add compression support for bodies of POST/PUT operations

ChangeLog

@@ -1,3 +1,7 @@
+Fri 03 May 2019 05:36:10 PM CEST
+    Add support for compressing bodies during HTTP uploads to
+    exchange and auditor. -CG
+
 Thu 02 May 2019 09:15:37 PM CEST
     Pass hash of denomination public key in operations from
     clients to exchange instead of the (larger) full public key.

src/lib/Makefile.am

@@ -27,7 +27,8 @@ libtalerexchange_la_SOURCES = \
   exchange_api_reserve.c \
   exchange_api_track_transaction.c \
   exchange_api_track_transfer.c \
-  exchange_api_wire.c
+  exchange_api_wire.c \
+  teah_common.c teah_common.h
 libtalerexchange_la_LIBADD = \
   libtalerauditor.la \
   $(top_builddir)/src/json/libtalerjson.la \
@@ -46,7 +47,8 @@ libtalerauditor_la_SOURCES = \
   auditor_api_curl_defaults.c auditor_api_curl_defaults.h \
   auditor_api_handle.c auditor_api_handle.h \
   auditor_api_deposit_confirmation.c \
-  auditor_api_exchanges.c
+  auditor_api_exchanges.c \
+  teah_common.c teah_common.h
 libtalerauditor_la_LIBADD = \
   $(top_builddir)/src/json/libtalerjson.la \
   $(top_builddir)/src/util/libtalerutil.la \

src/lib/auditor_api_deposit_confirmation.c

@@ -49,9 +49,10 @@ struct TALER_AUDITOR_DepositConfirmationHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -338,26 +339,26 @@ TALER_AUDITOR_deposit_confirmation (struct TALER_AUDITOR_Handle *auditor,
   dh->url = MAH_path_to_url (auditor, "/deposit-confirmation");
 
   eh = TAL_curl_easy_get (dh->url);
-  GNUNET_assert (NULL != (dh->json_enc =
-                          json_dumps (deposit_confirmation_obj,
-                                      JSON_COMPACT)));
-  json_decref (deposit_confirmation_obj);
-  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
-              "URL for deposit-confirmation: `%s'\n",
-              dh->url);
-
   GNUNET_assert (CURLE_OK ==
                  curl_easy_setopt (eh,
                                    CURLOPT_CUSTOMREQUEST,
                                    "PUT"));
-  GNUNET_assert (CURLE_OK ==
+  if (GNUNET_OK !=
-                 curl_easy_setopt (eh,
+      TEAH_curl_easy_post (&dh->ctx,
-                                   CURLOPT_POSTFIELDS,
+                           eh,
-                                   dh->json_enc));
+                           deposit_confirmation_obj))
-  GNUNET_assert (CURLE_OK ==
+  {
-                 curl_easy_setopt (eh,
+    GNUNET_break (0);
-                                   CURLOPT_POSTFIELDSIZE,
+    curl_easy_cleanup (eh);
-                                   strlen (dh->json_enc)));
+    json_decref (deposit_confirmation_obj);
+    GNUNET_free (dh->url);
+    GNUNET_free (dh);
+    return NULL;
+  }
+  json_decref (deposit_confirmation_obj);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "URL for deposit-confirmation: `%s'\n",
+              dh->url);
   ctx = MAH_handle_to_context (auditor);
   dh->job = GNUNET_CURL_job_add (ctx,
 				 eh,
@@ -383,7 +384,7 @@ TALER_AUDITOR_deposit_confirmation_cancel (struct TALER_AUDITOR_DepositConfirmat
     deposit_confirmation->job = NULL;
   }
   GNUNET_free (deposit_confirmation->url);
-  GNUNET_free (deposit_confirmation->json_enc);
+  TEAH_curl_easy_post_finished (&deposit_confirmation->ctx);
   GNUNET_free (deposit_confirmation);
 }
 

