
+  job->easy_handle = eh;
+  job->ctx = ctx;
+  job->jcc = jcc;
+  job->jcc_cls = jcc_cls;
+  GNUNET_CONTAINER_DLL_insert (ctx->jobs_head,
+                               ctx->jobs_tail,
+                               job);
+  return job;
+}
+
+
+/**
+ * Cancel a job.  Must only be called before the job completion
+ * callback is called for the respective job.
+ *
+ * @param job job to cancel
+ */
+void
+GNUNET_CURL_job_cancel (struct GNUNET_CURL_Job *job)
+{
+  struct GNUNET_CURL_Context *ctx = job->ctx;
+
+  GNUNET_CONTAINER_DLL_remove (ctx->jobs_head,
+                               ctx->jobs_tail,
+                               job);
+  GNUNET_break (CURLM_OK ==
+                curl_multi_remove_handle (ctx->multi,
+                                          job->easy_handle));
+  curl_easy_cleanup (job->easy_handle);
+  GNUNET_free_non_null (job->db.buf);
+  GNUNET_free (job);
+}
+
+
+/**
+ * Obtain information about the final result about the
+ * HTTP download. If the download was successful, parses
+ * the JSON in the @a db and returns it. Also returns
+ * the HTTP @a response_code.  If the download failed,
+ * the return value is NULL.  The response code is set
+ * in any case, on download errors to zero.
+ *
+ * Calling this function also cleans up @a db.
+ *
+ * @param db download buffer
+ * @param eh CURL handle (to get the response code)
+ * @param[out] response_code set to the HTTP response code
+ *             (or zero if we aborted the download, i.e.
+ *              because the response was too big, or if
+ *              the JSON we received was malformed).
+ * @return NULL if downloading a JSON reply failed
+ */
+static json_t *
+download_get_result (struct DownloadBuffer *db,
+                     CURL *eh,
+                     long *response_code)
+{
+  json_t *json;
+  json_error_t error;
+  char *ct;
+
+  if ( (CURLE_OK !=
+        curl_easy_getinfo (eh,
+                           CURLINFO_CONTENT_TYPE,
+                           &ct)) ||
+       (NULL == ct) ||
+       (0 != strcasecmp (ct,
+                         "application/json")) )
+  {
+    /* No content type or explicitly not JSON, refuse to parse
+       (but keep response code) */
+    if (CURLE_OK !=
+        curl_easy_getinfo (eh,
+                           CURLINFO_RESPONSE_CODE,
+                           response_code))
+    {
+      /* unexpected error... */
+      GNUNET_break (0);
+      *response_code = 0;
+    }
+    return NULL;
+  }
+
+  json = NULL;
+  if (0 == db->eno)
+  {
+    json = json_loadb (db->buf,
+                       db->buf_size,
+                       JSON_REJECT_DUPLICATES | JSON_DISABLE_EOF_CHECK,
+                       &error);
+    if (NULL == json)
+    {
+      JSON_WARN (error);
+      *response_code = 0;
+    }
+  }
+  GNUNET_free_non_null (db->buf);
+  db->buf = NULL;
+  db->buf_size = 0;
+  if (NULL != json)
+  {
+    if (CURLE_OK !=
+        curl_easy_getinfo (eh,
+                           CURLINFO_RESPONSE_CODE,
+                           response_code))
+    {
+      /* unexpected error... */
+      GNUNET_break (0);
+      *response_code = 0;
+    }
+  }
+  return json;
+}
+
+
+/**
+ * Run the main event loop for the Taler interaction.
+ *
+ * @param ctx the library context
+ */
+void
+GNUNET_CURL_perform (struct GNUNET_CURL_Context *ctx)
+{
+  CURLMsg *cmsg;
+  struct GNUNET_CURL_Job *job;
+  int n_running;
+  int n_completed;
+  long response_code;
+  json_t *j;
+
+  (void) curl_multi_perform (ctx->multi,
+                             &n_running);
+  while (NULL != (cmsg = curl_multi_info_read (ctx->multi,
+                                               &n_completed)))
+  {
+    /* Only documented return value is CURLMSG_DONE */
+    GNUNET_break (CURLMSG_DONE == cmsg->msg);
+    GNUNET_assert (CURLE_OK ==
+                   curl_easy_getinfo (cmsg->easy_handle,
+                                      CURLINFO_PRIVATE,
+                                      (char **) &job));
+    GNUNET_assert (job->ctx == ctx);
+    j = download_get_result (&job->db,
+                             job->easy_handle,
+                             &response_code);
+    job->jcc (job->jcc_cls,
+              response_code,
+              j);
+    GNUNET_CURL_job_cancel (job);
+  }
+}
+
+
+/**
+ * Obtain the information for a select() call to wait until
+ * #GNUNET_CURL_perform() is ready again.  Note that calling
+ * any other GNUNET_CURL-API may also imply that the library
+ * is again ready for #GNUNET_CURL_perform().
