Allow sending of file transfer requests with length 0 but don't allocate

any file number for them in core.

These can be used to tell friends we don't have an avatar set or to unset
a set avatar.

auto_tests/tox_test.c

@@ -202,6 +202,10 @@ void tox_file_chunk_request(Tox *tox, uint32_t friend_number, uint32_t file_numb
     }
 
     if (length == 0) {
+        if (file_sending_done) {
+            ck_abort_msg("File sending already done.");
+        }
+
         file_sending_done = 1;
         return;
     }

toxcore/Messenger.c

@@ -1091,7 +1091,7 @@ static int file_sendrequest(const Messenger *m, int32_t friendnumber, uint8_t fi
  *  return -2 if filename length invalid.
  *  return -3 if no more file sending slots left.
  *  return -4 if could not send packet (friend offline).
- *
+ *  return -5 if succesfully sent file send request with filesize 0.
  */
 long int new_filesender(const Messenger *m, int32_t friendnumber, uint32_t file_type, uint64_t filesize,
                         const uint8_t *file_id, const uint8_t *filename, uint16_t filename_length)
@@ -1115,18 +1115,22 @@ long int new_filesender(const Messenger *m, int32_t friendnumber, uint32_t file_
     if (file_sendrequest(m, friendnumber, i, file_type, filesize, file_id, filename, filename_length) == 0)
         return -4;
 
-    struct File_Transfers *ft = &m->friendlist[friendnumber].file_sending[i];
-    ft->status = FILESTATUS_NOT_ACCEPTED;
-    ft->size = filesize;
-    ft->transferred = 0;
-    ft->requested = 0;
-    ft->slots_allocated = 0;
-    ft->paused = FILE_PAUSE_NOT;
-    memcpy(ft->id, file_id, FILE_ID_LENGTH);
+    /* Only init file if filesize isn't 0. */
+    if (filesize) {
+        struct File_Transfers *ft = &m->friendlist[friendnumber].file_sending[i];
+        ft->status = FILESTATUS_NOT_ACCEPTED;
+        ft->size = filesize;
+        ft->transferred = 0;
+        ft->requested = 0;
+        ft->slots_allocated = 0;
+        ft->paused = FILE_PAUSE_NOT;
+        memcpy(ft->id, file_id, FILE_ID_LENGTH);
 
-    ++m->friendlist[friendnumber].num_sending_files;
-
-    return i;
+        ++m->friendlist[friendnumber].num_sending_files;
+        return i;
+    } else {
+        return -5;
+    }
 }
 
 int send_file_control_packet(const Messenger *m, int32_t friendnumber, uint8_t send_receive, uint8_t filenumber,
@@ -2044,11 +2048,23 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
             net_to_host((uint8_t *) &filesize, sizeof(filesize));
             struct File_Transfers *ft = &m->friendlist[i].file_receiving[filenumber];
 
-            ft->status = FILESTATUS_NOT_ACCEPTED;
-            ft->size = filesize;
-            ft->transferred = 0;
-            ft->paused = FILE_PAUSE_NOT;
-            memcpy(ft->id, data + 1 + sizeof(uint32_t) + sizeof(uint64_t), FILE_ID_LENGTH);
+            if (ft->status != FILESTATUS_NONE)
+                break;
+
+            uint32_t real_filenumber = UINT32_MAX;
+
+            if (filesize) {
+                /* Don't */
+                ft->status = FILESTATUS_NOT_ACCEPTED;
+                ft->size = filesize;
+                ft->transferred = 0;
+                ft->paused = FILE_PAUSE_NOT;
+                memcpy(ft->id, data + 1 + sizeof(uint32_t) + sizeof(uint64_t), FILE_ID_LENGTH);
+
+                real_filenumber = filenumber;
+                real_filenumber += 1;
+                real_filenumber <<= 16;
+            }
 
             uint8_t filename_terminated[filename_length + 1];
             uint8_t *filename = NULL;
@@ -2060,9 +2076,6 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
                 filename = filename_terminated;
             }
 
-            uint32_t real_filenumber = filenumber;
-            real_filenumber += 1;
-            real_filenumber <<= 16;
 
             if (m->file_sendrequest)
                 (*m->file_sendrequest)(m, i, real_filenumber, file_type, filesize, filename, filename_length,

toxcore/Messenger.h

@@ -618,7 +618,7 @@ int file_get_id(const Messenger *m, int32_t friendnumber, uint32_t filenumber, u
  *  return -2 if filename length invalid.
  *  return -3 if no more file sending slots left.
  *  return -4 if could not send packet (friend offline).
- *
+ *  return -5 if succesfully sent file send request with filesize 0.
  */
 long int new_filesender(const Messenger *m, int32_t friendnumber, uint32_t file_type, uint64_t filesize,
                         const uint8_t *file_id, const uint8_t *filename, uint16_t filename_length);

toxcore/tox.c

@@ -1000,6 +1000,10 @@ uint32_t tox_file_send(Tox *tox, uint32_t friend_number, uint32_t kind, uint64_t
         case -4:
             SET_ERROR_PARAMETER(error, TOX_ERR_FILE_SEND_FRIEND_NOT_CONNECTED);
             return UINT32_MAX;
+
+        case -5:
+            SET_ERROR_PARAMETER(error, TOX_ERR_FILE_SEND_OK_ZERO_LENGTH);
+            return UINT32_MAX;
     }
 
     /* can't happen */

toxcore/tox.h

@@ -1610,7 +1610,12 @@ typedef enum TOX_ERR_FILE_SEND {
      * Too many ongoing transfers. The maximum number of concurrent file transfers
      * is 256 per friend per direction (sending and receiving).
      */
-    TOX_ERR_FILE_SEND_TOO_MANY
+    TOX_ERR_FILE_SEND_TOO_MANY,
+    /**
+     * A file request packet was successfully sent to the friend however since it was zero
+     * length, no file number was allocated for the file transfer.
+     */
+    TOX_ERR_FILE_SEND_OK_ZERO_LENGTH
 } TOX_ERR_FILE_SEND;
 
 /**
@@ -1629,6 +1634,9 @@ typedef enum TOX_ERR_FILE_SEND {
  * When a friend goes offline, all file transfers associated with the friend are
  * purged from core.
  *
+ * if file_size is 0, this function will not allocate a file transfer in core and so
+ * will not return a valid file number however it will send a file request packet.
+ *
  * If the file contents change during a transfer, the behaviour is unspecified
  * in general. What will actually happen depends on the mode in which the file
  * was modified and how the client determines the file size.
@@ -1779,6 +1787,8 @@ void tox_callback_file_chunk_request(Tox *tox, tox_file_chunk_request_cb *functi
  * control command before any other control commands. It can be accepted by
  * sending TOX_FILE_CONTROL_RESUME.
  *
+ * If file_size is zero, the file_number is invalid and should be ignored.
+ *
  * @param friend_number The friend number of the friend who is sending the file
  *   transfer request.
  * @param file_number The friend-specific file number the data received is