src/lib/auditor_api_handle.c

@@ -15,7 +15,7 @@
   <http://www.gnu.org/licenses/>
 */
 /**
- * @file auditor-lib/auditor_api_handle.c
+ * @file lib/auditor_api_handle.c
  * @brief Implementation of the "handle" component of the auditor's HTTP API
  * @author Sree Harsha Totakura <sreeharsha@totakura.in>
  * @author Christian Grothoff
@@ -462,6 +462,16 @@ TALER_AUDITOR_connect (struct GNUNET_CURL_Context *ctx,
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Connecting to auditor at URL `%s'.\n",
               url);
+  /* Disable 100 continue processing */
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CURL_append_header (ctx,
+                                           "Expect:"));
+#if COMPRESS_BODIES
+  /* Tell auditor we compress bodies */
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CURL_append_header (ctx,
+                                           "Content-encoding: deflate"));
+#endif
   auditor = GNUNET_new (struct TALER_AUDITOR_Handle);
   auditor->ctx = ctx;
   auditor->url = GNUNET_strdup (url);

src/lib/auditor_api_handle.h

@@ -22,7 +22,7 @@
 #include "platform.h"
 #include <gnunet/gnunet_curl_lib.h>
 #include "taler_auditor_service.h"
-
+#include "teah_common.h"
 
 /**
  * Get the context of a auditor.

src/lib/exchange_api_deposit.c

@@ -60,9 +60,10 @@ struct TALER_EXCHANGE_DepositHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -581,21 +582,22 @@ TALER_EXCHANGE_deposit (struct TALER_EXCHANGE_Handle *exchange,
   dh->coin_value = dki->value;
 
   eh = TEL_curl_easy_get (dh->url);
-  GNUNET_assert (NULL != (dh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (deposit_obj,
+      TEAH_curl_easy_post (&dh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           deposit_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (deposit_obj);
+    GNUNET_free (dh->url);
+    GNUNET_free (dh);
+    return NULL;
+  }
   json_decref (deposit_obj);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "URL for deposit: `%s'\n",
               dh->url);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   dh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (dh->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   dh->job = GNUNET_CURL_job_add (ctx,
 				 eh,
@@ -621,7 +623,7 @@ TALER_EXCHANGE_deposit_cancel (struct TALER_EXCHANGE_DepositHandle *deposit)
     deposit->job = NULL;
   }
   GNUNET_free (deposit->url);
-  GNUNET_free (deposit->json_enc);
+  TEAH_curl_easy_post_finished (&deposit->ctx);
   GNUNET_free (deposit);
 }
 

src/lib/exchange_api_handle.c

@@ -33,6 +33,7 @@
 #include "exchange_api_handle.h"
 #include "exchange_api_curl_defaults.h"
 #include "backoff.h"
+#include "teah_common.h"
 
 /**
  * Which revision of the Taler protocol is implemented
@@ -1783,6 +1784,12 @@ TALER_EXCHANGE_connect
   GNUNET_break (GNUNET_OK ==
 		GNUNET_CURL_append_header (ctx,
 					   "Expect:"));
+#if COMPRESS_BODIES
+  /* Tell exchange we compress bodies */
+  GNUNET_break (GNUNET_OK ==
+		GNUNET_CURL_append_header (ctx,
+                                   "Content-encoding: deflate"));
+#endif
   exchange = GNUNET_new (struct TALER_EXCHANGE_Handle);
   exchange->ctx = ctx;
   exchange->url = GNUNET_strdup (url);
@@ -1816,6 +1823,7 @@ TALER_EXCHANGE_connect
 }
 
 
+
 /**
  * Initiate download of /keys from the exchange.
  *

src/lib/exchange_api_handle.h

@@ -24,7 +24,7 @@
 #include "taler_auditor_service.h"
 #include "taler_exchange_service.h"
 #include "taler_crypto_lib.h"
-
+#include "teah_common.h"
 
 /**
  * Entry in DLL of auditors used by an exchange.

