4 files changed, 44 insertions, 27 deletions

diff --git a/toxcore/Messenger.c b/toxcore/Messenger.c
index 2914cf36..607630b6 100644
--- a/toxcore/Messenger.c
+++ b/toxcore/Messenger.c
@@ -1196,6 +1196,28 @@ int file_control(const Messenger *m, int32_t friendnumber, uint32_t filenumber,
     return 0;
 }
 
+/* return packet number on success.
+ * return -1 on failure.
+ */
+static int64_t send_file_data_packet(const Messenger *m, int32_t friendnumber, uint8_t filenumber, const uint8_t *data,
+                                     uint16_t length)
+{
+    if (friend_not_valid(m, friendnumber))
+        return -1;
+
+    uint8_t packet[2 + length];
+    packet[0] = PACKET_ID_FILE_DATA;
+    packet[1] = filenumber;
+
+    if (length) {
+        memcpy(packet + 2, data, length);
+    }
+
+    return write_cryptpacket(m->net_crypto, friend_connection_crypt_connection_id(m->fr_c,
+                             m->friendlist[friendnumber].friendcon_id), packet, sizeof(packet), 1);
+}
+
+#define MAX_FILE_DATA_SIZE (MAX_CRYPTO_DATA_SIZE - 2)
 #define MIN_SLOTS_FREE (CRYPTO_MIN_QUEUE_LENGTH / 4)
 /* Send file data.
  *
@@ -1204,7 +1226,7 @@ int file_control(const Messenger *m, int32_t friendnumber, uint32_t filenumber,
  *  return -2 if friend not online.
  *  return -3 if filenumber invalid.
  *  return -4 if file transfer not transferring.
- *  return -5 if trying to send too much data.
+ *  return -5 if bad data size.
  *  return -6 if packet queue full.
  *  return -7 if wrong position.
  */
@@ -1228,13 +1250,17 @@ int file_data(const Messenger *m, int32_t friendnumber, uint32_t filenumber, uin
     if (ft->paused != FILE_PAUSE_NOT)
         return -4;
 
-    if (length > MAX_CRYPTO_DATA_SIZE - 2)
+    if (length > MAX_FILE_DATA_SIZE)
         return -5;
 
     if (ft->size) {
         if (ft->size - ft->transferred < length) {
             return -5;
         }
+
+        if (length != MAX_FILE_DATA_SIZE && (ft->transferred + length) != ft->size) {
+            return -5;
+        }
     }
 
     if (position != ft->transferred) {
@@ -1246,13 +1272,7 @@ int file_data(const Messenger *m, int32_t friendnumber, uint32_t filenumber, uin
                                         m->friendlist[friendnumber].friendcon_id)) < MIN_SLOTS_FREE)
         return -6;
 
-    uint8_t packet[2 + length];
-    packet[0] = PACKET_ID_FILE_DATA;
-    packet[1] = filenumber;
-    memcpy(packet + 2, data, length);
-
-    int64_t ret = write_cryptpacket(m->net_crypto, friend_connection_crypt_connection_id(m->fr_c,
-                                    m->friendlist[friendnumber].friendcon_id), packet, sizeof(packet), 1);
+    int64_t ret = send_file_data_packet(m, friendnumber, filenumber, data, length);
 
     if (ret != -1) {
         //TODO record packet ids to check if other received complete file.
@@ -1262,7 +1282,7 @@ int file_data(const Messenger *m, int32_t friendnumber, uint32_t filenumber, uin
             --ft->slots_allocated;
         }
 
-        if (length == 0 || ft->size == ft->transferred) {
+        if (length != MAX_FILE_DATA_SIZE || ft->size == ft->transferred) {
             ft->status = FILESTATUS_FINISHED;
             ft->last_packet_number = ret;
         }
@@ -1346,7 +1366,7 @@ static void do_reqchunk_filecb(Messenger *m, int32_t friendnumber)
             if (free_slots == 0)
                 break;
 
-            uint16_t length = MAX_CRYPTO_DATA_SIZE - 2;
+            uint16_t length = MAX_FILE_DATA_SIZE;
 
             if (ft->size) {
                 if (ft->size == ft->requested) {
@@ -1980,7 +2000,7 @@ static int handle_packet(void *object, int i, uint8_t *temp, uint16_t len)
 
             ft->transferred += file_data_length;
 
