mime: do not perform more than one read in a row

Input buffer filling may delay the data sending if data reads are slow.
To overcome this problem, file and callback data reads do not accumulate
in buffer anymore. All other data (memory data and mime framing) are
considered as fast and still concatenated in buffer.
As this may highly impact performance in terms of data overhead, an early
end of part data check is added to spare a read call.
When encoding a part's data, an encoder may require more bytes than made
available by a single read. In this case, the above rule does not apply
and reads are performed until the encoder is able to deliver some data.

Tests 643, 644, 645, 650 and 654 have been adapted to the output data
changes, with test data size reduced to avoid the boredom of long lists of
1-byte chunks in verification data.
New test 667 checks mimepost using single-byte read callback with encoder.
New test 668 checks the end of part data early detection.

Fixes #4826
Reported-by: MrdUkk on github

5 files changed, 253 insertions, 10 deletions

diff --git a/tests/libtest/Makefile.inc b/tests/libtest/Makefile.inc
index 9652f03fe..a8a148e66 100644
--- a/tests/libtest/Makefile.inc
+++ b/tests/libtest/Makefile.inc
@@ -22,7 +22,7 @@ noinst_PROGRAMS = chkhostname libauthretry libntlmconnect                \
  lib571 lib572 lib573 lib574 lib575 lib576        lib578 lib579 lib582   \
  lib583 lib585 lib586 lib587 lib589 lib590 lib591 lib597 lib598 lib599   \
  lib643 lib644 lib645 lib650 lib651 lib652 lib653 lib654 lib655 lib658   \
- lib659 lib661 \
+ lib659 lib661 lib667 lib668 \
  lib670 lib671 lib672 lib673 \
  lib1156 \
  lib1500 lib1501 lib1502 lib1503 lib1504 lib1505 lib1506 lib1507 lib1508 \
@@ -349,6 +349,14 @@ lib659_CPPFLAGS = $(AM_CPPFLAGS)
 lib661_SOURCES = lib661.c $(SUPPORTFILES)
 lib661_CPPFLAGS = $(AM_CPPFLAGS)
 
+lib667_SOURCES = lib667.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib667_LDADD = $(TESTUTIL_LIBS)
+lib667_CPPFLAGS = $(AM_CPPFLAGS)
+
+lib668_SOURCES = lib668.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
+lib668_LDADD = $(TESTUTIL_LIBS)
+lib668_CPPFLAGS = $(AM_CPPFLAGS)
+
 lib670_SOURCES = lib670.c $(SUPPORTFILES) $(TESTUTIL) $(WARNLESS)
 lib670_LDADD = $(TESTUTIL_LIBS)
 lib670_CPPFLAGS = $(AM_CPPFLAGS) -DLIB670
diff --git a/tests/libtest/lib643.c b/tests/libtest/lib643.c
index 08c0f2e80..5af0f4a14 100644
--- a/tests/libtest/lib643.c
+++ b/tests/libtest/lib643.c
@@ -26,11 +26,9 @@
 static char data[]=
 #ifdef CURL_DOES_CONVERSIONS
   /* ASCII representation with escape sequences for non-ASCII platforms */
-  "\x74\x68\x69\x73\x20\x69\x73\x20\x77\x68\x61\x74\x20\x77\x65\x20\x70"
-  "\x6f\x73\x74\x20\x74\x6f\x20\x74\x68\x65\x20\x73\x69\x6c\x6c\x79\x20"
-  "\x77\x65\x62\x20\x73\x65\x72\x76\x65\x72\x0a";
+  "\x64\x75\x6d\x6d\x79\x0a";
 #else
-  "this is what we post to the silly web server\n";
+  "dummy\n";
 #endif
 
 struct WriteThis {
diff --git a/tests/libtest/lib654.c b/tests/libtest/lib654.c
index 45051a9c7..f9c8b9118 100644
--- a/tests/libtest/lib654.c
+++ b/tests/libtest/lib654.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2018, 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
@@ -26,11 +26,9 @@
 static char data[]=
 #ifdef CURL_DOES_CONVERSIONS
   /* ASCII representation with escape sequences for non-ASCII platforms */
-  "\x74\x68\x69\x73\x20\x69\x73\x20\x77\x68\x61\x74\x20\x77\x65\x20\x70"
-  "\x6f\x73\x74\x20\x74\x6f\x20\x74\x68\x65\x20\x73\x69\x6c\x6c\x79\x20"
-  "\x77\x65\x62\x20\x73\x65\x72\x76\x65\x72\x0a";
+  "\x64\x75\x6d\x6d\x79\x0a";
 #else
-  "this is what we post to the silly web server\n";
+  "dummy\n";
 #endif
 