src/lib/exchange_api_payback.c

@@ -49,9 +49,10 @@ struct TALER_EXCHANGE_PaybackHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Denomination key of the coin.
@@ -321,29 +322,23 @@ TALER_EXCHANGE_payback (struct TALER_EXCHANGE_Handle *exchange,
   ph->cb = payback_cb;
   ph->cb_cls = payback_cb_cls;
   ph->url = TEAH_path_to_url (exchange, "/payback");
-
+  eh = TEL_curl_easy_get (ph->url);
-  ph->json_enc = json_dumps (payback_obj,
+  if (GNUNET_OK !=
-                             JSON_COMPACT);
+      TEAH_curl_easy_post (&ph->ctx,
-  json_decref (payback_obj);
+                           eh,
-  if (NULL == ph->json_enc)
+                           payback_obj))
   {
     GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (payback_obj);
     GNUNET_free (ph->url);
     GNUNET_free (ph);
     return NULL;
   }
-  eh = TEL_curl_easy_get (ph->url);
+  json_decref (payback_obj);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "URL for payback: `%s'\n",
               ph->url);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   ph->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (ph->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   ph->job = GNUNET_CURL_job_add (ctx,
 				 eh,
@@ -369,7 +364,7 @@ TALER_EXCHANGE_payback_cancel (struct TALER_EXCHANGE_PaybackHandle *ph)
     ph->job = NULL;
   }
   GNUNET_free (ph->url);
-  GNUNET_free (ph->json_enc);
+  TEAH_curl_easy_post_finished (&ph->ctx);
   GNUNET_free (ph);
 }
 

src/lib/exchange_api_refresh.c

@@ -834,9 +834,10 @@ struct TALER_EXCHANGE_RefreshMeltHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -1206,18 +1207,19 @@ TALER_EXCHANGE_refresh_melt (struct TALER_EXCHANGE_Handle *exchange,
   rmh->url = TEAH_path_to_url (exchange,
                               "/refresh/melt");
   eh = TEL_curl_easy_get (rmh->url);
-  GNUNET_assert (NULL != (rmh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (melt_obj,
+      TEAH_curl_easy_post (&rmh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           melt_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (melt_obj);
+    GNUNET_free (rmh->url);
+    GNUNET_free (rmh);
+    return NULL;
+  }
   json_decref (melt_obj);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   rmh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (rmh->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   rmh->job = GNUNET_CURL_job_add (ctx,
                           eh,
@@ -1245,7 +1247,7 @@ TALER_EXCHANGE_refresh_melt_cancel (struct TALER_EXCHANGE_RefreshMeltHandle *rmh
   free_melt_data (rmh->md); /* does not free 'md' itself */
   GNUNET_free (rmh->md);
   GNUNET_free (rmh->url);
-  GNUNET_free (rmh->json_enc);
+  TEAH_curl_easy_post_finished (&rmh->ctx);
   GNUNET_free (rmh);
 }
 
@@ -1270,9 +1272,10 @@ struct TALER_EXCHANGE_RefreshRevealHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -1634,18 +1637,19 @@ TALER_EXCHANGE_refresh_reveal (struct TALER_EXCHANGE_Handle *exchange,
                               "/refresh/reveal");
 
   eh = TEL_curl_easy_get (rrh->url);
-  GNUNET_assert (NULL != (rrh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (reveal_obj,
+      TEAH_curl_easy_post (&rrh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           reveal_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (reveal_obj);
+    GNUNET_free (rrh->url);
+    GNUNET_free (rrh);
+    return NULL;
+  }
   json_decref (reveal_obj);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   rrh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (rrh->json_enc)));
   ctx = TEAH_handle_to_context (rrh->exchange);
   rrh->job = GNUNET_CURL_job_add (ctx,
                                   eh,
@@ -1671,7 +1675,7 @@ TALER_EXCHANGE_refresh_reveal_cancel (struct TALER_EXCHANGE_RefreshRevealHandle
     rrh->job = NULL;
   }
   GNUNET_free (rrh->url);
-  GNUNET_free (rrh->json_enc);
+  TEAH_curl_easy_post_finished (&rrh->ctx);
   free_melt_data (rrh->md); /* does not free 'md' itself */
   GNUNET_free (rrh->md);
   GNUNET_free (rrh);

src/lib/exchange_api_refund.c

@@ -49,9 +49,10 @@ struct TALER_EXCHANGE_RefundHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -368,21 +369,22 @@ refund_obj = json_pack ("{s:o, s:o," /* amount/fee */
                      refund_fee);
 