+ *
+ * Basically, a client should use this API to prepare for select(),
+ * then block on select(), then call #GNUNET_CURL_perform() and then
+ * start again until the work with the context is done.
+ *
+ * This function will NOT zero out the sets and assumes that @a max_fd
+ * and @a timeout are already set to minimal applicable values.  It is
+ * safe to give this API FD-sets and @a max_fd and @a timeout that are
+ * already initialized to some other descriptors that need to go into
+ * the select() call.
+ *
+ * @param ctx context to get the event loop information for
+ * @param read_fd_set will be set for any pending read operations
+ * @param write_fd_set will be set for any pending write operations
+ * @param except_fd_set is here because curl_multi_fdset() has this argument
+ * @param max_fd set to the highest FD included in any set;
+ *        if the existing sets have no FDs in it, the initial
+ *        value should be "-1". (Note that `max_fd + 1` will need
+ *        to be passed to select().)
+ * @param timeout set to the timeout in milliseconds (!); -1 means
+ *        no timeout (NULL, blocking forever is OK), 0 means to
+ *        proceed immediately with #GNUNET_CURL_perform().
+ */
+void
+GNUNET_CURL_get_select_info (struct GNUNET_CURL_Context *ctx,
+                             fd_set *read_fd_set,
+                             fd_set *write_fd_set,
+                             fd_set *except_fd_set,
+                             int *max_fd,
+                             long *timeout)
+{
+  long to;
+  int m;
+
+  m = -1;
+  GNUNET_assert (CURLM_OK ==
+                 curl_multi_fdset (ctx->multi,
+                                   read_fd_set,
+                                   write_fd_set,
+                                   except_fd_set,
+                                   &m));
+  to = *timeout;
+  *max_fd = GNUNET_MAX (m, *max_fd);
+  GNUNET_assert (CURLM_OK ==
+                 curl_multi_timeout (ctx->multi,
+                                     &to));
+
+  /* Only if what we got back from curl is smaller than what we
+     already had (-1 == infinity!), then update timeout */
+  if ( (to < *timeout) &&
+       (-1 != to) )
+    *timeout = to;
+  if ( (-1 == (*timeout)) &&
+       (NULL != ctx->jobs_head) )
+    *timeout = to;
+}
+
+
+/**
+ * Cleanup library initialisation resources.  This function should be called
+ * after using this library to cleanup the resources occupied during library's
+ * initialisation.
+ *
+ * @param ctx the library context
+ */
+void
+GNUNET_CURL_fini (struct GNUNET_CURL_Context *ctx)
+{
+  /* all jobs must have been cancelled at this time, assert this */
+  GNUNET_assert (NULL == ctx->jobs_head);
+  curl_share_cleanup (ctx->share);
+  curl_multi_cleanup (ctx->multi);
+  curl_slist_free_all (ctx->json_header);
+  GNUNET_free (ctx);
+}
+
+
+/**
+ * Initial global setup logic, specifically runs the Curl setup.
+ */
+__attribute__ ((constructor))
+void
+GNUNET_CURL_constructor__ (void)
+{
+  CURLcode ret;
+
+  if (CURLE_OK != (ret = curl_global_init (CURL_GLOBAL_DEFAULT)))
+  {
+    CURL_STRERROR (GNUNET_ERROR_TYPE_ERROR,
+                   "curl_global_init",
+                   ret);
+    curl_fail = 1;
+  }
+}
+
+
+/**
+ * Cleans up after us, specifically runs the Curl cleanup.
+ */
+__attribute__ ((destructor))
+void
+GNUNET_CURL_destructor__ (void)
+{
+  if (curl_fail)
+    return;
+  curl_global_cleanup ();
+}
+
+/* end of curl.c */
diff --git a/src/include/Makefile.am b/src/include/Makefile.am
index 82fa9006b..92893f7c7 100644
--- a/src/include/Makefile.am
+++ b/src/include/Makefile.am
@@ -45,6 +45,7 @@ gnunetinclude_HEADERS = \
   gnunet_conversation_service.h \
   gnunet_core_service.h \
   gnunet_crypto_lib.h \
+  gnunet_curl_lib.h \
   gnunet_datacache_lib.h \
   gnunet_datacache_plugin.h \
   gnunet_datastore_service.h \
diff --git a/src/include/gnunet_curl_lib.h b/src/include/gnunet_curl_lib.h
new file mode 100644
index 000000000..098b4dc37
--- /dev/null
+++ b/src/include/gnunet_curl_lib.h
@@ -0,0 +1,155 @@
+/*
+  This file is part of GNUnet
+  Copyright (C) 2014, 2015, 2016 GNUnet e.V.
+
+  GNUnet 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; either version 3, or (at your option) any later version.
+
+  GNUnet 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
+  GNUnet; see the file COPYING.  If not, If not, see
+  <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file src/include/gnunet_curl_lib.h
+ * @brief library to make it easy to download JSON replies over HTTP
+ * @author Sree Harsha Totakura <sreeharsha@totakura.in>
+ * @author Christian Grothoff
+ *
+ * @defgroup curl CURL integration library
+ * Download JSON using libcurl.
