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AP_Frsky_Telem: fixes #5862

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MAVLink strings of exactly 50 characters are not NULL terminated, so
instead we must check that the 50th character has been reached.
This commit is contained in:
Florent Martel 2017-03-14 11:21:08 -05:00 committed by Francisco Ferreira
parent 8a95550034
commit 02c0885cfd
1 changed files with 11 additions and 18 deletions
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27
libraries/AP_Frsky_Telem/AP_Frsky_Telem.cpp
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@ -421,32 +421,25 @@ bool AP_Frsky_Telem::get_next_msg_chunk(void)
return false; return false;
} }
if (_msg_chunk.repeats == 0) { if (_msg_chunk.repeats == 0) { // if it's the first time get_next_msg_chunk is called for a given chunk
_msg_chunk.chunk = 0; uint8_t character;
uint8_t character = _statustext_queue[0]->text[_msg_chunk.char_index++]; _msg_chunk.chunk = 0; // clear the 4 bytes of the chunk buffer
if (character) { for(int i = 3; i > -1 && _msg_chunk.char_index < sizeof(_statustext_queue[0]->text); i--) {
_msg_chunk.chunk |= character<<24;
character = _statustext_queue[0]->text[_msg_chunk.char_index++]; character = _statustext_queue[0]->text[_msg_chunk.char_index++];
if (character) { if (!character) {
_msg_chunk.chunk |= character<<16; break;
character = _statustext_queue[0]->text[_msg_chunk.char_index++];
if (character) {
_msg_chunk.chunk |= character<<8;
character = _statustext_queue[0]->text[_msg_chunk.char_index++];
if (character) {
_msg_chunk.chunk |= character;
}
}
} }
_msg_chunk.chunk |= character << i * 8;
} }
if (!character) { // we've reached the end of the message (string terminated by '\0') if ((!character)||(_msg_chunk.char_index == sizeof(_statustext_queue[0]->text))) { // we've reached the end of the message (string terminated by '\0' or last character of the string has been processed)
_msg_chunk.char_index = 0; _msg_chunk.char_index = 0; // reset index to get ready to process the next message
// add severity which is sent as the MSB of the last three bytes of the last chunk (bits 24, 16, and 8) since a character is on 7 bits // add severity which is sent as the MSB of the last three bytes of the last chunk (bits 24, 16, and 8) since a character is on 7 bits
_msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x4)<<21; _msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x4)<<21;
_msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x2)<<14; _msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x2)<<14;
_msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x1)<<7; _msg_chunk.chunk |= (_statustext_queue[0]->severity & 0x1)<<7;
} }
} }
_msg_chunk.repeats++; _msg_chunk.repeats++;
if (_msg_chunk.repeats > 2) { // repeat each message chunk 3 times to ensure transmission if (_msg_chunk.repeats > 2) { // repeat each message chunk 3 times to ensure transmission
_msg_chunk.repeats = 0; _msg_chunk.repeats = 0;