-            if (ft->size && ft->transferred >= ft->size) {
+            if ((ft->size && ft->transferred >= ft->size) || file_data_length != MAX_FILE_DATA_SIZE) {
                 file_data_length = 0;
                 file_data = NULL;
                 position = ft->transferred;
diff --git a/toxcore/Messenger.h b/toxcore/Messenger.h
index 0cbef76d..5dec83df 100644
--- a/toxcore/Messenger.h
+++ b/toxcore/Messenger.h
@@ -637,7 +637,7 @@ int file_control(const Messenger *m, int32_t friendnumber, uint32_t filenumber,
  *  return -2 if friend not online.
  *  return -3 if filenumber invalid.
  *  return -4 if file transfer not transferring.
- *  return -5 if trying to send too much data.
+ *  return -5 if bad data size.
  *  return -6 if packet queue full.
  *  return -7 if wrong position.
  */
diff --git a/toxcore/tox.c b/toxcore/tox.c
index c527ce96..5dfac2c8 100644
--- a/toxcore/tox.c
+++ b/toxcore/tox.c
@@ -960,7 +960,7 @@ bool tox_file_send_chunk(Tox *tox, uint32_t friend_number, uint32_t file_number,
             return 0;
 
         case -5:
-            SET_ERROR_PARAMETER(error, TOX_ERR_FILE_SEND_CHUNK_TOO_LARGE);
+            SET_ERROR_PARAMETER(error, TOX_ERR_FILE_SEND_CHUNK_INVALID_LENGTH);
             return 0;
 
         case -6:
diff --git a/toxcore/tox.h b/toxcore/tox.h
index d23065ff..eb6b4f31 100644
--- a/toxcore/tox.h
+++ b/toxcore/tox.h
@@ -1645,11 +1645,11 @@ typedef enum TOX_ERR_FILE_SEND_CHUNK {
      */
     TOX_ERR_FILE_SEND_CHUNK_NOT_TRANSFERRING,
     /**
-     * Attempted to send more data than requested. The requested data size is
+     * Attempted to send more or less data than requested. The requested data size is
      * adjusted according to maximum transmission unit and the expected end of
-     * the file. Trying to send more will result in no data being sent.
+     * the file. Trying to send less or more than requested will return this error.
      */
-    TOX_ERR_FILE_SEND_CHUNK_TOO_LARGE,
+    TOX_ERR_FILE_SEND_CHUNK_INVALID_LENGTH,
     /**
      * Packet queue is full.
      */
@@ -1664,12 +1664,12 @@ typedef enum TOX_ERR_FILE_SEND_CHUNK {
  * Send a chunk of file data to a friend.
  *
  * This function is called in response to the `file_request_chunk` callback. The
- * length parameter should be equal to or less than the one received though the
- * callback. If it is zero, the transfer is assumed complete. For files with
- * known size, Core will know that the transfer is complete after the last byte
- * has been received, so it is not necessary (though not harmful) to send a
- * zero-length chunk to terminate. For streams, it is necessary for the last
- * chunk sent to be zero-length.
+ * length parameter should be equal to the one received though the callback. 
+ * If it is zero, the transfer is assumed complete. For files with known size, 
+ * Core will know that the transfer is complete after the last byte has been 
+ * received, so it is not necessary (though not harmful) to send a zero-length 
+ * chunk to terminate. For streams, core will know that the transfer is finished 
+ * if a chunk with length less than the length requested in the callback is sent.
  *
  * @return true on success.
  */
@@ -1694,10 +1694,7 @@ bool tox_file_send_chunk(Tox *tox, uint32_t friend_number, uint32_t file_number,
  * In response to receiving this callback, the client should call the function
  * `tox_file_send_chunk` with the requested chunk. If the number of bytes sent
  * through that function is zero, the file transfer is assumed complete. A
- * client may choose to send less than requested, if it is reading from a
- * stream that doesn't have more data, yet, and it still wants to send some
- * data to the other side. However, this will generally be less efficient than
- * waiting for a full chunk size of data to be ready.
+ * client must send the full length of data requested with this callback.
  *
  * @param friend_number The friend number of the receiving friend for this file.
  * @param file_number The file transfer identifier returned by tox_file_send.