+ * @{
+ */
+#ifndef GNUNET_CURL_LIB_H
+#define GNUNET_CURL_LIB_H
+#include <curl/curl.h>
+#include <jansson.h>
+#include <gnunet/gnunet_util_lib.h>
+
+
+/**
+ * Initialise this library.  This function should be called before using any of
+ * the following functions.
+ *
+ * @return library context
+ */
+struct GNUNET_CURL_Context *
+GNUNET_CURL_init (void);
+
+
+/**
+ * Obtain the information for a select() call to wait until
+ * #GNUNET_CURL_perform() is ready again.  Note that calling
+ * any other TALER_EXCHANGE-API may also imply that the library
+ * is again ready for #GNUNET_CURL_perform().
+ *
+ * Basically, a client should use this API to prepare for select(),
+ * then block on select(), then call #GNUNET_CURL_perform() and then
+ * start again until the work with the context is done.
+ *
+ * This function will NOT zero out the sets and assumes that @a max_fd
+ * and @a timeout are already set to minimal applicable values.  It is
+ * safe to give this API FD-sets and @a max_fd and @a timeout that are
+ * already initialized to some other descriptors that need to go into
+ * the select() call.
+ *
+ * @param ctx context to get the event loop information for
+ * @param read_fd_set will be set for any pending read operations
+ * @param write_fd_set will be set for any pending write operations
+ * @param except_fd_set is here because curl_multi_fdset() has this argument
+ * @param max_fd set to the highest FD included in any set;
+ *        if the existing sets have no FDs in it, the initial
+ *        value should be "-1". (Note that `max_fd + 1` will need
+ *        to be passed to select().)
+ * @param timeout set to the timeout in milliseconds (!); -1 means
+ *        no timeout (NULL, blocking forever is OK), 0 means to
+ *        proceed immediately with #GNUNET_CURL_perform().
+ */
+void
+GNUNET_CURL_get_select_info (struct GNUNET_CURL_Context *ctx,
+                             fd_set *read_fd_set,
+                             fd_set *write_fd_set,
+                             fd_set *except_fd_set,
+                             int *max_fd,
+                             long *timeout);
+
+
+/**
+ * Run the main event loop for the Taler interaction.
+ *
+ * @param ctx the library context
+ */
+void
+GNUNET_CURL_perform (struct GNUNET_CURL_Context *ctx);
+
+
+/**
+ * Cleanup library initialisation resources.  This function should be called
+ * after using this library to cleanup the resources occupied during library's
+ * initialisation.
+ *
+ * @param ctx the library context
+ */
+void
+GNUNET_CURL_fini (struct GNUNET_CURL_Context *ctx);
+
+
+/**
+ * Entry in the context's job queue.
+ */
+struct GNUNET_CURL_Job;
+
+/**
+ * Function to call upon completion of a job.
+ *
+ * @param cls closure
+ * @param response_code HTTP response code from server, 0 on hard error
+ * @param json response, NULL if response was not in JSON format
+ */
+typedef void
+(*GNUNET_CURL_JobCompletionCallback)(void *cls,
+                                     long response_code,
+                                     json_t *json);
+
+
+/**
+ * Schedule a CURL request to be executed and call the given @a jcc
+ * upon its completion. Note that the context will make use of the
+ * CURLOPT_PRIVATE facility of the CURL @a eh.
+ *
+ * This function modifies the CURL handle to add the
+ * "Content-Type: application/json" header if @a add_json is set.
+ *
+ * @param ctx context to execute the job in
+ * @param eh curl easy handle for the request, will
+ *           be executed AND cleaned up
+ * @param add_json add "application/json" content type header
+ * @param jcc callback to invoke upon completion
+ * @param jcc_cls closure for @a jcc
+ * @return NULL on error (in this case, @eh is still released!)
+ */
+struct GNUNET_CURL_Job *
+GNUNET_CURL_job_add (struct GNUNET_CURL_Context *ctx,
+                     CURL *eh,
+                     int add_json,
+                     GNUNET_CURL_JobCompletionCallback jcc,
+                     void *jcc_cls);
+
+
+/**
+ * Cancel a job.  Must only be called before the job completion
+ * callback is called for the respective job.
+ *
+ * @param job job to cancel
+ */
+void
+GNUNET_CURL_job_cancel (struct GNUNET_CURL_Job *job);
+
+#endif
+/** @} */  /* end of group */
+
+/* end of gnunet_curl_lib.h */
diff --git a/src/json/json.c b/src/json/json.c
index aa74bfd48..a2d1a9608 100644
--- a/src/json/json.c
+++ b/src/json/json.c
@@ -46,6 +46,8 @@ GNUNET_JSON_parse (const json_t *root,
   unsigned int i;
   json_t *pos;
 
+  if (NULL == root)
+    return GNUNET_SYSERR;
   for (i=0;NULL != spec[i].parser;i++)
   {
     if (NULL == spec[i].field)