   eh = TEL_curl_easy_get (rh->url);
-  GNUNET_assert (NULL != (rh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (refund_obj,
+      TEAH_curl_easy_post (&rh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           refund_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (refund_obj);
+    GNUNET_free (rh->url);
+    GNUNET_free (rh);
+    return NULL;
+  }
   json_decref (refund_obj);
   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
               "URL for refund: `%s'\n",
               rh->url);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   rh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (rh->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   rh->job = GNUNET_CURL_job_add (ctx,
 				 eh,
@@ -408,7 +410,7 @@ TALER_EXCHANGE_refund_cancel (struct TALER_EXCHANGE_RefundHandle *refund)
     refund->job = NULL;
   }
   GNUNET_free (refund->url);
-  GNUNET_free (refund->json_enc);
+  TEAH_curl_easy_post_finished (&refund->ctx);
   GNUNET_free (refund);
 }
 

src/lib/exchange_api_reserve.c

@@ -677,9 +677,10 @@ struct TALER_EXCHANGE_ReserveWithdrawHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -1022,25 +1023,26 @@ reserve_withdraw_internal (struct TALER_EXCHANGE_Handle *exchange,
   if (NULL == withdraw_obj)
   {
     GNUNET_break (0);
+    GNUNET_free (wsh);
     return NULL;
   }
 
   wsh->ps = *ps;
   wsh->url = TEAH_path_to_url (exchange, "/reserve/withdraw");
-
   eh = TEL_curl_easy_get (wsh->url);
-  GNUNET_assert (NULL != (wsh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (withdraw_obj,
+      TEAH_curl_easy_post (&wsh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           withdraw_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (withdraw_obj);
+    GNUNET_free (wsh->url);
+    GNUNET_free (wsh);
+    return NULL;
+  }
   json_decref (withdraw_obj);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   wsh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (wsh->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   wsh->job = GNUNET_CURL_job_add (ctx,
                           eh,
@@ -1199,7 +1201,7 @@ TALER_EXCHANGE_reserve_withdraw_cancel (struct TALER_EXCHANGE_ReserveWithdrawHan
     sign->job = NULL;
   }
   GNUNET_free (sign->url);
-  GNUNET_free (sign->json_enc);
+  TEAH_curl_easy_post_finished (&sign->ctx);
   GNUNET_free (sign);
 }
 

src/lib/exchange_api_track_transaction.c

@@ -49,9 +49,10 @@ struct TALER_EXCHANGE_TrackTransactionHandle
   char *url;
 
   /**
-   * JSON encoding of the request to POST.
+   * Context for #TEH_curl_easy_post(). Keeps the data that must
+   * persist for Curl to make the upload.
    */
-  char *json_enc;
+  struct TEAH_PostContext ctx;
 
   /**
    * Handle for the request.
@@ -322,18 +323,19 @@ TALER_EXCHANGE_track_transaction (struct TALER_EXCHANGE_Handle *exchange,
   dwh->depconf.coin_pub = *coin_pub;
 
   eh = TEL_curl_easy_get (dwh->url);
-  GNUNET_assert (NULL != (dwh->json_enc =
+  if (GNUNET_OK !=
-                          json_dumps (deposit_wtid_obj,
+      TEAH_curl_easy_post (&dwh->ctx,
-                                      JSON_COMPACT)));
+                           eh,
+                           deposit_wtid_obj))
+  {
+    GNUNET_break (0);
+    curl_easy_cleanup (eh);
+    json_decref (deposit_wtid_obj);
+    GNUNET_free (dwh->url);
+    GNUNET_free (dwh);
+    return NULL;
+  }
   json_decref (deposit_wtid_obj);
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDS,
-                                   dwh->json_enc));
-  GNUNET_assert (CURLE_OK ==
-                 curl_easy_setopt (eh,
-                                   CURLOPT_POSTFIELDSIZE,
-                                   strlen (dwh->json_enc)));
   ctx = TEAH_handle_to_context (exchange);
   dwh->job = GNUNET_CURL_job_add (ctx,
                           eh,
@@ -359,9 +361,9 @@ TALER_EXCHANGE_track_transaction_cancel (struct TALER_EXCHANGE_TrackTransactionH
     dwh->job = NULL;
   }
   GNUNET_free (dwh->url);
-  GNUNET_free (dwh->json_enc);
+  TEAH_curl_easy_post_finished (&dwh->ctx);
   GNUNET_free (dwh);
 }
 
