mime: latch last read callback status.

In case a read callback returns a status (pause, abort, eof,
error) instead of a byte count, drain the bytes read so far but
remember this status for further processing.
Takes care of not losing data when pausing, and properly resume a
paused mime structure when requested.
New tests 670-673 check unpausing cases, with easy or multi
interface and mime or form api.

Fixes #4813
Reported-by: MrdUkk on github
Closes #4833

3 files changed, 268 insertions, 2 deletions

diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 95ef8309b..9652f03fe 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -23,6 +23,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib583 lib585 lib586 lib587 lib589 lib590 lib591 lib597 lib598 lib599   \
  lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 lib655 lib658   \
  lib659 lib661 \
+ lib670 lib671 lib672 lib673 \
  lib1156 \
  lib1500 lib1501 lib1502 lib1503 lib1504 lib1505 lib1506 lib1507 lib1508 \
  lib1509 lib1510 lib1511 lib1512 lib1513 lib1514 lib1515         lib1517 \
@@ -348,6 +349,22 @@ lib659_CPPFLAGS = $(AM_CPPFLAGS)
 lib661_SOURCES = lib661.c $(SUPPORTFILES)
 lib661_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib670_SOURCES = lib670.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib670_LDADD = $(TESTUTIL_LIBS)
+lib670_CPPFLAGS = $(AM_CPPFLAGS) -DLIB670
+
+lib671_SOURCES = lib670.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib671_LDADD = $(TESTUTIL_LIBS)
+lib671_CPPFLAGS = $(AM_CPPFLAGS) -DLIB671
+
+lib672_SOURCES = lib670.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib672_LDADD = $(TESTUTIL_LIBS)
+lib672_CPPFLAGS = $(AM_CPPFLAGS) -DLIB672
+
+lib673_SOURCES = lib670.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib673_LDADD = $(TESTUTIL_LIBS)
+lib673_CPPFLAGS = $(AM_CPPFLAGS) -DLIB673
+
 lib1500_SOURCES = lib1500.c $(SUPPORTFILES) $(TESTUTIL)
 lib1500_LDADD = $(TESTUTIL_LIBS)
 lib1500_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/libtest/lib643.c b/tests/libtest/lib643.c
index 7432dfce8..08c0f2e80 100644
--- a/tests/libtest/lib643.c
+++ b/tests/libtest/lib643.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, 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
@@ -41,11 +41,20 @@ struct WriteThis {
 static size_t read_callback(char *ptr, size_t size, size_t nmemb, void *userp)
 {
 #ifdef LIB644
+  static int count = 0;
   (void)ptr;
   (void)size;
   (void)nmemb;
   (void)userp;
-  return CURL_READFUNC_ABORT;
+  switch(count++) {
+  case 0: /* Return a single byte. */
+    *ptr = '\n';
+    return 1;
+  case 1: /* Request abort. */
+    return CURL_READFUNC_ABORT;
+  }
+  printf("Wrongly called >2 times\n");
+  exit(1); /* trigger major failure */
 #else
 
