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 664 checks mimepost using single-byte read callback with encoder.
New test 665 checks the end of part data early detection.

Fixes curl#4826
Reported-by: MrdUkk on github

lib/mime.h

@@ -31,6 +31,7 @@
 /* Part flags. */
 #define MIME_USERHEADERS_OWNER  (1 << 0)
 #define MIME_BODY_ONLY          (1 << 1)
+#define MIME_FAST_READ          (1 << 2)
 
 #define FILE_CONTENTTYPE_DEFAULT        "application/octet-stream"
 #define MULTIPART_CONTENTTYPE_DEFAULT   "multipart/mixed"
@@ -87,7 +88,7 @@ typedef struct {
 typedef struct {
   enum mimestate state;       /* Current state token. */
   void *ptr;                  /* State-dependent pointer. */
-  size_t offset;              /* State-dependent offset. */
+  curl_off_t offset;          /* State-dependent offset. */
 }  mime_state;
 
 /* minimum buffer size for the boundary string */

tests/data/Makefile.inc

@@ -85,7 +85,7 @@ test626 test627 test628 test629 test630 test631 test632 test633 test634 \
 test635 test636 test637 test638 test639 test640 test641 test642 \
 test643 test644 test645 test646 test647 test648 test649 test650 test651 \
 test652 test653 test654 test655 test656 test658 test659 test660 test661 \
-test662 test663 \
+test662 test663 test664 test665 \
 test670 test671 test672 test673 \
 \
 test700 test701 test702 test703 test704 test705 test706 test707 test708 \

tests/data/test643

@@ -69,18 +69,18 @@ s/boundary=------------------------[a-z0-9]*/boundary=--------------------------
 POST /643 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 718
+Content-Length: 640
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------
 Content-Disposition: form-data; name="sendfile"; filename="postit2.c"
 
-this is what we post to the silly web server
+dummy
 
 ------------------------------
 Content-Disposition: form-data; name="callbackdata"
 
-this is what we post to the silly web server
+dummy
 
 ------------------------------
 Content-Disposition: form-data; name="filename"
@@ -99,18 +99,18 @@ blah blah
 POST /643 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 732
+Content-Length: 654
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------
 Content-Disposition: form-data; name="sendfile alternative"; filename="file name 2"
 
-this is what we post to the silly web server
+dummy
 
 ------------------------------
 Content-Disposition: form-data; name="callbackdata"
 
-this is what we post to the silly web server
+dummy
 
 ------------------------------
 Content-Disposition: form-data; name="filename"

tests/data/test644

@@ -44,7 +44,7 @@ s/boundary=------------------------[a-z0-9]*/boundary=--------------------------
 POST /644 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 718
+Content-Length: 640
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------

tests/data/test645

@@ -73,16 +73,42 @@ Transfer-Encoding: chunked
 Content-Type: multipart/form-data; boundary=----------------------------
 Expect: 100-continue
 
-2ce
+76
 ------------------------------
 Content-Disposition: form-data; name="sendfile"; filename="postit2.c"
 
-this is what we post to the silly web server
+d
+1
+u
+1
+m
+1
+m
+1
+y
+1
+
+
+65
 
 ------------------------------
 Content-Disposition: form-data; name="callbackdata"
 
-this is what we post to the silly web server
+
+1
+d
+1
+u
+1
+m
+1
+m
+1
+y
+1
+
+
+19a
 
 ------------------------------
 Content-Disposition: form-data; name="filename"
@@ -108,16 +134,42 @@ Transfer-Encoding: chunked
 Content-Type: multipart/form-data; boundary=----------------------------
 Expect: 100-continue
 
-2dc
+84
 ------------------------------
 Content-Disposition: form-data; name="sendfile alternative"; filename="file name 2"
 
-this is what we post to the silly web server
+d
+1
+u
+1
+m
+1
+m
+1
+y
+1
+
+
+65
 
