libs/http.obj: fix content_received overcount on chunked transfers (#569)

For chunked responses HTTP_receive added the whole buffer tail to
content_received every time it consumed a chunkline. When several
chunks arrived in one TCP segment, the same bytes were counted once
per chunkline (observed: content_received = 42 MB for an 83 KB page);
the value only became exact at got_all_data. A client trusting the
counter mid-transfer read far past the buffer and page-faulted.
In plain buffered mode recompute the exact value from the pointers
instead: min(chunk_ptr, write_ptr) - content_ptr, the same formula
.got_all_data_chunked uses. Data below chunk_ptr is decoded and
contiguous; bytes in [chunk_ptr, write_ptr) are still raw (unconsumed
chunkline + partial chunk). Stream/ring modes keep the running add:
there data is consumed as it arrives, so the incremental count is
correct.

---------

Co-authored-by: Burer <burer@kolibrios.org>
Reviewed-on: #569
Reviewed-by: hidnplayr <hidnplayr@gmail.com>
Reviewed-by: Burer <burer@kolibrios.org>
Co-authored-by: leency <lipatov.kiril@gmail.com>

programs/develop/libraries/http/http.asm

@@ -921,6 +921,7 @@ proc HTTP_receive identifier ;//////////////////////////////////////////////////
 ; Set chunk pointer where first chunk should begin.
         mov     eax, [ebp + http_msg.content_ptr]
         mov     [ebp + http_msg.chunk_ptr], eax
+        xor     eax, eax
 
 ;--------------------------------------------------------------
 ;
@@ -990,8 +991,11 @@ proc HTTP_receive identifier ;//////////////////////////////////////////////////
         mov     ecx, [ebp + http_msg.write_ptr]
         sub     ecx, [ebp + http_msg.chunk_ptr]
         sub     ecx, edx                                ; ecx is now number of received data bytes (without chunkline)
-; Update content_received counter
+; Update content_received counter.
+        test    [ebp + http_msg.flags], FLAG_STREAM or FLAG_RING
+        jz      .chunkline_counted
         add     [ebp + http_msg.content_received], ecx
+  .chunkline_counted:
 ; Calculate new write ptr
         sub     [ebp + http_msg.write_ptr], edx
         test    [ebp + http_msg.flags], FLAG_STREAM
@@ -1101,7 +1105,19 @@ proc HTTP_receive identifier ;//////////////////////////////////////////////////
         sub     [ebp + http_msg.write_ptr], ebx
   @@:
         ; We only got a partial chunk, or need more chunks, update content_received and request more data
+        test    [ebp + http_msg.flags], FLAG_STREAM or FLAG_RING
+        jz      .nmdc_exact
         add     [ebp + http_msg.content_received], eax
+        jmp     .nmdc_ret
+  .nmdc_exact:
+        mov     eax, [ebp + http_msg.chunk_ptr]
+        cmp     eax, [ebp + http_msg.write_ptr]
+        jbe     @f
+        mov     eax, [ebp + http_msg.write_ptr]
+  @@:
+        sub     eax, [ebp + http_msg.content_ptr]
+        mov     [ebp + http_msg.content_received], eax
+  .nmdc_ret:
         popa
         xor     eax, eax
         dec     eax