   struct WriteThis *pooh = (struct WriteThis *)userp;
diff --git a/tests/libtest/lib670.c b/tests/libtest/lib670.c
new file mode 100644
index 000000000..62e22623e
--- /dev/null
+++ b/tests/libtest/lib670.c
@@ -0,0 +1,240 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2020, 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 https://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 <time.h>
+
+#include "test.h"
+
+#include "memdebug.h"
+
+#define PAUSE_TIME      2
+
+
+static const char name[] = "field";
+
+struct ReadThis {
+  CURL *easy;
+  time_t origin;
+  int count;
+};
+
+
+static size_t read_callback(char *ptr, size_t size, size_t nmemb, void *userp)
+{
+  struct ReadThis *pooh = (struct ReadThis *) userp;
+  time_t delta;
+
+  if(size * nmemb < 1)
+    return 0;
+
+  switch(pooh->count++) {
+  case 0:
+    *ptr = '\x41'; /* ASCII A. */
+    return 1;
+  case 1:
+    pooh->origin = time(NULL);
+    return CURL_READFUNC_PAUSE;
+  case 2:
+    delta = time(NULL) - pooh->origin;
+    *ptr = delta >= PAUSE_TIME? '\x42': '\x41'; /* ASCII A or B. */
+    return 1;
+  case 3:
+    return 0;
+  }
+  fprintf(stderr, "Read callback called after EOF\n");
+  exit(1);
+}
+
+#if !defined(LIB670) && !defined(LIB672)
+static int xferinfo(void *clientp, curl_off_t dltotal, curl_off_t dlnow,
+                    curl_off_t ultotal, curl_off_t ulnow)
+{
+  struct ReadThis *pooh = (struct ReadThis *) clientp;
+
+  (void) dltotal;
+  (void) dlnow;
+  (void) ultotal;
+  (void) ulnow;
+
+  if(pooh->origin && time(NULL) - pooh->origin >= PAUSE_TIME)
+    curl_easy_pause(pooh->easy, CURLPAUSE_CONT);
+
+  return 0;
+}
+#endif
+
+int test(char *URL)
+{
+#if defined(LIB670) || defined(LIB671)
+  curl_mime *mime = NULL;
+  curl_mimepart *part;
+#else
+  CURLFORMcode formrc;
+  struct curl_httppost *formpost = NULL;
+  struct curl_httppost *lastptr = NULL;
+#endif
+#if defined(LIB670) || defined(LIB672)
+  CURLM *multi = NULL;
+  CURLMcode mres;
+  CURLMsg *msg;
+  int msgs_left;
+  int still_running = 0;
+#endif
+
+  struct ReadThis pooh;
+  CURLcode result;
+  int res = TEST_ERR_FAILURE;
+
+  /*
+   * Check proper pausing/unpausing from a mime or form read callback.
+   */
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  pooh.origin = (time_t) 0;
+  pooh.count = 0;
+  pooh.easy = curl_easy_init();
+
+  /* First set the URL that is about to receive our POST. */
+  test_setopt(pooh.easy, CURLOPT_URL, URL);
+
+  /* get verbose debug output please */
+  test_setopt(pooh.easy, CURLOPT_VERBOSE, 1L);
+
+  /* include headers in the output */
+  test_setopt(pooh.easy, CURLOPT_HEADER, 1L);
+
+#if defined(LIB670) || defined(LIB671)
+  /* Build the mime tree. */
+  mime = curl_mime_init(pooh.easy);
+  part = curl_mime_addpart(mime);
+  result = curl_mime_name(part, name);
+  if(!result)
+    res = curl_mime_data_cb(part, (curl_off_t) 2, read_callback,
+                            NULL, NULL, &pooh);
+
+  if(result) {
+    fprintf(stderr,
+            "Something went wrong when building the mime structure: %d\n",
+            (int) result);
+    goto test_cleanup;
+  }
+
+  /* Bind mime data to its easy handle. */
+  if(!res)
+    test_setopt(pooh.easy, CURLOPT_MIMEPOST, mime);
+#else
+  /* Build the form. */
+  formrc = curl_formadd(&formpost, &lastptr,
+                        CURLFORM_COPYNAME, name,
+                        CURLFORM_STREAM, &pooh,
+                        CURLFORM_CONTENTLEN, (curl_off_t) 2,
+                        CURLFORM_END);
+  if(formrc) {
+    fprintf(stderr, "curl_formadd() = %d\n", (int) formrc);
+    goto test_cleanup;
+  }
+
+  /* We want to use our own read function. */
+  test_setopt(pooh.easy, CURLOPT_READFUNCTION, read_callback);
+
+  /* Send a multi-part formpost. */
+  test_setopt(pooh.easy, CURLOPT_HTTPPOST, formpost);
+#endif
+
+#if defined(LIB670) || defined(LIB672)
+  /* Use the multi interface. */
+  multi = curl_multi_init();
+  mres = curl_multi_add_handle(multi, pooh.easy);
+  while(!mres) {
+    struct timeval timeout;
+    int rc = 0;
+    fd_set fdread;
+    fd_set fdwrite;
+    fd_set fdexcept;
+    int maxfd = -1;
+
+    mres = curl_multi_perform(multi, &still_running);
+    if(!still_running || mres != CURLM_OK)
+      break;
+
+    if(pooh.origin && time(NULL) - pooh.origin >= PAUSE_TIME)
+      curl_easy_pause(pooh.easy, CURLPAUSE_CONT);
+
+    FD_ZERO(&fdread);
+    FD_ZERO(&fdwrite);
+    FD_ZERO(&fdexcept);
+    timeout.tv_sec = 0;
+    timeout.tv_usec = 1000000 * PAUSE_TIME / 10;
+    mres = curl_multi_fdset(multi, &fdread, &fdwrite, &fdexcept, &maxfd);
+    if(mres)
+      break;
+#ifdef _WIN32
+    if(maxfd == -1)
+      Sleep(100);
+    else
+#endif
+    rc = select(maxfd + 1, &fdread, &fdwrite, &fdexcept, &timeout);
+    if(rc == -1) {
+      fprintf(stderr, "Select error\n");
+      break;
+    }
+  }
+
+  if(mres != CURLM_OK)
+    for(;;) {
+      msg = curl_multi_info_read(multi, &msgs_left);
+      if(!msg)
+        break;
+      if(msg->msg == CURLMSG_DONE) {
+        result = msg->data.result;
+        res = (int) result;
+      }
+    }
+
+  curl_multi_remove_handle(multi, pooh.easy);
+  curl_multi_cleanup(multi);
+
+#else
+  /* Use the easy interface. */
+  test_setopt(pooh.easy, CURLOPT_XFERINFODATA, &pooh);
+  test_setopt(pooh.easy, CURLOPT_XFERINFOFUNCTION, xferinfo);
+  test_setopt(pooh.easy, CURLOPT_NOPROGRESS, 0L);
+  result = curl_easy_perform(pooh.easy);
+  res = (int) result;
+#endif
+
+
+test_cleanup:
+  curl_easy_cleanup(pooh.easy);
+#if defined(LIB670) || defined(LIB671)
+  curl_mime_free(mime);
+#else
+  curl_formfree(formpost);
+#endif
+
+  curl_global_cleanup();
+  return res;
+}