 ------------------------------
 Content-Disposition: form-data; name="callbackdata"
 
-this is what we post to the silly web server
+
+1
+d
+1
+u
+1
+m
+1
+m
+1
+y
+1
+
+
+19a
 
 ------------------------------
 Content-Disposition: form-data; name="filename"

tests/data/test650

@@ -63,7 +63,7 @@ Transfer-Encoding: chunked
 Content-Type: multipart/form-data; boundary=----------------------------
 Expect: 100-continue
 
-60a
+361
 ------------------------------
 Content-Disposition: form-data; name="fieldname"
 Content-Type: text/plain
@@ -89,19 +89,25 @@ This is data from a file.
 Content-Disposition: attachment; filename="test650.filedata"
 Content-Type: text/whatever
 
+
+a5
 This is data from a file.
 
 ------------------------------
 Content-Disposition: attachment; filename="test650.filedata"
 Content-Type: text/whatever
 
+
+af
 This is data from a file.
 
 --------------------------------
 
 ------------------------------
 Content-Disposition: form-data; name="filecontents"
 
+
+10f
 This is data from a file.
 
 ------------------------------
@@ -112,8 +118,12 @@ Content-Disposition: form-data; name="formlength"
 Content-Disposition: form-data; name="standardinput"
 Content-Type: application/octet-stream
 
+
+16
  Some data from stdin
 
+30
+
 --------------------------------
 
 0

tests/data/test654

@@ -81,7 +81,7 @@ Transfer-Encoding: chunked
 Content-Type: multipart/form-data; boundary=----------------------------
 Expect: 100-continue
 
-20c
+1af
 ------------------------------
 Content-Disposition: form-data; name="greeting"
 Content-Type: application/X-Greeting
@@ -98,7 +98,21 @@ This is data from a file
 ------------------------------
 Content-Disposition: form-data
 
-this is what we post to the silly web server
+
+1
+d
+1
+u
+1
+m
+1
+m
+1
+y
+1
+
+
+30
 
 --------------------------------
 

tests/data/test664

@@ -0,0 +1,85 @@
+<testcase>
+<info>
+<keywords>
+HTTP
+HTTP POST
+HTTP MIME POST
+</keywords>
+</info>
+
+#
+# Server-side
+<reply>
+<data>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake swsclose
+Connection: close
+Content-Type: text/html
+
+hello
+</data>
+<datacheck>
+HTTP/1.1 200 OK
+Date: Thu, 09 Nov 2010 14:49:00 GMT
+Server: test-server/fake swsclose
+Connection: close
+Content-Type: text/html
+
+hello
+</datacheck>
+</reply>
+
+# Client-side
+<client>
+<server>
+http
+</server>
+# tool is what to use instead of 'curl'
+<tool>
+lib664
+</tool>
+
+ <name>
+HTTP chunked mimepost using single-byte read callback with encoder
+ </name>
+ <command>
+http://%HOSTIP:%HTTPPORT/664
+</command>
+</client>
+
+#
+# Verify data after the test has been "shot"
+<verify>
+<strippart>
+s/^--------------------------[a-z0-9]*/------------------------------/
+s/boundary=------------------------[a-z0-9]*/boundary=----------------------------/
+</strippart>
+# Note that the stripping above removes 12 bytes from every occurrence of the
+# boundary string and since 5 of them are in the body contents, we see
+# (5*12) == 60 bytes less
+<protocol>
+POST /664 HTTP/1.1
+Host: %HOSTIP:%HTTPPORT
+Accept: */*
+Transfer-Encoding: chunked
+Content-Type: multipart/form-data; boundary=----------------------------
+Expect: 100-continue
+
+7f
+------------------------------
+Content-Disposition: form-data; name="field"
+Content-Transfer-Encoding: base64
+
+
+4
+ZHVt
+34
+bXk=
+--------------------------------
+
+0
+
+</protocol>
+</verify>
+</testcase>