 
-/* end of exchange_api_deposit_wtid.c */
+/* end of exchange_api_track_transaction.c */

src/lib/teah_common.c

@@ -0,0 +1,105 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2019 GNUnet e.V.
+
+  TALER 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.
+
+  TALER 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 TALER; see the file COPYING.  If not, see
+  <http://www.gnu.org/licenses/>
+*/
+
+/**
+ * @file lib/teah_common.c
+ * @brief Helper routines shared by libtalerexchange and libtalerauditor
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "teah_common.h"
+
+#if COMPRESS_BODIES
+#include <zlib.h>
+#endif
+
+
+/**
+ * Add the @a body as POST data to the easy handle in
+ * @a ctx.
+ *
+ * @param ctx[in,out] a request context (updated)
+ * @param eh easy handle to use
+ * @param body JSON body to add to @e ctx
+ * @return #GNUNET_OK on success #GNUNET_SYSERR on failure
+ */
+int
+TEAH_curl_easy_post (struct TEAH_PostContext *ctx,
+                     CURL *eh,
+                     const json_t *body)
+{
+  char *str;
+  size_t slen;
+
+  str = json_dumps (body,
+                    JSON_COMPACT);
+  if (NULL == str)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  slen = strlen (str);
+#if COMPRESS_BODIES
+  {
+    Bytef *cbuf;
+    uLongf cbuf_size;
+    int ret;
+
+    cbuf_size = compressBound (slen);
+    cbuf = GNUNET_malloc (cbuf_size);
+    ret = compress (cbuf,
+                    &cbuf_size,
+                    (const Bytef *) str,
+                    slen);
+    if (Z_OK != ret)
+    {
+      /* compression failed!? */
+      GNUNET_break (0);
+      GNUNET_free (cbuf);
+      return GNUNET_SYSERR;
+    }
+    free (str);
+    slen = (size_t) cbuf_size;
+    ctx->json_enc = (char *) cbuf;
+  }
+#else
+  ctx->json_enc = str;
+#endif
+  GNUNET_assert (CURLE_OK ==
+                 curl_easy_setopt (eh,
+                                   CURLOPT_POSTFIELDS,
+                                   ctx->json_enc));
+  GNUNET_assert (CURLE_OK ==
+                 curl_easy_setopt (eh,
+                                   CURLOPT_POSTFIELDSIZE,
+                                   slen));
+  return GNUNET_OK;
+}
+
+
+/**
+ * Free the data in @a ctx.
+ *
+ * @param ctx[in] a request context (updated)
+ */
+void
+TEAH_curl_easy_post_finished (struct TEAH_PostContext *ctx)
+{
+  GNUNET_free_non_null (ctx->json_enc);
+}

src/lib/teah_common.h

@@ -0,0 +1,74 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2019 GNUnet e.V.
+
+  TALER 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.
+
+  TALER 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 TALER; see the file COPYING.  If not, see
+  <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file lib/teah_common.h
+ * @brief Helper routines shared by libtalerexchange and libtalerauditor
+ * @author Christian Grothoff
+ */
+#ifndef TEAH_COMMON_H
+#define TEAH_COMMON_H
+
+#include <gnunet/gnunet_curl_lib.h>
+#include "taler_json_lib.h"
+
+/**
+ * Should we compress PUT/POST bodies with 'deflate' encoding?
+ */
+#define COMPRESS_BODIES 0
+
+/**
+ * State used for #TEAL_curl_easy_post() and
+ * #TEAL_curl_easy_post_finished().
+ */
+struct TEAH_PostContext
+{
+  /**
+   * JSON encoding of the request to POST.
+   */
+  char *json_enc;
+
+};
+
+
+/**
+ * Add the @a body as POST data to the easy handle in
+ * @a ctx.
+ *
+ * @param ctx[in,out] a request context (updated)
+ * @param eh easy handle to use
+ * @param body JSON body to add to @e ctx
+ * @return #GNUNET_OK on success #GNUNET_SYSERR on failure
+ */
+int
+TEAH_curl_easy_post (struct TEAH_PostContext *ctx,
+                     CURL *eh,
+                     const json_t *body);
+
+
+/**
+ * Free the data in @a ctx.
+ *
+ * @param ctx[in] a request context (updated)
+ */
+void
+TEAH_curl_easy_post_finished (struct TEAH_PostContext *ctx);
+
+
+
+#endif