 struct WriteThis {
diff --git a/tests/libtest/lib667.c b/tests/libtest/lib667.c
new file mode 100644
index 000000000..8bf7be43f
--- /dev/null
+++ b/tests/libtest/lib667.c
@@ -0,0 +1,117 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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 "test.h"
+
+#include "memdebug.h"
+
+static char data[]=
+#ifdef CURL_DOES_CONVERSIONS
+  /* ASCII representation with escape sequences for non-ASCII platforms */
+  "\x64\x75\x6d\x6d\x79";
+#else
+  "dummy";
+#endif
+
+struct WriteThis {
+  char *readptr;
+  curl_off_t sizeleft;
+};
+
+static size_t read_callback(char *ptr, size_t size, size_t nmemb, void *userp)
+{
+  struct WriteThis *pooh = (struct WriteThis *)userp;
+  int eof = !*pooh->readptr;
+
+  if(size*nmemb < 1)
+    return 0;
+
+  eof = pooh->sizeleft <= 0;
+  if(!eof)
+    pooh->sizeleft--;
+
+  if(!eof) {
+    *ptr = *pooh->readptr;           /* copy one single byte */
+    pooh->readptr++;                 /* advance pointer */
+    return 1;                        /* we return 1 byte at a time! */
+  }
+
+  return 0;                         /* no more data left to deliver */
+}
+
+int test(char *URL)
+{
+  CURL *easy = NULL;
+  curl_mime *mime = NULL;
+  curl_mimepart *part;
+  CURLcode result;
+  int res = TEST_ERR_FAILURE;
+  struct WriteThis pooh;
+
+  /*
+   * Check proper handling of mime encoder feature when the part read callback
+   * delivers data bytes one at a time. Use chunked encoding for accurate test.
+   */
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  easy = curl_easy_init();
+
+  /* First set the URL that is about to receive our POST. */
+  test_setopt(easy, CURLOPT_URL, URL);
+
+  /* get verbose debug output please */
+  test_setopt(easy, CURLOPT_VERBOSE, 1L);
+
+  /* include headers in the output */
+  test_setopt(easy, CURLOPT_HEADER, 1L);
+
+  /* Prepare the callback structure. */
+  pooh.readptr = data;
+  pooh.sizeleft = (curl_off_t) strlen(data);
+
+  /* Build the mime tree. */
+  mime = curl_mime_init(easy);
+  part = curl_mime_addpart(mime);
+  curl_mime_name(part, "field");
+  curl_mime_encoder(part, "base64");
+  /* Using an undefined length forces chunked transfer. */
+  curl_mime_data_cb(part, (curl_off_t) -1, read_callback, NULL, NULL, &pooh);
+
+  /* Bind mime data to its easy handle. */
+  test_setopt(easy, CURLOPT_MIMEPOST, mime);
+
+  /* Send data. */
+  result = curl_easy_perform(easy);
+  if(result) {
+    fprintf(stderr, "curl_easy_perform() failed\n");
+    res = (int) result;
+  }
+
+test_cleanup:
+  curl_easy_cleanup(easy);
+  curl_mime_free(mime);
+  curl_global_cleanup();
+  return res;
+}
diff --git a/tests/libtest/lib668.c b/tests/libtest/lib668.c
new file mode 100644
index 000000000..c0b608a0a
--- /dev/null
+++ b/tests/libtest/lib668.c
@@ -0,0 +1,122 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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 "test.h"
+
+#include "memdebug.h"
+
+static char data[]=
+#ifdef CURL_DOES_CONVERSIONS
+  /* ASCII representation with escape sequences for non-ASCII platforms */
+  "\x64\x75\x6d\x6d\x79";
+#else
+  "dummy";
+#endif
+
+struct WriteThis {
+  char *readptr;
+  curl_off_t sizeleft;
+};
+
+static size_t read_callback(char *ptr, size_t size, size_t nmemb, void *userp)
+{
+  struct WriteThis *pooh = (struct WriteThis *)userp;
+  size_t len = strlen(pooh->readptr);
+
+  (void) size; /* Always 1.*/
+
+  if(len > nmemb)
+    len = nmemb;
+  if(len) {
+    memcpy(ptr, pooh->readptr, len);
+    pooh->readptr += len;
+  }
+  return len;
+}
+
+int test(char *URL)
+{
+  CURL *easy = NULL;
+  curl_mime *mime = NULL;
+  curl_mimepart *part;
+  CURLcode result;
+  int res = TEST_ERR_FAILURE;
+  struct WriteThis pooh1, pooh2;
+
+  /*
+   * Check early end of part data detection.
+   */
+
+  if(curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK) {
+    fprintf(stderr, "curl_global_init() failed\n");
+    return TEST_ERR_MAJOR_BAD;
+  }
+
+  easy = curl_easy_init();
+
+  /* First set the URL that is about to receive our POST. */
+  test_setopt(easy, CURLOPT_URL, URL);
+
+  /* get verbose debug output please */
+  test_setopt(easy, CURLOPT_VERBOSE, 1L);
+
+  /* include headers in the output */
+  test_setopt(easy, CURLOPT_HEADER, 1L);
+
+  /* Prepare the callback structures. */
+  pooh1.readptr = data;
+  pooh1.sizeleft = (curl_off_t) strlen(data);
+  pooh2 = pooh1;
+
+  /* Build the mime tree. */
+  mime = curl_mime_init(easy);
+  part = curl_mime_addpart(mime);
+  curl_mime_name(part, "field1");
+  /* Early end of data detection can be done because the data size is known. */
+  curl_mime_data_cb(part, (curl_off_t) strlen(data),
+                    read_callback, NULL, NULL, &pooh1);
+  part = curl_mime_addpart(mime);
+  curl_mime_name(part, "field2");
+  /* Using an undefined length forces chunked transfer and disables early
+     end of data detection for this part. */
+  curl_mime_data_cb(part, (curl_off_t) -1, read_callback, NULL, NULL, &pooh2);
+  part = curl_mime_addpart(mime);
+  curl_mime_name(part, "field3");
+  /* Regular file part sources early end of data can be detected because
+     the file size is known. In addition, and EOF test is performed. */
+  curl_mime_filedata(part, "log/file668.txt");
+
+  /* Bind mime data to its easy handle. */
+  test_setopt(easy, CURLOPT_MIMEPOST, mime);
+
+  /* Send data. */
+  result = curl_easy_perform(easy);
+  if(result) {
+    fprintf(stderr, "curl_easy_perform() failed\n");
+    res = (int) result;
+  }
+
+test_cleanup:
+  curl_easy_cleanup(easy);
+  curl_mime_free(mime);
+  curl_global_cleanup();
+  return res;
+}